WO2009127879A2

WO2009127879A2 - Improvements in and relating to steam wastage measurement and management

Info

Publication number: WO2009127879A2
Application number: PCT/GB2009/050386
Authority: WO
Inventors: Ashley Elkins; Ian Thomas Harvey
Original assignee: Hydralogica Ip Limited
Priority date: 2008-04-17
Filing date: 2009-04-17
Publication date: 2009-10-22
Also published as: GB0823318D0; GB2459319A; GB0807000D0; WO2009127879A3

Abstract

An apparatus for detecting leakage of steam within a steam operating system, the apparatus comprising detection means (4, 6) operable to detect vibrational signals from a region of a steam operating system (1) such as a steam trap (2, 3), indicative of steam leakage, and comparison means (5) for comparing the vibrational signals detected by the detection means in the region to vibrational signals previously measured or calculated indicative of leakage of steam from a control region indicative of a known quantity of steam leakage, to thereafter indicate an actual or calculated quantity of steam leakage at the region being tested without reference to temperature or pressure of the steam. A method of detecting the amount of steam leaking in a steam operating system (1) which method includes the steps of measuring or calculating a plurality of vibrational signals indicative of a given quantity ofsteam leakage in a plurality of regions or apparatuses, such as a plurality of different makes and models of steam traps (2, 3), for the steam operating system under test, and storing the indicative signals for subsequent access, measuring or calculating actual vibrational signals indicative of steam leakage at a chosen region in the steam operating system, such as at or near a steam trap, and comparing the signals obtained with the corresponding stored signals, and thereafter calculating actual steam loss in that region of the steam operating system without reference to temperature or pressure of the steam.

Description

Improvements in and relating to steam wastage measurement and management

This invention relates to improved steam wastage measurement and management in industrial plant, with the object of suggesting the most efficient steam plant maintenance programmes so as to reduce losses and overall energy consumption.

It is well known to survey steam generating and steam operating systems used in industrial plant to estimate steam losses. Steam traps are provided in order to discharge condensate, air and other incondensable gases from a steam system while not permitting the escape of live steam. The need to prevent or inhibit the escape of live steam is a consequence of the relatively high cost of steam under pressure which is used in all kinds of industry, ranging from direct electrical power production to manufacture of products. In all such systems the steam traps themselves are prone to failure and where such failure is other than catastrophic it can result in small but nevertheless significant losses of steam from the system. This may be caused by steam traps which are inherently faulty i.e. from when they were manufactured to steam traps which become faulty over time. In either event, detection of leaks has traditionally been achieved by measuring a perceived rate of loss of steam, such as by use of the computerised steam trap management system described in US patent 4898022 which, effectively, provides a means of assessing the scale of leakage from 1 to 15, with 15 being the most acute and 1 being the most benign. However, a problem with such steam leakage detection systems is that whilst they can indicate a level of seriousness in terms of leakage they are unable to quantify the amount of leakage and therefore the relative importance of curing the leak to the overall efficiency of the steam system. In addition, it is clear from this prior art disclosure and the disclosures of US5136876, US5719785, US2001 /0005138A1 and EP0892326 that the analysis of the vibrations detected and subsequent comparison with previously obtained test data traditionally uses simple signal processing methods (such as simple energy thresholding) and requires the use of temperature sensors to assess the steam leakage. These methods provide minimal protection against extraneous noise from what is an inherently noisy environment e.g. a steam operating plant. Even in cases where more complex frequency domain analysis is performed i.e. using traditional Fast Fourier Transform (FFT) methods, not only are these methods computationally intensive, requiring correspondingly high power levels, they also do not provide inherent protection against extraneous impact-type events. When analyzing using frequency domain methods, these extraneous impact events can cover a large proportion of the frequency spectra which can negatively affect the accuracy of the steam wastage estimation being produced. The prior art also requires measurement of temperature and hence pressure to estimate the quantity of steam leakage.

According to a first aspect of the invention, there is provided apparatus for detecting leakage of steam within a steam operating system, the apparatus comprising detection means operable to detect vibrational signals from a region of a steam operating system, such as a steam trap, indicative of steam leakage, and comparison means for comparing the vibrational signals detected by the detection means in the region to vibrational signals previously measured or calculated indicative of leakage of steam from a control region indicative of a known quantity of steam leakage, to thereafter indicate an actual or calculated quantity of steam leakage at the region being tested without reference to temperature or pressure of the steam.

