Method and apparatus for leak detection

Abstract

The leakage test device (44) is designed to test for leakage from and between a first conduit (38) and a second conduit (40) that may be part of a heat exchange system. The device (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) disposed at various positions within each corresponding channel (48, 50). Each channel (48, 50) is connected to a conduit (38, 40) to form a respective closed-loop system, and the flow control system (46) is adapted to actively maintain the fluid pressure within each closed-loop system at a set level. In a closed-loop system set to a pressure, detection of flow indicates the presence of a leak. Use of multiple flow sensors (F1.1, F1.2, F2.1, F2.2) at different positions allows the location of possible leaks to be differentiated. Shut-off valves may provide a mechanism by which the test sequence of the test device on the conduits (38, 40) can be controlled. The device can be used in-line to test heat exchangers of various designs and can be scaled up to test complex systems.

Description

Technical Field

[0001] The present invention relates to the field of leak detection, and more particularly to leak detection in a conduit that can form part of a heat exchanger.

Background Art

[0002] Heat exchangers are widely used in industry and have many applications that require heat transfer from one object to another. Heat exchangers can be classified by design or function, and examples include, among others, single-pass and multi-pass, tube-type, plate-type or surface-expanding type, direct-contact or indirect-contact heaters, coolers and condensers. When fluids are involved in the transfer process, a physical barrier must be maintained between the fluids. If a leak occurs between the two sides of such a heat exchanger, for example, food may be contaminated or chemical products may lack the required purity. Defective products must be discarded and operations must be stopped while repairs are being made. This is a costly operation.

[0003] Since the development of heat exchangers in the early 1920s, the industry has continued to demand cheaper, more efficient designs with improved system performance. More recently, the reduction of the carbon footprint has been further promoted. Such requirements for design have been met at the expense of some sacrifice in reliability, performance, and durability. For example, plate heat exchangers are a commonly used design, and the heat transfer area is increased by allowing the heat exchange fluid to flow along the surface of the metal plates. With technological development, the plates have become much thinner, resulting in an increased risk of manufacturing defects, material defects, and malfunctions during operation. This latter problem is particularly severe in processes that utilize corrosive fluids during manufacturing or cleaning cycles. This includes the manufacture of many chemicals and foods, and in such industries, pitting corrosion is likely to occur. Furthermore, even without corrosive fluids, the heat exchanger plates themselves repeatedly undergo thermal expansion and contraction, resulting in work hardening and, as a result, the possibility of cracking or fissuring.

[0004] Therefore, test devices have been developed for the purpose of detecting early leaks in heat exchangers. From manual inspections, various designs for leak detection based on different principles are known, ranging from the detection of markers or tracer fluids crossing the separation barrier. However, most of the known techniques have a major drawback: they require the heat exchanger to be mechanically disconnected from the production line and prepared before the leak test can be carried out. This is time-consuming and seriously disrupts the production schedule. For example, to perform a gas leak test, it may take several hours to prepare the heat exchange system and over six hours to actually carry out the test. After that, the heat exchanger has to be reconnected and the entire system has to be cleaned before the heat exchanger can be put back into service. Such losses in production time are undesirable for plant operators.

[0005] Therefore, recently, there has been a focus on the development of in-line test methods that can be carried out without mechanically removing the heat exchanger and that can maintain the reliability and accuracy of defect detection.

[0006] European Patent No. 3740078 (Patent Document 1) describes an in-line test device for a complex heat exchange system used for the pasteurization of milk. The pasteurization heat exchanger includes a heating stage, a cooling stage, and a regeneration stage, where the regeneration stage is the stage of initially heating the untreated product using the heat from the treated product. To use this test device, the complex heat exchange system is equipped with a plurality of valves, pumps, and sensors that can be operated by a controller to sequentially isolate the components of the system. Each isolated component is sequentially tested for leaks using a pressure decay test. When conducting this test, 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 changes: the fluid pressure rises on the low-pressure side and drops on the high-pressure side. Therefore, if a pressure drop is detected, it is concluded that it is due to a leak.

[0007] In an initial system based on the principle of pressure decay, it has been found difficult to ensure the consistency of results: when the leakage is small, the pressure change is relatively small, which may be masked by temperature fluctuations within the system. Therefore, it has been found difficult to obtain accurate measurement values within a practical time scale. To improve the accuracy, the pressure on the high-pressure side of the system described in Patent Document 1 is maintained at a set level under the control of the pump. This enables the system to distinguish between leakage between the plates and leakage that can escape, for example, from the gasket to the atmosphere.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

[0009] An in-line test is advantageous in that the heat exchanger does not need to be disconnected from the processing plant. However, the system described in European Patent No. 3740078 has a very special design for the heat exchanger and the test device. These two components are integrated, and the test device lacks the flexibility to be used with heat exchangers of different types and structures. Furthermore, in the method employed, it is necessary to fill both sides of the heat exchanger with a significant pressure difference. Such a high pressure difference is required to ensure a sufficient flow rate through the leakage part in order to observe a detectable pressure change over a reasonable period. However, this drawback is that the high pressure difference may damage the components of the heat exchanger, especially the plates, over time.

Summary of the Invention

Problems to be Solved by the Invention

[0010] There is a recognized need for an alternative system for testing the integrity of a heat exchanger that can reliably detect a wide range of defects and perform in-line tests on various heat exchangers.

Means for Solving the Problems

[0011] According to a first aspect, the present invention is a leak test apparatus comprising: a first channel having an inflow path and an outflow path connectable to spatially separated positions within a first conduit to form a first closed loop system; a second channel having an inflow path and an outflow path connectable to spatially separated positions within a second conduit to form a second closed loop system; a flow control system comprising a flow controller in communication with a pump and a pressure sensor, fluidly communicating with the first channel and the second channel, and adapted to pump fluid at a flow rate that actively maintains the pressure within the first closed loop system and the second closed loop system at or near a predetermined level; a first flow sensor disposed in the inflow path of the first channel and a second flow sensor disposed in the inflow path of the second channel and provides a leak test apparatus.

[0012] The design of this test apparatus is based on an approach that is fundamentally different from prior art leakage detection methods. The present invention attempts to detect the flow of fluid in a closed channel in a different manner, and thus such a flow indicates leakage. This approach is particularly suitable for the integrity testing of heat exchangers, but is also suitable for other applications that benefit from leakage detection across fluid boundaries. This approach has many advantages. First, since the pressure is actively maintained in both channels of the heat exchanger, this system is robust against temperature variations between different parts of the device or during the test procedure. Second, the accuracy with which the pressure in the channel can be maintained allows for accurate detection of low-level fluid flow. This means that in comparison with the prior art pressure decay method, it is not necessary to generate a high pressure difference across the entire heat exchange barrier, and the flow across the barrier can be detected on a sufficiently short time scale at a much smaller pressure difference and at a pressure much closer to the operating conditions of the heat exchanger. Thus, compared with prior art integrity testing, the use of the present invention means that the test process itself is less likely to damage the heat exchanger. Third, the only requirement for the heat exchanger is to have two fluid conduits that can be connected to the test apparatus. This means that there are few practical constraints and that the application of this test apparatus is very flexible, i.e., this test apparatus can be used with various different heat exchanger constructions and designs, and even with fluid flow devices outside the field of heat exchangers. In this regard, the present invention can detect liquid leakage from hydraulic systems and gas leakage from pneumatic systems. Fourth, with such a simple connection configuration, the test system has the flexibility to be used as an in-line test system that can be opened and closed as required for connection to the heat exchanger. Heat exchangers are sometimes used in very important systems, and the leakage levels that can be detected and monitored by the system according to the present invention represent a significant advance over prior art leakage test systems.

[0013] In one embodiment, the leak test apparatus includes a proportional valve, and the flow controller is configured to adjust the control voltage applied to the pump and the opening degree of the proportional valve in response to signals received from the pressure sensor to maintain the pressures in the first closed-loop system and the second closed-loop system. Thereby, an exemplary mechanism is provided in which the pressure is dynamically maintained at a predetermined level.

[0014] Preferably, the leak test apparatus comprises: a first channel proportional valve and a first channel pressure sensor disposed in the inflow path of the first channel, and a second channel proportional valve and a second channel pressure sensor disposed in the inflow path of the second channel and is provided with The flow controller is configured to adjust the opening degree 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 in the first closed-loop system at or near a first predetermined level. The flow controller is further configured to adjust the opening degree 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 in the second closed-loop system at or near a second predetermined level. The first predetermined level is different from the second predetermined level, whereby a pressure difference is maintained between the first conduit and the second conduit.

[0015] In this embodiment, a mechanism is provided for maintaining two different conduits at different pressures using a single pump. The prior art approach to this problem uses two separate pumps, but this configuration has been found to be able to stabilize the system at two target pressures within an acceptable time frame. Furthermore, experience makes it possible to set an initial start configuration of the proportional valve and the pump voltage that leads to a faster convergence to the target pressure. That is, the disadvantages of using a single pump are quickly minimized and, in any case, are more than compensated for by the miniaturization of the single pump test system in many applications.

[0016] It is highly preferable that the leakage test device further comprises a third flow sensor installed in the outflow path of the first channel and a fourth flow sensor installed in the outflow path of the second channel. These additional flow sensors enhance the ability of the test device to distinguish various leaks that can be detected. Detecting a 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 is across the fluid barrier separating the two systems. Otherwise, the leak from the first closed-loop system is a leak to the atmosphere caused, for example, by a leak in a valve, gasket or internal connection.

[0017] The device preferably comprises shut-off valves corresponding to each of the inflow and outflow paths. These valves provide a mechanism by which the test device can control the order of tests performed on the first and second conduits.

[0018] In the most preferred application of the present invention, the first and second conduits are the first and second flow paths in a heat exchanger suitable for the transfer of thermal energy between the internal fluids. Heat exchangers are used in many applications and it is often important to be able to detect leaks at a very early stage. This is particularly true when the fluid in one path contaminates the quality-controlled product in the other path across the boundary. The test device of the present invention can detect very small leaks by monitoring the flow in a closed path provided within the heat exchanger. The information obtained enables the operator of the heat exchanger to determine when it is best to shut down the heat exchanger and repair the leak.

