A three-valve manifold is a device that is used to ensure that the capsule will not be over-ranged. It also allows isolation of the transmitter from the process loop. It consists of two block valves high pressure and low pressure block valve and an equalizing valve.A valve manifold is a standard accessory for pressure transmitters and differential pressure transmitters. Providing a valve manifold in the tool enables the tool to be calibrated or changed without the need to shut down the plant.