Method and device for leakage detection

Abstract

A leak test device (44) is designed to test leaks between a first conduit (38) and a second conduit (40), which may be part of a heat exchange system. The apparatus (44) includes a first channel (48) and a second channel (50), a flow control system (46), and flow sensors (F1.1, F1.2, F2.1, F2.2) located at respective locations within each respective channel (48, 50). Each passage (48, 50) is connected to a conduit (38, 40) to form a respective closed-loop system, and a flow control system (46) is adapted to actively maintain fluid pressure at a set level within each closed-loop system. In a set pressure closed loop system, any detected flow is indicative of a leak. The use of a plurality of flow sensors (F1.1, F1.2, F2.1, F2.2) at different locations allows the possible leakage locations to be distinguished. The shut-off valve may provide a mechanism by which the test device can control a test sequence to be performed on the conduit (38, 40). The apparatus may be used online to test various designs of the heat exchanger, and may be amplified to test complex systems.

Description

[0001] The present invention relates to the field of leak detection and in particular to leak detection in pipes which may form part of a heat exchanger.

[0002] Heat exchangers are widely used in industry, and there are many applications where heat needs to be transferred from one body to another. They can be classified by design or function, such as single-pass and multi-pass; tubular, plate-like or extended surface; direct contact or indirect contact; heaters, coolers and condensers, etc. If fluids are involved in the transfer process, a physical barrier must be maintained between them. If a leak develops between the two sides of such a heat exchanger, for example, food may be contaminated, or a chemical product will lack the necessary purity. The defective product must then be discarded, and the operation shut down while repairs are carried out. This is an expensive undertaking.

[0003] Since the development of the first heat exchanger in the 1920s, the industry has been demanding cheaper, more efficient designs with improved system performance. Recently, there has been an additional drive to reduce carbon footprint. Such requirements for design have paid some price in terms of reliability, performance and durability. For example, plate heat exchangers are a widely used design in which the heat exchange area is increased by guiding the exchange fluid to flow along the surface of the metal plate. Technological developments have caused these plates to become thinner, with the risk of increased manufacturing defects, material defects and failure development during operation. This latter problem is particularly serious in processes utilizing corrosive fluids (in production or during cleaning cycles). This includes the production of many chemicals and foods, and in such industries, the possibility of pitting is very large. In addition, even without corrosive fluids, the heat exchanger plates themselves are repeatedly subjected to thermal expansion and contraction, potentially leading to subsequent development of work hardening and cracks or cracks.

[0004] Therefore, test devices have been developed that are intended to detect leaks in heat exchangers at an early stage. A variety of designs are known, in which leak detection is based on principles ranging from manual inspection to detection of markers or tracer fluids that pass through a separation barrier. However, most of the known technologies have significant disadvantages: they require the heat exchanger to be mechanically disconnected from the production line and prepared before a leak test can be performed. This takes time and represents a serious disruption to production schedules. For example, in order to perform a gas leak test, it may take several hours to prepare the heat exchange system, and then more than six hours to perform the actual test. After this, the heat exchanger must be reconnected and the system completely cleaned before the heat exchanger can be put back into service. This loss of production time is a loss that plant operators wish to avoid.

[0005] Therefore, recently, attention has been paid to developing in-line testing methods that can be performed without mechanically disassembling the heat exchanger and still maintain reliability and accuracy in defect detection.

[0006] EP 3740078 describes an on-line test rig for a complex heat exchange system for pasteurization of milk. The pasteurization heat exchanger comprises a heating, cooling and regeneration phase, the latter being the phase in which the heat from the treated product is used to provide the initial heating of the untreated product. In order to use this test rig, the complex heat exchange system is equipped with a plurality of valves, pumps and sensors which are operable by a controller so as to thereby isolate parts of the system. Each isolated part is then tested for leakage in turn using a pressure decay test. When the test is performed, one side of the heat exchanger is filled with a high pressure fluid and the other side is filled with a low pressure fluid. If there is a leak across the separation barrier, the fluid pressure will change: an increase on the low pressure side and a decrease on the high pressure side. Therefore, if a pressure drop is detected, the conclusion is that the leak is the cause.

[0007] Early systems based on the principle of pressure decay found it difficult to ensure consistency of results: a small leak would only cause a relatively small pressure change, which could be masked by temperature fluctuations in the system. It therefore proved difficult to obtain accurate measurements within a feasible time scale. To improve accuracy, the pressure on the high pressure side of the system described in EP 3740078 is maintained at a set level under the control of a pump. This also allows the system to distinguish between leaks through the plate and leaks that may pass from, for example, a gasket to the atmosphere.

[0008] Although online testing is advantageous (as it avoids disconnecting the heat exchanger from the process facility), the system described in EP 3740078 is very specific in the design of its heat exchanger and test rig. The two components are integrated, and the test rig lacks any flexibility for use with heat exchangers of different types and configurations. Furthermore, the method employed still requires that both sides of the heat exchanger be filled with a significant pressure differential. This high pressure differential is required to ensure sufficient flow through the leak in order to observe detectable pressure changes within a reasonable period of time. However, a disadvantage is that the high pressure differential can damage components of the heat exchanger over time, particularly the plates.

[0009] Therefore, there was a perceived need for an alternative system for testing heat exchanger integrity that could provide in-line testing capability for a range of heat exchangers and reliably detect a wide range of defects.

[0010] According to a first aspect, the present invention provides a leakage testing device, the leakage testing device comprising:

[0011] a first channel having an inflow path and an outflow path, the inflow path and the outflow path being connectable to spatially separated locations in the first conduit to form a first closed loop system;

[0012] a second passage having an inflow path and an outflow path, the inflow path and the outflow path being connectable to spaced-apart locations in the second conduit to form a second closed-loop system;

[0013] a flow control system including a flow controller in communication with the pump and the pressure sensor, the flow control system being in fluid communication with the first passage and the second passage and adapted to pump fluid at a rate that actively maintains pressure at or near a predetermined level within the first closed-loop system and the second closed-loop system; and

[0014] a first flow sensor, the first flow sensor being located in an inflow path of the first channel; and

[0015] A second flow sensor is located in the inflow path of the second channel.

[0016] This design of the test device is based on a completely different approach from the prior art leak detection methods. The present invention is intended to detect fluid flow within an otherwise closed channel, which flow is therefore indicative of a leak. This approach is particularly suitable for integrity testing of heat exchangers, although it is also suitable for other applications that benefit from detecting leaks across fluid boundaries. It allows a number of advantages. First, the pressure is actively maintained in the two channels of the heat exchanger, making the system robust to temperature fluctuations between different parts of the device or over the duration of the test procedure. Secondly, the precision with which the pressure can be maintained in the channels allows accurate detection of low levels of fluid flow. This means that, compared to the pressure decay methods of the prior art, it is not necessary to generate a high pressure difference across the heat exchange barrier; the flow across the barrier can be detected with a smaller pressure difference and at a pressure closer to the operating conditions of the heat exchanger in a sufficiently short time scale. Therefore, compared to the integrity tests of the prior art, the use of the present invention means that the test process itself has a reduced possibility of causing damage to the heat exchanger. Thirdly, the only requirement for the heat exchanger is that it has two fluid conduits that can be connected to the test device. This represents very little practical limitation, and therefore means that the test apparatus is highly flexible in its application: it can be used with a variety of different heat exchanger configurations and designs, and even with fluid flow devices external to the heat exchanger field. In this respect, the invention can detect leaks of liquids from hydraulic systems and gases from pneumatic systems. Fourthly, by such a direct connection arrangement, the test system has the flexibility of being used as an in-line test system, with its connection to the heat exchanger being opened or closed as required. Heat exchangers can be used in very critical systems, and the levels of leaks that the system according to the invention is able to detect and monitor represent a considerable advance over prior art leak test systems.

[0017] In one embodiment, the leak test device includes a proportional valve, and the flow controller is configured to adjust the control voltage applied to the pump and the opening of the proportional valve in response to the signal received from the pressure sensor to maintain the pressure in the first closed-loop system and the second closed-loop system. This provides an exemplary mechanism by which the pressure is dynamically maintained at its predetermined level.

[0018] Preferably, the leak testing device comprises:

[0019] a first channel proportional valve and a first channel pressure sensor located in an inflow path of the first channel;

[0020] A second channel proportional valve and a second channel pressure sensor located in the inflow path of the second channel; and wherein,

[0021] the flow controller being configured to adjust the opening of the first channel proportional valve in response to signals received from the pressure sensor and the first channel pressure sensor to maintain the pressure at or near a first predetermined level within the first closed-loop system;

[0022] The flow controller is further configured to adjust the opening of the second channel proportional valve in response to signals received from the pressure sensor and the second channel pressure sensor to maintain the pressure at or near a second predetermined level within the second closed-loop system; and

[0023] The first predetermined level is different than the second predetermined level, thereby maintaining a pressure differential between the first conduit and the second conduit.

[0024] In this embodiment, a mechanism is provided in which a single pump is used to maintain two different conduits at different pressures. Prior art approaches to this problem use two separate pumps, but it has been found that this arrangement can allow the system to stabilize to two target pressures within an acceptable time frame. Furthermore, empirically, it will be possible to set the initial start-up configuration of the proportional valves, as well as the pump voltage, which will result in a faster convergence towards the target pressures. That is, the disadvantages of using a single pump will soon be minimal, and in any case, more than compensated by the reduced size of the single pump test system in many applications.

[0025] More preferably, the leak test device further comprises a third flow sensor in the outflow path of the first channel and a fourth flow sensor in the outflow path of the second channel. These additional flow sensors increase the ability of the test device to distinguish between various leaks that it may detect. The sensing of the flow in the inflow channel indicates that there is a leak in the corresponding closed-loop system. If a corresponding flow is detected in the outflow channel of the other closed-loop system, it can be concluded that the leak crosses the fluid barrier separating the two systems. Otherwise, the leak from the first closed-loop system will enter the atmosphere, for example, caused by a leaking valve, gasket or internal connection.

[0026] The apparatus preferably includes respective shut-off valves in each of the inflow and outflow paths.The valves provide a mechanism by which the test apparatus can control a series of tests performed on the first and second conduits.

[0027] In the most preferred application of the present invention, the first conduit and the second conduit are the first flow path and the second flow path of a heat exchanger adapted to transfer thermal energy between the fluids therein. Heat exchangers are used in many applications and it is often critical to be able to detect leaks at a very early stage. This will be particularly true if the fluid in one path crosses a boundary and contaminates a quality-controlled product in another path. The test device of the present invention is able to detect very small leaks by monitoring the flow within a closed path provided within the heat exchanger. The information obtained allows the operator of the heat exchanger to determine when it is best to take the heat exchanger out of operation and repair the leak.

[0028] Preferably, the flow controller is a PID (Proportional Integral Derivative) controller. The PID algorithm is known and is particularly designed for applications in which the controller is required to provide dynamic adjustment to compensate for continuously changing systems. In this application, the pressure in each of the two pipes is maintained at its set value regardless of the rate at which the fluid leaks from the system. Therefore, the use of a PID controller is a way to provide accurate control of pressure to the extent required to measure very small amounts of fluid flow.