[0019] Preferably, the flow controller is a PID (proportional integral derivative) controller. The PID algorithm is well-known and is designed for specific applications where a controller is required to perform dynamic adjustment to compensate for a continuously changing system. In this application, regardless of the flow rate of fluid leakage from the system, the pressure of each of the two conduits is maintained at a set value. Therefore, the use of a PID controller is one way to accurately control the pressure to the extent required for measuring a very small fluid flow rate.

[0020] To implement the PID algorithm, the flow controller comprises a microcontroller programmed with the PID control algorithm. The flow controller has a first target pressure corresponding to the target pressure to be maintained in the first closed-loop system and a second target pressure corresponding to the target pressure to be maintained in the second closed-loop system. The control algorithm is as follows: The adjustment of the control voltage applied to the pump and the opening degree of the proportional valve is configured to calculate the adjustment in response to the signal received from the pressure sensor so that when applied to the pump and the proportional valve, it adapts 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. This is the coarse control part. It operates when the pressure maintained in the flow control system is within a predetermined amount from its target value. The adjustment of the opening degree of the first channel proportional valve is configured to calculate the adjustment in response to the signal received from the first channel pressure sensor so that when applied to the first channel proportional valve, it adapts to maintain the pressure in the first closed-loop system within the allowable range of the first target pressure, and / or The adjustment of the opening degree of the second channel proportional valve is configured to calculate the adjustment in response to the signal received from the second channel pressure sensor so that when applied to the second channel proportional valve, it adapts to maintain the pressure in the second closed-loop system within the allowable range of the second target pressure, and / or Calculate the adjustment of the target value of the coarse control part of the PID control algorithm a fine adjustment part configured as such, and preferably has.

[0021] This configuration of maintaining the pressure (or actually other variables) at two different target values using a single PID controller is considered a novel implementation of the PID algorithm. By operating the controller in this way, the test system of the present invention can control the pressure on both sides of the heat exchanger with an accuracy that enables, firstly, the maintenance of the pressure difference and, secondly, the detection of a very small flow rate within the test system. This is the case even though the flow rate requirement changes during the test procedure. Consequently, the pressure stability 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 is a result of the use of a single controller and miniaturizes the test system, which is an important factor in a practical embodiment where the test system is installed together with the heat exchanger.

[0022] Each of the above adjustments is preferably calculated using a PID feedback loop.

[0023] In a second aspect, the present invention is a leak test system comprising: the above-described first test device connectable to a first conduit and a second conduit, and the above-described second test device connectable to a third conduit and a fourth conduit to form a third closed-loop system and a fourth closed-loop system, and a system management unit configured to provide a first test device with a predetermined level at which the pressure should be maintained in the first closed-loop system and the second closed-loop system, and to provide a second test device with a predetermined level at which the pressure should be maintained in the third closed-loop system and the fourth closed-loop system A leak test system is provided that includes.

[0024] In this mode, the test system is scaled up to test more complex heat exchangers with more sections and / or stages being tested, and thus more conduits and fluid boundaries. This makes this test system highly flexible in its ability to test any heat exchanger, regardless of the size, design, structure, or complexity of the heat exchanger. Without limitation, this test system can test tube-type, plate-type, surface extended-type, and regenerative heat exchangers, single-pass and multi-pass, gas-liquid, liquid-liquid, and phase change heat exchangers, two-fluid, three-fluid, or N-fluid, direct contact or indirect contact, and any heat exchanger that combines single-phase or two-phase convection on both sides of the fluid boundary. In fact, heat exchangers that combine convection and radiative heat transfer mechanisms can also be tested.

[0025] Each shut-off valve may be arranged in each inflow path and each outflow path of each test device, and the system management unit may further be configured to supply signals for opening and closing the shut-off valves to the shut-off valves of both test devices in an order according to the leakage test to be performed.

[0026] To further improve the flexibility of the application, the leakage test system may also include a third test device according to the above description. The third test device is arranged in each inflow path and each outflow path and is equipped with a shut-off valve that can be connected to a fifth conduit and a sixth conduit to form a fifth closed-loop system and a sixth closed-loop system. The system management unit may be further configured to provide signals for opening and closing the shut-off valve in an order according to the leakage test to be performed to the shut-off valve within the third test device.

[0027] Ideally, the first conduit, the second conduit, the third conduit, the fourth conduit, and, where appropriate, the fifth conduit and the sixth conduit each correspond to a flow path within a heat exchanger through which heat energy can be transferred between one or more pairs of flow paths.

[0028] In a third aspect, the present invention is a method of testing whether a fluid conduit connected to an inlet path and an outlet path of a first channel of a leak test apparatus is leaking in order to form a first closed loop system, the method comprising: a) pumping fluid via a flow control system to fill the first closed loop system to a predetermined pressure level; b) operating the flow control system to maintain the fluid pressure within the first closed loop system at the predetermined pressure level; c) using a flow sensor to measure the fluid flow rate in the inlet path; and providing a method including the above steps.

[0029] This test method represents a new approach to leak detection in fluid conduits. While European Patent No. 3740078 discloses dynamically maintaining the pressure within a conduit, this is for the purpose of improving the accuracy of measurements taken in a second conduit. Further, the measurements in the second conduit are of the pressure within the system. The present invention is based on the recognition that by maintaining the pressure within the conduit, a sufficiently accurate measurement of the flow rate can be made within the same conduit, thereby finding use in the detection of leaks within the conduit.

[0030] In a further aspect, the present invention is a method of testing a heat exchanger for leaks between a first fluid conduit and a second fluid conduit, the conduits being arranged within the heat exchanger to enable transfer of thermal energy between the internal fluids, the method comprising: a) arranging the first fluid conduit in fluid communication with a first channel within a test system, the first channel including a first inlet path and a first outlet path, such that the first conduit and the first channel form a first closed loop system; b) arranging the second fluid conduit in fluid communication with a second channel within the test system, the second channel including a second inlet path and a second outlet path, such that the second conduit and the second channel form a second closed loop system; c) pumping fluid through a flow control system in fluid communication with the first and second inlet paths; d) adjusting the first proportional valve of the flow control system, the second proportional valve of the first inlet path, and the third proportional valve of the second inlet path to reach a first predetermined fluid pressure and a second predetermined fluid pressure in the respective first and second channels, wherein the predetermined fluid pressure of the first channel is greater than the fluid pressure of the second channel; e) maintaining the pressures in the first and second channels while the first shut-off valve, the second shut-off valve, the third shut-off valve, and the fourth shut-off valve of the first inlet path, the first outlet path, the second inlet path, and the second outlet path are closed; f) while continuously maintaining the pressures in the first and second channels: i) opening the first shut-off valve and measuring the flow rate of the first inlet path using the first flow sensor; ii) opening the fourth shut-off valve and measuring the flow rate of the second inlet path using the second flow sensor; iii) observing a flow rate of the first inlet path that exceeds an acceptable level indicates a leak from the first conduit, and observing a flow rate of both paths that exceeds the acceptable level indicates a leak between the first conduit and the second conduit A method is provided that includes the above.

[0031] This method provides an accurate, flexible, and relatively rapid way to perform a integrity test on a heat exchanger. The device designed to implement this method is installed together with the heat exchanger and is expected to perform tests regularly to provide long-term monitoring capabilities and early detection of leaks. This enables the operator of the plant or process in which the heat exchanger is operating to evaluate when it is best to stop the operation and perform repairs. The speed at which the integrity test can be carried out by this method makes it suitable for integration with the clean-in-place (CIP) process of the production system. This is a standard procedure that is regularly performed in many production systems after the time set to remove normal dirt or when switching the processing line from one product to another. The test using this method is attractive in that the integrity test is relatively rapid compared to the CIP cycle. Since the processing plant is already stopped for production due to the CIP cycle, the additional loss of production time for performing the integrity test is minimal.

[0032] This method comprises: g) While continuously maintaining the pressures in the first channel and the second channel: i) Opening a third shut-off valve and measuring the flow rate in the second inflow path using a third flow sensor; ii) Observing a flow rate in the second inflow path that exceeds an acceptable level indicates a leak from the first conduit. may further comprise.

[0033] In a further aspect, the present invention provides: a channel having an inflow path and an outflow path connectable at spatially separated positions within the conduit to form a closed-loop system; a flow control system comprising a flow controller communicating with a pump and a pressure sensor, fluidly communicating with the channel, and adapted to pump fluid at a flow rate that actively maintains the pressure within the closed-loop system at or near a predetermined level; a flow sensor disposed in the inflow path of the channel; and a leak test device.

[0034] In this embodiment, the leakage test device is configured to test for leakage from a single conduit. This expands the application of the present invention. The leakage test can be performed not only on a single-conduit heat exchanger such as a radiator, but also on any system containing a fluid. All that is required is the ability to close the conduit being tested and access it via a connection point for forming a closed loop with the test device channel. The flow control system maintains the pressure within the closed loop, and all the flow rates detected in the inflow path of the channel indicate the outflow from the loop, i.e., leakage. This principle of maintaining the pressure within a separately closed system and monitoring the flow rate is not known in the prior art. The system described in European Patent No. 3740078 relies on maintaining the pressure in one conduit and then performing pressure measurements in a second, separate conduit where the pressure is allowed to vary.

[0035] This device may further comprise a second channel having an inflow path and an outflow path that can be connected to spatially separated second pairs of positions within the conduit to form a second closed-loop system, wherein the spatially separated second pairs of positions span the spatially separated first pairs of positions that can be connected to the first channel, a second flow sensor disposed in the outflow path of the second channel and the flow control system is further configured to pump the fluid at a flow rate that actively maintains the pressure within the second closed-loop system at or near a predetermined level, and thus the leakage test device can detect leakage from a valve that is disposed within the second closed-loop system but not within the first closed-loop system.

[0036] In this aspect, the test system is configured to detect leaks across the valves. This may be to confirm that the valves within the second closed-loop system are not leaking, but this will affect the integrity test performed on the conduits. The apparatus may also include a first pressure sensor disposed in the inflow path of the second channel and a second pressure sensor disposed in the outflow path of the second channel. In this configuration, the apparatus may be used to confirm whether there is a leak in a single-conduit heat exchanger such as an air conditioning system. The flow detected in the first channel may be caused by a boundary flow where harmful substances may be released into the environment, or a flow passing through one or both of the shut-off valves, or a combination of both. With the information provided by the pressure sensors and the information provided by the two flow rate sensors, any detected flow can be assigned to a boundary flow and a leak through each valve within the second closed-loop system. Therefore, this embodiment is advantageous in determining the environmental disasters that are likely to be caused by the continuous operation of the system during the test.

