At low flow rates, the mass flow meter shows no flow. Haiyou, please help analyze the reason. Thank you
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The situation is as follows: there is a flow of light oil, which is measured using a mass flow meter; an air-operated control valve is placed after the flow meter to regulate the output. The control valve has been leaking internally. Previously, the daily cumulative reading of the flow meter was around 5 to 6 tons; recently, it is less than 1 ton per day. If the shut-off valve in front of the control valve is closed and manual drainage is used, the cumulative amount per day is about 4 tons. Could experts help analyze whether there are any other reasons besides internal leakage in the control valve that could account for the decrease in the flow meter readings?
If the internal leakage of the control valve increases, won’t the flow meter accumulate more data? What does the landlord want to say?
The control valve leaks internally, so the flow meter cannot detect any flow; only when the control valve is opened can the flow meter detect flow.
The low-flow rate has been disabled; lower this parameter a bit – as long as the flow meter is working properly, it will be possible to measure the flow rate
The low-flow cut-off function is turned off, but the error at low flow rates is quite large... According to your analysis, if 5-6 tons were leaking per day before, the internal leakage must have increased now; yet instead of an increase in flow rate, it has decreased to 4 tons, right...? Is it possible that the leakage rate of the control valve has decreased? Or has the mass flow meter become inaccurate? I’ll offer you two options; you can try them out and see which works. Option 1: Take the control valve offline, remove the valve body, grind the valve core to reduce internal leakage, and then reassess the situation. Option 2: Take the flow meter offline and send it to a calibration facility for inspection to determine whether there is any drift in its zero point. Also, check the pressure at the beginning of the pipeline, and consider whether the pipeline might not be fully filled, or... I can’t think of anything else for now
The mass flow meter should be equipped with a low-signal cutoff function; however, the internal leakage of the control valve does not reach the threshold for this cutoff, which results in no accumulation of flow volume. Based on your description, there seems to be an issue with intermittent drainage. It is necessary to check whether there is a problem of insufficient fill level in the mass flow meter, and whether vaporization occurs with light oils.
That makes sense; it’s possible. Thank you, Haiyou, for your reply.
That makes sense; it’s possible. Thank you, Haiyou, for your reply.
That makes sense; thanks to Haiyou for sharing the experience.
There should be shut-off valves or globe valves (both of the manual type) on the pipeline; close them completely and then observe. According to what you said, this valve and instrument are not used during certain periods of time in the processing process. It’s advisable to conduct a test during those intervals. In my opinion, there is a high likelihood of the gauge drifting……
Internal leakage is one possible cause; if there are no other leaks, there may be an issue with the meter’s accuracy, and it needs to be sent to a calibration station for adjustment. Also, if there is a continuous amount of internal leakage, it is possible that no measurement takes place when the amount is small. The valves also need to be repaired