[0029] In order to implement the PID algorithm, it is preferred that the flow controller includes a microcontroller, the microcontroller is programmed with a PID control algorithm, the flow controller is provided with a first target pressure and a second target pressure, the first target pressure corresponds to a target pressure to be maintained in the first closed-loop system, the second target pressure corresponds to a target pressure to be maintained in the second closed-loop system, and the control algorithm has:

[0030] a coarse control portion configured to calculate, in response to a signal received from the pressure sensor, an adjustment of a control voltage applied to the pump and an opening of the proportional valve such that the adjustment, when applied to the pump and the proportional valve, is adapted to maintain the pressure in the flow control system at a value that is a function of the first target pressure and the second target pressure;

[0031] A fine control portion operates when the pressure maintained in the flow control system is within a predetermined amount of its target value and is configured to:

[0032] calculating an adjustment to the opening of the first channel proportional valve in response to a signal received from the first channel pressure sensor, such that when the adjustment is applied to the first channel proportional valve, the adjustment is adapted to maintain the pressure in the first closed-loop system at a value within a tolerance range of the first target pressure; and / or

[0033] Calculating an adjustment to the opening of the second passage proportional valve in response to a signal received from the second passage pressure sensor, such that the adjustment, when applied to the second passage proportional valve, is adapted to maintain the pressure in the second closed-loop system at a value within a tolerance range of the second target pressure; and / or

[0034] Calculates adjustments to the target value of the coarse control portion of the PID control algorithm.

[0035] This arrangement of using a single PID controller to dynamically maintain pressure (or indeed any other variable) at two different target values ​​is believed to be a novel implementation of a PID algorithm. By operating the controller in this manner, the test system of the present invention is able to control the pressure on both sides of a heat exchanger with an accuracy that enables, firstly, the pressure differential to be maintained and, secondly, very small flow rates within the test system to be detected. This is true despite the fact that the flow requirements change during the test procedure. The pressure stability, in turn, contributes to the accuracy with which leaks within the heat exchanger can be identified by this embodiment of the test system. The use of a single pump (which follows from the use of a single controller) reduces the size of the test system, an important factor in a practical implementation in which the test system is mounted in line with the heat exchanger.

[0036] Each of the adjustments mentioned above is preferably calculated using a PID feedback loop.

[0037] In a second aspect, the present invention provides a leakage testing system, the leakage testing system comprising:

[0038] The first test device as described above, the first test device can be connected to the first pipe and the second pipe;

[0039] The second test device as described above, the second test device can be connected to the third pipe and the fourth pipe to form a third closed loop system and a fourth closed loop system; and

[0040] A system management unit is configured to provide the first test device with predetermined levels of pressure to be maintained in the first and second closed-loop systems, and to provide the second test device with predetermined levels of pressure to be maintained in the third and fourth closed-loop systems.

[0041] In this regard, the test system is scaled up in order to test more complex heat exchangers having more sections and / or stages and therefore having pipes and fluid boundaries to be tested. This makes the test system very flexible in its ability to test the full range of heat exchangers, regardless of their size, design, construction or complexity. Without limitation, the test system is capable of testing tubular, plate, extended surface and regenerative heat exchangers; single-pass and multi-pass; gas-to-liquid, liquid-to-liquid and phase-change heat exchangers; two-fluid, three-fluid or N-fluid; indirect and direct contact types; and any heat exchanger with a combination of single-phase or two-phase countercurrent flow on either side of the fluid boundary, as well as heat exchangers that do have combined convection and radiation heat transfer mechanisms.

[0042] Corresponding shutoff valves may be positioned in each inflow and outflow path of each test device, and the system management unit may be further configured to provide signals to the shutoff valves in both test devices that sequentially open and close the shutoff valves according to the leak test to be performed.

[0043] In order to further improve application flexibility, the leakage testing system may also include a third testing device. According to the above description, the third testing device includes a stop valve located in each inflow path and outflow path and can be connected to the fifth pipeline and the sixth pipeline to form a fifth closed-loop system and a sixth closed-loop system; and wherein the system management unit can be further configured to provide signals to the stop valves in the third testing device, which open and close the stop valves in sequence according to the leakage test to be performed.

[0044] Ideally, the first conduit, the second conduit, the third conduit, the fourth conduit, and (if applicable) the fifth conduit and the sixth conduit each correspond to a flow path in the heat exchanger, wherein thermal energy can be transferred between one or more pairs of flow paths.

[0045] In a third aspect, the present invention provides a method for testing leakage of a fluid pipeline, the fluid pipeline being connected to an inflow path and an outflow path of a first channel of a leakage testing device to form a first closed-loop system, the method comprising:

[0046] a) pumping fluid through a flow control system to fill the first closed loop system to a predetermined pressure level;

[0047] b) operating the flow control system to maintain the fluid pressure in the first closed loop system at the predetermined pressure level; and

[0048] c) Use a flow sensor to measure the fluid flow rate through the inflow path.

[0049] This test method is a novel method for leak detection in a fluid pipeline. EP3740078 discloses dynamically maintaining pressure in a pipeline for the purpose of improving the accuracy of the measurement performed in a second pipeline. Furthermore, the measurement in the second pipeline is the pressure in the system. The present invention is based on the recognition that maintaining pressure in a pipeline enables sufficiently accurate flow measurement in the same pipeline, which finds application in the detection of leaks in the pipeline.

[0050] In another aspect, the present invention provides a method of testing a heat exchanger for leakage between a first fluid conduit and a second fluid conduit, the conduits being arranged in the heat exchanger to enable transfer of thermal energy between the fluids in the conduits, the method comprising:

[0051] a) placing a first fluid conduit in fluid communication with a first channel within the test system, the first channel comprising a first inflow path and a first outflow path, the first conduit and the first channel thereby forming a first closed loop system;

[0052] b) placing a second fluid conduit in fluid communication with a second channel within the test system, the second channel comprising a second inflow path and a second outflow path, the second conduit and the second channel thereby forming a second closed loop system;

[0053] c) pumping fluid through a flow control system in fluid communication with the first inflow path and the second inflow path;

[0054] d) adjusting a first proportional valve in the flow control system, a second proportional valve in the first inflow path, and a third proportional valve in the second inflow path so that a first predetermined fluid pressure and a second predetermined fluid pressure are reached in the corresponding first channel and second channel, wherein the predetermined fluid pressure in the first channel is greater than the predetermined fluid pressure in the second channel;

[0055] e) maintaining pressure in the first channel and the second channel while closing the first stop valve, the second stop valve, the third stop valve, and the fourth stop valve in the respective first inflow path, the first outflow path, the second inflow path, and the second outflow path;

[0056] f) while continuing to maintain the pressure in the first passage and the second passage:

[0057] ⅰ. Open the first stop valve and use the first flow sensor to measure the first inflow path

[0058] Flow rate in the path;

[0059] ⅱ open the fourth stop valve and use the second flow sensor to measure the flow rate in the second outflow path; thereby

[0060] iii. Observing a flow rate in the first inflow path, which is above a tolerance level indicating a leak from the first conduit, and observing a flow rate in both paths, which is above a tolerance level indicating a leak between the first conduit and the second conduit.

[0061] This method provides an accurate, flexible and relatively fast way in which integrity testing can be performed on a heat exchanger. It is envisioned that equipment designed to implement the method will be installed in line with the heat exchanger and that testing will be performed periodically to provide long-term monitoring capabilities and early leak detection. This will enable the operator of the facility or process in which the heat exchanger is operating to assess when it is best to stop operation and perform repairs. The speed with which integrity testing can be performed by this method makes it suitable for integration with the Cleaning in Place (CIP) process of a production system. This is a standard procedure that is run periodically by many production systems, after a set period of time to remove normal contaminants or when a production line is changed from one product to another. Testing using the present method is attractive because integrity testing is relatively fast compared to a CIP cycle. The process facility will have already stopped production for the CIP cycle, and therefore the additional loss of production time to perform the integrity test is minimal.

[0062] The method may further comprise the steps of:

[0063] a) While continuing to maintain the pressure in the first channel and the second channel:

[0064] i. Open the third stop valve and use a third flow sensor to measure the flow rate in the second inflow path; thereby

[0065] ii. Observe the flow rate in the second inflow path, which is above the tolerance level indicating leakage from the first conduit.

[0066] In yet a further aspect, the present invention provides a leak testing device, the leak testing device comprising:

[0067] a channel having an inflow path and an outflow path, the inflow path and the outflow path being connectable to spatially separated locations in the conduit to form a closed loop system;

[0068] a flow control system including a flow controller in communication with the pump and the pressure sensor, the flow control system being in fluid communication with the passage and adapted to pump fluid at a rate that actively maintains pressure at or near a predetermined level within the closed-loop system; and

[0069] Flow sensor,The flow sensor is located in the inflow path of the channel.

[0070] In this respect, the leak test device is configured to test the leak from a single pipeline. This expands the application of the present invention. Not only can be on a single pipeline heat exchanger (such as a radiator), but also can be tested for leaks on any fluid-containing system. All that is required is that the pipeline under test can be closed and accessed via a connection point to form a closed loop with the test device channel. The flow control system maintains the pressure in the closed loop and any flow indication detected in the inflow path of the channel flows out of the loop and therefore indicates a leak. This principle of maintaining pressure in another closed system and monitoring flow is unknown in the prior art. The system described in EP 3740078 relies on maintaining pressure in a pipeline and then measuring pressure in a different second pipeline that allows a change in pressure.

[0071] The device may also include:

[0072] a second channel having an inflow path and an outflow path connectable to a second pair of spaced-apart locations in the conduit to form a second closed loop system, the second pair of spaced-apart locations spanning the first pair of spaced-apart locations connectable to the first channel; and

[0073] a second flow sensor, the second flow sensor being positioned in an outflow path of the second channel; and wherein,

[0074] The flow control system is further adapted to pump the fluid at a rate that actively maintains the pressure at or near a predetermined level within the second closed-loop system; thereby

[0075] The leak testing device is capable of detecting a leak through a valve that may be located in the second closed loop system instead of the first closed loop system.

[0076] In this aspect, the test system is configured to detect leakage across the valve. This can be to check that the valve in the second closed-loop system has no leakage, which will have an impact on the integrity test performed on the pipeline. The device can also include a first pressure sensor located in the inflow path of the second channel and a second pressure sensor located in the outflow path of the second channel. In the configuration, the device can be used to check for leakage in a single-pipe heat exchanger (such as an air-conditioning system). The flow detected in the first channel can appear through a boundary flow, which will potentially cause harmful substances to be released into the environment, or flow through one or two stop valves, or a combination of the two. The information provided by the pressure sensor together with the information provided by the two flow sensors enables any flow detected to be distributed between the boundary flow and the leakage on each valve in the second closed-loop system. Therefore, the embodiment is conducive to determining the possible environmental hazards presented by the continuous operation of the system under test.