[0037] In another aspect, the present invention a flow control system having a pump, a pressure sensor, and a proportional valve, a first closed-loop system in fluid communication with the flow control system and including a first channel proportional valve and a first channel pressure sensor, a second closed-loop system in fluid communication with the flow control system and including a second channel proportional valve and a second channel pressure sensor a PID controller configured to maintain the pressure within a hydraulic or pneumatic system, the PID controller is configured to apply a variable control voltage to the pump and adjust the opening degrees of the proportional valve and the first (and second) channel proportional valves, a coarse control portion, a fine control portion and comprising The PID controller is configured to apply an adjustment to the control voltage applied to the pump and the opening degree of the proportional valve in response to a signal received from the pressure sensor, and the adjustment is calculated by a coarse control portion to maintain the pressure in the flow control system at a target value that is a function of a first target pressure and a second target pressure. When the pressure sensor indicates a pressure value within a predetermined amount from the target value, the PID controller: Applies an adjustment to the opening degree of the first channel proportional valve in response to a signal received from the first channel pressure sensor, and the adjustment is calculated by a fine control portion to maintain the pressure in the first closed-loop system at a value within an allowable range of the first target pressure, and / or Applies an adjustment to the opening degree of the second channel proportional valve in response to a signal received from the second channel pressure sensor, and the adjustment is calculated by a fine control portion to maintain the pressure in the second closed-loop system at a value within an allowable range of the second target pressure, and / or Provides a PID controller configured to adjust the target value of the coarse control portion that is a function of the first target pressure and the second target pressure.

[0038] In this aspect, the present invention provides a mechanism that can maintain hydraulic pressure in two different closed-loop systems with only a single pump. The pressure can be maintained even when a small leakage occurs from one or both of the nominally closed systems. This aspect is advantageous for any application where miniaturization of the pressure control system is desirable. 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 is an attractive option in many applications.

Brief Description of the Drawings

[0039]

Figure 1a

Figure 1b

Figure 1c

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7a

Figure 7b

Figure 7c

Figure 8a

Figure 8b

Figure 8c

Figure 9

Figure 10

[0040] Here, the present invention will be described by way of example only with reference to the accompanying drawings.

Mode for Carrying Out the Invention

[0041] Referring to FIG. 1a, a side view of a basic plate-type heat exchanger 10 having one boundary and one section is shown. The boundary is provided by an array of thin metal plates 12 that are spaced apart and sealed with a gasket or the like. Thus, the plates 12 define a parallel arrangement of channels 14a, 14b, 14c, 14d therebetween. The heating fluid flow path is defined within the heat exchanger 10 from the high-temperature input portion 16a, along the link passage 18 (upper part of the figure), through the first set of alternating parallel channels 14b, 14d among those defined by the plates 12 in the array, and is defined at the high-temperature output portion 20a. The cooling fluid passage is similarly defined from the low-temperature input portion 22a, along the second link passage 24 (lower part of the figure), through the second set of alternating parallel channels 14a, 14c among those defined by the plates 12, and is defined at the low-temperature output portion 26a. As shown in the drawing, this configuration enables the heating fluid and the cooling fluid to flow in opposite directions from both sides of the plate surface 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 physical separation. The terms may vary depending on the application. For example, when the product is heated within the heat exchanger, the two fluids may be referred to as the heating fluid and the heated product. When the product is cooled, the product is passed through the heat exchanger with the cooling fluid. However, the essential heat exchange process does not change.

[0042] Figure 1b shows a side view of a single - boundary multi - pass plate - type heat exchanger 28. This heat exchanger 28 differs from the simpler version in Figure 1a in that the heating fluid and the cooling fluid pass through the channels defined by the plate surfaces twice. In the first section 30, the flow circuit through the heat exchanger 28 is such that, like the exchanger in Figure 1a, the heating fluid and the cooling fluid have opposite flows through adjacent parallel channels defined by a first set of plates. The second section 32 is connected in series with the first section 30. In this section 32, the heating fluid and the cooling fluid pass through a further set of adjacent parallel channels defined by a second set of plates. If the sizes of the first section 30 and the second section 32 are the same, the heat - exchange surface area is substantially doubled.

[0043] The basic heat exchangers typified by the models shown in Figures 1a and 1b can vary widely in size, structure, and the material and number of plates, depending on the application and the fluid media used. The smallest ones are found in domestic boilers, and the largest ones used for district heating can be as large as a building. In industrial applications, the two flow paths are generally connected in combination with the production equipment.

[0044] Figure 1c is a schematic diagram of a single - stage heat exchanger commonly used in design drawings, such as those shown in Figures 1a and 1b. The heat exchangers 10, 28 are represented by a rectangular box 36. The two flow paths are indicated by inward - facing V - lines 38, 40 with inputs (starts) 16, 22 and outputs (ends) 20, 26 spaced along the width of the rectangular box 36. The lines 38, 40 indicating the flow paths cross twice inside the box, representing the transfer of thermal energy. The flow - path lines 38, 40 continue outside the box 36, showing the fluid flow between the heat exchangers 10, 28 and other parts of the processing plant or heating system in which they are incorporated.

[0045] The test system of the present invention is designed to be used with heat exchangers of any type or complexity. When easily adaptable, heat exchangers installed in production lines are modified to be connectable to 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 necessary.

[0046] The adaptation performed on the heat exchanger is shown in the schematic diagram of FIG. 1c. Shut-off valves 42a, 42b, 42c, 42d are arranged in each input line 16, 22 and each output line 20, 26 of both flow paths. These valves can be any suitable valve type operable to open and close the conduits. For example, the valves may be 2 / 2 valves, butterfly valves, ball valves, or seat valves, and any valve suitable for the application in which the heat exchanger is used would be preferred. Connection points (1), (2), (3), (4) are provided on the heat exchanger side of the shut-off valves in each line 16, 20, 22, 26. In some cases, the heat exchangers 10, 28 may already have valves and connection points in the appropriate positions, and in some cases, they may have to be incorporated into the heat exchanger in situ. As is apparent from the above, the shut-off valves 42a, 42b, 42c, 42d are arranged so that when they are closed, the heat exchanger is isolated from the rest of the production line in which it is incorporated.

[0047] Next, referring to FIG. 2 showing the fluid control components of the test system according to the present invention, test system 44 includes a gear-driven flow rate setting system (GDFS) 46 along with a first flow channel 48 (channel 1) and a second flow channel 50 (channel 2). GDFS 46, which will be described in more detail below, is arranged to create a controlled pressure maintained within channels 48, 50 of test system 44. Each channel 48, 50 is connected to respective flow paths within the heat exchanger being tested. For example, when testing heat exchangers 10, 28 of the type shown in FIG. 1c, 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). The test system is associated with a process controller (see FIG. 4), such as a microprocessor, programmed to control the execution of the test process.

[0048] As shown in FIG. 2, test system 44 includes the following components:

[0049] (Table 1) M pump G pressure sensor V valve T tank M water sensor F flow rate sensor O variable orifice P proportional valve

[0050] In the drawings, each component is assigned a reference symbol of the type Cm or Cm.n, where C indicates the type of component listed in the table above. Multiple components of the same type within the system or within a particular channel are distinguished using different numbers m. Components specific to one or the other channel are distinguished using a two-digit number n which is either 1 or 2 depending on whether the particular component forms part of the first channel 48 or the second channel 50.

[0051] Generally, the heat exchangers 10, 28 are part of the production system and are under the control of an industrial process controller during normal operation. The test system 44 is connected to the heat exchangers, but its valves are closed along with any sanitary isolation valves that can be part of the production system and under the control of the production system. Thus, the test system 44 remains isolated from the production system. When a test is scheduled, the industrial process controller closes the isolation valves 42a, 42b, 42c, 42d to isolate the heat exchangers from the rest of the production system. Thereby, the heat exchangers 10, 28 become a "closed system", and if a fluid flow out of the system is detected, it is considered an "outflow" caused by a defect at one or more of the system boundaries.

[0052] After isolation of the heat exchanger / test system, the test process controller takes over control, powers on the GDFS 46, and pumps water into the system. In some applications, an alternative test fluid, such as isopropyl alcohol, may be used, but water is assumed to be the most common, so water is used as an example in this description. At the start of the test, if the heat exchanger paths 38, 40 are not filled with fluid, the test process controller opens the valves V1.1 and V1.2 within their respective bypass flow paths 52a, 56a. These valves V1.1 and V1.2 facilitate filling the heat exchangers to the initial starting pressure within a reasonable period to allow for a relatively high water throughput. When the heat exchangers 10, 28 are filled with water, the valves V1.1 and V1.2 are closed and the remaining valves of the test system 44 are opened, getting ready to equalize to the test pressure. The pressure within the flow paths 38, 40 is raised to the user-selected value required for the test and is maintained with the flow being controlled by the GDFS 46. Importantly, the pressure at which the test is conducted will be of the order of the operating pressure of the production system. In such an embodiment, there is no need to fill the heat exchangers to a pressure significantly above the pressure at which the heat exchangers normally operate.

[0053] As an example of explaining the flow path within the test system 44, consider a situation where channel 1 is connected to a path through an external conduit, e.g., a heat exchanger, and fluid is pumped through an established circuit. As will become apparent later, there may or may not be flow within the circuit during the test process itself. Thus, this explanation is simply given to describe the function of the components of the system and how the test system 44 might support internal fluid flow. Valves V2.1 and V3.1 set the normal flow direction within the channel, i.e., along the inflow path 52, which in this example is the connection point (1) of the heat exchanger, through the heat exchanger to connection point (2), and then the return flow through the test system along the outflow path 54. The outflow path 54 leads to a tank T2 that functions as an expansion vessel to maintain the pressure within the system 44. A water sensor W2 monitors the water level within the tank T2 and, if the water level becomes too high, sends a signal to the test process controller to turn off GDFS46 and open valve V2 to allow air to be drawn in. The proportional valve P1.1 is adjusted in conjunction with valve V5.1 and orifice O1.1 to set the flow rate of the water pumped by GDFS46 along the inflow path 52 of channel 1, which is monitored by a flow sensor F1.1. A flow sensor F2.1 is configured to monitor the flow rate of the outflow path 54.

