2-Valve Manifold with a Differential Pressure Transmitter
Differential Pressure (DP) transmitters usually use either 3-Valve or 5-Valve manifold, controlling the process to both the low-pressure or high-pressure ports of the transmitter. However, there are times in which a DP transmitter is used as a Gauge Pressure (GP) transmitter by allowing the low-pressure process port to remain open to the atmosphere.
3-Valve and 5-Valve manifolds have an equalizing valve that links the high-pressure side and the low-pressure side. If a DP transmitter with a 3 or 5-Valve manifold is utilized as a GP transmitter and the equalization valve is open, a leak path is opened, releasing process medium into the atmosphere.
Therefore, when using the DP transmitter in this way, it is advisable to use a 2-Valve manifold. Since the 2-Valve manifold does not have an equalizing valve, the potential leak path is eliminated. When using a DP in this manner, make sure that the low-pressure side port is open to the atmosphere and not covered by the 2-Valve manifold.
