Pressure Transmitter

Can anybody tell me about the installation of Pressure Transmitter for steam service application? Can we use diaphragm seal type pressure transmitter for steam service application with siphon?

Or are siphons only used for pressure gauges & not for pressure transmitters?

Diaphragm and seal type of pressure transmitters are only used when installing on a pressurised vessel like digestors in pulp mills.

What is your application?
If you want to install on a steam line you do not need a siphon if you have a manifold.

swami

Firstly Diaphragm and Seal types of Pressure Transmitters are NOT only used for Pressurised Vessels they are commonly used where you do not want the Process (liquid or gas) to come into contact with the cell for example where you have a corrosive liquid.

I would not suggest that you use this type of transmitter for Steam measurement as they are rather expensive and not necessary.

The use of a standard Pressure Transmitter is all that is required and it needs to be installed below the Process Tapping Point to ensure the tubing/pipework is always full of condensate, if the tubing is allowed to drain the readings will be erratic until the Steam has condensed. Also if the installation is to be subjected to the possibility of low ambient air temps (freezing conditions) the installation should include a facility to fill the impulse line with some form of anti-freeze and be insulated.

Hope this helps.

If you mount the transmitter above the line you will need a siphon or something similar (e.g. come in from above) otherwise the live steam will heat up the transmitter to line temperature. Mounting the transmitter below the line acts just like a siphon, the steam condenses and cools protecting the transmitter from line temperature.

You could use a diaphragm seal but why go to that expense when all it takes is a simple installation detail.

One thing to keep in mind is the pipeline will move considerably with temperature change when the steam is turned on so if your transmitter is mounted to the building put a few bends in the tubing to allow for the thermal expansion.

Roy

Vinod,

It is not necessary to use diaphragm seal in this application, I have installed in our plant pressure transmitter in steam service without diaphragm seal, one important detail during the installation is that the transmitter must be ubicated below the process tap, I mean with a impulse line (tubing) slope to the transmitter in order to get a natural seal of water for to prevent direct steam coming in contact with the sensor.

Regards
J.Pinzon