[0077] In another aspect, the present invention provides a PID controller adapted to maintain pressure in a hydraulic system or a pneumatic system, the hydraulic system or the pneumatic system comprising:

[0078] A flow control system, the flow control system has a pump, a pressure sensor and a proportional valve;

[0079] a first closed-loop system in fluid communication with the flow control system and comprising a first channel proportional valve and a first channel pressure sensor; and

[0080] A second closed-loop system, the second closed-loop system is in fluid communication with the flow control system and includes a second channel proportional valve and a second channel pressure sensor;

[0081] The PID controller is adapted to apply a variable control voltage to the pump and adjust the opening of the proportional valve and the first (and second) channel proportional valve; and comprises

[0082] Coarse control section; and

[0083] Fine control part;

[0084] the PID controller being adapted to apply adjustments to a control voltage applied to the pump and an opening of the proportional valve in response to a signal received from the pressure sensor, the adjustments being calculated by the coarse control portion to maintain the pressure in the flow control system at a target value, the target value being a function of the first target pressure and the second target pressure; and

[0085] When the pressure sensor indicates a pressure value within a predetermined amount of the target value, the PID controller is adapted to:

[0086] applying an adjustment of the opening of the first channel proportional valve in response to a signal received from the first channel pressure sensor, the adjustment being calculated by the fine control portion to maintain the pressure in the first closed-loop system at a value within a tolerance range of the first target pressure; and / or

[0087] applying an adjustment of the opening of the second passage proportional valve in response to a signal received from the second passage pressure sensor, the adjustment being calculated by the fine control portion to maintain the pressure in the second closed-loop system at a value within a tolerance range of the second target pressure; and / or

[0088] The rough control portion is regulated by a target value of a function of the first target pressure and the second target pressure.

[0089] In this regard, the present invention provides a mechanism by which hydraulic pressure can be maintained in two different closed loop systems with only a single pump. Pressure can be maintained even in the event of a small leak from one or both nominally closed systems. This aspect is advantageous for all applications where it is desired to reduce the size of the pressure control system. The pump and its associated electronics together occupy a relatively large space. Therefore, a controller that can simultaneously pressurize two separate systems using only a single pump presents an attractive option in many applications.

[0090] The present invention will now be described by way of example only and with reference to the accompanying drawings, in which:

[0091] Figure 1a It is a schematic diagram of a general single-pass single-section heat exchanger;

[0092] Figure 1b is a schematic diagram of a general multi-pass single-zone heat exchanger;

[0093] Figure 1c Yes Figure 1a and Figure 1b Both illustrate schematic representations of a single zone heat exchanger with connection points shown for attachment to a test apparatus according to the invention;

[0094] Figure 2 is a simplified diagram showing the fluid control components of a test device according to the present invention;

[0095] Figure 3 is a schematic diagram of a flow setting component of a test device according to the present invention;

[0096] Figure 4 is a schematic representation of a test device according to the present invention, illustrating control components of the test device;

[0097] Figure 5 is a flow chart showing the steps involved in performing a test procedure on a heat exchange system according to the present invention;

[0098] Figure 6 is a flow chart representing the steps of an algorithm that may be used to set flow rates within the test system of the present invention;

[0099] Figure 7a It is a schematic diagram of a general single-pass two-zone heat exchanger;

[0100] Figure 7b yes Figure 7a A schematic representation of a two-zone heat exchange illustrated in FIG. 1 with connection points shown for attachment to a test apparatus according to the present invention;

[0101] Figure 7cThe fluid control component of the test device of the present invention is expanded to Figure 7a and Figure 7b Illustration of the master / slave arrangement when performing tests on a two-zone heat exchanger;

[0102] Figure 8a It is a schematic diagram of a complex multi-pass three-zone heat exchanger;

[0103] Figure 8b yes Figure 8a a schematic representation of a three-zone heat exchanger illustrated in FIG. 1 with connection points shown for attachment to a test apparatus according to the invention;

[0104] Figure 8c The fluid control component of the test device of the present invention is expanded to Figure 8a and Figure 8b Illustration of the master / slave arrangement when performing tests on a three-zone heat exchanger;

[0105] Fig. 9 is a schematic representation of a single zone heat exchanger with connection points shown for attachment to a test device also arranged for testing the integrity of the isolation valve; and

[0106] Fig.10 is a schematic representation of a representative single pass single zone heat exchanger having a liquid to gas (atmosphere) boundary and having connection points shown for attachment to the test apparatus of the present invention.

[0107] See also Figure 1a, shows a side view of a base plate heat exchanger 10 having one boundary and one section. The boundary is provided by an array of thin metal plates 12 that are spaced apart and sealed with gaskets or the like. Thus, the plates 12 define a parallel arrangement of channels 14a, 14b, 14c, 14d therebetween. A heating fluid flow path is defined within the heat exchanger 10: from a hot input 16a, along a connecting passage 18 (upper portion of the figure), through a first set of alternating parallel channels 14b, 14d of those defined by the plates 12 in the array, to a hot output 20a. A cooling fluid path is similarly defined: from a cold input 22a, along a second connecting passage 24 (lower portion of the figure), through a second set of alternating parallel channels 14a, 14c of those defined by the plates 12, to a cold output 26a. As shown in the figure, this arrangement enables heating and cooling fluids to flow in opposite directions through the plate surfaces on opposite sides of each plate 12. Thus, each plate 12 provides a large heat exchange surface area that promotes heat transfer from the heating fluid to the cooling fluid while maintaining their physical separation. The terminology may vary depending on the application. For example, if the product is heated within the heat exchanger, the two fluids may be referred to as the heating fluid and the product. If the product is cooled, it will pass through the heat exchanger together with the cooling fluid. However, the basic heat exchange process remains the same.

[0108] Figure 1b A side view of a single boundary multi-pass plate heat exchanger 28 is shown. The heat exchanger 28 and Figure 1a The simpler version of 28 differs in that the heating fluid and the cooling fluid make two passes through the channels defined by the plate surfaces. In the first section 30, the flow circuit through the heat exchanger 28 is such that (as in Figure 1a The heat exchanger in the embodiment of the present invention has a heating fluid and a cooling fluid with opposite flows through adjacent parallel channels defined by the first set of plates. The second section 32 is connected in series with the first section 30, and in this section 32, the heating fluid and the cooling fluid pass through another set of adjacent parallel channels defined by the second set of plates. If the first section 30 and the second section 32 are of equal size, the heat exchange surface area is effectively doubled.

[0109] Figure 1a and Figure 1b The basic heat exchanger represented by the model shown in can vary considerably in size and construction as well as plate material and number, depending on the application and the fluid medium used. The smallest version can be found in residential boilers, and the largest version used for community heating can be as large as a building. In industrial applications, the two flow paths are usually connected in a straight line with the production facility.

[0110] Figure 1c Is a single-stage heat exchanger (such as Figure 1a and Figure 1bSchematic representations of heat exchangers 10, 28 are typically used in design drawings and the like. Heat exchangers 10, 28 are represented by rectangular boxes 36. Two flow paths are indicated by inner V-shaped lines 38, 40, with inputs (starts) 16, 22 and outputs (ends) 20, 26 spaced apart along the width of rectangular box 36. The lines 38, 40 representing the flow paths cross twice within the box, indicating the transfer of thermal energy. The flow path lines 38, 40 continue outside of the box 36, indicating the flow of fluids into and out of other parts of the process facility or heating system in which the heat exchangers 10, 28 are incorporated.

[0111] The test system of the present invention is designed to be used with any heat exchanger of any type or complexity. By direct adaptation, the heat exchanger is modified while it is in the production line to allow connection with the test system. Once the connection is established, the test system can be used to test the integrity of the heat exchanger at predetermined intervals or when required.

[0112] Adaptation of the heat exchanger Figure 1c Indicated on the schematic diagram of . Shut-off valves 42a, 42b, 42c, 42d are placed in each input 16, 22 and output 20, 26 of the two flow path lines. These valves can be any suitable valve type that can be operated to open and close the pipeline. For example, they can be 2 / 2, butterfly valves, ball valves or seat valves, no matter which valve is preferred in the application where the heat exchanger is placed. Then establish connection points ①, ②, ③, ④ to the heat exchanger side of the shut-off valve in each line 16, 20, 22, 26. In some cases, the heat exchangers 10, 28 may already have valves and connection points in place; in other cases, they will have to be established in the original heat exchanger. As will be clear from the above, the shut-off valves 42a, 42b, 42c, 42d are positioned so that when these shut-off valves are closed, the heat exchanger is isolated from the rest of the production line in which the heat exchanger is combined.

[0113] See now Figure 2 , Figure 2 The fluid control components of a test system according to the present invention are shown, and the test system 44 includes a gear driven flow setting system (GDFS) 46 and a first flow channel 48 (channel 1) and a second flow channel 50 (channel 2). The GDFS 46 (described in more detail below) is arranged to generate a controlled pressure maintained in the channels 48, 50 of the test system 44. Each channel 48, 50 is connected to a corresponding flow path in the heat exchanger to be tested. For example, when the test Figure 1c When heat exchangers 10 and 28 of the type shown in FIG. 1 are used, channel 1 is connected to the heating flow path 38 at connection points ① and ②, and channel 2 is connected to the cooling flow path 40 via connection points ③ and ④. Test system and process controller (see Figure 4) (e.g., a microprocessor) that is programmed to control the execution of the testing process.

[0114] like Figure 2 As shown, the test system 44 includes the following components:

[0115] M Pump G Pressure Sensor

[0116] V valve T tank

[0117] M Water sensor F Flow sensor

[0118] OVariable orifice P proportional valve

[0119] In the figures, each component is given a reference number of the type Cm or Cm.n, where C represents the component type, as listed in the table above. Different numbers m are used to distinguish multiple components of the same type within a system or within a particular channel. Components unique to one or other channels are distinguished by using a second number n, which is 1 or 2, depending on whether the particular component forms part of the first channel 48 or the second channel 50, respectively.

[0120] Typically, the heat exchanger 10, 28 will be part of a production system under the control of an industrial process controller during normal operation. The test system 44 is connected to the heat exchanger, but its valves are closed along with any sanitary shut-off valves that may be part of and controlled by the production system. The test system 44 is thus kept isolated from the production system. When the test is planned, the industrial process controller will close the shut-off valves 42a, 42b, 42c, 42d to isolate the heat exchanger from the rest of the production system. The heat exchanger 10, 28 thus becomes a "closed system" and if a fluid flow leaving the system is detected, it will be considered to be an "exit flow" generated by a defect in one or more system boundaries.

[0121] After the isolation of the heat exchanger / test system, the test process controller takes over control and opens the GDFS 46 to pump water through the system. In some applications, alternative test fluids, such as isopropyl alcohol, can be used, but it is envisioned that water will be the most common and therefore water is used as an example in this specification. If the heat exchanger paths 38, 40 are not filled with fluid at the beginning of the test, the test process controller will open valves V1.1 and V1.2 in the respective bypass flow paths 52a, 56a. These valves V1.1 and V1.2 allow a relatively high amount of water to pass through and therefore help to fill the heat exchanger to the initial starting pressure within a reasonable period of time. Once the heat exchangers 10, 28 are filled with water, valves V1.1 and V1.2 are closed, and the remaining valves in the test system 44 are opened, ready to balance to the test pressure. The flow is managed by the GDFS 46 so that the pressure in the flow paths 38, 40 accumulates to the value selected by the user required for the test and then maintained at the value selected by the user required for the test. Importantly, the pressure at which the test is performed can be the operating pressure around the production system. In such an embodiment, there is no need to charge the heat exchanger to a pressure significantly higher than the pressure at which it normally operates.