Conveniently, the comparison means includes a look-up table of known vibrations measured or calculated at a region of a corresponding steam operating system, such as a steam trap, and an algorithm by which the actual steam wastage in mass per unit time can be calculated to thereafter indicate the actual level of leakage at the region under test.

The comparison means may be incorporated with the detection means at the region of the steam operating system under test, or may be calculated remotely, such as by a PDA after the PDA has recorded vibrational signals from the region under test and analysed them, or via a fixed installation, which may be wired or wireless, which continuously monitors one or more detection means situated at required points around the steam operating system.

According to a second aspect of the invention, there is provided a method of detecting the amount of steam leaking in a steam operating system, which method includes the steps of measuring or calculating a plurality of vibrational signals indicative of a given quantity of steam leakage in a plurality of regions or apparatuses, such as a plurality of different makes and models of steam traps, for the steam operating system under test, and storing the indicative signals for subsequent access, measuring or calculating actual vibrational signals indicative of steam leakage at a chosen region in the steam operating system, such as at or near a steam trap, and comparing the signals obtained with the corresponding stored signals, and thereafter calculating actual steam loss in that region of the steam operating system without reference to temperature or pressure of the steam.

Preferably, the detected vibrational signals are compared with previously measured or calculated signals indicative of leakage of steam from a control region by the use of Time Encoded Signal Processing and Recognition (TESPAR) techniques of the type described in our patent EP 0882288B, the disclosure of which is incorporated herein by reference. However, it will be understood that other calculation and analysis techniques may be used if preferred.

According to a third aspect of the invention, there is provided apparatus for detecting, measuring and displaying the amount of leakage of steam within a steam operating system in real time, the apparatus comprising or including in combination a comparison means and a detection means, said detection means being operable to detect vibrational signals from a region of a steam operating system under test, such as a steam trap, indicative of actual steam leakage, the comparison means including a look-up table indicative of known vibrations previously measured or calculated at a region of a corresponding steam operating system, such as a corresponding steam trap forming part of a test rig, in which the vibrations have been analysed and interpreted using Time Encoded Signal Processing and Recognition (TESPAR), the detection means carrying out, in use, corresponding TESPAR analysis of the detected vibrational signals to thereafter indicate an actual quantity of steam leakage in the region being tested following comparison with identical or similar data in the look-up table. Conveniently, the apparatus is further characterised in that the detection means, in use, is operable to carry out TESPAR analysis of vibrational signals detected by said detection means to subtract therefrom signals caused by extraneous noise not associated with steam leakage by the use of TESPAR- based analysis of the vibrational signals being detected. By analyzing the same signal in the time domain using TESPAR, these extraneous impact events cover only a fraction of the TESPAR components produced for the signal under investigation and therefore have a negligible impact on the final assessment. Moreover, due to these impact events covering very few TESPAR components, they can be easily removed from the analysis.

The comparison means may be incorporated with the detection means for use at the region of the steam operating system under test, or via a fixed installation, which may be wired or wireless, which continuously monitors one or more detection means situated at required points around the steam operating system.

According to a fourth aspect of the invention, there is provided a method of detecting the amount of steam leaking in a steam operating system, which method includes the steps of measuring or calculating a plurality of vibrational signals indicative of a given quantity of steam leakage in a plurality of regions or apparatuses, such as a plurality of different makes and models of steam traps, for the steam operating system under test, analysing the plurality of vibrational signals and interpreting them using Time Encoded Signal Processing and Recognition (TESPAR) and storing the steam leakage indicative signals in a look-up table for subsequent access, measuring or calculating actual vibrational signals indicative of steam leakage at a chosen region in the steam operating system, such as at or near a steam trap, analysing and interpreting the actual vibrational signals using TESPAR and comparing the signals obtained with the corresponding stored signals in the look-up table, and thereafter calculating and displaying actual steam loss in that region of the steam operating system.

Preferably, the method also includes the steps of subtracting by TESPAR analysis extraneous noise forming part of the detected vibrational signals and comparing the remaining data with the data from the look-up table to thereafter calculate actual steam loss without being adversely affected by extraneous noise.

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

Figure 1 is a schematic outline of leakage detection apparatus being used in part of a steam operating system, and

Figure 2 is a schematic block diagram showing the method of operation of the apparatus shown in Figure 1.

