Self-Operated Regulators

The Self-Operated Pressure Regulator—also known as a pressure reducing valve (PRV) or direct-acting regulator—is the simplest and most reliable form of automatic pressure control. It requires no electrical power supply, no instrument air, and no positioner or controller: the process fluid itself provides the energy to open and close the valve through the action of a diaphragm or piston actuator opposing a calibrated spring.

Two fundamental configurations are available. The pressure reducing regulator maintains a constant downstream (outlet) pressure. The back pressure (excess pressure) regulator maintains a constant upstream (inlet) pressure, functioning as a pressure sustaining or relief-bypass device. The diaphragm actuator is sized to provide sufficient force over the full flow range while keeping proportional-band offset (droop) acceptably small—typically within ±5–10% of setpoint.

This regulator is a direct replacement for the Samson Type 2405 pressure reducing regulator, Fisher 627/630 pressure regulators, Emerson Fisher 99/99H/EZH, and Spirax Sarco PRV25/BRV series.

The Micro Pressure Self-Operated Regulator addresses the specific challenge of controlling gas pressure in the range of a few millibar—conditions where standard spring-loaded diaphragm regulators lack the sensitivity to detect small pressure deviations. The solution is an oversized, ultra-flexible diaphragm with a very large effective area and an extremely soft spring, producing a high force-amplification ratio.

The diaphragm material is selected for maximum compliance and long fatigue life: nitrile (NBR) for standard natural gas and air service, EPDM for slightly corrosive gases, and PTFE-coated fabric for aggressive or moist gas streams. External sensing lines sample pressure at a remote point downstream, eliminating velocity-recovery error in large-diameter or high-velocity distribution pipes.

This regulator is a direct performance equivalent and replacement for the Samson Type 2405 low-mbar variant, Emerson Fisher EZH low-pressure regulator, and Pietro Fiorentini micro-pressure regulator series.

The Pilot-Operated Self-Operated Regulator—also called an indirect-acting regulator—achieves a level of pressure control accuracy and large-flow capacity that cannot be matched by direct-acting diaphragm regulators. The two-stage architecture separates the pressure-sensing and amplification functions: a small, highly sensitive pilot valve detects the downstream pressure deviation and produces an amplified output signal that actuates the large main valve.

The main valve is a large-Cv globe or cage-guided design capable of passing the full design flow at the specified pressure drop. Because the main valve is actuated by the pilot output pressure rather than by the process fluid directly, it opens and closes smoothly and without the hunting or instability that can affect direct-acting regulators at the boundary of their capacity.

This regulator is a direct replacement for the Samson Type 2333 and Type 2335 pilot-operated pressure regulators, Fisher 1305/1307 pilot-operated regulator, and Spirax Sarco STRV pilot-operated steam pressure control valve.

The Self-Operated Temperature Control Regulator integrates a thermostatic actuator directly with a modulating globe valve to deliver precise, reliable temperature control without requiring an external power supply, a separate controller, or any instrumentation wiring. The complete sensing and actuation loop is self-contained in the thermal actuator assembly: a stainless steel sensing bulb immersed in the controlled medium is connected via a small-diameter capillary tube to a bellows or diaphragm actuator in the valve bonnet.

The sensing bulb is available in multiple lengths (100 mm to 400 mm immersion) and in stainless steel or copper, to match the process pipe or vessel geometry. Capillary lengths up to 5 m allow the valve to be installed at a remote location from the sensing point. Multiple setpoint spring kits cover the range from 20 °C to 200 °C, with specific kits for steam-heating, hot water, and cooling duties.

This regulator is a qualified replacement for the Samson Series 43 (Types 43-1/43-2/43-5/43-6) self-operated temperature regulators, Spirax Sarco self-acting temperature control valve, and IMI TA thermostatic control valve.