Method and device for detecting and displaying leakage losses of a compressed air system

Abstract

Leakage losses in compressed air systems are a major cause of energy and therefore financial losses; however, they are often overlooked by system operators. Compressed air systems often have a so-called master control unit that monitors and coordinates the individual compressors. A special operating principle of such a control unit allows leakage losses – including the associated costs – to be continuously monitored and displayed clearly and concisely, without any effort on the part of the compressed air system operator.

Description

[0001] The invention relates to a method and a device for detecting and displaying leakage losses of a compressed air system. State of the art:

[0002] Leakage losses occur more frequently in compressed air systems due to aging and wear. This usually happens at connections and hoses. Leakage losses cause costs and unnecessary energy consumption. According to current best practices, leakage measurements are usually carried out during periods of inactivity, at night, or on weekends when the intended compressed air consumption is close to or equal to zero. (See, for example, DE202008013127U, from Boge, DE202010015450U from Boge, or the "Compressed Air Compendium" from Boge, Hoppenstedt Publishing, 6th edition 2004, section 7.3.2). This assumes that the leakage remains virtually unchanged over time, independent of other consumers. A complementary method is leak detection using suitable measuring instruments to locate leakage losses. This method does not provide a more precise indication of the leakage loss.Methods for leakage monitoring are also described in DE102012010055A (Monitoring of a single component or a compressed air subnetwork, HyPneu 2013) or DE 10 2019 100 788 A (Monitoring of pressure gradients in a compressed air system during compressed air delivery breaks, Wabco, 2020) or DE102007039793 A (Frequency analysis of the pressure signal from a compressed air system, Daimler, 2009).

[0003] The invention is based on the objective of creating a method and / or device for detecting leakage losses in a compressed air system with minimal technical effort, in particular to enable a reliable assessment of the condition of a compressed air system with regard to leakage losses and preferably also to indicate changes over time. Advantageously, an indicator for these leakage losses should also be determined, which allows operators to quickly classify the leakage losses even without in-depth knowledge.

[0004] To solve the problem, the method according to the invention has the features of claim 1. Further advantageous and / or optional features of the invention will become apparent from the further claims and from the description in the remainder of the text. This also applies to the apparatus, computer software, and compressed air system.

[0005] Leakage detection is advantageously performed using a software function on a higher-level control system connected to the compressors of one or more compressed air networks that supply a factory with compressed air. Such a higher-level control system typically includes an electronic data processing unit (EPU), connections for data lines, an internal timer with calendar function, a screen (often called a display today), and control buttons. The compressed air system consists of one or more compressed air networks, i.e., interconnected compressed air lines, compressors, consumers, and usually also storage tanks and compressed air treatment equipment such as dryers and filters.

[0006] The central control system measures the pressure at a point in the compressed air network that is characteristic of the pressure level, controls the individual compressors, and ensures efficient operation of the compressed air system. A characteristic pressure level value is usually found at a central point between compressed air generation and consumption – the pressure there indicates whether the connected consumers are being adequately supplied. The pressure near a critical consumer can also be characteristic. The advantage of implementing the software function on a central control system lies in the availability of all information from the connected compressed air generators, as well as knowledge of the current compressed air consumption. Additionally, by applying compressed air profiles, it is determined when and in what form compressed air is needed, in order to coordinate the timing of leak detection. For example...A consumption profile is given for a production facility that operates from Monday to Friday or Saturday, where operations are suspended on weekends and no compressed air is required.

[0007] Leakage detection is preferably based on the aforementioned information, not linked to a fixed time after activation, but rather to profiles that define periods of inactivity (i.e., time without production and no intended compressed air demand), or periods without compressed air demand (where only production without compressed air takes place). These periods must be defined by the user, and leakage detection must be parameterized as "possible" for these profiles. Such a profile has the advantage of covering the most common scenarios with minimal setup effort during commissioning.

[0008] For compressed air systems that do not allow the use of such a profile, for example, due to a lack of operational downtime, it is possible to connect to a data processing system operated by the production plant. In this case, the information that must be provided to the higher-level control system is a collected feedback from the consumers indicating that there is currently no demand for compressed air. This feedback signals to the higher-level control system that leak detection is fundamentally possible. This signal can be provided via a digital contact or a data protocol such as Modbus TCP, OPC UA, or similar. The advantage of this approach is that even without a profile, the times favorable for leakage measurement are recorded.