[0054] Similarly, channel 2 may also support fluid flow through an external conduit. The one-way valves V2.2 and V3.2 set the direction of flow along the inflow path 56, which in this example is the connection point (3) of the heat exchanger, through the heat exchanger to connection point (4), and then back to the test system along the outflow path 58 that is open to the atmosphere. The proportional valve P1.2 is adjusted in conjunction with valve V5.2 and orifice O1.2 to set the flow rate of the water pumped by GDFS46 along the inflow path 56 of channel 2. Flow sensors F1.2 and F2.2 are configured to monitor the flow rates along the inflow path 56 and the outflow path 58, respectively.

[0055] The operation of the GDFS46 is described in detail below, but basically, the proportional valves P1, P1.1, and P1.2 are adjusted to control the flow rate until the system stabilizes at the required pressure. These pressures are such that a pressure difference is maintained between the two channels 48 and 50 through the relative opening degrees of P1.1 and P1.2. Equilibrium is reached when the flow rates through the proportional valves P1.1 and P1.2 driven by the GDFS46 and the proportional valve P1 balance the hydraulic pressures in the respective test channels 48, 50 and the heat exchanger flow paths 38, 40. The excess flow through P1.1 exits the system through the valves V5.1 and the variable orifice O1.1. In the absence of leakage from the heat exchanger, the water in the heat exchangers 10, 28 and in the channel 1 downstream of the connection node with the valve V5.1 is stationary, and no flow is observed at any of the flow sensors F1.1, F2.1 in this test system channel 48. Similarly, the excess flow through P1.2 exits the system through the valves V5.2 and the variable orifice O1.2. In the absence of leakage, the water in the heat exchangers 10, 28 and in the channel 2 downstream of the connection node with the valve V5.2 is stationary, and no flow is observed at any of the flow sensors F1.2, F2.2 in this test system channel 50. However, in the presence of leakage, flow through one or more of these flow sensors F1.1, F2.1, F1.2, F2.2 is observed.

[0056] As an example, consider testing the heat exchanger shown in FIG. 1c using the test system of the present invention. Flow sensors F1.1, F2.1, F1.2, and F2.2 measure the flow rates 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, there should be an additional flow to connection point (1) that balances the loss from channel 1 to maintain the equilibrium pressure within the system. Thus, the flow is observed by flow sensor F1.1. Similarly, if there is a leak to the atmosphere in the cooling flow path 40, an equilibrium flow rate is detected by flow sensor F1.2 (connection point (3)). On the other hand, if there is a leak across the boundary of the heat exchangers 10, 28, a boundary flow occurs from the high-pressure channel (e.g., the heating flow path 38 connected to channel 1) to the low-pressure channel (cooling flow path 40). Under the equilibrium conditions in this situation, an inflow to connection point (1) that balances the loss from channel 1 due to the leak and an outflow from connection point (4) that balances the increase in flow rate to channel 2 occur. Thus, the test system 44 will observe non-zero flow rate measurements at both sensor F1.1 and sensor F2.2. These different observations show how the flow rates measured by these four flow sensors F1.1, F2.1, F1.2, F2.2 can enable, firstly, the detection of leaks and, secondly, the identification of the location of the leak, i.e., whether the leak is across the boundary or through a gasket or seal.

[0057] In the standard operating mode, the test system 44 allows flow from the inlet paths 52, 56 through the connection points (1) and (3), through the heat exchangers, and then from the connection points (2) and (4) to the outlet paths 54, 58. However, the flow direction can be reversed by opening valves V4.1 and V4.2. The flow from the proportional valve P1.1 diverges through valve 4.1 into the channel arm connected to connection point (2). As a result, it flows through the heat exchangers 10, 28 in the reverse direction to connection point (1), from where the flow diverges again through valve 4.1 into the outlet path 54. A similar reversal of the flow through connection points (3) and (4) is observed in channel 2. Such flexibility is advantageous when testing more complex multi-section heat exchangers where access may not be possible at all preferred connection points.

[0058] It should be noted that regardless of the direction of flow through the heat exchangers 10, 28, leakage is observed as inflow through flow sensor F1.1 or F1.2 and / or outflow through flow sensor F2.1 or F2.2.

[0059] The test system 44 of the present invention is designed to detect very small leaks within the heat exchangers 10, 28. Naturally, if the leak is small, it will be obvious that the observed equilibrium flow rate will also be small. As a result, accurate flow sensors are required to measure the flow rate within the test channels 48, 50. Suitable examples for use in the present invention are available from Sensirion, which supplies a series of flow sensors capable of measuring flow rates in the range of milliliters and microliters per minute. These sensors are based on the principle of heat transfer. Each sensor is basically a tubular structure with a central pressure-stabilizing membrane. A heating element is located in the center of the membrane, and temperature sensors are arranged on both its upstream and downstream sides. When there is flow along the bore of the tube, through the membrane and the heating element, the liquid passing through the tube transfers heat from the heating element, and a temperature rise is observed at the downstream sensor. The flow rate can be inferred from the generation of the temperature difference between the upstream and downstream sensors.

[0060] 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 placed in the outflow paths 54, 58 to ensure that water is flowing through the sensor. Thus, this arrangement reduces the risk of another liquid flowing from the heat exchanger under test and compromising the flow sensor's measurements.

[0061] In some applications of the present invention, different test fluids can be supplied from the test system and used for leak detection. For example, the test fluid may be a liquid such as glycol, isopropyl alcohol, or liquid natural gas (LNG). Alternatively, the test fluid can also be a gas such as methane, argon, nitrogen, steam, or a refrigerant gas such as R32 (difluoromethane). In such embodiments, tanks T1.1, T1.2 are filled with the alternative test fluid and the flow sensor is calibrated for use with this fluid.

[0062] In addition to accurate measurement of the flow rate, it is important that pressure fluctuations within the system do not create flows that mask leaks. For this reason, the test system 44 of the present invention is designed to accurately maintain the pressure within the heat exchangers 10, 28. Such pressure control is achieved using the GDFS control system, which is described next with reference to FIG. 3.

[0063] Figure 3 shows GDFS46 and the inflow paths 52, 56 of two channels of the test system 44. At the center of GDFS46, there is a voltage control pump M1 that operates in conjunction with a feedback loop controlled by a test process controller according to pre-programmed PID (Proportional Integral Derivative) algorithms and proportional valves P1, P1.1, and P1.2. Valve V1 opens and closes the supply line 60 to tank T1. Water (or other fluid used in the test) is drawn from tank T1 by pump M1 and supplied to the output line 62. There are three branches in the output line. The first two branches form the respective channel inflow paths 52, 56, and the third branch 64 is a flow path through proportional valve P1, which leads to the drain. The total flow rate of the output line 62 is monitored by flow sensor F1, and the pressure is monitored by pressure sensor G1. In the first case, the flow rate of the pumped fluid is determined by the operating voltage of pump M1 and the opening degree of proportional valve P1. The proportion of the fluid pumped by pump M1 and exiting the system via flow path 64 is controlled by the opening size within proportional valve P1. The larger the opening, the more fluid is discharged from the system, and the flow to the test channels 52, 56 decreases. Conversely, reducing the opening degree of proportional valve P1 increases the flow rate to the test channels 52, 56. Similarly, the opening degrees of proportional valves P1.1 and P1.2 determine the proportion of the flow to the corresponding test channels 52, 56. Excessive flow is discharged via orifices O1.1 and O1.2 under the control of valves V5.1 and V5.2. During the integrity test procedure, the voltage to pump M1 and the opening degrees of valves P1, P1.1, and P1.2 are continuously adjusted using the PID control algorithm. The pressure within system 44 is continuously monitored by pressure sensor G1 at the pump output line 62 and by pressure sensors G3.1 and G3.2 at channels 1 (52) and 2 (56) respectively. This provides dynamic control to maintain the flow rate through the system regardless of any changes in requirements for flow due to leakage within the system. Although the details of the algorithm will be described later, basically, the operating pressure is first approached by closing valves P1.1 and P1.2 and guiding all the pumped fluid to the output flow path 64.The voltage to pump M1 and the opening degree of valve P1 are set to their initial values. Through experience, approximate values for stabilizing at the operating pressure within a specific system during testing are known, thereby shortening the time required to reach equilibrium. In either case, the pressure at sensor G1 is notable for these values of the initial voltage and valve orifice size. If the pressure at G1 is higher than the target pressure, first the pump voltage and then the opening degree of P1 are adjusted by an amount determined by the PID algorithm to lower the pressure within the system. Similarly, if the measured pressure at G1 is less than the target pressure, the pump voltage may be increased and / or the orifice size of proportional valve P1 may be decreased to increase the pressure within the system. After repeating these steps in a series of feedback loops, the measured pressure at G1 moves within a certain range (e.g., 100 Pa) of the target pressure. At this point, proportional valves P1.1 and P1.2 are opened together with valves V5.1 and V5.2, and the pressure is measured at G1, G3.1, and G3.2. For this stage, the target pressure is the pressure measured by the two test channels 48, 50, i.e., pressure sensors G3.1 and G3.2. The PID control loop is repeated to bring the pressures at G3.1 and G3.2 closer to the target values.

[0064] By this technique of continuously adjusting the voltage of pump M1 and the opening degrees of proportional valves P1, P1.1, and P1.2, a very accurate pressure can be maintained within the test system and the connected heat exchanger. Since the pressure is monitored and adjusted independently of the flow rate within the system, the pressure is maintained at the required level regardless of whether there is a leak or not.

[0065] As shown in FIG. 4, the test system 44 includes both a hydraulic component 44a and a control component 44b. In the above description, the hydraulic component 44a has been mainly described, and here the control component 44b will be described in more detail. As shown in FIG. 4, in one embodiment, the control component includes 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 grid. All control components 66-70 are connected to an information network 72 such as the Internet or a LAN.

[0066] The SMU 67 is a central processing unit in which software necessary for overall management of the test process is stored. This includes, in particular, software for data analysis, processing of user input, operation of the user interface, communication with cloud-based instructions, communication 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 which is part of it. In particular, the microcontroller is programmed with firmware instructions that enable the microcontroller to operate as a PID controller in the pressure setting algorithm using the GDFS 46. Further firmware instructions enable the GPIO unit 70 to receive and decode information from the sensors and the SMU 67.