[0122] By way of illustration of the flow paths within the test system 44, consider the following situation: channel 1 is connected to an external pipe, such as a path through a heat exchanger, and fluid is pumped through the established circuit. As will become clear later, there may or may not be any flow within the circuit during the test process itself, and so this description is simply provided to illustrate the function of the components of the system and how the test system 44 has the potential to support fluid flow within it. Valves V2.1 and V3.1 set the normal flow direction within the channel: in this example, along the inflow path 52 to the heat exchanger's connection point ①, through the heat exchanger to the connection point ②, and then back through the test system along the outflow path 54. The outflow path 54 leads to tank T2, which acts as an expansion vessel to maintain pressure within the system 44. Water sensor W2 monitors the amount of water in tank T2 and sends a signal to the test process controller if the water level rises too high, which then closes the GDFS 46 and opens valve V2 to allow air to be drawn in. Proportional valve P1.1 in conjunction with valve V5.1 and orifice O1.1 is adjusted to set the rate at which water pumped by GDFS 46 flows along inflow path 52 of channel 1, which is monitored by flow sensor F1.1. Flow sensor F2.1 is configured to monitor the flow rate in outflow path 54.

[0123] Similarly, channel 2 also has the potential to support fluid flow through external piping. Check valves V2.2 and V3.2 set the direction of flow: in this example, along inflow path 56 to connection point ③ of the heat exchanger, through the heat exchanger to connection point ④, and then back to the test system along outflow path 58, which leads to the atmosphere. Proportional valve P1.2 in conjunction with valve V5.2 and orifice O1.2 is adjusted to set the rate at which water pumped by GDFS 46 flows along inflow path 56 of channel 2. Flow sensors F1.2, F2.2 are configured to monitor flow rates along inflow path 56 and outflow path 58, respectively.

[0124] The operation of the GDFS 46 will be explained in more detail below, but essentially proportional valves P1, P1.1 and P1.2 are adjusted to control the flow rates until the system stabilizes at the desired pressures. These pressures are such that a pressure differential is maintained between the two channels 48, 50 through the relative openings of P1.1 and P1.2. Balance is reached when the flow rates through proportional valves P1.1 and P1.2 driven by the GDFS 46 and proportional valve P1 balance the pressures of the water in the corresponding test channels 48, 50 and heat exchanger flow paths 38, 40. Excess flow through P1.1 leaves the system through valve V5.1 and variable orifice O1.1. If there is no leakage from the heat exchanger, the water within the heat exchanger 10, 28 and in channel 1 with valve V5.1 downstream of the connection node is static and no flow is observed at either flow sensors F1.1, F2.1 in this test system channel 48. Similarly, excess flow through P1.2 leaves the system through valve V5.2 and variable orifice O1.2. If there is no leak, the water in the heat exchanger 10, 28 and in channel 2 downstream of the connection node with valve V5.2 is static and no flow is observed at either flow sensors F1.2, F2.2 in the test system channel 50. However, if there is a leak, flow will be observed through one or more of these flow sensors F1.1, F2.1, F1.2, F2.2.

[0125] By way of example, consider using the test system of the present invention to test Figure 1c. Flow sensors F1.1, F2.1, F1.2 and F2.2 measure the flow through connection points ①, ②, ③ and ④, respectively. If there is a leak from the heating flow path 38, for example, from a leaking seal or gasket, then in order to maintain a balanced pressure within the system, there must be an additional flow into the connection point ①, which balances the loss of channel 1 through the leak. Therefore, the flow is observed at the flow sensor F1.1. Similarly, an atmospheric leak in the cooling flow path 40 will result in a balanced flow detected at the flow sensor F1.2 (connection point ③). On the other hand, if there is a leak across the boundary of the heat exchanger 10, 28, there will be a boundary flow from a higher pressure channel (such as the heating flow path 38 connected to channel 1) to a lower pressure channel (cooling flow path 40). In this case, under balanced conditions, there will be a flow into the connection point ① (the flow balances the loss caused by the leak from channel 1) and a flow out of the connection point ④ (the flow balances the increased flow into channel 2). The test system 44 will therefore observe non-zero flow readings on the two sensors F1.1 and F2.2. These different observations indicate how the flow rates measured at the four flow sensors F1.1, F2.1, F1.2, F2.2 enable firstly the detection of a leak and secondly the identification of the location of the leak, i.e. whether the leak is across a boundary or through a gasket or seal.

[0126] In its standard operating mode, the test system 44 allows flow from inflow paths 52, 56 to connection points ① and ③, through the heat exchanger, and then from connection points ② and ④ to outflow paths 54, 58. However, the flow direction can be reversed by opening valves V4.1 and V4.2. The flow from proportional valve P1.1 is then diverted through valve 4.1 to the channel arm connected to connection point ②. This causes flow to pass through the heat exchanger 10, 28 in the opposite direction to reach connection point ①, and the flow is reversed from connection point ① again through valve 4.1 to the outflow path 54. A similar reversal of flow through connection points ③ and ④ is observed in channel 2. The advantage of this flexibility is the testing of more complex multi-zone heat exchangers, in which access may not be possible at all preferred connection points.

[0127] It will be noted that regardless of the direction of flow through the heat exchanger 10, 28, leakage will be observed as an inflow through the flow sensor F1.1 or F1.2 and / or an outflow through the flow sensor F2.1 or F2.2.

[0128] The test system 44 of the present invention is designed to detect very small leaks in the heat exchanger 10, 28. Of course, it will be clear that if the leak is small, any observed equilibrium flow rate will also be small. Therefore, an accurate flow sensor is needed to measure the flow rate in the test channel 48, 50. Suitable examples for the present invention can be obtained from Sensirion, Switzerland, which provides a series of flow sensors capable of measuring flow rates in the milliliter and microliter / minute range. These sensors are based on the principle of heat transfer. Each sensor is basically a tubular structure with a central pressure-stabilizing membrane. The heating element is located in the center of the membrane, and temperature sensors are placed on its upstream and downstream sides. If there is a flow through the membrane and the heating element along the hole of the tube, the liquid passing along the tube transfers heat from the heating element and a temperature increase is observed at the downstream sensor. The flow rate can be derived from the development of the temperature difference between the upstream sensor and the downstream sensor.

[0129] The flow sensor is calibrated for use with a specific fluid, in this case water. Tanks T1.1 and T1.2 are filled with water and are positioned in the outflow paths 54, 58 to ensure that it is water that flows through the sensor. This arrangement therefore mitigates the risk of alternative liquids flowing out of the heat exchanger under test and corrupting the flow sensor readings.

[0130] In some applications of the invention, different test fluids can be supplied by the test system and used for leak detection. For example, the test fluid can be a liquid such as ethylene glycol, isopropanol or liquefied natural gas (LNG). Alternatively, it can be a gas such as methane, argon, nitrogen, steam or a refrigerant gas such as R32 (difluoromethane). In such an embodiment, the tanks T1.1, T1.2 are filled with alternative test fluids and the flow sensors are calibrated for use with the fluids.

[0131] In addition to accurate measurement of flow rate, it is important that pressure fluctuations within the system do not cause flow that would mask any leaks. To this end, the test system 44 of the present invention is designed to maintain accurate pressure within the heat exchangers 10, 28. This pressure control is accomplished using a GDFS control system, which will now be described. Figure 3 Describe it.

[0132] Figure 3The inflow paths 52, 56 of the two channels of the GDFS 46 and the test system 44 are shown. At the heart of the GDFS 46 is a voltage-controlled pump M1, which operates in series with proportional valves P1, P1.1 and P1.2 and a feedback loop, which is controlled by the test process controller according to a pre-programmed PID (proportional integral differential) algorithm. Valve V1 opens and closes the supply line 60 entering the tank T1. Water (or other fluid to be used in the test) is pumped from the tank T1 by the pump M1 and supplied to the output line 62. The output line has three branches: the first two branches form the corresponding channel inflow paths 52, 56, and the third branch 64 is the flow path through the proportional valve P1 to the discharge port. The total flow in the output line 62 is monitored by the flow sensor F1 and the pressure is monitored by the pressure sensor G1. In the first case, the flow rate of the pumped fluid is determined by the operating voltage on the pump M1 and the opening of the proportional valve P1. The proportion of fluid pumped by pump M1 and leaving the system via flow path 64 is controlled by the aperture size in proportional valve P1. The larger the opening, the more fluid is discharged from the system and the flow into test channels 52, 56 is reduced. Conversely, reducing the opening of proportional valve P1 increases the flow rate into test channels 52, 56. In a similar manner, the opening of proportional valves P1.1 and P1.2 determines the proportion of the flow entering the corresponding test channels 52, 56. Under the control of valves V5.1 and V5.2, the excess flow is discharged via orifices O1.1 and O1.2. Throughout the integrity test process, the voltage on pump M1 and the opening of valves P1, P1.1 and P1.2 are continuously adjusted using a PID control algorithm. The pressure in the system 44 is continuously monitored by pressure sensor G1 in the pump output line 62 and by pressure sensors G3.1 and G3.2 in channel 152 and channel 256, respectively. This provides a dynamic control by which the flow rate through the system is maintained regardless of any changes in flow demand due to any leaks within the system. The details of the algorithm will be described in more detail later, but essentially, the operating pressure is first approached by closing valves P1.1 and P1.2 and directing all pumped fluid to the output flow path 64. The voltage on pump M1 and the opening of valve P1 are set to their initial values. With experience, approximate values ​​for stabilizing at the operating pressure within the particular system under test will become known, and the time taken to reach equilibrium will therefore be reduced. In any case, the pressure at sensor G1 is recorded for these values ​​of initial voltage and valve orifice size. If the pressure at G1 is higher than the target pressure, the pump voltage is first adjusted by an amount determined by the PID algorithm and then the opening of P1 is adjusted in order to reduce the pressure in the system. Likewise, if the pressure measured at G1 is lower than the target pressure, the pump voltage may be increased and / or the orifice size of proportional valve P1 may be reduced in order to increase the pressure within the system.After repeating these steps in a series of feedback loops, the pressure measured at G1 will move within a certain range (e.g., 100 Pa) of the target pressure. At this point, proportional valves P1.1 and P1.2 and valves V5.1 and V5.2 are open, and pressures are measured on G1, G3.1 and G3.2. For this stage, the target pressure is the pressure in the two test channels 48, 50, i.e. as measured at pressure sensors G3.1 and G3.2. The PID control loop is repeated in order to move the G3.1 and G3.2 pressures towards their target values.

[0133] This technique of constantly adjusting the pump M1 voltage and opening the proportional valves P1, P1.1, P1.2 allows a very precise pressure to be maintained within the test system and the connected heat exchanger. The pressure is monitored and regulated independently of any flow within the system and is therefore maintained at the required level regardless of any leaks.

[0134] like Figure 4 As shown, the test system 44 includes both a hydraulic component 44a and a control component 44b. The above description focusing on the hydraulic component 44a and the control component 44b will now be described in more detail. Figure 4 As shown, in one embodiment, the control components include a power supply unit 66, a test system management unit (SMU) 67, a switch 68, a firewall 69, and a GPIO unit 70. A power line 71 connects the power supply unit 66 to a power source, such as a main power distribution network. All control components 66-70 are connected to an information network 72, such as the Internet, a LAN, etc.

