GB2457924A

GB2457924A - Steam trap monitoring

Info

Publication number: GB2457924A
Application number: GB0803699A
Authority: GB
Inventors: Richard Quentin Carmichael; Christopher Michael Roland Agard Poczka; Nishal Ramadas
Original assignee: Spirax Sarco Ltd
Current assignee: Spirax Sarco Ltd
Priority date: 2008-02-28
Filing date: 2008-02-28
Publication date: 2009-09-02
Anticipated expiration: 2028-02-28
Also published as: GB2457924B; GB0803699D0

Abstract

An arrangement for storing cumulative steam trap data corresponding to a given operational period comprises a sensor 5 associated with a steam trap, the sensor intermittently sensing a condition of the steam trap and generating a corresponding output signal; a processor 6 connected to the sensor for processing each output signal to derive operational data corresponding to the steam trap; and a memory 7 connected to the processor 6 for cumulatively storing the operational data for subsequent retrieval during a steam trap maintenance survey.

Description

I

Developments in or Relating to Steam Trao Monitoring The present invention relates to a steam trap arrangement and corresponding method for storing steam trap data relating to a given operational period, in particular to storage of such data for subsequent retrieval of that data during a steam trap maintenance survey.

It is well known to provide a steam plant for generating and distributing useful energy, contained in steam, to the point of use in various industrial applications, where that energy can then be extracted for use in a given thermal process by condensing the steam.

The presence of condensate in the main steam plant is undesirable because it acts as a further barrier to heat transfer and can also lead to damaging "water-hammer" and possibly even corrosion of the pipelines. The condensate is therefore drained from the lowest points of the steam plant through steam traps, which are self-acting valves designed to pass condensate but prevent the escape of useful live" steam from the plant.

Steam traps are relatively robust and reliable. However, it is inevitable that some steam traps will fail or will leak steam to a greater or lesser degree. Therefore, in order to maintain process efficiency, checking and maintenance of steam traps is an essential part of plant management. Conventionally, a detailed manual maintenance survey of steam traps will be periodically carried out to identify faulty steam traps, possibly as part of a larger system audit aimed at identifying key areas for improved efficiency.

However, the data collected during such an energy auditing process can sometimes be inadequate for gaining an accurate picture of the operational characteristiCS of the plant, particularly if, during the survey, sections of the plant are out of operation so that only a proportion of the steam traps can actually be surveyed.

The present invention seeks to provide the basis for an improved energy auditing process.

According to the present invention there is provided a steam trap arrangement for storing cumulative steam trap data corresponding to a given operational period, the arrangement comprising a sensor associated with a steam trap, the sensor being operable for intermittently sensing a condition of the steam trap during said operational period and generating a corresponding output signal; a processor operably connected to the sensor for processing each output signal to derive operational data corresponding to the steam trap, and a memory operably connected to the processor for cumulatively storing such operational data for subsequent retrieval during a steam trap survey.

Preferably, a controller is operably connected to the sensor for automatically controlling the frequency of said intermittent sensing.

The sensor and one or more of the processor, controller and memory may form part of a single sensor unit positioned in proximity to the steam trap.

The memory may comprise one or more counters for storing an incremental cumulative count of the number of occurrences, determined by the processor on the basis of said output signal, for each of a set of pre-determined operating states for the steam trap.

The sensor preferably incorporates an acoustic sensor element. In the context of the present invention, the term uacoustic embraces sonic (i.e audible), ultrasonic and infrasonic frequencies.

The sensor may additionally or alternatively incorporate a temperature sensor element.

The sensor may be situated at or adjacent the outlet of the steam trap. The flow regime through the outlet generates an acoustic signature that varies with the operative condition of the trap. Thus, operational trap data can be derived from the output signal generated by an acoustic sensor. Since the temperature of the trap outlet also varies depending on certain trap conditions, operational trap data can also be derived from the output signal generated by a temperature sensor.