Turning firstly to Figure 1 , there is schematically shown part of a steam operating system which includes steam pipe 1 and conventional steam traps 2,3 being tested. Steam trap 2 is being tested for steam leakage by means of a portable steam trap monitor shown generally at 4 which, during the test, communicates with a PDA-type device 5, in a manner to be described, and steam trap 3 is being tested by a permanently installed steam trap monitor shown generally at 6.

The portable steam monitor 4 has at its tapered end 7 an integral ultrasonic microphone (not shown) which, by being placed a short distance from steam trap 2, such as between 50mm and 250mm, can therefore detect ultrasonic vibrations in the pipe 1 indicative of steam passing through or out of the steam trap 2, whereafter the steam wastage result generated by the portable steam trap monitor 4 can be transferred to and between the portable PDA device 5 via a suitable radio link, such as a Bluetooth link.

Similarly, it will be seen that the permanently installed steam trap monitor 6 includes a collar 8 by which it is permanently affixed to the pipe 1 at a suitable distance downstream from the steam trap 3 and includes at its lower end a narrow stem portion 9 on the end of which adjacent to the pipe 1 is a vibration detector in the form of an ultrasonic microphone (not shown), producing vibration detection signals, which signals are processed by the permanently affixed device that sends the steam wastage result to the portable PDA device 5 via a radio link. It will, of course, be understood that other types of communication links may be used with both the portable and permanently installed steam trap monitors 4,6 and the PDA type device 5 may even be wholly incorporated within the portable steam trap monitor 4 or the permanently fixed monitor 6.

Turning now to Figure 2 there is shown a block diagram of a suitable system for detecting, measuring and displaying steam leakage by means of the apparatus shown in Figure 1 and carrying out the method of the invention in its second aspect. The block diagram is more suited to the system requirements for the portable steam trap monitor 4 although its basic operation is essentially the same as for the permanently installed steam trap monitor 6 in this particular embodiment of the invention. A micro controller 10 is the main controller for the steam trap monitor 4 and is powered by a battery 11 which can be recharged via a charging connector 12, the battery voltage being regulated by a switched mode monitor and regulation circuit 13 which provides suitable rail voltages for the electronics and other components of the monitor 4. Circuitry is provided to and from the various parts of the monitor 4, which includes an LCD display 14, up switch 15, down switch 16, power/select switch 17 and trigger 18. The micro controller 10 is also connected via a Heterodyne circuit 19 to a vibration sensor in the form of an ultra-sonic microphone 20 close-coupled to the tip of the tapered lower end 7 (shown in Figure 1 ) of the portable monitor 4 such that when it is placed against the steam pipe 1 in the position shown it can 'listen' to the steam trap 2 and, in a manner to be described below, the portable monitor 4 can interface with the PDA-type device 5 for the purposes of monitoring and calculating steam wastage for display on the PDA-type device, or remotely if the data is collected and stored e.g. electronically on a machine-readable card.

An audio output circuit 21 provides a link to an audio headphone 22 and is provided with a gain switch having discrete volume steps allowing a listener to hear a lower frequency output of an originally ultra-sonic input signal received by the ultra-sonic microphone 20.

In order to connect to a device such as the PDA-type device 5 a radio interface 23 is provided and, where a hard wired connection is required, such as via a USB port, a serial interface 24 is connected to a data connector 25 for transmitting data measured, analysed and calculated by the micro-controller software. The micro controller 10 includes a data memory log 26, which may be FLASH memory, application software 27 for controlling the various functions of the monitor 4 and TESPAR (Time Encoded Signal Processing And Recognition) software 28 for analysing Heterodyne signals from the Heterodyne circuit 19 for the subsequent generation of test results which can be stored in the data log 26 or transmitted via the radio interface 23 or serial interface 24 to a PDA device 5 or some other suitable device. The PDA 5 (or other suitable device) stores all known data about trap type, trap model, trap size etc and this information is selectively downloaded by the monitor when a test is to be carried out.

