In a certain device, more than 20 mass flow meters are used. Its accuracy should be 0.15% according to the instrument manufacturer's sample, but the field test results are all below 0.3%.

Fault inspection and analysis: After calculation, the model selection is correct, and all are fully filled. The on-site inspection found that there are problems in the installation:

1. The mass flowmeter is installed near the pump, and the large vibration after the pump is started will definitely interfere with the normal operation of the flowmeter.

2. The instrument support column of the flowmeter is generally thin, and some mass flowmeters have only one support frame on one side. When the pipeline stress is transmitted to the instrument installation section, its support is not enough to resist the pipeline stress, which will reduce the measurement accuracy of the mass flowmeter.

3. The supports of the mass flowmeter are connected together. When one of the mass flow meters is subjected to vibration interference and stress, it will inevitably be transmitted to the other flow meters, and resonance may occur.

4. Some vertically installed mass flow meters cannot stabilize the heavier and larger diameter mass flow meters. Vibration in the pipeline due to the passage of fluid or stress in the pipeline will affect the correct measurement of the mass flow meter.

5. If the support is installed on the flow tube or connecting flange of the flowmeter, it may also cause stress and interfere with the vibration frequency of the flow tube, resulting in precision deviation.

Troubleshooting: In summary, the reason for the decline in the accuracy of the mass flowmeter is the interference of vibration and the influence of stress. The measures taken in this regard are:

6. Keep away from the vibration pump for more than 3m.

7. The position of the support is within 15D upstream and downstream of the flow meter. Two fixed support brackets are set on both sides of the meter to resist the vibration and the stress of the pipeline when the fluid flows through the pipeline (especially when there are heavy valves nearby Time). The support bracket must be removed from the meter body and be of sufficient diameter to support the weight of the mass flow meter body and piping and isolate vibration.

8. When the vertical pipe diameter is large and it is difficult to manufacture the support, the pipe where the flowmeter is installed can be designed in a horizontal form.

9. The supports of each mass flow meter cannot be shared or connected together, and must be separated.

10. The outlet pipeline of the instrument should preferably be higher than the pipeline behind the second support frame of the flowmeter to generate a small back pressure and avoid siphon phenomenon.

f. For areas with excessive vibration, shock absorbers should be installed or other vibration reduction measures should be adopted.

Failure inspection and analysis: After inspection, it is found that the amount of hydrochloric acid added during trial production is less than that in normal production. When the stop valve at the rear of the mass flow meter is fully opened, the hydrochloric acid cannot completely fill the medium, which affects the measurement of the instrument.

Troubleshooting: slightly close the rear stop valve and re-test, the result is consistent with the process experience value. After normal production, fully open the globe valve flowmeter also works normally.