I m using a Honeywell differential pressure type level transmitter and of late the readings of the tx jumps to the newly attained value instead of following a linear curve as was the case earlier. please suggest what can be the most probable cause and how to rectify it...

 

You may want to check your sensing lines for plugging.

Plug-On?
RDWagner PE

 

1) The sludge build-up against the flanged diaphragm or in the cavity formed by the housing and the diaphragms of the sensor prevents small elevation pressure changes from physically reaching the sensing diaphragm. Vibration or increased pressure moves the sludge the pressure gets through, the sensor sees the change.

Some brands detect "clogged" impulse lines by sensing unchanging pressure over a time period.

2) A mechanically damaged diaphragm can manifest this problem. Did the last guy who removed it from service clean the sensing diaphragm with a stiff wire brush or better yet, a 9" angle grinder with a wire wheel?