What is a Wet Leg?
A wet leg is a low side impulse line kept full of liquid, used for DP level where vapour would condense in the line.
Wet Leg Explained
With steam or condensing vapours, liquid collects in the LP line anyway. Filling it deliberately, with a seal pot at the top, gives a known and constant head that can be ranged out.
The fill must stay at a constant height and density. Evaporation, leaks or heating of the leg cause drift.
Wet Leg Formula
| ρwl | fill density |
| Hwl | vertical height of the leg |
Calculators for Wet Leg
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Frequently Asked Questions
What is a Wet Leg?
A wet leg is a low side impulse line kept full of liquid, used for DP level where vapour would condense in the line.
Wet leg or remote seal?
Seals avoid maintenance of the fill but add temperature error and cost. Wet legs are simple where the fill can be kept stable.
What fill is used?
Often the condensed process liquid, or a stable liquid such as glycol mix where freezing is a risk.
Learn more on the blog
DP level transmitter calibration: zero suppression and zero elevation
A practical guide on instrumentationblog.in with more detail on wet leg and how it is applied on real plants.
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