[0135] The SMU 67 is a central processing unit on which is stored the software necessary for the overall management of the test process. This includes software specifically for analyzing data, processing user input, operating the user interface, communicating with cloud-based instructions, communicating with the GPIO unit 70, and overall management of the test system 44. The GPIO unit 70 includes a microcontroller and associated connections for various sensors and control valves incorporated in the hydraulic section of the test system 44a, of which the GPIO unit is a part. Specifically, the microcontroller is programmed with firmware instructions that enable it to operate as a PID controller in a pressure setting algorithm using the GDFS 46. Further firmware instructions enable the GPIO unit 70 to receive and decode information from the sensors and SMU 67.

[0136] exist Figure 4 In the representation of the test system 44 shown, connection points ①, ②, ③ and ④ are indicated in positions on the hydraulic circuit 44 a where the connection pipes 73 are coupled to the channels in the heat exchangers 10 , 28 in operation.

[0137] As indicated above, the test system of the present invention has the ability to establish and accurately maintain pressure, and is also capable of measuring small flow levels. These features, along with the available control methods, enable the test system 44 of the present invention to perform integrity testing on many different types and kinds of heat exchange systems. In fact, the test system 44 can be used to test for leaks across any fluid boundary, and is not limited to testing boundaries within a heat exchange system. Figure 5 Describes an example of a protocol that may be followed when performing testing on a heat exchanger component of an industrial process line.

[0138] At step S10, the parameters of the test are retrieved from the data storage facility via the network connection 72. Typically, the storage facility will be a repository in the cloud managed by the test provider. This will be a database in which the details of the heat exchanger type and the industrial process using the heat exchanger are stored together with the test parameters (such as inflation pressure, pressure difference, location where flow measurement is performed, order of measurement, tolerance of error alarms, etc.). Alternatively, the test parameters can be stored locally and managed by the facility controller, but this loses the opportunity to benefit from updated information, which is derived from the test program run by similar test devices at other facilities. In either case, the test parameters are retrieved S10 by the test system management unit (SMU) 67 and the heat exchanger being tested is verified to be correct. At step S12, the facility or production line process controller closes the shutoff valves 42a, 42b, 42c, 42d and transfers the operational control of the now isolated heat exchanger to the SMU 67. The first step S14 of performing the test is to fill the test system to the required fluid volume. In other words, a predetermined set pressure is established at the sensors G1.1 and G1.2. These will vary from system to system, but in most cases will be similar to the operating pressures that the heat exchanger experiences in its production line. For example, a pressure of 8 bar in the product side (at G.1.1) and a pressure of 7.5 bar in the coolant side (at G1.2), leaving a pressure difference of 0.5 bar. If the system fails to reach a stable pressurization within an acceptable time period, this is notified to the user, who can then make a decision S16 to abort the test. Any test failure returns the test system 44 to idle mode S18 and presents the user with an interface that reports the cause of the failure. Such a cause of failure could be, for example, a catastrophic leak within the system or a failure in the isolation of the heat exchanger. Alternatively, if no cause for the failure is found, the user can choose to cancel this alarm and continue the test.

[0139] In order to repair the leak, the heat exchanger must be disassembled and this incurs a significant loss of production time. It is therefore obviously important to ensure that if a leak is detected by the test system, it is not caused by a defect in the test system 44 itself. To this end, in one embodiment, the system of the present invention is designed to perform a self-test S20 immediately after a successful filling. Once filled, the test system can be isolated from the heat exchanger and see Figure 2 , the test system valves V1.1, V2.1, V3.1, V4.1, V1.2, V2.2, V3.2, V4.2 in the channels 48, 50 connected to the heat exchanger are all closed. At this point, the system is filled to a stable pressure through the GDFS 46. The pressure will reach the higher end of the range provided by the GDFS 46 and will be the same in both channels. The flow through the GDFS is recorded using the flow sensor F1, and the pressure is monitored using the pressure sensors G1.1, G2.1, G3.1, G1.2, G2.2, G3.2. As the first part of the self-test, and after a short stabilization time, the flow sensors F1.1, F1.2 in the inflow paths 52, 56 are checked. The detection of flow on any of the flow sensors F1.1, F1.2 indicates a leak in the corresponding intake valve V2.1, V2.2. The inflow path 52, 56 valves V2.1, V4.1, V2.1, V4.2 are opened and then any flow indications from the flow sensors F2.1 and F2.2 in the outflow paths 54, 58 are checked. If flow is detected, this is attributed to leakage in the corresponding outflow valves V3.1, V3.2. As a final part of the self-test, the inflow path valves V2.1, V4.1, V2.1, V4.2 are closed again and the bypass valves V1.1 and V1.2 are tested to ensure their integrity. If a leak is detected at any stage, the self-test fails and the test system 44 will return to its idle mode S18. Only when the test device 44 passes all stages of the self-test is it allowed to start the leak test at step S22. If it fails at any stage, the test device 44 returns to its idle stage S18 and a warning is sent to the user. The integrity of the heat exchanger cannot be tested by this system 44 until the cause of the self-test failure is determined and repaired.

[0140] At step S22, the test system 44 tests the heat exchanger 10, 28 to which it is attached. There are many options for the order in which the valves within the test system 44 may be opened and closed in order to detect and locate any leaks within the heat exchanger, but in this embodiment, the routine employed to test a single boundary heat exchanger 10, 28 is as follows. Referring again to Figure 2, both valves V2.1 and V2.2 in the channel inflow paths 52, 56 are opened, which places both halves of the heat exchanger in fluid communication with the test apparatus 44. Once a steady flow is observed at flow sensor F1 in the GDFS 46, flow sensor F1.1 is checked for an indication of flow along the inflow path 52 of channel 1. If any flow is observed, the path of the heat exchanger 10, 28 to which channel 1 is connected (at Figure 1c In the example of the inflow channel, there is a defect in the connection point ①) entering the heating path 38. Next, open the valve V3.2 in the second channel outflow path 58 and check the indication of the flow sensor F2.2 for any flow in this channel. In other words, is there a corresponding flow flowing out from the cooling path 40 and the connection point ④. If flow is detected at both flow sensors F1.1, F2.2, this indicates a defect at the boundary of the heat exchanger. If it is only detected in the inflow channel flow sensor F1.1, the defect is in some other part of the tested isolated path of the heat exchanger 10, 28 (in this example, the heating path 38). If the defect crosses the boundary, the test can be stopped: the heat exchanger has failed and the leak has been identified and isolated. Otherwise, or if the possibility of further leaks needs to be investigated, check the flow sensor F1.2 in the second channel inflow path 56. If flow is detected, this indicates that there is a defect in that path of the heat exchanger 10, 28 to which channel 2 is connected (in Figure 1c In the example of , a leak comes from the connection point ③) of the cooling path 40. For the last part of the flow test, the valve V3.1 in the first channel outflow path 54 is opened, and the flow indication of the flow sensor F2.1 in this channel is checked. In other words, check whether there is a corresponding flow outflowing from the heating path 38 and the connection point ② in the case of the inflow channel 2. If a flow is detected at both flow sensors F1.2, F2.1, this indicates a defect at the boundary of the heat exchanger. If it is only detected at the inflow channel flow sensor F1.2, the defect is in some other part of the cooling path 40. If, at the end of the procedure, no flow is detected in any inflow channel 52, 56 or outflow channel 54, 58 of the test system 44, the heat exchanger 10, 28 has passed its integrity test.

[0141] In the event that flow is detected at any flow sensor F1.1, F1.2, F2.1, F2.2 during the integrity test of the heat exchanger, the test system 44 presents the details of the observed flow to the user at step S24. This provides the user with an opportunity to assess the severity of the leak and decide whether action should be taken. In some applications, a small leak that passes through a seal or gasket but does not cross a boundary may be acceptable. Therefore, the user can set parameters within the test system 44 that determine an acceptable level of the detected flow. In such a case, the heat exchanger can continue to be used in the industrial process. If the detected flow is higher than the acceptable tolerance, the user confirms that the integrity test of the heat exchanger 10, 28 has failed. The test system 44 then returns to its idle state S18. Otherwise, the user can indicate that the test has passed, and some warnings may continue. In some embodiments of the present invention, the test results are communicated to a cloud-based server for storage and further analysis.

[0142] To verify the test results, the test system 44 will then perform a second self-test at step S26. This checks that the test system has not been damaged during the actual testing of the heat exchanger. After completion of the second self-test S26 or after any failure S18 in any part of the test sequence, the test system process controller hands control back to the industrial process controller S28. The test cycle is complete.

[0143] In the above description, reference is made to a user of the test system 44. Such a user may be a person at the site of the industrial process, perhaps someone responsible for supervising performance. Alternatively, the user may be remote, for example, a person not connected to the entity running the industrial process but experienced in a test program using the test system 44 of the present invention. Such a user typically has access to test results from installations of multiple such test systems 44 in various industrial settings and locations. This arrangement is therefore advantageous because it provides the opportunity to accumulate data about multiple tests and systems, and therefore enables better interpretation of the results (possibly with the help of machine learning algorithms). This may further enable prediction of heat exchanger failures and preventive repairs to be performed at the appropriate time.

[0144] As will be appreciated from the above description, critical to the reliability of the results is the ability of this test system 44 to maintain the set pressure levels within the two halves 38, 40 of the heat exchanger to a high degree of accuracy. Figure 6 is a flow chart showing an example of a PID control algorithm that may be used to operate the GDFS 46 so that a steady pressure is maintained at a preselected value in the heat exchanger system. The algorithm consists essentially of two parts: a coarse control portion 74 and a fine control portion 76.

[0145] In order to begin charging the system 44 to test pressure, the required target information must be provided to the SMU 67. This will be in the form of two channel pressures, one for channel 1 and the second for channel 2, with which the heat exchanger test is performed. These pressures will generally be close to the pressures that replicate the conditions in the heat exchanger during normal operation of the heat exchanger. A pressure difference must be maintained between the two channels so that there is flow in the event of a leak at the boundary. Therefore, the first step S32 is a request from the test / pre-test code to provide different pressures in channels 1 and 2. The SMU 67 receives the request and transmits the target pressure information in the form of target values ​​for the pressure sensors G3.1, G3.2 in the channel flow paths 52, 56 to the GPIO unit 70. This is because the GPIO unit 70 is responsible for the PID pressure control algorithm. By way of example only, and as an aid to illustration, it is assumed that a pressure difference of 50 kPa is maintained. That is, if the target pressure at the pressure sensor G3.1 of channel 1 is y kPa, then the target pressure at the sensor G3.2 of channel 2 will be (y+50) kPa.