The arrangement may further comprise a portable terminal for wirelessly retrieving said operational data from said memory during a steam trap survey.

In one embodiment, the arrangement comprises a plurality of said sensors, the sensors being associated respectively with a plurality of steam traps.

According to another aspect of the present invention, there is provided a method for storing cumulative steam trap data corresponding to a given operational period, the method comprising the steps of: using a sensor to intermittently sense a condition of the steam trap during said operational period and generate a corresponding output signal; deriving operational data from each output signal, and cumulatively storing such operational data in a memory for subsequent retrieval during a steam trap survey.

The cumulative stored operational data may comprise a cumulative, incremental count of the number of occurrences for each of a set of pre-determined operating states for the steam trap.

The cumulative stored operational data may additionally or alternatively comprise a cumulative history of the estimated steam leakage through the steam trap during said operational period.

Conveniently, the sensor is used to sense a condition of the steam trap every one to two hours.

According to a yet further aspect of the present invention, there is provided a method of surveying a steam trap, comprising retrieving and analysing cumulative steam trap data corresponding to the steam trap that has been derived and stored in accordance with any of claims 9 to 12.

Where the memory is located in a sensor unit attached to the steam trap, the method of surveying the steam trap may comprise using a portable reader device to wirelessly retrieve said operational data from the memory for subsequent analysis.

Embodiments of the invention will now be described in more detail, by of example, with reference to the accompanying drawings, in which: FIGURE 1 is a perspective view showing a steam trap arrangement including a sensor unit; FIGURE 2is a schematic diagram Illustrating one possible functional layout of the sensor unit In Figure 1; FIGURE 3 is a schematic diagram illustrating a possible functional structure for the memory shown as part of the sensor unit in Figure 2; and FIGURE 4 is a flow chart illustrating a method of cumulatively storing operational data corresponding to a steam trap.

Figure 1 shows a steam trap arrangement 1 comprising a drain line 2 for draining condensate from a steam plant (not shown) through a steam trap 3 to a condensate main (not shown). The steam trap arrangement I further comprises a sensor unit 4 positioned In proximity to the steam trap 3, in this case clamped to the drain line 2 immediately downstream of the steam trap 3.

Figure 2 gives an overview of the functional layout of the sensor unit 4, which comprises a sensor 5, a processor 6, a memory 7, a controller 8 and a transceiver 9, one or more of which may be Integrated as part of a single microcontroller, for example the microcontroller 10 indIcated schematically In Figure 2 (which in this case does not Include the sensor 5).

The arrows shown in Figure 2 are intended to provide an indication of the flow of data between the various functional elements within the sensor unit 4.

The sensor S may be any suitable sensor configured for sensing a condition of the steam trap, for example an acoustic sensor for sensing the aacoustic signature" of the trap 3 during operation, or a temperature sensor for sensing the temperature in the drain line 2 and/or the trap 3. In any event, the sensor 5 senses a condition of the steam trap 3, for example the acoustic signature or temperature, and provides a corresponding output signal to the processor 6.

The processor 6 is configured for receIving the output signal from the sensor 5, processing the output signal to derive operational data corresponding to the steam trap 3 and transmitting the operational data to the memory 7.

Processing of the output signal may be any suitable form of conventional signal conditioning and processing for analysing the signal, and may utilise a suitable algorithm stored in the memory 7. The processor 6 might thus comprise a conventional micro-processing unit (MPU), as well as any suitable signal conditioning system elements such as a digital-to-analogue converter (DAC) on the input channel from the sensor 5, as well as any required filters.

The memory 7 is operably connected to the processor 6 and is configured for receiving and cumulatively stonn9 the operational data derived by the processor 6, as well as for conventional ROM storage, including storing one or more suitable algorithms for use by the processor 6 to derive the operational data.

The memory 7 might be any suitable form of memory but preferably comprises a non-volatile, re-programmable memory element such as EPROM or Flash memory.

