1 reply to this topic

[deltaChe]

As we know that D/P level transmitter’s sensing line going to the upper tank

Connection becomes a “reference leg” of constant pressure head.

Care must be taken in applying reference legs when the atmosphere may

Alternate from condensing to non-condensing. So, wet-legs defines as that it

Can dry out over a period of time or a dry-leg may begin to fill with liquid.

If a diaphragm and capillary sensing system should be considered, it is definitely choose the dry leg instead of wet leg.

I&C staff ask us to fill out the process fluid vapor pressure for them

Unfortunately, one D/P LT located at high pressure water vessel OP~18 barg

So in this case, what is vapor pressure of water at 18 barg?

And, I am not sure this vapor pressure value for wet leg is used for.

Is that mean the higher the vapor pressure can drive the transmitter more efficiently or other reason.



Please help me out.Thank you very much for your help.

[Zauberberg]

HSWang,

Please don't take it personally, but I often find your questions to be quite chaotic and in some kind of disorder. It would be very convenient if you can formulate them in a well organized manner before posting it in the forum, perhaps by re-phrasing sentences in MS Word. That way your posts will get more attention from the members of ChE Resources, which also means that the probability of getting structured and appropriate answers will increase as well.

And now to the point: vapor pressure of water (or any other substance) at 18 barg can be any value, because it depends on the fluid temperature. In which way you will set the transmitter connections depends on the nature and conditions of process fluid inside the vessel. Different concepts apply for cryogenic liquids, for liquids well below their bubble points, and in general where the possibility of condensation/vaporization due to ambient heat transfer can exist. Read more at:

http://www.omega.com...4-11-LEVEL.html

And also find attached the Omega Textbook where you can read in more details how different concepts of level measurement are applied in process industry.

Best regards,

Attached Files

•  Transactions - Flow and Level Measurement.pdf   2.17MB   39 downloads