[0146] refer to Figure 2 and Figure 6Both, at step S36, the control voltage on the GDFS pump M1 and the opening size of the GDFS proportional valve P1 are set. Initially, these will be predetermined starting values. At this stage, all valves V1.1, V2.1, V3.1, V1.2, V2.2, V3.2, V5.1, V5.2 in the test system channel are closed, and the pump of the GDFS 46 is operated with these flow circuit parameters, and a reading is taken from the GDFS pressure sensor G1. At step S38, the reading is compared with the target value and an error value is derived. At this stage, before opening the test channel valves V5.1, V5.2, the target pressure of the GDFS pressure sensor G1 must be higher than the two target values ​​of the pressure sensors G3.1 and G3.2. Again, by way of example only, and not to be considered a limitation of this algorithm, the target pressure of the sensor G1 is set to 50kPa higher than the larger of the two target values ​​of the pressure sensors G3.1 and G3.2. That is, the target pressure for sensor G1 is (y+100) kPa. The next step depends on whether the pressure at G1 is within a predetermined range of its target, such as within ±10 kPa of (y+100) kPa in this example. If the G1 pressure is outside this range (i.e., the error value>10 kPa), the algorithm proceeds to step S40 and performs PID calculations based on the size of the error value and preset values ​​for the first set of proportional gain, integral gain, and derivative gain to determine adjustments to be made to the control voltage applied to the GDFS pump M1 and / or to the opening of the proportional valve P1. At step S42, the adjustments to the pump voltage and valve opening are applied to the pump M1 and proportional valve P1 of the GDFS 46. The process then returns to step S36, the GDFS 46 pump is operated with these corrected flow circuit parameters, and new readings are taken from the GDFS pressure sensor G1. Steps S36 to S42 are repeated until the G1 pressure falls within a predetermined range (±10 kPa) of its target ((y+100) kPa). Once the target is close enough, the PID algorithm moves to its fine control portion 76.

[0147] At step S44, the proportional valves P1.1, P1.2 of channel 1 and channel 2 are opened according to the set degree. Initially, they will be opened according to a predetermined amount, with the valve in the high pressure channel being opened further. Valves V5.1 and V5.2 are opened to allow flow through the proportional valves P1.1, P1.2 to exit the system. The GDFS 46 is then operated by the pump voltage and the GDFS proportional valve P1 opening maintained by the coarse control portion 74 of the PID algorithm and by the channel proportional valves P1.1, P1.2 being opened to their set degree. Readings are taken from the flow channel pressure sensors G3.1, G3.2. At step S46, these readings are compared with their target values ​​(e.g., y kPa for G3.1 and (y+50) kPa for G3.2), and corresponding error values ​​are derived. If one or other of the error values ​​is outside a certain range, such as the target pressure ±1 kPa, the algorithm moves to step S48. At step S48, for each individual pressure (G3.1, G3.2) reading, a PID calculation is performed to produce an adjustment to the opening of the corresponding proportional valve P1.1, P1.2. The adjustment calculation is based on the corresponding pressure error value and the preset values ​​for the second set of proportional gain, integral gain and derivative gain. At step S50, the opening values ​​of the channel proportional valves P1.1, P1.2 are adjusted as calculated at step S48. The process then returns to step S44, and the proportional valves P1.1, P1.2 of channels 1 and 2 are opened by their degree of adjustment and the updated readings obtained from the flow channel pressure sensors G3.1, G3.2. Steps S44 to S50 are repeated until the G3.1 and G3.2 pressures fall within a predetermined range (±1 kPa) of their respective targets (y kPa, (y+100) kPa).

[0148] Once target pressures are reached in both channels, the pressures at the flow channel pressure sensors G3.1, G3.2 are continuously monitored S52 and subsequent adjustments S48, S50 are made to the flow channel proportional valve P1.1, P1.2 openings to actively maintain these pressures close to their target values.

[0149] At step S54, a check is performed after a set number of iterations of the PID loop S44-S50 to verify that the pressure at the flow channel sensors G3.1, G3.2 is converging towards its target value. If there is no convergence, the algorithm returns to the coarse control portion 74 and attempts to repeat the PID pressure stabilization routine S34 with a new value of the pump M1 control voltage and the opening of the GDFS proportional valve P1.

[0150] Using a PID control loop to actively maintain two different pressure levels is a novel implementation of this algorithm. A more typical approach and one known in the prior art is to use two separate pumps, one for each channel 48, 50. Each pump is associated with a corresponding proportional valve and a PID control loop so that the pressure in each channel 48, 50 can be independently maintained at its target value. However, using a single pump and a PID controller to stabilize the pressure in the two flow channels is advantageous in reducing the size of the test system. This is an important consideration for considering the test system 44, which is permanently connected to the heat exchanger but will only be used periodically. The disadvantage is that for more adjustable components, the PID loop will take longer to stabilize the system. That is, at least in the initial stage, there is a trade-off between the cost and size of the test system and the time it takes to run the test sequence. However, using the system of the present invention, data is shared centrally, and it is therefore expected that in a relatively short period of time, it will be possible to access the initial pump and valve settings that will be reliably close to its operating value. Therefore, convergence to the target pressure will be faster, largely offsetting the disadvantages of the longer stabilization period of the two flow channels.

[0151] The test system 44 described above can be scaled up for use with more complex heat exchangers having multiple zones and therefore multiple boundaries to be checked. However, it has been found that balancing the pressure in more than two channels using one PID controller is very time consuming. Therefore, in embodiments of the test system 44 to be used with more complex heat exchangers, a different approach is taken. This is to expand the capabilities of the test system by using a master and slave test system, such as Figure 7c and Figure 8c As shown.

[0152] Figure 7a A conventional single-pass two-zone heat exchanger 78 is shown in FIG. Figure 7b, a schematic representation thereof for a flow control diagram is shown in . The heat exchanger 78 shown in side view has a heating section 80 and a cooling section 82. Each section 80, 82 has a respective boundary provided by an array of respective parallel arranged thin metal plates defining channels 84, 86. Within the heat exchanger 78, a product line (product flow path) 88 extends from a product input 90, through a first set of alternating channels 84 in the heating section 80, through a connecting line to the cooling section 82, where the product line (product flow path) 88 reaches a product outlet 94 through a second set of alternating channels 86. In the heating section 80, the heating fluid channel extends from the heating input 96 through the first set of alternating parallel channels 84 to the heating fluid output 98. In the cooling section, the cooling fluid channel extends from the cooling input 100 through the second set of alternating parallel channels 86 to the cooling fluid output 102. Within the first set of alternating channels 84 and the second set of alternating channels 86, the physical boundaries provided by the plates maintain physical separation, but allow thermal contact to be formed between the product and the heating fluid and the product and the cooling fluid, respectively. That is, in the heating section 80, the product is heated by heat transferred from the heating fluid, and in the cooling section 82, the product is cooled by transferring heat away from the product. This design of heat exchanger can be used, for example, in applications where the product is cooked or sterilized and then must be cooled for packaging. Multiple sections also enable energy reuse: post-heating process products are used to preheat products entering the heating process.

[0153] Figure 7bis a schematic representation of a two-section heat exchanger 104. Each section 106, 108 is represented by a rectangular box, and the flow paths therein are represented by internal V-shaped lines 110a, 110b, 110c, 110d, which extend outside the box to indicate connecting flow paths outside the heat exchanger sections 106, 108. Schematic 104 represents a heat exchanger consisting of a heating section 106 and a regeneration section 108, which reuses energy to heat the product with improved efficiency. There is one heating fluid flow path 110d extending from the heating fluid input 112 to the heating fluid output 114 within the heating section 106. The remaining flow paths 110a, 110b, 110c are all connected. The product path extends from the product input 116 along the pre-heating path 110a to the regeneration section 108 until it leaves the regeneration section 108 at the connecting passage 118. The product path continues into the heating section 106 and passes along path 110c where it is in thermal contact with the fluid in the heating flow path 110d. The heated product then follows return path 120 back to the regeneration section on its second passage 110b on the other side of the section boundary. In this section 108, thermal energy from the now cooled product is transferred to the product entering the heat exchanger on the preheating path 110a and is thus used to provide a degree of preheating. The product line leaves the heat exchanger at product outlet 122.

[0154] In the figure, it is indicated that the test system according to the present invention and the Figure 7b 1. Exemplary connections made between heat exchangers of the type represented by the schematic diagram of . Shut-off valves 124a, 124b, 124c, 124d are assembled at the heat exchanger inputs 112, 116 and outlets 114, 122. Then, corresponding connection points ①, ②, ⑦, ⑧ are established on the heat exchanger side of each shut-off valve, which in this example are located in three of the four heat exchanger lines 110a, 110b, 110d. It should be noted that while connection points ① and ② are located at the input and output of a single path through a single section of the heat exchanger, connection points ⑦ and ⑧ are not. Connecting these connection points ⑦ and ⑧ to a single channel of the test system 44 will enable detection of leaks somewhere within the three heat exchanger paths extending between these connection points ⑦ and ⑧, but it is not possible to further locate such leaks. For his reasons, additional connections and valves are necessary in multi-section heat exchangers. Ideally, access is available to all connectors that connect a path through a first section of the heat exchanger with a path through a second section. Figure 7b, to the connecting passage 118 and to the return path 120. If such access is available, shut-off valves 126a, 126b are incorporated in each corresponding passage with two connection points ⑤, ⑥; ③, ④ (one on each side of the valve). In this way, each valve 126a, 126b isolates the portion of the connecting path extending through the first section 106 of the heat exchanger from the portion extending through the second section 108. The additional connection points ⑤, ⑥; ③, ④ available within each portion of the connecting path allow the test system 44 to be connected so that each side of the heat exchanger in each section 106, 108 can be addressed in turn. For example, the path 110c that transports the product through the heating section 106 of the heat exchanger can be isolated by closing the valve 126a in the connecting passage 118 and the valve 126b in the return path 122. Leaks within the heat exchanger path 110c can be identified by connecting the channel of the test system 44 to the connection points ③ and ⑤. Similarly, with valve 126a in connecting passage 118 closed together with 124c on product input 116, by connecting one channel of test system 44 to connection points ⑥ and ⑦, a leak in product path 110a on its first passage through the heat exchanger can be detected and located. Obviously, heating flow path 110d can be tested by connecting the channel to connection points ① and ②. Similarly, path 110b for the second product passage through the regeneration side can be tested through connection points ④ and ⑧.

[0155] Figure 7c The method according to the present invention and suitable for testing is illustrated in Figure 7b 1. In this embodiment, the test system 144 includes a master system 146a and a slave system 146b. The hydraulic components 148a, 148b of the master 146a and the slave 146b are identical to each other and also identical to the reference 1. Figure 2 and Figure 4 The hydraulic components 44a of the embodiment of the test system described are identical. That is, each master device 146a and slave device 146b has two test channels that can be connected to the flow path within the heat exchanger whose integrity is to be tested. These channels are indicated by connection labels ①, ②, ④, ⑧ on the master device 146a and by connection labels ③, ⑤, ⑥, ⑦ on the slave device 146b. This arrangement corresponds to Figure 7b The connection points used on the test system 144 are marked: a connection is made from the connection point ① of the test system 144 to the connection point ① on the heat exchanger to perform the heat exchanger test. In addition, each master device 146a and slave device 146b has its own power and water supply, network connection, drainage facilities and connection to the atmosphere. Among them, the difference between these systems 146a, 146b lies in their control components and software.

[0156] The control components of the master system 146a are identical to the control components 44b of the previously described test system 44. They include a power supply unit 66, a test system management unit (SMU) 67, a switch 68, a firewall 69, and a GPIO unit 70. As with the previously described standalone units, the SMU 67 is responsible for the overall management of the test system 144, and the GPIO unit 70 is primarily responsible for establishing and maintaining pressure in the two test channels of the master system 146a using the master GDFS 46 and the previously described PID algorithm.