The controller 8 is confi9ured for controlling the frequency of readings taken by the sensor 5 and may be programmed to operate automatically in accordance with pre-determined operating parameters. The controller 8 is shown as a separate functional element in Figure 2 for the purposes of clarity, but In practice the function of the controller may be performed by the same conventional MPU that performs the function of the processor 6.

The transceIver 9 is configured for wirelessly transmitting and receiving external data or control signals, for example using RFID technology andlor in accordance with a suitable conventional wireless communication or networking protocol such as Bluetooth, or Wi-Fl. Control signals received by the transceiver 9 may be inputted to the controller 8 for remote control of the sensor 5 or may be inputted to the processor 6 for remote retrieval of cumulative data stored in the memory 7. In one embodiment, it is envisaged that the transceiver 9 might be configured to provide direct memory access (DMA) to the memory 7 for retrieval of cumulative data stored in the memory 7. Where cumulative data is retrieved from the memory 7, this data can then be transmitted externally of the sensor unit 4 by the transceiver 9.

The precise structure of the memory 7 may be varied depending upon the nature of the operational data being stored.

For example, where the sensor 5 incorporates both an acoustic sensor element and temperature sensor element, it is envisaged that the processor 6 might utilise a steam wastage estimation algorithm (represented only very schematically by the reference numeral 11 in Figure 3) to analyse the output signal of the sensor 5 and classify the output signal as representing one of four conditions for the steam trap 3: either that the steam trap 3 is working satisfactorily, that the steam trap 3 is leaking steam, that the steam trap 3 is waterlogged or that the steam trap 3 is not in use.

In such a case, the memory 7 may be provided with the structure shown in Figure 3, where the memory 7 comprises four separate counters 7a, 7b, 7c, 7d, each being assigned" to one of the abovementioned four possible operating conditions for the steam trap 3, along with a separate flash memory element 7e. Cumulative operational data corresponding to the steam trap 3 might then be stored using a method according to the operational flowchart shown in Figure 4.

Thus, referring to Figure 4, at step 12 the sensor 5 (in response to a control signal output from the controller 8) provides an output signal, comprising both a temperature output signal and an acoustic output signal. Following suitable signal conditioning and conventional signal error estimation by the processor 6 at steps 13 and 14, the processor 6 then utlllses the algorithm 11 at step 15 to analyse the acoustic and temperature output signals In order to determine which of the four possible operating conditions of the steam trap 3 are represented by the output signals from the sensor 5.

DependIng upon the determined operating condition for the steam trap 3, the processor 6 stores a record of the determined operating condition by incrementing the count in the relevant respective counter la, 7b, 7c, 7d in the memory 7. Thus, In the case where the steam trap 3 is determined to be working satisfactorily, the procesSor 6 Incrementally updates the count recorded in the counter 7a, at step 16. Alternatively, dependIng upon whether the processor 6 had determined the steam trap 3 to be leaking, waterlogged or not in use, the processor might Increment the count in the respective counter 7b, 7c or 7d, as illustrated In the alternative steps 17, 18 and 19 in Figure 4.

It will be appreciated that, for a plurality of readings taken by the sensor 5 during a given operational period of the steam trap 3, the corresponding incremental count recorded in each of the counters 7a, 7b, 7c and 7d provides a cumulative record of the proportional occurrence of each of the four operating conditions for the steam trap 3 during the operational period. In this manner, operational data for the steam trap 3, operating over a given operational period, can be cumulatively stored in the memory 7 for subsequent retrieval and analysis.

The sensor 5 (which is controlled by the controller 8) may take intermittent readings at regular intervals, for example hourly intervals during the relevant operational period, or at irregular intervals during the operational period.

