Profile: Ruelco, Inc. manufactures instrumentation controls. Our products include pressure switches, level switches, cages, relays, tattletale indicators, quick exhausts, sand probes, hydraulic controllers, fuse plugs, vent screens, panel accessories, filler tubes and relief valves. SS series differential pressure switch is a three way block and bleed valve that is operated by pressure acting on a piston opposing an adjustable spring force. It functions as either a normally closed or normally open valve, depending on through which of the two ports the instrument pressure is supplied. Pressure applied to the sense port will cause the valve to operate. Interface valve is a normally closed 3-way block and bleed hydraulic controller. The valve allows the system to control pressures as high as 10,000 PSI with a pilot supply pressure of 100 PSI. The unique soft seal design ensures zero leakage and also prevents damage from foreign particles.