DP Transmitter Level Measurement for Closed Tank – Dry Leg Method
Simply when LP side of the DP transmitter is filled with any gas/air then we call it as Dry Leg & we apply Dry Leg Method for calculations.
At zero level (LRV) = pressure acting on HP leg – Pressure acting on LP leg
=H2 x specific gravity – 0
= 200 x 0.9 – 0
= 180 mmwc
At 100 % level (URV) = pressure acting on HP leg – Pressure acting on LP leg
= (H2+H1) x specific gravity – 0
= (200 + 500) x 0.9 – 0
= 630 mmwc
Range = URV – LRV = 630 – 180 mmwc = 450 mmwc
So, we have to set Lower Range Value (LRV) = 180 mmwc and Upper Range Value (URV) = 630 mmwc in the DP Transmitter using HART communicator.
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