In addition to determining the operating condition of the steam trap 3, it is envisaged that for each reading taken using the sensor 5 the processor 6 would also use a suitable algorithm, such as the algorithm 11, to quantify the estimated steam leakage through the steam trap 3, which may be expressed in any relevant units such as for example Kg, MJ or cost in �, $ etc. In each case where the steam trap 3 is determined by the processor 6, at step 15 in Figure 4, to be leaking steam, step 17 would then additionally include recording an estimated steam leakage log entry" in the Flash memory 7e as indicated in Figure 4. In this manner, for the same operational period.

operational data in the form of a cumulative "history" or "log" of estimated steam leakage through the steam trap 3 is built up in the Flash memory 7e for subsequent retrieval and analysis.

In an alternative embodiment, an estimate of the steam leakage is also recorded in the Flash memory 7e following the alternative steps 16, 18 and 19, not just following step 17.

The cumulative log of estimated steam wastage may be stored in the Flash memory 7e using a "queue" or "First-In, First-out (FIFO)" data structure, shown very schematically in Figure 3, which allows for convenient retrieval of the data whilst retaining the chronological order of the cumulative log. Other suitable linear data structures can alternatively be used such as a "stack" or "First-in, Last-out (FILO)" data structure.

In the case where an estimate of steam leakage is recorded in the Flash memory 7e following each of steps 16, 17, 18 and 19 in Figure 4 (i.e. following every reading taken by the sensor 5), a linear data structure such as a "queue" or "stack" data structure should allow the chronological order of the cumulative log of estimated steam leakage to be readily quantified, provided that the readings are taken at predetermined time intervals (e.g. under the control of the controller 8). However, where this is not the case, It is nevertheless envisaged that the chronological order of log entries in the cumulative log can be quantified if an appropriate timestamp is stored with each log entry in the Flash memory 7e; in such circumstances the use of a TMqueue" or stack data structure in the Flash memory 7e may be less important.

Whilst in Figure 4, the storage of a cumulative log of estimated steam leakage in memory 7 is in addition to the storage of an incremental count in the counters 7a, 7b1 7c, 7d, the cumulative log is itself operational data corresponding to the steam trap' which can be stored cumulatively within the memory 7 without storage of any corresponding incremental count in counters 7a, 7b, 7c, 7d.

It is intended that the cumulative operational data stored in the memory 7 for the steam trap 3 would be subsequently retrieved during or for the purposes of a scheduled maintenance survey of the steam trap 3. Thus, a method of surveying the steam trap 3 might indude retrieving the cumulative operational data for the steam trap 3 and analysing the operational data in the memory 7 to determine the NhistoricalN behaviour of the steam trap 3 in the context of the overall steam trap survey. It will be appreciated that access to cumulative historical data relating to the steam trap 3 will increase the amount of information available during the survey and allow steam trap performance to be assessed over an extended period of time, rather than on the basis of an instantaneous usnapshor of the trap at the time of the survey; this may be particularly advantageous in circumstances where no information can be obtained directly from the steam trap 3 during the survey because, for example, the steam trap 3 is not in use at the time of the survey.

During a tmmanual" steam trap survey, a survey engineer might visit the location of the steam trap 3. In this case, the cumulative operational data stored in the memory 7 may be retrieved from the memory 7 by downloading the operational data, via the transceiver 9, to a portable terminal configured for short-range wireless communication with the transceiver 9 e.g. a conventional laptop' computer. Further analysis of the operational data can then be carried out by the engineer in-situ using the portable terminal or may be carried out elsewhere at some other remote terminal.

It is envisaged that, in addition to the cumulative operational data stored in the memory 7, further data may be transmitted by the transceiver 9 to the portable terminal, for example data identifying the steam trap 3. Particularly in cases where there may be a hIgh number density of steam traps In a given area, the transceiver 9 might transmit data to the portable terminal only in response to a trap-specific interrogation signal transmitted by the portable terminal.

Alternatively, the operational data derived by the processor 6 may be transmitted externally of the sensor unit 4, via the transceiver 9, in response to a request from some other remote terminal such as a remote central data recorder, which may be wirelessly networked to the sensor unit. In this case, the memory 7 may itself be located externally of the sensor unit 4 at a remote location, for example, as part of the remote central data recorder, and the operational data transmitted directly by the processor 6 to the memory 7, across a suitable wireless network, for cumulative storage and subsequent analysis at, or onward transfer from, that remote location.