[0067] In the representation of the test system 44 shown in FIG. 4, connection points (1), (2), (3), and (4) are shown at positions on the hydraulic circuit 44a and, during operation, have connection pipes 73 that connect to the channels of the heat exchangers 10, 28.

[0068] As described above, the test system of the present invention has the ability to set and accurately maintain pressure and can measure low flow levels. These features, along with the available control methods, enable the test system 44 of the present invention to perform integrity tests on many different types and kinds of heat exchange systems. In fact, the test system 44 may be used to test for leaks across any fluid boundary and is not limited to testing boundaries within heat exchange systems. An example of a protocol that may be followed when performing tests on heat exchanger components in industrial process lines will be described with reference to FIG. 5.

[0069] In step S10, the test parameters are obtained from the data storage facility via the network connection 72. Typically, the storage facility is a repository on the cloud managed by a test provider. This becomes a database where details of the type of heat exchanger and the industrial process in which it is used are stored together with test parameters such as filling pressure, pressure difference, locations where flow rate measurements are taken, order of measurements, tolerance for error warnings, etc. Alternatively, the test parameters can be locally stored and managed by the equipment controller, but this would result in losing the opportunity to benefit from updated information obtained from test procedures executed by similar test setups in other equipment. In any case, the test parameters are obtained (S10) by the test system management unit (SMU) 67 and verified to be correct for the heat exchanger under test. In step S12, the process controller of the equipment or production line closes the shut-off valves 42a, 42b, 42c, 42d and transfers the operation control of the isolated heat exchanger to the SMU 67. The first step S14 in conducting the test is to fill the test system to the required fluid volume. In other words, it is to store up to a predetermined set pressure at the sensors G1.1 and G1.2. These vary depending on the system, but often they are similar to the operating pressures that the heat exchanger receives in its production line. For example, the pressure on the product side (G.1.1) is 8 bar, the pressure on the coolant side (G1.2) is 7.5 bar, resulting in a pressure difference of 0.5 bar. If the system does not reach stable pressurization within an acceptable time, this is notified to the user and the user may decide to abort the test (S16). If the test fails, the test system 44 is returned to the idle mode (S18) and an interface for viewing a report of the cause of failure is presented to the user. Such causes of failure can be, for example, a catastrophic leak within the system or a failure of the isolation of the heat exchanger. Alternatively, if no such cause of failure is found, the user can ignore this warning and continue the test.

[0070] To repair a leak, the heat exchanger has to be disassembled, which results in a significant loss of production time. Therefore, it is clearly important to confirm that, when a leak is detected by the test system, it is not caused by a defect in the test system 44 itself. For this reason, in one embodiment, the system of the present invention is designed to perform a self-test S20 immediately after being filled. Once filled, the test system can be isolated from the heat exchanger, and referring to FIG. 2, all 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 connecting to the heat exchanger are closed. At this point, the system is filled to a stable pressure by the GDFS 46. This pressure reaches the upper limit of the range given by the GDFS 46 and is 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, after a short stabilization time, the flow sensors F1.1, F1.2 in the inflow paths 52, 56 are checked. Detection of flow in either of the flow sensors F1.1, F1.2 indicates a leak in the respective inflow valves V2.1, V2.2. The valves V2.1, V4.1, V2.1, V4.2 in the inflow paths 52, 56 are opened, and then the flow sensors F2.1, F2.2 in the outflow paths 54, 58 are checked for signs of flow. If flow is detected, this is due to a leak in the respective outflow valves V3.1, V3.2. As the 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 confirm their integrity. If a leak is detected at any stage, the self-test fails and the test system 44 returns to the idle mode (S18). Only when the test device 44 passes all stages of the self-test is it permitted to start the leak test in step S22. If it fails at any stage, the test device 44 returns to the 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 investigated and repaired.

[0071] In step S22, the test system 44 conducts tests on the heat exchangers 10, 28 to which the test system 44 is attached. To detect and identify any leaks within the heat exchanger, there are many options for the order in which the valves within the test apparatus 44 can be opened and closed. However, in this embodiment, the routine adopted to test the single boundary heat exchangers 10, 28 is as follows. Referring again to FIG. 2, both valves V2.1 and V2.2 of the channel inflow paths 52, 56 are opened, whereby the two halves of the heat exchanger are in fluid communication with the test apparatus 44. When a stable flow is observed at the flow rate sensor F1 by GDFS46, the flow rate sensor F1.1 checks whether there are signs of flow along the inflow path 52 of channel 1. If any flow is observed, there is a defect in the path of the heat exchangers 10, 28 to which this channel 1 is connected (connection point (1) to the heating path 38 in the example of FIG. 1c). Next, the valve V3.2 of the second channel outflow path 58 is opened, and the flow rate sensor F2.2 checks whether there are signs of flow in this channel. In other words, it is to check whether there is an outflow corresponding to the cooling path 40 and the connection point (4). If flow is detected by both flow rate sensors F1.1 and F2.2, this indicates a defect at the boundary of the heat exchanger. If it is detected only by the flow rate sensor F1.1 of the inflow channel, the defect is in other parts of the isolation path (heating path 38 in this example) during the test of the heat exchangers 10, 28. If the defect crosses the boundary, the heat exchanger is malfunctioning, the leak is identified and isolated, so the test can be aborted. Otherwise, or if it is necessary to investigate the possibility of further leaks, the flow rate sensor F1.2 of the second channel inflow path 56 is checked. If flow is detected, this indicates a leak in the path of the heat exchangers 10, 28 to which this channel 2 is connected (connection point (3) to the cooling path 40 in the example of FIG. 1c). As the final part of the flow rate test, the valve V3.1 of the first channel outflow path 54 is opened, and the flow rate sensor F2.1 checks whether there are signs of flow in this channel. In other words, if there is flow to the second channel, it is checked whether there is also a corresponding outflow from the heating path 38 and the connection point (2). If flow is detected by both flow rate sensors F1.2 and F2.1, this indicates a defect at the boundary of the heat exchanger.If detected only by the flow sensor F1.2 in the inlet channel, the defect is in another part of the cooling path 40. At the end of this procedure, if no flow is detected in any of the inlet channels 52, 56 or the outlet channels 54, 58 of the test system 44, the heat exchangers 10, 28 have passed the integrity test.

[0072] If flow is detected by any of the flow sensors F1.1, F1.2, F2.1, F2.2 during the integrity test of the heat exchanger, the test system 44 presents the user with the details of the flow observed at step S24. This gives the user the opportunity to evaluate the severity of the leak and decide whether to take countermeasures. Depending on the application, small leaks through seals or gaskets that do not cross boundaries may be acceptable. Therefore, the user may set parameters within the test system 44 that determine the level of detectable flow that is acceptable. In such a case, the heat exchanger can continue to be used in the industrial process. If the detected flow exceeds the acceptable range, the user confirms the failure of the integrity test by the heat exchangers 10, 28. Thereafter, the test system 44 returns to its idle state (S18). Otherwise, the user can indicate that the test has passed, perhaps with specific warnings in the future. In some embodiments of the present invention, the test results are communicated to a cloud-based server for storage and further analysis.

[0073] To verify the test results, the test system 44 then performs a second self-test at step S26. This is to confirm that the test system has not been impaired during the actual test of the heat exchanger. After completion of this second self-test S26, or after a failure S18 in any part of the test sequence, the test system process controller returns control to the industrial process controller (S28). The test cycle is complete.

[0074] The above description refers to the user of the test system 44. Such a user may be a person on the site of an industrial process, perhaps a performance supervisor. Alternatively, the user may be located remotely, such as an expert in test procedures who uses the test system 44 of the present invention but is unrelated to the entity executing the industrial process. Such a user generally accesses test results obtained from the installation of a plurality of such test systems 44 in various industrial environments and locations. Thus, this configuration is advantageous in that it provides an opportunity to accumulate data regarding multiple tests and systems and possibly enables better interpretation of the results with the assistance of machine learning algorithms. This may enable prediction of heat exchanger failures and preventive repairs at appropriate times.

[0075] As can be understood from the foregoing description, important for the reliability of the results is the ability of this test system 44 to maintain the set pressure levels within both halves 38, 40 of the heat exchanger with high accuracy. FIG. 6 is a flowchart showing an example of a PID control algorithm that can be used to operate the GDFS 46 so that a stable pressure within the heat exchanger system is maintained at a predetermined value. This algorithm basically consists of two parts: a coarse control part 74 and a fine control part 76.

[0076] To begin filling system 44 to the test pressure, the SMU 67 must be provided with the necessary target information. This takes the form of the two channel pressures of channel 1 and channel 2 in which the heat exchanger test is being performed. These pressures will generally be pressures close to those that would reproduce the situation in the heat exchanger during its normal operation. For there to be flow in the event of a leak at the boundary, a pressure difference must be maintained between the two channels. Thus, the first step S32 is a request from the test / preliminary test code to supply different pressures to channel 1 and channel 2. The SMU 67 receives this request and passes the target pressure information to the GPIO unit 70 in the form of target values for the pressure sensors G3.1, G3.2 in the channel inflow paths 52, 56. This is because it is the GPIO unit 70 that is responsible for the PID pressure control algorithm. As a mere example and for the assistance of explanation, assume that a pressure difference of 50 kPa is maintained. That is, if the target pressure at the pressure sensor G3.1 in channel 1 is y kPa, the pressure at the sensor G3.2 in channel 2 will be (y + 50) kPa.