[0009] Alternatively, there is the option of trend monitoring of compressed air consumption. This trend monitoring considers a typical compressed air consumption pattern for unused / inactive compressed air generators and continuously compares the characteristics of these patterns to determine time periods for leak detection or to define characteristics that enable leak detection. For example, a typical compressed air consumption pattern for unused compressed air generators is a consistently low value, resulting in a slowly decreasing pressure.

[0010] For specific system configurations, it may be advantageous to deviate from these methods and link leak detection to an adjustable minimum consumption level. If compressed air consumption is below this limit, there is presumably no intended demand from a compressed air consumer, and therefore, during this period, compressed air demand exists solely due to leakage – which can then be detected.

[0011] The leakage is now recorded and tracked successively, for example, linked to these profiles. This results in an average leakage value over time, as well as information on the progression of the recorded leakage over each week of the past year. The operator is thus able to assess their system over a period of time with regard to leakage. In addition, the operator can quickly access the status of their system via a leakage indicator on the dashboard or in the chart area. These thresholds for the leakage indicator (red, yellow, or green) can be freely defined, or the predefined thresholds in this registration can be used.Dashboard, literally translated as "instrument panel like in a car," is a term that has become popular in computer technology in recent years. It illustrates that, just as the most important readings for the driver (speed, coolant temperature, and warning lights for low oil pressure, etc.) are displayed together on a single screen, the most important status data is clearly presented. The advantage lies in the clear, easy-to-understand display of the leakage status for the compressed air system operator.

[0012] Leakage losses in compressed air systems are a major cause of energy and therefore financial losses; however, they are often overlooked by system operators. Compressed air systems often have a so-called master control unit that monitors and coordinates the individual compressors. A special operating principle of such a control unit allows leakage losses – including the associated costs – to be continuously detected and displayed clearly and concisely, without any effort on the part of the compressed air system operator.

[0013] The preferred working method is exemplified by the images of Fig. 1 to 3 explained: Fig. Figure 1 shows a typical compressed air system with compressors K1 to K3, connecting compressed air lines (represented as thick lines "Compressed Air-L"), consumers V1 to V3, a compressed air dryer T, a compressed air storage tank SB, and an example leak L at a hose connection to consumer V2. A characteristic pressure is measured by the pressure gauge M at the interface between compressed air generation and consumption. A data processing unit DV records the respective states via electrical lines (Data-L); it can simultaneously act as a higher-level control system for the compressed air system and includes a precise clock and date function.

[0014] The compressed air supplied to the compressed air system is determined from the compressors' delivery rates (their catalog values ​​can be used for simplicity). To determine the current compressed air consumption, it should be taken into account that the compressed air storage tank (SB) stores or releases compressed air in response to pressure changes (the internal volume of the compressed air network, essentially determined by the volume of the storage tank, must be entered by the user during commissioning; the pressure of the compressed air in this volume can fluctuate, thus storing air mass and dampening pressure fluctuations). From this, the data processing unit (DV) calculates the compressed air consumption trend over a week. Fig. 2. With a typical consumption profile, there are peak consumption on weekdays in the morning and afternoon, while on weekends there is no operation and consumption is very low. If there is any intended compressed air requirement at all, then consumption is negligible, for example, by a pneumatic smoke extraction ceiling window control system, accounting for less than 2% of the compressor's total delivery capacity.

[0015] If there is no intended compressed air consumption by the consumers, the consumption is determined via the leakage L. With such a standard consumption profile, the consumption can be determined weekly during a time interval ZI without intended compressed air consumption, thus providing a measure of the leakage. There are special cases where a small continuous consumer, such as a measuring machine with aerostatic bearings (or the aforementioned ceiling window control), also consumes compressed air during this interval. This should then be subtracted from the determined air consumption. The data processing unit allows the input of this consumption so that, for example, the determined leakage costs are adjusted for this continuous consumption.

