GB2459319A

GB2459319A - Calculating steam loss by comparison of a vibration signal to a previously generated record that correlates vibration and leakage quantity

Info

Publication number: GB2459319A
Application number: GB0823318A
Authority: GB
Inventors: Ashley Elkins; Ian Thomas Harvey
Original assignee: HYDRALOGICA IP Ltd
Current assignee: HYDRALOGICA IP Ltd
Priority date: 2008-04-17
Filing date: 2008-12-22
Publication date: 2009-10-21
Also published as: WO2009127879A2; GB0823318D0; WO2009127879A3; GB0807000D0

Abstract

A method and apparatus for detecting the amount of steam leaking from part of a steam operating system 1 (e.g. a steam trap 2, 3). Initially, vibration signals indicative of a given quantity of gas leakage in a plurality of regions or apparatuses of the system (e.g. different makes and models of steam traps) are measured or calculated and stored for subsequent access. Thereafter, selected regions may be tested by measuring vibration signals (using detectors 4, 6) and comparing these signals with the corresponding stored signals in order to calculate and indicate to the user the actual quantity of steam-loss at each region. The comparison means may include a look-up table and may either be incorporated with the detector or be remote from it (e.g. in a PDA or in a fixed installation that continuously monitors fixed or moveable detectors situated around the system). Signal analysis may use Time Encoded Signal Processing and Recognition (TESPAR) software.

Description

I

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 afl kinds of industry, ranging from direct electrical power production to manufacture of products. In all such systems the * S. steam traps themselves are prone to failure and where such failure is other than * S.. * * *.*.

catastrophic it can result in small but nevertheless significant losses of steam S. * from the system. This may be caused by steam traps which are inherently faulty *S*.SS S. 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 I to 15, with 15 being the most acute and I 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. It is therefore an object of the present invention to provide an apparatus arid method by which the amount of steam leakage can be measured or calculated.

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. * **

:::::: Conveniently, the comparison means includes a look-up table of known S...

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 ***SSS *: 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.

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.

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 I 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 FDA 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 FDA 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 and measuring steam leakage by meansof 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, I... * *

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 Iö S. 55 : 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 I 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.

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.

In addition to the ultra-sonic sensing capability provided by the microphone 20, the monitor 4 also includes a directional infra-red temperature sensor 26 which is used to detect when a steam trap under test is in operation and produces a temperature reading that is subsequently used to calculate the pressure in the trap.

The micro controller 10 includes a data memory log 27, which may be FLASH memory, application software 28 for controlling the various functions of the monitor 4 and TESPAR (Time Encoded Signal Processing And Recognition) software 29 for analysing Heterodyne signals from the Heterodyne circuit 19 and * *** signals from the infra-red temperature sensor 26 for the subsequent generation ** of test results which can be stored in the data log 27 or transmitted via the radio interface 23 or serial interface 24 to a PDA device 5 or some other suitable r** 20 device. The PDA 5 (or other suitable device) stores all known data about trap S. S : 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 to thereafter 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 a preferred 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 S*.*.

* TESPAR via the TES PAR software 29.

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. 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 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). However, it will be understood that other types of signal analysis may be used which may be more or less complicated than TESPAR by which comparison may be made between vibrational signals measured or calculated, from a test rig to actual vibrational signals measured at a chosen region in the steam operating system, such as next to a steam trap.

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 S...

data signatures from a selected part of a look-up table with the data signature *..: obtained during a test.

*5.*..

* 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 look-

up 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 can be calculated with reasonable S. * accuracy instead of adopting the prior art techniques of choosing an arbitrary scale, such as from 1-15, indicative of the seriousness of a leak within a steam * operating system. In turn, 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. * ** * * * * ** **** * * * *** ** . * * * * *e

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S..... * S *. ** *. S * * S. * * S * S.

Claims

Claims 1. 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.
2. Apparatus according to claim I 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 * 20 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, 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.
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. A method of operating apparatus for detecting leakage of steam within a *....S * steam operating system substantially as hereinbefore described with reference * 20 to Figure 1 and/or Figure 2.