[0077] Referring to FIGS. 2 and 6, in step S36, the control voltage to the GDFS pump M1 and the opening size of the GDFS proportional valve P1 are set. Initially, these are set to predetermined starting values. At this stage, all the 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 GDFS46 pump is operated with these flow circuit parameters, and a measured value is obtained from the GDFS pressure sensor G1. In step S38, this measured value 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 both of the two target values of the pressure sensors G3.1 and G3.2. Here, again, as merely an example, this algorithm should not be regarded as restrictive, but the target pressure of the sensor G1 is set 50 kPa higher than the larger of the two target values of the pressure sensors G3.1 and G3.2. That is, the target pressure of the sensor G1 is (y + 100) kPa. The next step depends on whether the pressure of G1 is within a predetermined range of its target value, for example, within ±10 kPa of (y + 100) kPa in this example. If the G1 pressure is outside this range (i.e., the error value is >10 kPa), the algorithm proceeds to step S40, and a PID calculation is performed based on the magnitude of the error value and the preset values for the first set of proportional, integral, and derivative gains to determine the adjustments to be made to the control voltage applied to the GDFS pump M1 and / or the opening degree of the proportional valve P1. In step S42, the adjustment values of the pump voltage and the valve opening degree are applied to the pump M1 and the proportional valve P1 of the GDFS46. Then, this process returns to step S36, the GDFS46 pump is operated with these flow circuit parameters, and a new measured value is obtained from the GDFS pressure sensor G1. These steps S36 to S42 are repeated until the G1 pressure falls within the predetermined range (±10 kPa) of its target value ((y + 100) kPa). When this target is close enough, the PID algorithm moves to its micro-control part 76.

[0078] In step S44, the proportional valves P1.1 and P1.2 of channels 1 and 2 are opened by the set opening degrees. Initially, they are opened by a predetermined amount, and the valve of the channel with the higher pressure is further opened. The valves V5.1 and V5.2 are opened so that the flow passing through the proportional valves P1.1 and P1.2 can flow out of the system. Thereafter, GDFS46 is operated with the pump voltage and the opening degree of the GDFS proportional valve P1 maintained from the rough control part 74 of the PID algorithm, and the channel proportional valves P1.1 and P1.2 are opened to the set degree. Measurement values are obtained from the flow channel pressure sensors G3.1 and G3.2. In step S46, these measurement values are compared with the target values, for example, y kPa for G3.1 and (y + 50) kPa for G3.2, and the respective error values are derived. If one or the other error value is outside a certain range, for example, outside the range of the target pressure ±1 kPa, the algorithm proceeds to step S48. In step S48, for each measured value of the individual pressures (G3.1, G3.2), PID calculations are performed to generate adjustments to the opening degrees of the respective proportional valves P1.1 and P1.2. The adjustment calculations are based on the respective pressure error values and the preset values for a second set of proportional, integral, and derivative gains. In step S50, the adjustments calculated in step S48 are made to the opening degree values of the channel proportional valves P1.1 and P1.2. Thereafter, the process returns to step S44, and the proportional valves P1.1 and P1.2 of channels 1 and 2 are opened only by their adjusted opening degrees and the updated measurement values obtained from the flow channel pressure sensors G3.1 and G3.2. These steps S44 to S50 are repeated until the pressures of G3.1 and G3.2 are within the predetermined ranges (±1 kPa) of their respective target values (y kPa, (y + 100) kPa).

[0079] When the target pressures are reached in both channels, the pressures of the flow channel pressure sensors G3.1 and G3.2 are continuously monitored (S52), and as a result, adjustments are made to the opening degrees of the flow channel proportional valves P1.1 and P1.2 (S48, S50) in order to actively maintain these pressures so that they approach the target values.

[0080] In step S54, in order to verify that the pressures of the flow channel sensors G3.1 and G3.2 are converging toward the target value, confirmation is performed after the repeated setting times of the PID loops S44 to S50. If not converging, the algorithm returns to the rough control part 74 and attempts to repeat the PID pressure stabilization routine (S34) using the pump M1 control voltage of the new value and the opening degree of the GDFS proportional valve P1.

[0081] Using a PID control loop to actively maintain two different pressure levels is a novel embodiment of this algorithm. A more typical approach, known in the prior art, is to use two separate pumps, one for each channel 48, 50. Each pump is associated with its respective proportional valve and PID control loop, enabling the pressure within each channel 48, 50 to be independently maintained at the target value. However, using a single pump and PID controller to stabilize the pressures of the two flow channels is advantageous for miniaturizing the test system. This is an important consideration in the installation (take up) of the test system 44 that is permanently connected to the heat exchanger but only used periodically. The drawback is that as the number of adjustable components increases, it takes the PID loop longer to stabilize the system. That is, at least in the initial stage, a trade-off is required between the cost and size of the test system and the time required to execute the test sequence. However, in the system of the present invention, since the data is shared centrally, it is expected that the initial settings of the pump and valve can be reliably accessed close to their operating values in a relatively short time. Therefore, the convergence to the target pressure becomes faster, and the drawback of the longer stabilization period for the two flow channels is almost eliminated.

[0082] The above-described test system 44 can be scaled up for use in more complex heat exchangers having a plurality of sections to be verified and thus a plurality of boundaries. However, it has been found that using one PID controller to equalize the pressures of more than two channels is unduly time-consuming. Thus, in embodiments of the test system 44 used in more complex heat exchangers, a different approach is taken. This is to expand the capabilities of the test system by using a master test system and a slave test system, as shown in FIGS. 7c and 8c.

[0083] A general single-pass two-section heat exchanger 78 is shown in FIG. 7a, and a schematic diagram for use in a flow control diagram is shown in FIG. 7b. The heat exchanger 78 shown in a side view has a heating section 80 and a cooling section 82. Each section 80, 82 has respective boundaries provided by an array of thin metal plates that define respective parallel arrangements of 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 of the heating section 80, through a connection line to the cooling section 82, and through a second set of alternating channels 86 to a product outlet 94. In the heating section 80, a heating fluid passage extends from a heating input 96 through the first set of alternating parallel channels 84 to a heating fluid output 98. In the cooling section, a cooling fluid passage extends from a cooling input 100 through the second set of alternating parallel channels 86 to a 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 while allowing thermal contact between the product and the heating and cooling fluids respectively. That is, in the heating section 80, the product is heated by heat transfer from the heating fluid, and in the cooling section 82, the product is cooled by heat transfer from the product. This designed heat exchanger may be used, for example, in applications where the product must be cooled for packaging after being cooked or sterilized. The multiple sections also enable energy reuse, i.e., the product after heat treatment is used to preheat the product entering the heat treatment.

[0084] FIG. 7b is a schematic diagram of a two-section heat exchanger 104. Each section 106, 108 is represented by a rectangular box, and the internal flow paths are shown by inward V-shaped lines 110a, 110b, 110c, 110d that extend outside the box to show the connecting flow paths outside the heat exchanger sections 106, 108. This schematic diagram 104 represents a heat exchanger consisting of a heating section 106 and a regeneration section 108 that reuses energy to heat the product with improved efficiency. Inside the heating section 106, there is one heating fluid flow path 110d that extends from the heating fluid input portion 112 to the heating fluid output portion 114. The remaining flow paths 110a, 110b, 110c are all connected. The product path extends from the product input portion 116 along the preheating path 110a to the regeneration section 108 and exits the regeneration section 108 through the connection passage 118. The product path continues to the heating section 106 and passes through the path 110c that is in thermal contact with the fluid in the heating flow path 110d. The heated product then returns to the regeneration section through the return path 120, and its second path 110b is on the opposite side of the section boundary. In this section 108, the thermal energy from the product that is currently being cooled is transferred to the product entering the heat exchanger in the preheating path 110a and is thus used to perform a certain degree of preheating. The product line exits the heat exchanger at the product outlet 122.

[0085] An exemplary connection made between a test system according to the present invention and a heat exchanger of the type represented by the schematic of FIG. 7b is shown in the figure. Shut-off valves 124a, 124b, 124c, 124d are attached to the inlets 112, 116 and outlets 114, 122 of the heat exchanger. Each connection point (1), (2), (7), (8) is provided on the heat exchanger side of each shut-off valve and is in three of the four heat exchanger lines 110a, 110b, 110d in this example. Note that connection points (1) and (2) are located at the input and output of a single path through a single section of the heat exchanger, while connection points (7) and (8) are not. Connecting these connection points (7) and (8) to a single channel of the test system 44 enables detection of a leak somewhere in the three heat exchanger paths extending between these connection points (7) and (8), but it is not possible to further locate such a leak. For this reason, additional connections and valves are necessary in a multi-section heat exchanger. Ideally, access to all connectors connecting the path through the first section of the heat exchanger to the path through the second section is made available. That is, in the example of FIG. 7b, access to the connection passage 118 and the return path 120. If such access is available, shut-off valves 126a, 126b are incorporated into their respective passages together 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 connection path that extends through the first section 106 of the heat exchanger from the portion that extends through the second section 108. The additional connection points (5), (6), (3), (4) made available within each portion of the connection path enable the test system 44 to be connected so as to address each side of the heat exchanger of each section 106, 108 in turn. For example, the path 110c carrying the product through the heating section 106 of the heat exchanger may be isolated by closing the valve 126a in the connection passage 118 and the valve 126b in the return path 122. A leak within this heat exchanger path 110c can be identified by connecting one channel of the test system 44 to connection points (3) and (5).Similarly, with the valve 126a of the connection passage 118 closed together with the valve 124c of the product input section 116, leakage within the product path 110a in its first passage through the heat exchanger can be detected and identified by connecting one channel of the test system 44 to connection points (6) and (7). Clearly, the heating flow path 110d can be tested by connecting the channel to connection points (1) and (2). Similarly, the path 110b for the second product to pass through the regeneration side can be tested through connection points (4) and (8).

[0086] A test system 144 according to the present invention suitable for testing a two-section heat exchanger of the type depicted in FIG. 7b is shown in FIG. 7c. 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 hydraulic component 44a of the embodiment of the test system described with reference to FIGS. 2 and 4. That is, each of the master 146a and the slave 146b has two test channels connectable to the flow paths within the heat exchanger whose integrity is to be tested. These channels are indicated on the master 146a by connection labels (1), (2), (4), (8) and on the slave 146b by connection labels (3), (5), (6), (7). This arrangement corresponds to the labeling of the connection points used in FIG. 7b, and for performing the heat exchanger test, a connection is made from connection point (1) of the test system 144 to connection point (1) of the heat exchanger. Further, each master 146a and each slave 146b have their own power supply, water supply, network connection, drainage facility, and connection to the atmosphere. The difference between these systems 146a, 146b lies in the control components and software.

[0087] The control components of the master system 146a are the same as those of the control component 44b of the test system 44 described above. 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. Similar to the stand-alone unit described above, the SMU 67 is responsible for the overall management of the test system 144, and the GPIO unit 70 is mainly responsible for establishing and maintaining the pressure in the two test channels of the master system 146a using the master GDFS 46 and the PID algorithm described above.