[0016] A simple and clear representation of the leakage provides Fig. Figure 3. This is how the display appears on the screen of the higher-level control system when the "Leakage" item is accessed. Here, the weekly leakage values ​​for each of the last calendar weeks ("CW") are plotted sequentially. The bar chart is particularly clear. The increase in the leakage value from CW 5 to CW 12 is easily recognizable. This corresponds to the trend in compressed air systems that leaks develop and slowly increase over time – for example, because a porous area on a hose becomes more porous due to aging. The value for CW 8 can be identified as an outlier, and the operator of the compressed air system might recall – oh, we had an extra shift on Sunday with a high demand for compressed air. This weekly display, as a diagram for the leakage over the last four or more weeks, illustrates – unlike the previously common displays – that the leakage changes over time, and in most cases, increases.This overall representation also includes a traffic light with the colors red, yellow and green (from top to bottom).

[0017] The red indicator then displays a leakage value – determined in the last time interval (ZI) – which, extrapolated to a week and divided by the total compressed air consumption for the week, exceeds 20%. It may be more advantageous to use a threshold value of 18% of the total compressed air consumption for the week + 1% of the total compressor output capacity (= total compressed air volume of all compressors * 168 hours of the week), as this is because experience has shown that in large compressed air networks with many compressors and simultaneously low consumption – due to, for example, short-time work – the threshold for an unreasonably high leakage level needs to be set higher.

[0018] Below a leakage threshold of 12% of the total compressed air consumption, the green light is highlighted; at values ​​in between, the yellow light is highlighted. Highlighting a color can be achieved by making the corresponding round area glow brightly in that color, while the other two areas remain off, or they are gray, or the other colors are only present in pastel shades, or as in the... Fig. 3 by using radial rings around a surface.

[0019] A display in euros showing the annual electricity costs caused solely by leakage makes the issue even more tangible. This facilitates the decision that it's worthwhile to take action against the leak. A small traffic light indicator for the leakage status can also appear on the main display of the higher-level control system, which shows the most important values, or on an individual dashboard. This ensures that the operator of the compressed air system keeps track of the often little-known leakage losses. The leakage indicator, as well as the aforementioned evaluation and display of key performance indicators, can be specific to a single compressed air network, but can also provide information about all compressed air networks and thus the entire compressed air system. The main display refers to the screen display that appears after switching on and, if necessary,a login screen appears, and from which you can switch to other displays - connection status, individual machine displays, hour counters and maintenance warnings, priority settings, etc.

[0020] To put the leakage indicator into operation immediately after installation, without the operator having to read the manual or make any entries, default values ​​corresponding to a typical compressed air system are programmed in. The operator only needs to change these values ​​in the event of deviations from the typical situation: for example, electricity price €0.2 / kWh; threshold above which the indicator shows "red": 18% of the total weekly compressed air consumption + 1% of the total compressor output capacity; threshold below which the indicator shows "green": 12% of the total weekly compressed air consumption, with "yellow" in between; leakage measurement in a 2-hour interval on Sundays from 2 to 4 a.m.; a new reading is provided every Monday; the graph displays the leakage trend over the past weeks (according to... Fig.3) This includes the previous 55 calendar weeks (but the number of 4 weeks – corresponding to approximately one month, 30 weeks – corresponding to half a year, or 110 weeks – corresponding to 2 years – as typical time periods in which leakage remediation is considered would also be advantageous). The linking to the system profile should ideally be carried out during initial commissioning, defining which profiles will be used and which of these profiles allow for leakage measurement.

[0021] The application of a leak detection system is not limited to the method of determining leakage using compressor run times during periods of low or no intended compressed air consumption. Other methods can also be used, such as determining a characteristic pressure drop rate, as described in DE202008013127U, paragraphs 50 to 57. Further methods arise from new pattern recognition techniques, such as those being developed under the heading of "artificial intelligence." These techniques can infer from significant changes in compressed air demand that compressed air consumers are being switched on and off—while the leakage remains almost constant—and from periods of consistently low compressed air demand, inferences can be drawn about periods of inactivity.From many measured compressed air consumption curves, in which the times without intended compressed air consumption are known, pattern recognition software can then determine the characteristics for such times without intended compressed air consumption - possibly even without these characteristics being mathematically formulated, but via artificial neural networks.

