Diaphragm and Bourdon Tube Pressure Switch

Mechanical process pressure switches remain the preferred choice for alarm and shutdown functions because they need no power, fail in a defined way and are easy to proof-test. The diaphragm element gives high sensitivity in the low ranges from 16 mbar, while the Bourdon tube element covers medium and high pressures up to 600 bar; both are available in vacuum and compound ranges.

The switching element is one or two microswitches in SPDT or DPDT configuration, with a fixed or adjustable deadband so the reset point can be tuned to the process. Repeatability is better than 1 % of span. Wetted parts are 316 / 316L stainless steel, PTFE, Monel or Hastelloy for aggressive media, and the process temperature range is −30 to +85 °C, extendable with syphons or diaphragm seals for hot or viscous fluids.

Housings are available for weatherproof and hazardous-area installation, with an Ex ia intrinsically safe option and SIL 2 / SIL 3 versions for use in safety instrumented systems. Mounting is via threaded or flanged process connection with wall or pipe brackets.

Applications include pump and compressor protection, high and low pressure alarms, ESD trips and process monitoring across oil and gas, petrochemical, chemical, power, water treatment, food and beverage and pharmaceutical plants.