Pneumatic pressure switches are on/off pneumatic controls used to operate equipment, alarms, and shutdown systems. Pneumatic pressure switches are also called pressure pilots and are of two basic types: stick pilots and Bourdon tube pilots.
Stick pilots are spring piston sensors with a three-way spool valve block-and-bleed device. Spring and piston size is determined by the pressure range. They are used in wellheads and flow lines in production fields because they are resistant to plugging by solids. Stick pilots should be constructed of 316 stainless steel with Viton O-rings. The trip point should have a repeatability of 3% of the set pressure or 5 psi, whichever is least. The connection for the transmitted air signal should be ¼-inch NPT.
Bourdon tube pressure pilots are pressure switches with a 0% to 2% proportional band to give on/off control. The range is determined by the Bourdon tube. They are available in high switch point only, low only, and high/low configurations. Bourdon tube pressure pilots are used in producing applications that are not subject to plugging by solids.