SONAPHONE. Performance test of steam traps Supplement to the operating manual

Transcription

1 SONAPHONE Performance test of steam traps Supplement to the operating manual

2 SONOTEC Ultraschallsensorik Halle GmbH Nauendorfer Str Halle (Saale), Germany Phone: +49 (0) Fax: +49 (0) Internet: sonotec@sonotec.de SONOTEC Ultraschallsensorik Halle GmbH All rights reserved The content of this manual is the property of SONOTEC Ultraschallsensorik Halle GmbH and is protected by copyright. Duplication and distribution in any form, particularly reprinting, photographic, mechanical or electronic reproduction, or in the form of storage in data processing systems or data networks, is prohibited without the consent of the copyright holder. Version: 2; Revised:

3 1 Performance test of steam traps 1 Performance test of steam traps A periodical testing of steam traps is recommended. Typically, such tests are performed periodically on an annual basis. The trap testing frequency crucially depends on trap size, operating pressure and the functioning or rather the position in the system. Steam traps operate on a number of different principles which show distinctive characteristics. For the evaluation of data in comparative and long-time tests it is recommended to put the sensors always at the same position of the steam trap and to test or measure under the same conditions. Only if steam traps of the same type are compared with each other a reliable result of the performance test is guaranteed. Notes 1. Pay attention to the safety instructions in the operating manual of the SONAPHONE, when operating the device. 2. For a correct functional test the steam trap must have the usual operating temperature. Run the test only during operation! 3. Additional noise sources may influence the value of ultrasound. If possible, switch-off ultrasound emitting components and devices before starting the test! For a correct performance test and evaluation of steam traps two kinds of tests must be carried out: determination of the emitted ultrasonic level temperature measurement. Based on the values of the two tests it is possible to estimate the status of the steam traps depending on the type. Systematic planning as well as a good preparation can help to perform the tests efficiently. To perform the tests it is recommended to equip the traps with a label (ID) It is also helpful to mark measuring points on the trap. The minimum acquired data is: label or the ID respectively, location, steam pressure, date of test, ultrasonic level and temperature values. The more information you collect the better. Data such as trap model (manufacturer), trap size, application, trap test function or special features can be added for further information. Performance test of steam traps 3

4 To perform the test, the following is required: 2 Determination of ultrasound level the ultrasonic testing device SONAPHONE K, M or E, the structure-borne sound probe L52 with solid probe tip made of stainless steel the surface temperature sensor, a suitable method to record and manage measurement data and results, e. g. with the data logger and the software of the SONAPHONE M and E, a computer or check lists. Performance test of steam traps 4

5 2 Determination of ultrasound level 2 Determination of ultrasound level For determining the ultrasound level put the ultrasonic probe vertically with constant, slight pressure either directly onto the housing, the hood, the cap or the cover of the steam trap. The optimal test point at thermostatic, bimetallic and membrane steam traps is located on the cover, between the cover and the flange or at the side of the cover: The optimal test point at float traps is located on the highest point on the cover or at a high point on the side of the cover: At steam traps with a low steam pressure a minor level of ultrasound is generated. Hence the values shown on the display are most probably not significant enough for a correct assessment. In such a case, the use of head phones is strongly recommended. Note Additionally determine the value of ultrasound on the pipeline, in order to assess the ultrasonic noise in the system. The values of ultrasound at the steam trap can only be evaluated in relation to the ultrasonic noise in the steam system. Performance test of steam traps 5

6 3 Measurement of temperature 3 Measurement of temperature Note The measurement of a thermocouple is based on a comparative measuring procedure. For this purpose the temperature difference between the thermocouple junction (probe tip) and the reference junction is determined. In this case the cold junction is the SONAPHONE. Before starting the measurement make sure, that the temperature of the SONAPHONE corresponds to the surrounding temperature. Put the temperature probe onto the surface of the steam trap at a flat part next to the inlet and the outlet. Depending on the type of steam trap statements about the condition of the device can be made by means of the values or the temperature difference between inlet and outlet. Since the temperature measurement is carried out outside of the pipeline or at the steam trap, the difference to the inner temperature of the installation must be taken into account. The following is applicable: T inside T outside x 1.1 Performance test of steam traps 6