[0088] The control components of the slave system 146b include all of the above components of the master system, except for the system management unit 67 and the firewall 69. Also, the switch 68 is removed unless the system is composed of multiple slave systems. In particular, the slave 146b includes its own GPIO unit 150. The slave GPIO unit 150 is responsible for the PID control of the pressure setting in the two test channels of the slave system 146b using the slave GDFS. Further, the slave GPIO unit 150 reports sensor data to the SMU 67 of the master system 146a.

[0089] In other words, each slave system 146b is capable of establishing and maintaining pressure in its inlet and outlet channels, but this is in accordance with the pressure requirements provided by the master SMU 67. Further, all processing of user commands and setting of test parameters, including the sequence in which the test valves are opened and closed during the test procedure, is performed by the SMU 67 located in the master for both the master 146a and the slave 146b units.

[0090] Each master 146a and slave 146b system has two test channels that can be respectively connected to test one flow path in the heat exchange system. Therefore, for a complete test for leakage detection and location identification of a two-stage heat exchanger as shown in Fig. 7b, a single combination of master and slave is sufficient, and one channel is connected to each pair of the connection points identified above.

[0091] The slave 146b system has two test channels, but there are applications where a second channel is unnecessary, such as when testing a heat exchanger with, for example, three internal fluid paths. In this case, the valves V2.2 and V3.2 of one channel remain closed, and the difference in target pressure at the flow channel sensors G3.1 and G3.2 can be set to zero.

[0092] This procedure can be extended to more complex heat exchangers, such as the three-section multi-pass plate heat exchanger 160 shown in Figs. 8a and 8b. There are two paths through each section of the heat exchanger, and a total of 12 connections and 6 channels are required in the test system 144 to separate each path individually. To test this type of heat exchanger, as shown in Fig. 8c, it is necessary to connect the master system 146a to two slave systems 146b and 146c.

[0093] This type of heat exchanger often has a heating loop and a cooling loop for separate products, with a recovery section between them, and is often used in pasteurization applications. In an ideal scenario, it is possible to make 12 connections between this type of heat exchanger and the test system of the present invention. However, it should be noted that in practice, such access may not be possible, so the test system has to be connected with a number less than the ideal number of connections. This means that it is not possible to separately test all the paths within each section. Leakage detection is still possible, but the effectiveness of location identification is reduced.

[0094] It should be apparent 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 a heat exchanger system of any complexity. The number of slave systems required depends on the number of required and accessible connection points.

[0095] As can be understood from the above description, the test system 44 of the present invention can accurately measure a flow rate of about several microliters per minute. However, a leakage from a heat exchanger system, such as from a valve in a heat exchanger channel, for example, cannot be distinguished from an internal leakage of the test system 44 itself. For this reason, in many applications, the test system 44 is configured to perform a self-test before, and in some cases after, a integrity test of the heat exchanger. Further, there may be a leakage in the shut-off valves 42a, 42b, 42c, 42d used to isolate the heat exchanger from an industrial process plant in which the heat exchanger is incorporated. If a leakage occurs here, as a result, a flow is observed in the test system.

[0096] Therefore, depending on the application, the test system 44 of the present invention may be configured to perform an additional test regarding the integrity of these shut-off valves 42a, 42b, 42c, 42d. Referring to FIG. 9, a schematic view of heat exchangers 10, 28 having shut-off valves 42a, 42b, 42c, 42d operable to isolate the heat exchangers 10, 28 in preparation for an integrity test is shown. To test the integrity of these valves, test valves 150a, 150b, 150c, 150d are arranged on the opposite side of the shut-off valves 42a, 42b, 42c, 42d from the heat exchangers 10, 28 isolated by the shut-off valves 42a, 42b, 42c, 42d at each input 16, 22 and output 20, 26 lines of both flow paths. Connection points (5), (6), (7), (8) are provided on each line 16, 20, 22, 26 between the shut-off valves 42a, 42b, 42c, 42d and the test valves 150a, 150b, 150c, 150d.

[0097] A test system 144 of the type shown in FIG. 7c is connected to connection points (1) to (8). The master system 146a is arranged to perform a integrity test of the heat exchangers 10, 28 by connecting its channels 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 explain the test procedure in this scenario, for example, consider that the master system 146a detects an outflow from its channel 1 connected to connection points (1) and (2). If there is a leak in the shut-off valve 42b between connection points (2) and (6), a flow to the slave system 146b will occur at connection point (6). This is detected as a flow in the outflow path 54 of the slave channel 1 and is detected by the flow rate sensor F2.1. On the other hand, if there is a leak in the shut-off valve 42a between connection points (1) and (5), the flow enters the slave system 146b at connection point (5). This is detected by the flow rate sensor F1.1 as a flow in the inflow path 52 of the slave system 146b. Therefore, when the master system 146a detects a leak from channel 1, the corresponding inflow test through connection point (5) or (6) can be sequentially performed by opening and closing the valve V4.1 of the slave system 146b. If an inflow through connection point (5) is observed, there is a leak through the shut-off valve 42b, and if an inflow is observed through connection point (6), there is a leak through the shut-off valve 42a. If no flow through the slave system 146b is observed, the leak detected by the master system 146a is due to a defect in the heat exchanger rather than a defect in the shut-off valve. Similarly, the remaining shut-off valves 42c, 42d can be tested as potential causes of the leak from its channel 2 detected by the master system 146a.

[0098] Figure 10 shows a schematic diagram of a heat exchanger 154 of a different design, showing another use of the test apparatus of the present invention. This heat exchanger 154 includes an air conditioning cassette 155 and only one conduit 156 that exchanges thermal energy with the external environment (air). A fan 158 blows air onto the conduit 156 to increase the air flow on the heat exchanger boundary. In this example, the heat exchange fluid is R32 refrigerant gas. This gas constantly changes its state between its liquid and gas phases depending on the pressure applied at a specific stage of the refrigeration cycle. Since R32 may be regarded as a harmful substance in a confined space, it is important to confirm that there is no leakage in the heat exchanger 154.

[0099] In preparing the heat exchanger 154 for a leakage test using the test system 44 according to the present invention, shut-off valves 160a, 160b are installed at the input and output of the conduit 156. Next, connection points (1), (2) of the shut-off valves to the heat exchanger side of the conduit 156 are provided. This is the same preparation required for testing the heat exchangers 10, 28 described above. However, in this application, two additional shut-off valves 162a, 162b are installed at the input and output of the conduit 156, respectively. The additional shut-off valves 162a, 162b are arranged on the opposite side of the shut-off valves 160a, 160b as viewed from the heat exchanger 154. Connection points (3), (4) are provided at the input and output, respectively, between the shut-off valves 160a, 160b and the corresponding additional shut-off valves 162a, 162b of the conduit 156.

[0100] To test this heat exchanger 154, connect channel 1 of the test system 44 to connection points (1) and (2), and connect channel 2 to connection points (3) and (4). First, perform additional pressure monitoring with the pressure sensors G1.2 and G2.2 of channel 2 in accordance with the standard test procedure described above. When the system is pressurized, valves V2.1 and V3.1 of channel 1 are opened to confirm the flow through the flow sensor F1.1 (see Figure 2) and the inflow path 52 of channel 1. If no flow is detected, there is no leakage from the heat exchanger 154. On the other hand, if flow is detected by the flow sensor F1.1, it may indicate that refrigerant gas is leaking from the conduit 156. To verify this, the measured values of the pressure sensors of channel 2 are recorded and compared.

[0101] Next, valves 2.2 and 3.2 of channel 2 are opened, and it is checked whether there is a flow along the outflow path 58 of channel 2. If there is no flow along these paths and the measured values of the pressure sensors in this path do not change, this indicates that the shut-off valves 160a and 160b are sound and no flow from channel 2 along conduit 156 is passing through. Therefore, all the flow observed in channel 1 is the result of leakage through the boundary of the conduit. That is, there is a leakage of the refrigerant gas. On the other hand, if flow is observed by flow sensor F2.2, there is clearly flow through shut-off valves 160a and 160b, which can exist regardless of the presence or absence of flow across the conduit boundary. To characterize the flow observed in the test channel of channel 1, the flow in this path (measured by flow sensor F1.1) is compared with the flow observed in the outflow path of channel 2 using flow sensor F2.2. The measured value of channel 2 represents the flow rate through valves 160a and 160b, and the difference between the measured values of channel 1 and channel 2 (F1.1 - F2.2) is the flow through the boundary. If there is no difference, there is no flow across the boundary. Now, return to the pressure measurement value of channel 2 measured using sensors G1.2 and G2.2 before opening valves V2.2 and V3.2 of channel 2. In this situation, the pressure observed by sensor G1.2 is the result of the inflow through connection point (3) because all other valves in the channel remain closed. Similarly, the pressure observed by sensor G2.2 is the result of the inflow through connection point (4). By comparing these two measured values, the total flow rate through the valves (observed by sensor F2.2) can be assigned to each of the shut-off valves 160a and 160b.

[0102] Another use of the apparatus of the present invention is the detection of air voids. Since the air trapped within the system has a cascading effect on the efficiency of the production system, it is advantageous to detect and remove air voids. When the integrity test is initiated, the heat exchanger paths 38, 40 are filled with fluid up to the initial starting pressure. By monitoring the amount of fluid flowing through the sensor each time the test is initiated, the standard fill volume of the heat exchanger can be determined. In subsequent test sequences, note that if less water volume is required based on the flow rate and the time required to achieve the test conditions, the difference in the water volume may be due to an air gap. Detection of the air gap enables further investigation to be carried out.

Claims

1. A leak test device (44), comprising: A first channel (48) having an inlet path (52) and an outlet path (54) connectable to spatially separated positions within a first conduit (38) for forming a first closed loop system; A second channel (50) having an inlet path (56) and an outlet path (58) connectable to spatially separated positions within a second conduit (40) for forming 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), fluidly communicating with the first channel (48) and the second channel (50), and adapted to pump fluid at a flow rate that actively maintains the pressure within the first closed loop system and the second closed loop system at or near a predetermined level; A first flow sensor (F1.1) disposed in the inlet path (52) of the first channel (48) and a second flow sensor (F1.2) disposed in the inlet path (56) of the second channel (50); A leak test device (44) comprising the above.