[0022] Based on information indicating that no intended compressed air consumption is present, either according to a compressed air consumption profile or based on reports from users, an action can be taken. For example, during such periods without intended compressed air consumption, the compressed air system is temporarily shut down, the pressure can drop significantly below the operating setpoint, and leakage losses are reduced. Before the end of the period without intended consumption, as determined by the compressed air consumption profile, or after reports from users indicating a need for compressed air, the compressed air system is restarted and the pressure is increased to the setpoint.

[0023] For example, if a compressed air consumption profile indicates no anticipated demand from Friday at 8 p.m. to Monday at 5 a.m., the compressed air system can be shut down from Friday at 8 p.m. to Monday at 4 a.m. The time required to refill the compressed air network before the start of anticipated consumption can be set between 10 and 100 minutes, depending on the system's internal volume. A slow refill can facilitate the compressed air treatment process (drying and filtration). A sensible exception to this rule is when leakage losses are very low, less than, for example, 5% of the generated compressed air (this threshold should be adjustable between 1% and 15%). In such cases, weekend shutdown is not worthwhile and should be omitted.

[0024] It should be noted that the leak detection methods described here are not successful in compressed air systems with a continuous compressed air demand throughout the week, especially if this demand fluctuates slowly. However, this only applies to a small proportion of existing compressed air systems.

[0025] The clear advantage of this invention is this: Those responsible for compressed air systems in factories regularly have other, more important tasks; they are rarely trained in compressed air systems and have little time for them. The often considerable costs of leakage are not something they consider.

[0026] According to the current state of the art, the operator of a compressed air system can evaluate the compressed air consumption curves (determined as standard in higher-level control systems) with a calculation regarding leakage - he searches the curves for the operating idle times and determines the leakage, which even with experience takes him about a quarter of an hour per evaluation, would be due every few weeks and is therefore hardly ever done.

[0027] Another state-of-the-art method allows the control system to be instructed before a shutdown to record and display the consumption for the next few hours, which will then consist of leakage – this, too, is rarely done. It is also possible to define weekly observation periods via certain control system settings, after which the leakage values ​​can be read in a submenu. This requires carefully reading the operating instructions beforehand and configuring the control system – but hardly any compressed air manager is willing to invest the additional time of about an hour when commissioning a new, higher-level control system. The leakage remains undetected and is not rectified.

[0028] With the present invention, however, a compressed air consumption profile can be entered during commissioning in the vast majority of cases – requiring an additional minute – and the control system then has, for example, the information "There is a period of inactivity on weekends, so leakage can be detected." Alternatively, a pattern recognition function for the compressed air consumption curve can be set during commissioning, which then determines the periods of inactivity – it remains to be seen in practical application which method will be better received by the customer. Both methods require less than a minute of installation time. And with both methods, after commissioning, the higher-level control system automatically records the leakage weekly and displays it in easily understandable values ​​via a traffic light indicator, and / or weekly diagram, and / or as a monetary value of the leakage losses.Then the person responsible for the compressed air system can no longer overlook these values ​​and will also be shown when they should do something about leaks. Reference symbol list as part of the description: K1 to K3 compressors 1 to 3 Compressed air line Data line IT data processing T dryer for compressed air SB compressed air storage tank M Manometer for the pressure of the compressed air V1 to V3 L L Leakage Mon Tue Wed Days of a week Week 5 Week 6 Calendar weeks of the current year QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 202008013127U [0002, 0021] DE 202010015450U

[0002] DE 102012010055A

[0002] DE 10 2019 100 788 A

[0002] DE 102007039793 A

[0002] Cited non-patent literature

[0000] Boge Company or the “Compressed Air Compendium” by Boge Company, Hoppenstedt Publishing House, 6th edition 2004

[0002]

