Answer / santosh nanavati

We are doing the impulse tubing work on HP &/LP side DP
transmitter for level measurement of atmospheric close or
open vessel as per the process application. If the LP side
of tubing is filled with suitable fluid (water or process
fluid), it is called wet leg. Under this circumtances, the
transmitter zero condition will be towards negative
pressure range equivalent to the pressure head of filled
fluid in the LP side tubing. Vice versa if side of tubing
is not filled any fluid & kept empty i.e.dry, it is called
as dry leg. Under this condition,the transmitter zero
condition will not be towards negative pressure range.

Answer / sabry

If the impulse line connected to the low side of the differential pressure instrument is filled with a suitable fluid, it's called (wet leg).

If the impulse line is empty, it's called (dry leg).

Dry leg & Wet leg is a technique used in differential pressure measuremnt for 2 main reasons:

1 - We use (wet leg) to prevent the dangerous fluid from harming the sensitive instrument.

2 - In closed tank application, we use (wet leg) to prevent vapour condenstion due to temperature variation, so we get a stable/accurate measurement.

Good Luck

Ahmed Sabry
I&C Senior Engineer
Cell:+2 (0122) 1367310

Answer / ranish

Generally dry leg means without water ex: temperature
measurement thermo meter with out cloth or shield directily
to atm and with cloth ( we want to make it wet for
measurement)and subjected to atm or process

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