However, as indicated previously, the PDA device 5 may operate to simply receive vibrational signals, such as analogue signals, from the steam trap monitors 4, 6, and thereafter carry out the calculation and analysis of the signals and comparison with signals previously measured or calculated indicative of leakage of steam from a control region in the form of a look-up table which can then be used to indicate an actual or calculated quantity of steam leakage at the region being tested. Similarly, the PDA type of approach, which is effectively the same as carrying out a survey of the steam leakage around the steam operating system and thereafter deciding whether the results warrant the closing down of the system for repairs, may be replaced with a permanently installed monitoring system in which a fixed installation continually monitors, by wired or wireless connection, a number of steam leak detection devices which detect vibrational signals from e.g. steam traps around the steam operating signal so as to provide a continuous assessment of steam plant efficiency, thereby permitting an overall assessment to be made as to when to close down the steam operating system most economically.

In accordance with this method of carrying out the invention the steps include receiving an ultra-sonic signal from the microphone 20, collected on the steam trap 2,3 under test, or on the pipe 1 directly surrounding the steam trap, and interpreting the said signal using the advanced signal processing technique TESPAR via the TESPAR software 28.

Time Encoded Signal Processing and Recognition (TESPAR) is a known collection of signal analysis, recognition and classification techniques that can be universally applied to describing and classifying complex band-limited signals as can be seen from our patent EP0882288B, the disclosure of which is incorporated herein by reference. It makes use of a precise mathematical description of waveforms, based on polynomial theory, and the location of the zeros of "entire functions".

Two key advantages of the TESPAR-based approach to signal analysis according to the invention are, firstly, their robust classification capabilities in high noise environments and, secondly, their low memory and power requirements. These factors make TESPAR ideally suited for implementation on real-time embedded platforms and smart sensors that incorporate fixed-point microprocessors and digtial signal processors (DSPs). This may be contrasted with prior art apparatus and methods which rely upon arithmetical analysis of frequency data which necessarily includes extraneous noise and therefore imposes an upper limit on the accuracy obtainable, whereas in accordance with the invention in both its aspects it is also possible to subtract from the actual vibrational signals measured at a chosen region in e.g. a steam operating system those which are due to extraneous noise, thereby improving the accuracy of the resulting data signature before it is compared to pre-determined data in the look-up table to subsequently produce an end result more accurately reflective of actual steam wastage from e.g. a steam trap in situ.

The method of converting the ultrasonic signal into the actual steam wastage estimations involves essentially two stages - the first stage being an initial data acquisition stage that processes a representative amount of data to create a look-up table of unique data signatures; the second stage being a localised real-time detection of vibrational signals indicative of steam leakage followed by comparison and analysis that compares the previously stored unique data signatures from a selected part of a look-up table with the data signature obtained during a test.

For these purposes, it is assumed that a unique data signature will be produced for each trap type, such that when a trap type is to be tested, the appropriate reference data signature from the look-up table is used to generate the steam wastage assessment. Although this description assumes one data signature is associated with each trap type, the invention covers all scenarios where data signatures are produced using any combination of steam related characteristics. Examples of these characteristics include, but are not limited to, steam trap type, manufacturer, model, pressure, condensate load and pipe size, all of which may contribute to a unique data signature for insertion into the lookup table.

A preferred mode of carrying out the invention is to generate each unique data signature using the steam related characteristics of trap type or of trap type manufacturer and model, i.e. for each combination of trap type, manufacturer and model that exists, and a unique data signature for each combination is therefore generated and stored in the look-up table.

In order to produce the data signatures for the initial data acquisition stage, it is necessary to have available a certified steam wastage test rig that allows the different operating conditions to be set (such as pressure, condensate load, pipe size etc), along with an ultra-sonic sensor and accompanying data collection software. This equipment allows the ultra-sonic signal for each steam trap to be recorded whilst the steam trap is being tested to determine the amount of steam it is wasting over time.

The invention therefore provides a means whereby the actual quantity in terms of kilograms per hour of steam wastage is calculated, which is superior to the prior art techniques of producing an arbitrary scale, such as from 1 -15, indicative of the seriousness of a leak within a steam operating system. This invention, by calculating or measuring the actual level of steam wastage this can be used to assess when it is most economical to shut down the steam system for repair or replacement of parts, including steam traps which are or have become faulty.

Although specific embodiments and methods of the invention have been described, it will be understood that the invention is intended to include alternative embodiments and methods.

Claims

1. Apparatus for detecting leakage of steam within a steam operating system, the apparatus comprising detection means (4, 6) operable to detect vibrational signals from a region of a steam operating system (1 ), such as a steam trap (2, 3), indicative of steam leakage, and comparison means (5) for comparing the vibrational signals detected by the detection means in the region to vibrational signals previously measured or calculated indicative of leakage of steam from a control region indicative of a known quantity of steam leakage, to thereafter indicate an actual or calculated quantity of steam leakage at the region being tested without reference to temperature or pressure of the steam.