Claims

[1] Method for detecting leakage losses in a compressed air system with one or more compressed air sources, preferably compressors (K1, K2, K3...), whose running times are known to a data processing device (DV) in this compressed air system, whereby an evaluation of the leakage is derived from the running times in periods with no, or insignificant, intended compressed air consumption as a diagram for the last 4 or more weeks, preferably as a bar chart, and / or as a traffic light display. [2] Method according to claim 1, wherein the periods with no or insignificant intended compressed air consumption are taken from a weekly compressed air profile in which periods of regular downtime are recorded. [3] Method according to claim 1, wherein in addition to the running times of the compressed air sources, the pressure curve at one or more characteristic points of the compressed air system and the internal volume of the compressed air system are used to determine the instantaneous compressed air consumption. [4] Method according to one of the preceding claims, wherein the consumption value of continuous consumers operating even during non-operational periods can be deducted from the determined instantaneous compressed air consumption in order to obtain the leakage. [5] Method according to one of the preceding claims, wherein a diagram is output as a characteristic value for the leakage over the course of the last 4 or more weeks, in which the determined leakage value is listed in chronological order for each of the weeks. [6] Method according to one of the preceding claims, wherein a traffic light display appears as a characteristic value for the leakage, which preferably highlights a red light if the leakage value for the last week is more than 20% of the total compressed air generated during this time, a green light if the leakage value is preferably less than 12% and a yellow light if the leakage value is in between. [7] Method for recording leakage losses in a compressed air system over several weeks, in particular according to one of the preceding claims, where on the screen of the higher-level control system - which records at least the running times and estimated delivery quantities of the compressors in the compressed air system, controls the compressors and includes data processing - preferably after calling up the item leakage, at least 2 of the 3 features - a diagram of the leakage over the last few weeks, preferably as a bar chart - a traffic light indicator for the leakage level and - a cost value for the leak, preferably as an annual sum of money, should be displayed at the same time. [8] Method for recording the leakage losses in a compressed air system, which are preferably determined according to one of the preceding claims, wherein on the main display screen, or a collective display of the most important system values, recently often called a "dashboard", on a control system superordinate to the compressor system - which at least records the running times and estimated delivery quantities of the compressors in the compressed air system, controls the compressors and includes data processing - a traffic light display with the values ​​"red", "yellow" and "green" shows the evaluation of the leakage loss level. [9] Method according to one of the preceding claims, wherein the period of leakage detection is not linked to a profile, but to an active feedback of the compressed air consumers by means of a data interface or digital contact. [10] Method for recording leakage losses in a compressed air system, whereby the period of leakage detection is not linked to a profile, but to an observation of the compressed air consumption, which takes into account a typical course of compressed air consumption for non-requested / running compressed air generators and continuously compares the characteristics of these courses in order to determine periods for a leakage detection or to define characteristics that enable a leakage detection. [11] Method for detecting leakage losses in a compressed air system, whereby the period of leakage detection is not linked to a profile, but to an adjustable minimum consumption - according to the rule that if the compressed air consumption is below this limit, there is no intended demand from a compressed air consumer, but only leakage air consumption. [12] Method for recording leakage losses in a compressed air system, whereby a compressed air consumption profile is determined from the temporal course of the compressed air consumption over several weeks by means of pattern recognition methods, in which times without intended compressed air consumption can be recognized, in which the existing consumption can then be understood as a leak and evaluated. [13] Method in which, in particular by means of one of the methods described in the preceding claims, periods without intended consumption are determined and then, in the following weeks, the production of compressed air is suspended during these periods - this corresponds to a compressor shutdown to avoid leakage. [14] Method according to claim 13, in which the compressed air production is restarted between 10 and 100 minutes before the start of new compressed air consumption. [15] Method according to claim 13 or 14, wherein the compressor is switched off during periods without intended compressed air consumption only if the determined leakage losses are above a threshold value of 1 to 15%, preferably 5%, of the compressed air produced. [16] Computer software for carrying out the method according to one of claims 1 to 15. [17] Device, in particular control, with software according to claim 16. [18] Device according to claim 17, comprising - Data lines to the compressed air sources of a compressed air system and to at least one pressure measuring device M of a compressed air system, - an electronic data processing system, - a screen display for the leak status, which includes either a traffic light display, and / or a graph display for at least the last 4 weeks, and / or a cost value for the leak. [19] Compressed air system, containing a device according to claim 17, Compressed air sources, especially compressors (K1, K2, K3 ...), Compressed air consumers (V1, V2, V3 ...), Compressed air lines that connect the compressed air sources with the compressed air consumers.

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