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 degree of the proportional valve (P1) in response to a signal received from the pressure sensor (G1) to maintain the pressure within the first closed loop system and the second closed loop system.

3. A first channel proportional valve (P1.1) and a first channel pressure sensor (G3.1) disposed in the inlet path (52) of the first channel (48); A second channel proportional valve (P1.2) and a second channel pressure sensor (G3.2) disposed in the inlet path (54) of the second channel (50); Further comprising: The flow controller is configured to adjust the opening degree 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) to maintain the pressure within the first closed loop system at or near a first predetermined level. The flow controller is further configured to adjust the opening degree 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) to maintain the pressure in the second closed loop system at or near a second predetermined level. The leakage test device (44) according to claim 2, wherein the first predetermined level is different from the second predetermined level, thereby maintaining a pressure difference between the first conduit and the second conduit.

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

5. The leakage test device (44) according to any one of claims 1 to 3, further comprising respective shut-off valves (V2.1, V3.1, V2.2, V3.2) in each inflow path (52, 56) and each outflow path (54, 58).

6. The leakage test device (44) according to any one of claims 1 to 4, wherein the first conduit (38) and the second conduit (40) are a first flow path and a second flow path suitable for heat energy transfer between internal fluids of a heat exchanger.

7. The leakage test device (44) according to any one of claims 1 to 5, wherein the flow controller is a PID controller.

8. The flow controller includes a microcontroller programmed with a PID control algorithm. The flow controller has a first target pressure corresponding to a target pressure to be maintained in the first closed loop system and a second target pressure corresponding to a target pressure to be maintained in the second closed loop system. The control algorithm is as follows: A coarse control part (74) configured to calculate the adjustment in response to a signal received from the pressure sensor (G1) such that the adjustment of the control voltage applied to the pump (M1) and the opening degree of the proportional valve (P1) is 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 when applied to the pump (M1) and the proportional valve (P1). Operates when the maintained pressure in the flow control system is within a predetermined amount from its target value: When the adjustment of the opening degree of the first channel proportional valve (P1.1) is applied to the first channel proportional valve (P1.1), the pressure in the first closed-loop system is maintained within an acceptable range of the first target pressure. In response to the signal received from the first channel pressure sensor (G3.1), the adjustment is calculated, and / or When the adjustment of the opening degree of the second channel proportional valve (P1.2) is applied to the second channel proportional valve (P1.2), the pressure in the second closed-loop system is maintained within an acceptable range of the second target pressure. In response to the signal received from the second channel pressure sensor (G3.2), the adjustment is calculated, and / or Calculate the adjustment of the target value of the rough control part (74) of the PID control algorithm A fine adjustment part (76) configured as The leak test device (44) according to claim 3, comprising

9. The leak test device according to claim 8, wherein each adjustment is calculated using a PID feedback loop.

10. A leak test device (44), comprising: A first channel (48) having an inflow path (52) and an outflow path (54) connectable to spatially separated positions within a conduit (156) to form a first closed-loop system; A second channel (50) having an inflow path (56) and an outflow path (58) connectable to a second pair of spatially separated positions within the conduit (156) to form a second closed-loop system, wherein the second pair of spatially separated positions straddle the first pair of spatially separated positions connectable to the first channel (48). A second channel (50); A flow control system (46) comprising a flow controller in communication with a pump (M1) and a pressure sensor (G1), fluidly communicating with the channel (48), and adapted to pump fluid at a flow rate that actively maintains the pressure within the first closed-loop system and the second closed-loop system at or near a predetermined level; A first flow sensor (F1.1) disposed in the inflow path (52) of the first channel (48) and a second flow sensor (F2.2) disposed in the outflow path (58) of the second channel (50); Comprising The leak test device (44) can detect leakage through a valve that can be arranged in the second closed loop system but not in the first closed loop system, the leak test device (44).

11. The device further comprises a first pressure sensor (G1.2) arranged in the inflow path (56) of the second channel (50) and a second pressure sensor (G2.2) arranged in the outflow path (58) of the second channel (50), the leak test device (44) according to claim 10.

12. A leak test system (144) comprising: A first test device (146a) according to any one of claims 1 to 5, connectable to a first conduit (110a) and a second conduit (110b); A second test device (146b) according to any one of claims 1 to 5, connectable to a third conduit (110c) and a fourth conduit (110d) to form a third closed loop system and a fourth closed loop system; A system management unit (67) configured to provide a first test device (146a) with a predetermined level at which pressure should be maintained in the first closed loop system and the second closed loop system, and to provide a second test device (146b) with a predetermined level at which pressure should be maintained in the third closed loop system and the fourth closed loop system A leak test system including.

13. Each shut-off valve (V2.1, V3.1, V2.2, V3.2) is arranged in each inflow path (52, 56) and each outflow path (54, 58) of each test device (146a, 146b), and the system management unit (67) supplies signals for opening and closing the shut-off valves (V2.1, V3.1, V2.2, V3.2) to the shut-off valves (V2.1, V3.1, V2.2, V3.2) of both test devices in an order according to the leak test to be performed, the leak test system (144) according to claim 12.

14. The system also includes a third test device according to any one of claims 1 to 5, the third test device being arranged in each inflow path (52, 56) and each outflow path (54, 58) and being connectable to a fifth conduit and a sixth conduit to form a fifth closed-loop system and a sixth closed-loop system, and having shut-off valves (V2.1, V3.1, V2.2, V3.2), the system management unit (67) being further configured to provide signals for opening and closing the shut-off valves to the shut-off valves (V2.1, V3.1, V2.2, V3.2) in the third test device in an order according to the leakage test to be performed, the leakage test system (144) according to claim 13.

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

16. A method of testing whether a fluid conduit (156) with a valve is leaking, wherein a first section of the fluid conduit (38, 40) without a valve is connected to an inflow path (52) and an outflow path (54) of a first channel of a leak 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 is connected to an inflow path (56) and an outflow path (58) of a second channel (50) of the leak test device to form a second closed-loop system: 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; c) measuring the fluid flow rate through the inflow path (52) of the first channel (48) using a first flow sensor (F1.1) and measuring the fluid flow rate through the outflow path (58) of the second channel (50) using a second flow sensor (F2.2). A method comprising the above.

17. A method for testing a heat exchanger for leakage between a first fluid conduit (38) and a second fluid conduit (40), wherein said conduits (38, 40) are arranged within said heat exchanger to enable transfer of thermal energy between internal fluids, said method comprising: a) arranging said first fluid conduit (38) in fluid communication with a first channel (48) within a test system (44), said first channel including a first inflow path (52) and a first outflow path (54), whereby said first conduit (38) and said first channel (48) form a first closed-loop system; b) arranging said second fluid conduit (40) in fluid communication with a second channel (50) within said test system (44), said second channel including a second inflow path (56) and a second outflow path (58), whereby said second conduit (40) and said second channel (50) form a second closed-loop system; c) pumping fluid through a flow control system (46) in fluid communication with said first inflow path (52) and said second inflow path (56); d) adjusting a first proportional valve (P1) of said flow control system (46), a second proportional valve (P1.1) of said first inflow path (52), and a third proportional valve (P1.2) of said second inflow path (56) to reach a first predetermined fluid pressure and a second predetermined fluid pressure in respective first channel (48) and second channel (50), wherein said predetermined fluid pressure of said first channel (48) is greater than the fluid pressure of said second channel (50); e) maintaining the pressure within said first channel (48) and said second channel (50) while closing a first shut-off valve (V2.1), a second shut-off valve (V3.1), a third shut-off valve (V2.2), and a fourth shut-off valve (V3.2) in said first inflow path (52), said first outflow path (54), said second inflow path (56), and said second outflow path (58), respectively; f) while continuing to maintain the pressure of said first channel (48) and said second channel (50): i) opening a first shut-off valve (V2.1) and measuring the flow rate of said first inflow path (52) using a first flow sensor (F1.1); ii) opening the fourth shut-off valve (V3.2) and measuring the flow rate of the second inflow path (58) using the second flow sensor (F2.2); iii) observing a flow rate of the first inflow path (52) that exceeds an acceptable level indicates a leak from the first conduit (38), and observing a flow rate of both paths (52, 58) that exceeds the acceptable level indicates a leak between the first conduit (38) and the second conduit (40); A method comprising the steps of: **Claim 18** g) While continuously maintaining the pressures in the first channel (48) and the second channel (50): i) opening the third shut-off valve (V2.1) and measuring the flow rate of the second inflow path (56) using the third flow sensor (F1.2); ii) observing a flow rate of the second inflow path (56) that exceeds an acceptable level is a further step indicating a leak from the first conduit (40); The method according to claim 17, comprising the steps of: **Claim 19** A PID controller adapted to maintain pressure in a hydraulic or pneumatic system, comprising: a flow control system (46) 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); a second closed-loop system in fluid communication with the flow control system and comprising a second channel proportional valve (P1.2) and a second channel pressure sensor (G3.2); A PID controller configured to maintain pressure in a hydraulic or pneumatic system, comprising: The PID controller is configured to apply a variable control voltage to the pump (M1) and adjust the opening degrees of the proportional valve (P1) and the first channel proportional valve (P1.1) and the second channel proportional valve (P1.2); a coarse control portion (74); a fine control portion (76); The PID controller is configured to apply an adjustment of the control voltage applied to the pump (M1) and the opening degree of the proportional valve (P1) in response to a signal received from the pressure sensor (G1), and the adjustment is calculated by the coarse control portion (74) to maintain the pressure in the flow control system (46) at a target value that is a function of a first target pressure and a second target pressure. ​ When the pressure sensor (G1) indicates a pressure value within a predetermined amount from the target value, the PID controller: in response to the signal received from the first channel pressure sensor (G3.1), applies an adjustment to the opening degree of the first channel proportional valve (P1.1), the adjustment being calculated by the micro control part (76) so as to maintain the pressure within the first closed loop system at a value within the tolerance range of the first target pressure, and / or in response to the signal received from the second channel pressure sensor (G3.2), applies an adjustment to the opening degree of the second channel proportional valve (P1.2), the adjustment being calculated by the micro control part (76) so as to maintain the pressure within the second closed loop system at a value within the tolerance range of the second target pressure, and / or adjusts the target value of the coarse control part (74) which is a function of the first target pressure and the second target pressure is configured as such, a PID controller.

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