[0157] The control components of the slave system 146b include all of the above components of the master system except the system management unit 67 and the firewall 69. The switch 68 is also removed unless the system is set up with multiple slave systems. Specifically, the slave 146b includes its own GPIO unit 150. The slave GPIO unit 150 is responsible for the PID control of the pressure settings in the two test channels of the slave system 146b using the slave GDFS. In addition, the slave GPIO unit 150 reports back the sensor data to the SMU 67 of the master system 146a.

[0158] In other words, each slave system 146b is capable of establishing and maintaining pressure in its inflow and outflow channels, but this is secondary to the pressure request provided by the master SMU 67. In addition, all processing and setting of test parameters commanded by the user (including the sequence of opening and closing test valves during the test procedure) are performed by the SMU 67 located in the master for both the master 146a and slave 146b units.

[0159] Each master device 146a and slave device 146b has two test channels, each of which can be connected to test a flow path in the heat exchange system. Therefore, a single master device and slave device combination is sufficient to operate as follows: Figure 7b Complete test for leak detection and location of the two-stage heat exchanger shown in - one channel is connected to each pair of connection points identified above.

[0160] Although the slave device 146b system has two test channels, there are some applications where the second channel is not necessary: ​​for example, in testing a heat exchanger with three internal fluid paths. In this case, the valves V2.2, V3.2 in one channel will remain closed, and the difference between the target pressures at the flow channel sensors G3.1, G3.2 can be zero.

[0161] This procedure can be extended to more complex heat exchangers, e.g. Figure 8a and 8bThere are two paths through each section of the heat exchanger, and therefore isolating each path individually would require a total of 12 connections and 6 channels within the test system 144. To test this type of heat exchanger, Figure 8c As shown, the master device system 146a will need to be connected to two slave device systems 146b, 146c.

[0162] This type of heat exchanger is often used in pasteurization applications where there are separate product heating and cooling circuits and a recovery section between the two. Although it is noted that the ideal situation would enable 12 connections to be made between this type of heat exchanger and the test system of the present invention, in practice such access may not be possible and therefore the test system will have to be connected with less than the ideal number of connections. This will mean that not all paths within each section can be individually isolated and tested. Leak detection is still possible, but localization is less effective.

[0163] It should be clear to those skilled in the art that the principle of using one master system 146a and multiple slave systems 146b, 146c can be scaled up to accurately test the integrity of any heat exchanger system of any complexity. The number of slave systems required will depend on the number of connection points required and accessible.

[0164] As will be appreciated from the above description, the test system 44 of the present invention is capable of providing accurate measurements of flow rates on the order of a few microliters per minute. However, leaks from the heat exchanger system (e.g., from valves within the heat exchanger channels) will not be distinguishable from internal leaks within the test system 44 itself. For this reason, in many applications, the test system 44 is arranged to perform a self-test before and possibly after integrity testing of the heat exchanger. In addition, it is also possible that leaks may occur within the shut-off valves 42a, 42b, 42c, 42d, which are used to isolate the heat exchanger from the industrial process equipment in which it is incorporated. If any leaks occur here, this will also result in the flow observed in the test system.

[0165] Therefore, in some applications, the test system 44 of the present invention can be configured to perform additional tests on the integrity of the shutoff valves 42a, 42b, 42c, 42d. Fig. 9, shows a schematic diagram of a heat exchanger 10, 28 with shutoff valves 42a, 42b, 42c, 42d, which are operable to isolate the heat exchanger 10, 28 in preparation for integrity testing. In order to test the integrity of these valves, a test valve 150a, 150b, 150c, 150d is placed in each of the input 16, 22 lines and output 20, 26 lines of the two flow paths to the side of the shutoff valves 42a, 42b, 42c, 42d opposite to the heat exchanger 10, 28 they isolate. Connection points ⑤, ⑥, ⑦, ⑧ are established between the shutoff valves 42a, 42b, 42c, 42d and the test valves 150a, 150b, 150c, 150d in each line 16, 20, 22, 26.

[0166] Figure 7c A test system 144 of the type shown in is connected to connection points ① to ⑧. The master system 146a is arranged to perform integrity tests on the heat exchangers 10, 28 by connecting the channels of the heat exchangers 10, 28 to connection points ①, ②, ③ and ④. At the same time, channel 1 of the slave system is connected to connection points ⑤, ⑥ and channel 2 is connected to connection points ⑦, ⑧. To illustrate the test procedure in this case, for example, consider that the master system 146a detects the flow out of its channel 1, which is connected to connection points ① and ②. If there is a leak at the stop valve 42b between connection points ② and ⑥, this will result in an inflow into the slave system 146b at connection point ⑥. This will be detected as a flow in the outflow path 54 of the slave channel 1 and detected at the flow sensor F2.1. On the other hand, if there is a leak at the stop valve 42a between connection points ① and ⑤, the flow will enter the slave system 146b at connection point ⑤. This will be detected by the flow sensor F1.1 as a flow in the inflow path 52 of the slave system 146b. Thus, when the master system 146a detects a leak leaving channel 1, opening and closing valve V4.1 in the slave system 146b enables a test of the corresponding inflow through connection point ⑤ or ⑥ in sequence. If an inflow through connection point ⑤ is observed, there is a leak through stop valve 42b; if an inflow through connection point ⑥ is observed, there is a leak through stop valve 42a. If no flow is observed through the slave system 146b, the leak detected by the master system 146a is due to a defect in the heat exchanger, not due to a defect in the stop valve. In a similar manner, the remaining stop valves 42c, 42d can be tested as potential causes of any leaks detected by the master system 146a from its channel 2.

[0167] Fig.10Schematic representations of different designs of heat exchanger 154 are shown, illustrating another application of the test equipment of the present invention. Heat exchanger 154 includes an air conditioning box 155 and a single pipe 156 that only exchanges heat energy with the external environment (air). Fan 158 blows air on pipe 156 to increase the airflow on the boundary of the heat exchanger. In this example, the heat exchange fluid is R32 refrigerant gas. Depending on the pressure applied at a specific stage of the refrigeration cycle, this gas constantly changes state between its liquid phase and gas phase. R32 can be considered as a harmful substance in a closed space, and it is therefore important to ensure that heat exchanger 154 has no leaks.

[0168] When preparing the heat exchanger 154 for leak testing using the test system 44 according to the present invention, the stop valves 160a, 160b are installed in the input and output of the pipe 156. Then the connection points ①, ② to the heat exchanger side of the stop valves are established in the pipe 156. This is similar to the preparation required for the test of the heat exchangers 10, 28 described previously. However, in this application, two additional stop valves 162a, 162b are installed in the input and output of the pipe 156, respectively. The additional stop valves 162a, 162b are placed on the side of the stop valves 160a, 160b opposite to the heat exchanger 154. Connection points ③, ④ are established in each input and output of the pipe 156 between the stop valves 160a, 160b and their corresponding additional stop valves 162a, 162b.

[0169] To test this heat exchanger 154, channel 1 of the test system 44 is connected to connection points ① and ②, and channel 2 is connected to connection points ③ and ④. Initially, the standard test procedure described above is followed, wherein additional pressure is monitored at pressure sensors G1.2, G2.2 at channel 2. When the system is pressurized, valves V2.1, V3.1 of channel 1 are opened to check the pressure through flow sensor F1.1 (see Figure 2 ) and the flow rate of the inflow path 52 of channel 1. If no flow is detected, then there is no leakage from the heat exchanger 154. On the other hand, if flow is detected at the flow sensor F1.1, this may indicate a possible leakage of refrigerant gas from the pipe 156. To verify this, record and compare the pressure sensor reading of channel 2.

[0170] To proceed, the channel 2 valves 2.2, 3.2 are opened and any flow along the channel 2 outflow path 58 is checked. If there is no flow along these paths and the pressure sensor readings in this path are unchanged, this indicates that the stop valves 160a, 160b are intact and do not allow flow from channel 2 along the pipe 156. It therefore follows that all flow observed in channel 1 is the result of leakage across the pipe boundary. That is, there is an escape of refrigerant gas. On the other hand, if flow is observed at flow sensor F2.2, then there is obviously flow through the stop valves 160a, 160b, which may or may not exist across the pipe boundary. In order to characterize the flow observed in the channel 1 test channel, the flow in this path (measured at flow sensor F1.1) is compared to the flow observed on the channel 2 outflow path using flow sensor F2.2. The channel 2 reading represents the flow through the valves 160a, 160b, and the difference between the channel 1 reading and the 2 reading (F1.1-F2.2) is the flow across the boundary. If there is no difference, there is no flow across the boundary. Returning now to channel 2, the pressure readings obtained using sensors G1.2, G2.2 are taken before opening channel 2 valves V2.2, V3.2. In this case, any pressure observed at sensor G1.2 will be due to inflow through connection point ③, since all other valves in the channel remain closed. Similarly, any pressure observed at sensor G2.2 will be due to inflow through connection point ④. Comparing these two readings, the total flow allowed through the valve (observed on sensor F2.2) is allocated to each shutoff valve 160a, 160b.

[0171] Another application of the apparatus of the present invention is for detecting air voids. Air trapped in the system has a knock-on effect on the efficiency of the production system, and it is therefore advantageous to detect and then remove them. When the integrity test is initiated, the heat exchanger paths 38, 40 are filled with fluid up to an initial start-up pressure. Monitoring the volume of fluid flowing through the sensor at the start of each test enables a standard fill volume for the heat exchanger to be determined. If in a subsequent test sequence it is noted that a smaller volume of water is required based on the flow rate and time taken to reach the test conditions, the difference in volume can be attributed to the air voids. Its detection then allows further investigation to be conducted.

Claims

1. A leak testing device (44), comprising: a first channel (48) having an inflow path (52) and an outflow path (54), the inflow path and the outflow path of the first channel (48) being connectable to spatially separated locations in the first conduit (38) to form a first closed loop system; a second channel (50) having an inflow path (56) and an outflow path (58), the inflow path and the outflow path of the second channel (50) being connectable to spatially separated locations in the second conduit (40) to form a second closed loop system; a flow control system (46) comprising a flow controller in communication with a pump (M1) and a pressure sensor (G1), the flow control system (46) being in fluid communication with the first passage (48) and the second passage (50) and adapted to pump fluid at a rate that actively maintains pressure at or near a predetermined level within the first closed-loop system and the second closed-loop system; as well as A first flow sensor (F1.1) and a second flow sensor (F1.2), wherein the first flow sensor is located in an inflow path (52) of the first channel (48), and the second flow sensor is located in an inflow path (56) of the second channel (50).

2. The leak test device (44) according to claim 1, wherein: The flow control system (46) includes a proportional valve (P1), and the flow controller is configured to adjust a control voltage applied to the pump (M1) and an opening of the proportional valve (P1) in response to a signal received from the pressure sensor (G1) to maintain the pressure in the first closed-loop system and the second closed-loop system.

3. The leak test device (44) of claim 2, further comprising: A first channel proportional valve (P1.1) and a first channel pressure sensor (G3.1) located in the inflow path (52) of the first channel (48); a second channel proportional valve (P1.2) and a second channel pressure sensor (G3.2) located in the inflow path (54) of the second channel (50); and wherein, The flow controller is configured to adjust the opening of the first channel proportional valve (P1.1) in response to signals received from the pressure sensor (G1) and the first channel pressure sensor (G3.1) so as to maintain the pressure at or near a first predetermined level within the first closed-loop system; The flow controller is further configured to adjust the opening of the second channel proportional valve (P1.2) in response to signals received from the pressure sensor (G1) and the second channel pressure sensor (G3.2) so as to maintain the pressure at or near a second predetermined level within the second closed-loop system; and The first predetermined level is different from the second predetermined level, thereby maintaining a pressure differential between the first conduit and the second conduit.