2. Apparatus according to claim 1 in which the comparison means includes a look-up table of known vibrations measured or calculated at a region of a corresponding steam operating system, such as a steam trap, and an algorithm by which the actual steam wastage in mass per unit time can be calculated to thereafter indicate the actual level of leakage at the region under test.

3. Apparatus according to claim 1 or claim 2 in which the detected signals are analysed and interpreted using Time Encoded Signal Processing And Recognition (TESPAR) software.

4. Apparatus according to any preceding claim in which the comparison means is incorporated with the detection means for use at the region of the steam operating system under test.

5. Apparatus according to any one of claims 1 to 3 in which the comparison means is remote from the detection means, such as being incorporated in a PDA.

6. Apparatus according to any one of claims 1 to 3 in which the comparison means are stored within a fixed installation which continuously monitors one or more fixed or moveable detection means situated around the steam operating system being monitored.

7. A method of detecting the amount of steam leaking in a steam operating system (1 ), which method includes the steps of measuring or calculating a plurality of vibrational signals indicative of a given quantity of steam leakage in a plurality of regions or apparatuses, such as a plurality of different makes and models of steam traps (2, 3), for the steam operating system under test, and storing the indicative signals for subsequent access, measuring or calculating actual vibrational signals indicative of steam leakage at a chosen region in the steam operating system, such as at or near a steam trap, and comparing the signals obtained with the corresponding stored signals, and thereafter calculating actual steam loss in that region of the steam operating system without reference to temperature or pressure of the steam.

8. A method according to claim 7 in which the detected signals are analysed and interpreted using Time Encoded Signal Processing And Recognition (TESPAR) software.

9. Apparatus for detecting, measuring and displaying the amount of leakage of steam within a steam operating system in real time, the apparatus comprising or including in combination a comparison means and a detection means (4, 5, 6), said detection means being operable to detect vibrational signals from a region of a steam operating system under test, such as a steam trap (2, 3), indicative of actual steam leakage, the comparison means including a look-up table indicative of known vibrations previously measured or calculated at a region of a corresponding steam operating system, such as a corresponding steam trap forming part of a test rig, in which the vibrations have been analysed and interpreted using Time Encoded Signal Processing and Recognition (TESPAR), the detection means carrying out, in use, corresponding TESPAR analysis of the detected vibrational signals to thereafter indicate an actual quantity of steam leakage in the region being tested following comparison with identical or similar data in the look-up table

10. Apparatus according to claim 9 further characterised in that the detection means, in use, is operable to carry out TESPAR analysis of vibrational signals detected by said detection means to subtract therefrom signals caused by extraneous noise not associated with steam leakage by the use of TESPAR- based analysis of the vibrational signals being detected.

11. Apparatus according to claim 9 or claim 10 further characterised in being self-contained and portable.

12. Apparatus according to claim 9 or claim 10 adapted to be fixed, partially or wholly, to part of a steam operating system, such as a steam pipe adjacent a steam trap.

13. A method of detecting the amount of steam leaking in a steam operating system (1 ), which method includes the steps of measuring or calculating a plurality of vibrational signals indicative of a given quantity of steam leakage in a plurality of regions or apparatuses, such as a plurality of different makes and models of steam traps (2, 3), analysing the plurality of vibrational signals and interpreting them using Time Encoded Signal Processing and Recognition (TESPAR) and storing the steam leakage indicative signals in a look-up table for subsequent access, measuring or calculating actual vibrational signals indicative of steam leakage at a chosen region in the steam operating system, such as at or near a steam trap, analysing and interpreting the actual vibrational signals using TESPAR and comparing the signals obtained with the corresponding stored signals in the look-up table, and thereafter calculating actual steam loss in that region of the steam operating system.

14. A method according to claim 13 further characterised in including the steps of subtracting by TESPAR analysis extraneous noise forming part of the detected vibrational signals and comparing the remaining signals with the stored signals from the look-up table to thereafter calculate actual steam loss without reference to the extraneous noise signals.

15. A method of operating apparatus for detecting leakage of steam within a steam operating system substantially as hereinbefore described with reference to Figure 1 and/or Figure 2.