Piping connection for Differential pressure transmitter (DPT) on liquids, Gas and steam services


The differential pressure transmitter is a device which measures flow, which is used for both liquid, gas and steam flow measurement. The DPT is assembled with several other components in different lines, that are discussed below:

Liquid lines:

On liquid lines, the transmitter is mounted below the orifice plate because liquids have a property of self-draining.

Here the transmitter measures the differential pressure across the orifice plate. The transmitter can be any kind of DPT, which can’t be directly connected to the flow phase.

If the transmitter is directly connected to the flow it can damage the transmitter on an unexpected scenario (High flow). And the main point is connecting the transmitter directly to the line restrict maintenance.

3 way manifold valve:

It is an arrangement of three valves used for ensuring the protection of pressure transmitter or for isolating the transmitter from the process loop while the transmitter is under maintenance or to calibrate.

A three-valve manifold system consists of an equalising valve and two blocking valves. One blocking valve at the high-pressure side other at the low-pressure side.

Gas Service:

On gas service, the transmitter is mounted above the orifice plate because Gases have a property of self-venting and secondly condensate formation.

The same kind of three-way manifold setup used in liquid stream is used here also, for calibration purposes.

Steam Service:

On steam service, the transmitter is mounted below the orifice plate with condensate pots. The pots should be at the same level.

One extra component used in the steam service line is the condense pot, It is designed to trap any foreign material from the pipeline.

The condensate containers should be mounted in such a way that the liquid levels are the same in them. The function of condensate pots is to condense steam in a liquid (for example, to protect the transmitter from heat, to prevent dripping), to keep liquid levels unchanged with overflow and to collect air. The condensed water transmits the pressure to the transmitter, so that the transmitter is not in contact with the steam.