7 4 Comparative and long-time tests 4 Comparative and long-time tests If the boiling temperature of the system is unknown, measure additionally the surface temperature on the pipeline. Note In order to receive a correct temperature value the measurement point has to be chosen ahead of possible buffer areas of the steam trap. If the pipeline is coated e. g. with insulating material, the measured temperature value is not significant. The measurement point has to be chosen at a point of the pipeline, where the tip of the temperature sensor can be put directly onto the pipeline. In the case of steam, the values of pressure and temperature correlate. For checking the performance of steam traps the operational pressure of the installation as well as the boiling temperature have to be known. If one of these values is specified, the other one can be determined by using the following table. Differential pressure (bar) Boiling temperature ( C) Differential pressure (bar) Boiling temperature ( C) Table 1: Correlation between pressure and temperature 5 Long-time tests with SONAPHONE M and E If at intermittently operating steam traps a SONAPHONE M or E is used, it is recommended to utilize the Long-time test. The test duration and the test interval are adjustable. However, it should be noted that at least one opening and closing are recorded within one interval. For steam trap testing the following default parameters apply: 1 minute test duration with 1 measurement per second. If the results are insufficient, it is necessary to adjust the values. Performance test of steam traps 7

8 6 Evaluation of the determined values 6 Evaluation of the determined values For the evaluation of the steam traps the values have to be compared with the limit value curve. Note In order to ensure, that the determined ultrasound value is significant, verify that the steam trap has the required operating temperature. Depending on the type of steam trap and application the ultrasound value deviates. Note Individual characteristics like values from previous measurements or experiences and knowledge of the operating principle of a certain type of steam trap or an installation could lead to a divergent evaluation regarding the performance. The inlet temperature provides information about the steam pressure at the intake of the steam trap and the outlet temperature corresponds to the pressure existing in the condensate line. Performance test of steam traps 8

9 6 Evaluation of the determined values Temperature in C / Ultrasound Pressure in bar Figure 1: Limit value curve ultrasound and boiling temperature according to pressure Boiling curve for water vapor Limit value curve for ultrasound Performance test of steam traps 9

10 6 Evaluation of the determined values 6.1 Value of ultrasound remains stable below the limit value curve The steam trap is steam-tight and operates correctly, if the determined value of ultrasound remains stable below the limit value curve. Type of steam trap Operating temperature T inside Evaluation Thermostatic steam traps (depending on the type) 5 to 30 K below the boiling temperature The steam trap is working correctly Float steam trap Boiling temperature The steam trap is working correctly Thermostatic steam traps and float steam trap More than 30 K below the boiling temperature Table 2: Valuation of the steam trap: low ultrasonic level The steam trap is adjusted incorrectly, blocked or defective 6.2 Value of ultrasound fluctuates periodically If the steam trap operates in the intermittent mode, the value of ultrasound fluctuates between a minimum and a maximum value. In this case the steam trap opens and closes and thereby operates correctly. Type of steam trap Operating temperature T inside Evaluation Thermostatic steam traps (depending on the type) 5 to 30 K below the boiling temperature The steam trap is working correctly Float steam trap Boiling temperature The steam trap is working correctly Table 3: Valuation of the steam trap: periodically fluctuating ultrasonic level Performance test of steam traps 10

11 6 Evaluation of the determined values 6.3 Value of ultrasound remains stable above the limit value curves If the value of ultrasound remains stable above the limit value curve, two additional values have to be determined for a correct evaluation of the steam trap, the ultrasound levels at the pipeline ahead and behind the steam trap. (The test point depends on the installation! The distance between the test point and the steam trap should be approx. 20 to 30 cm.) 1. Value of ultrasound at the pipeline < value of ultrasound at the steam trap: the higher value at the steam trap is caused by a flow of steam or condensate. In this case the steam trap does not operate correctly. 2. Value of ultrasound at one of the test points on the pipeline > value of ultrasound at the steam trap: an additional sound source affects the determined value of ultrasound Type of steam trap Thermostatic steam trap Float steam trap Operating temperature T inside More than 5 to 10 K below the boiling temperature Boiling temperature Temperature difference between inlet and outlet Evaluation Condensate flow The steam trap is working correctly Steam flow The steam trap is defective > Boiling temperature Overheated steam The steam trap is defective Significant drop of temperature No significant temperature difference The steam trap is working correctly Steam flow The steam trap is defective Table 4: Valuation of the steam trap at a high ultrasound level Depending on the type of steam trap and application appropriate measures should be taken: Perform further tests (verify, if other sound sources interfere the ultrasonic signal, record data over a longer period of time etc.) Have steam trap repaired Change steam trap Performance test of steam traps 11

12 6 Evaluation of the determined values 6.4 Decision tree Performance test of steam traps 12