Steam Drum Level Measurement

[CLM]

Hi,
I am having problems getting reliable readings from three level transmitters mounted on to a steam drum. This is a new plant and we are in the process of starting up. The transmitters are Rosemount DP with capillary/diaphragm connections. The diaphragms are connected directly to tapping points on the drum and we do not have a "bridle" installed.
The transmitters drift randomly.
I know that there is a potential problem with the filling fluid regarding ambient temperature. The fluid is rated 32F to 599F which satisfies the high temperature in the drum but currently the ambient air temperature can drop to 15F. We have erected a "room" around the transmitters and diaphragms bringing the ambient temperature up around 45F but this still didn't help.
This is only the second installation I have come across where there was no "bridle" to connect the LT's to. The other one used displacer types and this had the same problem of drifting. I'm afraid I do not know the outcome of that installation.
Hoping for help/ideas.

CLM

 

[JLSeagull]

The capilaries on low differential pressure measurement using diaphragm seals make for pretty good temperature transmitters too. See if the drift is random or if there is a correlation with temperature.