Ultrasonic Flowmeter Measurement Problem

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Thread Starter

wangzhichao

During operation, we found the signal from the ultrasonic flowmeter jump to zero rapidly and recovered soon time and again. The curve of this output single shape like sawtooth wave.

Firstly, we suspect that there is bubble in the pipe that caused the missing signal of the ultrasonic and caused the jump of the signal. But we have no evidence for that, because the pipe size is only 2", where there is enough flow and it have enough lengths of both upstream and downstream pipeline.

So we have two questions:

1) How to prove if there is bubble in the pipe without cutting the pipe?

2) If the bubble exists in the pipe, how to eliminate the effect of the bubble to the ultrasonic flowmeter?
 
I have used two different clamp-on ultrasonic flow meters and neither had a minimum flow requirement. At zero flow, the meter would indicated zero flow without difficulty. In fact, I was told by the manufacturer in one case that best practice was to have a pair blocking valves used only to calibrate/establish a solid zero.

Upper flow limits, on the other hand, are pretty standard because the transmitter transducer's pulse energy can be blown past the receiving transducer at high speed.
 
Shut-off and bypass are common in custody transfer.

Look at the piping iso's or workout the piping layout by inspection. Sounds like a bubble or a partial full pipe.
 
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