They need to be compensated for temperature not pressure. It is a common issue in HP FWH's.
The water in the transmitter IF it is located away from the body of the FWH to any extent and outside of the insulation especially will be colder than the water in the heater and hence more dense.
Therefore it will take more head of less dense water inside the heater to balance the level of the colder more dense water in the transmitter or gage glass, so you need to do a calculation and estimate the error in the transmitter based on the geometry of the transmitter attachment to the heater.
The same is commonly done for boiler drum level indication as well. You may already have such a system for the boiler (if it has a drum, of course that is - not supercritical.)
They ate shell and tube preheaters. I always understood as you say that it would need to be compensated for temperature and not pressure. Apparently the pressure is used to compensate for the turbulence that occurs when steam condenses from the steam extraction.
Well, you got me there... "the turbulence that occurs when steam condenses from the turbine extraction".
I have no idea what that means.
There is a gradient from the end opposite the drain end (or there wouldn't be flow toward the drain) and there has to be some action caused by the droplets falling from tubing, but turbulence????
What would cause turbulence? And further more, if there is any, how would pressure compensate that?
Usually for feedwater flow measurements, temperature compensation is employed. For steam flow measurement, both temperature and pressure compensation are used.
