On site we have differential pressure transmitters used to measure drum level, at pressures of 110 bar, 25 bar and 4 bar respectively. the sensing legs of the DP trx have demin water. In the winter, the trace heating is not enough so when there is no generation the water lines get frost and the signal has problems. If we put glycol in the sensing legs, then probably we will need to make again the zero of the trx? is there any problem since glycol is more heavy than water?

<b>moderators note: could not figure out what "demin" was. Think it is a misspelling.</b>

 

demin is plant usage, though using untreated demin water in a boiler is risky as it can be very aggressive.

theoretically you can use glycol solution for the d/p but the fluid needs to be compatible with the process fluid. That done, the specific grav. correction to account for the elevation difference between the hi & lo connections is needed, znd the xmtr re-zeroed, you also have to refill the legs routinely to insure proper gravity...

the usual practice is to use heat tracing (electrical) for freeze protection and be done with it.

 

"Demin" water probably refers to "demineralized" water.

See http://en.wikipedia.org/wiki/Purified_water under "Deionization"

William (Bill) L. Mostia, Jr. PE
Sr. Consultant
SIS-TECH Solutions, LP

Any information is provided on Caveat Emptor basis.

 

You have identified the problem yourself, "in winter the trace heating is not enough" so why not rectify the problem you have already identified. Put in new or more tracing, make sure however that the tracing doesn't boil the water out. I wouldn't use glycol in a boiler drum, someone incorrectly stated that demin water would be harmful. I suspect gylcol would be really harmful especially when it starts to decompose under extreme heat and forms explosive gasses that may build up somewhere in your piping until one day someone is doing maintenance and welding on a new flange.