Pressure Tx installation -Process point below the TX

[INSDE08]

Hi everyone
I need to install a pressure transmitter on a pump oil line . I want to know how much would the accuracy effect if the transmitter is installed 1mtr above the process tapping point. Can the error be corrected by changing the setup and be compensated for the error.
Please let me know your thoughts

 

[quark]

The main error will be due to the 1m liquid column, which is about 0.1 bar. The transmitter reading will be 0.1 bar less than your process pressure. Accuracy of the transmitter reading shouldn't change.

 

[roydm]

It will read about 1 psi low, hardly worth worrying about unless it is a significant % of span.
Roy

 

[JimCasey]

And you can just adjust the zero so that it reads correctly anyway. I have always thought the terminology was reversed, but suppressed zero is what you would use if the level is above the device, and elevated zero is the term for having the transmitter lower than the level. Either way, most any transmitter can be zeroed to a nonzero value.

The span adjustment will set your full-signal point to the maximum level, even compensating for the specific gravity of the fluid if the SG is not variable.

It gets more complicated for a closed, pressurized tank because you have to run a reference leg to the top part of the tank to compensate for pressure in the tank. Then it's good practice to fill the reference leg so it can't fill itself with a variable height of condensate or splashover.
That gives you a stable reading, but the minimum differential then occurs with the tank FULL and max DP occurs with the tank EMPTY.

 

[INSDE08]

Thank You All .

 

[roydm]

To add to JimCasey, there are a few options for the upper connection.
I have had good results keeping the LP connection dry by running the tubing to a point 2-3 ft above the upper tap then back down, this prevents the overfill/splashing problem and allows any condensation to drip back into the tank.
For very corrosive fluids a gas purge may be required.
A condensate pot or 3,000# tee for steam service, this radiates the heat to ensure a fixed condensate level.
The same ideas are also apply to a pressure transmitter measuring wet vapour or steam pressure.
Roy