Reference Manual
00809-0100-4360, Rev BA
August 2008
Rosemount 1151
5-2
• The following performance limitations may inhibit efficient or safe operation.
Critical applications should have appropriate diagnostic and backup systems in
place. Pressure transmitters contain an internal fill fluid. It is used to transmit the
process pressure through the isolating diaphragms to the pressure sensing
element. In rare cases, oil leak paths in oil-filled pressure transmitters can be
created. Possible causes include physical damage to the isolator diaphragms,
process fluid freezing, isolator corrosion due to an incompatible process fluid, etc.
A transmitter with an oil fill fluid leak can continue to perform normally for a period
of time. Sustained oil loss will eventually cause one or more of the operating
parameters to exceed published specifications while a small drift in operating
point output continues. Symptoms of advanced oil loss and other unrelated
problems include:
• Sustained drift rate in true zero and span or operating point output
or both
• Sluggish response to increasing or decreasing pressure or both
• Limited output rate or very nonlinear output or both
• Change in output process noise
• Noticeable drift in operating point output
• Abrupt increase in drift rate of true zero or span or both
• Unstable output
• Output saturated high or low
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