4. The leakage test device (44) according to claim 3 further comprises a third flow sensor (F2.1) located in the outflow path (54) of the first channel (48) and a fourth flow sensor (F2.2) located in the outflow path (58) of the second channel (50).

5. The leak test device (44) according to any preceding claim, further comprising a respective shut-off valve (V2.1, V3.1, V2.2, V3.2) in each inflow path (52, 56) and outflow path (54, 58).

6. A leak testing device (44) according to any preceding claim, wherein: The first conduit (38) and the second conduit (40) are first and second flow paths of a heat exchanger adapted to transfer thermal energy between fluids in the first and second flow paths.

7. A leak testing device (44) according to any preceding claim, wherein: The flow controller is a PID controller.

8. The leak test device (44) according to claim 3, wherein: The flow controller includes a microcontroller, the microcontroller is programmed with a PID control algorithm, the flow controller is provided with a first target pressure and a second target pressure, the first target pressure corresponds to a target pressure to be maintained in the first closed-loop system, the second target pressure corresponds to a target pressure to be maintained in the second closed-loop system, and the control algorithm has: a coarse control portion (74) configured to calculate adjustments to the control voltage applied to the pump (M1) and the opening of the proportional valve (P1) in response to signals received from the pressure sensor (G1), such that the adjustments, when applied to the pump (M1) and the proportional valve (P1), are adapted to maintain the pressure in the flow control system (46) at a value that is a function of the first target pressure and the second target pressure; a fine control portion (76) which operates when the pressure maintained in the flow control system is within a predetermined amount of the target value of the pressure, and is configured to: calculating an adjustment of the opening of the first channel proportional valve (P1.1) in response to a signal received from the first channel pressure sensor (G3.1), such that the adjustment, when applied to the first channel proportional valve (P1.1), is adapted to maintain the pressure in the first closed-loop system at a value within a tolerance range of the first target pressure; and / or calculating an adjustment of the opening of the second channel proportional valve (P1.2) in response to a signal received from the second channel pressure sensor (G3.2), so that the adjustment, when applied to the second channel proportional valve (P1.2), is adapted to maintain the pressure in the second closed-loop system at a value within a tolerance range of the second target pressure; and / or An adjustment of a target value for the coarse control portion (74) of the PID control algorithm is calculated.

9. The leak testing device according to claim 8, wherein: Each adjustment is calculated using a PID feedback loop.

10. A leak testing device (44), comprising: a first channel (48) having an inflow path (52) and an outflow path (54), the inflow path and the outflow path of the first channel (48) being connectable to spatially separated locations in the conduit (156) to form a first closed loop system; a second channel (50) having an inflow path (56) and an outflow path (58), the inflow path and the outflow path of the second channel (50) being connectable to a second pair of spaced-apart locations in the conduit (156) to form a second closed-loop system, the second pair of spaced-apart locations spanning the first pair of spaced-apart locations connectable to the first channel (48); a flow control system (46) comprising a flow controller in communication with the pump (M1) and the pressure sensor (G1), the flow control system (46) being in fluid communication with the passage (48) and adapted to pump fluid at a rate that actively maintains pressure at or near a predetermined level within the first closed-loop system and the second closed-loop system; as well as a first flow sensor (F1.1) and a second flow sensor (F2.2), wherein the first flow sensor is located in an inflow path (52) of the first channel (48), and the second flow sensor is located in an outflow path (58) of the second channel (50); The leak test device (44) is capable of detecting a leak through a valve which can be located in the second closed loop system instead of the first closed loop system.

11. The leak test device (44) according to claim 10, wherein: The device also includes a first pressure sensor (G1.2) located in an inflow path (56) of the second channel (50) and a second pressure sensor (G2.2) located in an outflow path (58) of the second channel (50).

12. A leak testing system (144), comprising: A first test device (146a) according to any one of claims 1 to 5, the first test device (146b) being connectable to the first pipe (110a) and the second pipe (110b); The second test device (146b) according to any one of claims 1 to 5, the second test device (146b) being connectable to a third pipe (110c) and a fourth pipe (110d) to form a third closed loop system and a fourth closed loop system; as well as A system management unit (67) configured to provide the first test device (146a) with predetermined levels of pressure to be maintained in the first closed-loop system and the second closed-loop system, and to provide the second test device (146b) with predetermined levels of pressure to be maintained in the third closed-loop system and the fourth closed-loop system.

13. The leak testing system (144) of claim 12, wherein: Corresponding stop valves (V2.1, V3.1, V2.2, V3.2) are located in each inflow path (52, 56) and outflow path (54, 58) of each test device (146a, 146b), and wherein the system management unit (67) is configured to provide signals to the stop valves (V2.1, V3.1, V2.2, V3.2) in the two test devices to open and close the stop valves in sequence according to the leakage test to be performed.

14. The leak testing system (144) of claim 13, wherein: The system comprises a third test device according to any one of claims 1 to 5, the third test device comprising a shut-off valve (V2.1, V3.1, V2.2, V3.2), the shut-off valve being located in each inflow path (52, 56) and outflow path (54, 58) and being connectable to a fifth pipeline and a sixth pipeline to form a fifth closed-loop system and a sixth closed-loop system; and wherein the system management unit (67) is further configured to provide a signal to the shut-off valve (V2.1, V3.1, V2.2, V3.2) in the third test device so as to open and close the shut-off valve in sequence according to a leakage test to be performed.

15. The leak testing system (144) according to any one of claims 12 to 14, wherein: The first conduit (110a), the second conduit (110b), the third conduit (110c), the fourth conduit (110d) and, if applicable, the fifth conduit and the sixth conduit each correspond to a flow path in a heat exchanger, wherein thermal energy can be transferred between one or more pairs of flow paths.

16. A method for testing leakage of a fluid conduit (156) having a valve, wherein a valveless first section of the fluid conduit (38, 40) is connected to an inflow path (52) and an outflow path (54) of a first channel of a leakage test device to form a first closed loop system, and a second section of the fluid conduit (156) spanning the first section and at least one valve are connected to an inflow path (56) and an outflow path (58) of a second channel (50) of the leakage test device to form a second closed loop system, the method comprising: a) pumping fluid through a flow control system (46) to fill the first closed-loop system and the second closed-loop system to a predetermined pressure level; b) operating the flow control system (46) to maintain the fluid pressure in the first closed-loop system and the second closed-loop system at the predetermined pressure level; and c) using a first flow sensor (F1.1) to measure the fluid flow rate through the inflow path (52) of the first channel (48), and using a second flow sensor (F2.2) to measure the fluid flow rate through the outflow path (58) of the second channel (50).

17. A method of testing a heat exchanger for leakage between a first fluid conduit (38) and a second fluid conduit (40), the conduits (38, 40) being arranged in the heat exchanger to be able to transfer thermal energy between the fluids in the conduits (38, 40), the method comprising: a) placing the first fluid conduit (38) in fluid communication with a first channel (48) within a testing system (44), the first channel comprising a first inflow path (52) and a first outflow path (54), the first conduit (38) and the first channel (48) thereby forming a first closed loop system; b) placing the second fluid conduit (40) in fluid communication with a second channel (50) within the test system (44), the second channel comprising a second inflow path (56) and a second outflow path (58), the second conduit (40) and the second channel (50) thereby forming a second closed loop system; c) pumping fluid through a flow control system (46) in fluid communication with the first inflow path (52) and the second inflow path (56); d) adjusting a first proportional valve (P1) in the flow control system (46), a second proportional valve (P1.1) in the first inflow path (52), and a third proportional valve (P1.2) in the second inflow path (56) so that a first predetermined fluid pressure and a second predetermined fluid pressure are reached in the corresponding first channel (48) and second channel (50), wherein the predetermined fluid pressure in the first channel (48) is greater than the predetermined fluid pressure in the second channel (50); e) maintaining the pressure in the first channel (48) and the second channel (50) while closing the first stop valve (V2.1), the second stop valve (V3.1), the third stop valve (V2.2) and the fourth stop valve (V3.2) located in the corresponding first inflow path (52), the first outflow path (54), the second inflow path (56) and the second outflow path (58); f) while continuing to maintain the pressure in the first passage (48) and the second passage (50): i) opening the first stop valve (V2.1) and using the first flow sensor (F1.1) to measure the flow in the first inflow path (52); ii) opening the fourth shut-off valve (V3.2) and using the second flow sensor (F2.2) to measure the flow in the second outflow path (58); thereby iii) observing a flow rate in the first inflow path (52) above a tolerance level indicating leakage from the first conduit (38), and observing a flow rate in both paths (52, 58) above a tolerance level indicating leakage between the first conduit (38) and the second conduit (40).

18. The method according to claim 17, comprising the following additional steps: g) while continuing to maintain the pressure in the first passage (48) and the second passage (50): i) opening the third shut-off valve (V2.1) and using the third flow sensor (F1.2) to measure the flow in the second inflow path (56); thereby ii) observing the flow rate in the second inflow path (56), which is above a tolerance level indicating leakage from the first conduit (40).

19. A PID controller adapted to maintain pressure in a hydraulic system or a pneumatic system, the hydraulic system or the pneumatic system comprising: A flow control system (46), the flow control system having a pump (M1), a pressure sensor (G1) and a proportional valve (P1); a first closed loop system in fluid communication with the flow control system and comprising a first channel proportional valve (P1.1) and a first channel pressure sensor (G3.1); and A second closed-loop system, which is in fluid communication with the flow control system and includes a second channel proportional valve (P1.2) and a second channel pressure sensor (G3.2); wherein, The PID controller is adapted to apply a variable control voltage to the pump (M1) and adjust the opening of the proportional valve (P1) and the first channel proportional valve (P1.1) and the second channel proportional valve (P1.2); and comprises a coarse control section (74); and A fine control section (76); wherein the PID controller being adapted to apply adjustments to a control voltage applied to the pump (M1) and an opening of the proportional valve (P1) in response to a signal received from the pressure sensor (G1), the adjustments being calculated by the coarse control portion (74) to maintain a pressure in the flow control system (46) at a target value, the target value being a function of a first target pressure and a second target pressure; and When the pressure sensor (G1) indicates a pressure value within a predetermined amount of the target value, the PID controller is adapted to: applying an adjustment of the opening of the first channel proportional valve (P1.1) in response to a signal received from the first channel pressure sensor (G3.1), the adjustment being calculated by the fine control portion (76) to maintain the pressure in the first closed loop system at a value within a tolerance range of the first target pressure; and / or applying an adjustment of the opening of the second channel proportional valve (P1.2) in response to a signal received from the second channel pressure sensor (G3.2), the adjustment being calculated by the fine control portion (76) to maintain the pressure in the second closed loop system at a value within a tolerance range of the second target pressure; and / or The coarse control portion (74) is adjusted with a target value of a function of the first target pressure and the second target pressure.

Images