Three-Valve Manifolds

A three-valve manifold gives a differential pressure instrument the two things it needs in one block: isolation on both process legs, and an equalising valve to bring the two sides together so the transmitter can be zeroed without being taken off the line.

Eight configurations are published. Remote Mounting takes the valves out on three sides for an instrument sat away from the manifold on impulse lines. DM 1 and DM 2 both mount direct — DM 1 with all three valves on top where a straight valve would foul the instrument, DM 2 with a flanged body and the valves spread over three sides. The "T" type lands direct on the instrument with a screwed process side; the "H" type is flanged on both sides and will go direct or remote on oval / kidney flanges. The coplanar manifold assembles onto the base of particular transmitter models.

Two are built for steam rather than for an instrument's mounting face: the Valve Combination is a fabricated manifold to power generation regulations for control-room panels, and the superheated-steam manifold conforms to boiler regulations with a butt-weld process connection.

Dimensions across the range are for the standard 54 mm (2 1/8 in) instrument centre distance, with 55, 56 and 57 mm made to suit. Hydrostatic test is 620 kg/cm² on the body and 413 kg/cm² on the seat with a 40 kg/cm² pneumatic seat test; gland packing is PTFE as standard and Graphoil above 180 °C.