Flow Transmitter Not Giving Proper Reading

your reading at the DCS is 330 kg/hr even at zero flow condition because for your transmitter sensing the Delta P of just 0.805 mmH2O which is nearly zero but because of the impulse leg variation it is sensing and showing some flow of 330kg/hr.

To avoid this, normally LOW CUT OFF is configured in the DCS and below which when flow goes it will indicate zero flow to avoid impulse line error in actual zero flow condition.

I.E. if 500 kg/hr is kept at lowcutoff then the flow reading goes below 500 kg/hr it will show zero on the DCS. Usually 5% of the flow range is kept as a lowcutoff.

for DCS calculation flow reading = SQT(DP%)*10 %of flow range

in your range if the dp is 312.5 mmh20 means 25% then the flow reading will be:

flow reading = SQT(25)*10 % of 13000

=(5)*10 %of 13000

=50% of 13000

= 6500 kg/hr

One small note: Some flow transmitters do the square root function themselves, so there is no need to do that in the DCS. He will have to check the manual and setup on the flowmeter.

the pressure range is 0 to 500 mbar how to calcurate ma for 25 ,50 ,75and 100 percentage

Check your transmitter catalogue and see if there a parameter called "Low Flow Cut in" on your transmitter. This value might be fixed at 330, the reason why ur instrument is not indicating zero.