Although in the above embodiments only a single steam trap has been described, it will be appreciated that In practice a steam plant will incorporate a very large number of steam traps. Each individual steam trap could, of course, form part of a steam trap arrangement for cumulatively storing operational steam data corresponding to that trap, in the manner described above. The Individual steam traps may form part of corresponding steam trap arrangements configured for operating entirely autonomously from one another to cumulatively store operational data corresponding to the respective steam trap; alternatively, a single steam trap arrangement of the general type described above might serve a plurality of individual steam traps, for example by using a single processor and memory to process and store data derived from a plurality of respective trap sensors. In any event, it is envisaged that, during a maintenance survey the cumulative operational data can be retrieved in the manner described above, either by downloading the data from the relevant memory to a portable terminal during a 4manual" maintenance survey, or by transmitting the cumulative operational data to some other remote terminal for subsequent analysis.

Claims

CLAIMS1. A steam trap arrangement for storing cumulative steam trap data corresponding to a given operational period, the arrangement comprising: I) a sensor associated with a steam trap, the sensor being operable for Intermittently sensing a condition of the steam trap during said operational period and generating a corresponding output signal; ii) a processor operably connected to the sensor for processing each output signal to derive operational data corresponding to the steam trap, and iii) a memory operably connected to the processor for cumulatively storing such operational data for subsequent retrieval during a steam trap survey.
2. A steam trap arrangement according to claim I, further comprising a controller operably connected to the sensor for automatically controlling the frequency of said intermittent sensing.
3. A steam trap arrangement according to any preceding claim wherein the sensor and one or more of the processor, controller and memory form part of a single sensor unit positioned in proximity to the steam trap.
4. A steam trap arrangement according to any preceding claim wherein the memory comprises one or more counters for storing an incremental cumulative count of the number of occurrences, determined by the processor on the basis of said output signal, for each of a set of pre-determined operating states for the steam trap.
5. A steam trap arrangement according to any preceding daim wherein the sensor incorporates an acoustic sensor element.
6. A steam trap arrangement according to any preceding claim wherein the sensor incorporates a temperature sensor element.
7. A steam trap arrangement according to any preceding daim, further comprising a portable terminal for wirelessly retrieving said operational data from said memory during a steam trap survey.
8. A steam trap arrangement according to any preceding claim, wherein the arrangement comprises a plurality of said sensors, the sensors being associated respectively with a plurality of steam traps.
9. A method for storing cumulative steam trap data corresponding to a given operational period, the method comprising the steps of: i) using a sensor to intermittently sense a condition of the steam trap during said operational period and generate a corresponding output signal; ii) deriving operational data from each output signal, and iii) cumulatively storing such operational data in a memory for subsequent retrieval during a steam trap survey.
10. A method according to claim 9, wherein the cumulative stored operational data comprises a cumulative, incremental count of the number of occurrences for each of a set of predetermined operating states for the steam trap.
11. A method according to claim 9 or 10, wherein the cumulative stored operational data comprises a cumulative history of the estimated steam leakage through the steam trap during said operational period.
12. A method according to any of claims 9 to 11, wherein the sensor is used to sense a condition of the steam trap every one to two hours.
13. A method of surveying a steam trap, comprising retrieving and analysing cumulative steam trap data corresponding to the steam trap that has been derived and stored in accordance with any of claims 9 to 12.
14. A method of surveying a steam trap according to claim 13, wherein the memory is located in a sensor unit attached to the steam trap and the method of surveying the steam trap comprises using a portable reader device to wirelessly retrieve said operational data from the memory for subsequent analysis.
15. A monitoring arrangement substantially as described herein with reference to Figures 1,2 or4.
16. A method for storing cumulative steam trap data substantially as herein described.
17. A method of surveying a steam trap substantially as herein described.