Flow Transmitters


Thread Starter


SMART Flow Transmitters of Fisher-Rosemount are damaging one after the other. We have increased the lengths of the impluse lines (before and
after the orifice) up to 30 ft but still we are loosing transmitters.
Feed water pressure at pump discharge is 460psig,
feed water tempt. is 260 degrees F
Transmitters is located about 500 ft from pump discharge
Need help.
Can you give you give me the exact application? We have been using 3051 and 1151S since last three years and never faced a problem. May be I can help?
Can you give the Model number of the transmitter and the process details.

Also please indicate what exactly is the failure.

PP Muthu
Temperature and pressures do not seem that high if you have purchased correct units which I assumed you have.

You might try isolating diaphragms if you are having physical or chemical corroison problems.

Are the failures electrical or physcial in nature?

Might try replacing meter to mag-meter or votex also.

Also lengthing of impluse lines will decrease accuracy of your measurement.

Make sure your taps are in horizontal plane. If in vertical plane you might be trapping steam in them which may cause some problems.

Check the ph of your feed water to make sure it is not corrosive.

Make sure your impluse lines are installed so that lines slope down to transmitters.

If in cold climate you might want to make your impluse tubing or piping such that you can fill with glycol to protect against freezing.

Hope this helps.
Will you supply a bit more information on the problem.

1. Is the failure in the sensor portion or the electronics portion of
the transmitter?
2. What failure codes or descriptions are you getting?
3. What type of transmitter are you using, and at what range?
4. Are you using 4-20 ma, HART, or Fieldbus to commuicate with the
5. What material are your measuring, and a what pressure?
6. Are there substantial changes in the line pressure associated with
the failures?
7. Does the process exceed the maximum overrange pressure at any time?
8. What are the maximum and minimum temperatures of the process material?
9. What are the maximum and minimum temperatures of the transmitter?
10. How much vibration is the transmitter subjected to?
11. Have you tried another manufacturer's transmitter in this service?
12. Are you using current/voltage limiting barriers or other limiting
devices in the control loop?
13. What is the excitation voltage to the transmitter, and from what
14. Are there any other unusual conditions associated with the

With this information, troubleshooting is possible.

John Beck
Control System Specialist ( Retired)
Hi Abbas,

If you mount your transmitters integrally to process pipe, the water temperature 260oF will burn your transmitter sooner or later. You should
have some external coils or tubes to release heat of feed water before entering pressure sensor of the transmitter.


Hung Lam