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Whether the temperature of the medium affects the measurement results

A meter company deployed 14 air flow meters for a air compressor station of a diesel engine plant in Shanghai, which was used for the outlet flow of the reciprocating air compressor and the outlet flow measurement of the air compressor station. After the instrument was put into operation in summer, the standard state volume flow value displayed by the temperature-compensated vortex flowmeter was generally lower than that of the air compressor nameplate. The factory did not raise any objection to this. It is understandable because the old machine that has been used for several years to 40 years is not enough. However, in the winter, the value of the flowmeter generally increased significantly, and some of them were higher than the nameplate data, so the factory raised the following objection.
a. The exhaust flow of old machines that have been used for decades is so high impossible.
b. It is also impossible to discharge more than the nameplate data.
The instrument company explained that the increase of air compressor exhaust flow in winter is caused by the decrease of air temperature and the increase of density in the suction port of the air compressor. The volume of air taken in by one cylinder for each reciprocating is constant, but its mass is constant with air density. Proportional increase. In summer, the atmospheric temperature is 30 °C. According to the ideal gas law, when the atmospheric temperature drops to 0 °C, the air density increases by about 11%. In this case, the flow rate in winter may be 11% higher than that in summer.
3%,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, Therefore, it is normal for the exhaust flow rate to be higher than the nameplate data. After this analysis, the factory accepted this view.
In addition to compressors and pumps, there are a lot of equipment, and the nameplate data can be used as a reference when verifying the value of the flowmeter. In this respect, the knowledge of process engineers and equipment engineers is more abundant than that of instrumentation personnel. When using these data, they should be common. discuss.
In short, on-site verification of the accuracy of the flow measurement system is a very detailed task. It is a systematic method to verify whether the installed flow measurement system is accurate and reliable and meets the requirements for use. In every step of design condition determination, instrument selection and engineering design, instrument manufacturing and installation, open metering and system commissioning, the qualified instruments will not get satisfactory data.
There are many ways to verify, and you should pay special attention to safety when using the real-flow calibration method. When using the data for verification, you need to be careful and don't miss important factors. Extensive knowledge of production process knowledge and equipment can help you get your job done smoothly.
The practice of acceptance inspection shows that when the supplier or contractor undertakes the turnkey project, if it is necessary to make a commitment to the accuracy that the flow measurement system can achieve, it is appropriate to implement the segmentation commitment, that is, the flow value falls after the opening of the table. Within the scope of the table, the instrument measurement system can achieve higher accuracy; if the scope of the automatic control condition table is raised, the accuracy of the commitment is correspondingly reduced, so as to avoid unpleasant things during the acceptance check.

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