Self- actuated pressure regulator:
The self-actuated regulator is a diaphragm actuator variation and is normally used as the operating medium by the process fluid. Some self-actuated regulators use bellows for the actuator for pressure applications instead of diaphragms.
All regulators, used for pressure, level or flow control, fit into one of the following two basic categories:
1. Direct-operated: Direct-operated controllers are adequate for narrow-range control and where the permissible outlet pressure change can be 10 - 20% of the outlet pressure setting.
2. Pilot-operated: Pilot-operated controllers are preferred for wide-range control or if the permissible change in outlet pressure is required to be less than 10% of the outlet pressure setting.
With the pilot, pressure can be controlled, and set pressure is varied to individual requirements by the adjusting screw on the pilot. Pilot exhaust can be piped into the downstream line or vented to the atmosphere on gas service, but must always be piped downstream on liquid service.
Direct-operated regulators are used to provide pneumatic instrumentation and other control equipment with constantly decreased pressure. For applications involving pressure factor measurement, pilot-operated service regulators are optimal.
Self-Actuated Pressure Regulator Characteristic:
Adequate overpressure protection should be mounted to safeguard the regulator against overpressure and to safeguard all downstream facilities in case of failure of the regulator.
Significantly greater downstream pressures than the regulator pressure setting can harm soft seats and other components of the inner regulator.
The suggested port diameter choice should be the lowest port diameter to manage the flow.
Spring cases must be protected against the accumulation of water caused by condensation or other sources.
Control line links (if necessary) should be created downstream of any turbulence region such as elbows or block valves in a straight run of pipe 8 to 10 pipe diameters.
The body size of the regulator should never be greater than the size of the pipe. The regulator body should be one size smaller than the size of the pipe in many cases.
The self-operated regulators generally have a faster response to quick flow change than pilot-operated regulators.
Materials and temperature capabilities of the regulators must be checked to conform with process requirement. Stainless steel diaphragms and seats should be used for higher temperatures such as steam services