Emerson Exchange 365

If a station is unstable even after the 4 most common causes of regulator instability have been addressed, some regulators have additional troubleshooting techniques that can be tried. The following additional solutions increase the stability of the installation by decreasing the regulator’s responsiveness.

•  Add a pilot-supply regulator: Pilot-operated regulators can be desensitized by reducing the pressure to the pilot using a pilot supply regulator. A pilot supply regulator (ex: 67C, 1301, SA/2, 161EB, etc) lowers gain by decreasing the energy (in the form of loading pressure) available to open the main valve.
• Increase the size of the restrictor: Increasing the restrictor size on a pilot-operated regulator will decrease the speed at which the main valve opens which can solve instability. Products with variable restrictions can be adjusted on the fly while those with fixed restrictions require an on-hand replacement restrictor with a larger hole as well as the disassembly of the pilot.
• Use a heavier spring: If the next heavier control spring is advertised as able to control the required setpoint, then it can be used to reduce the sensitivity of the regulator; however, accuracy will decrease. Also, some pilot-operated regulators have alternative main springs available.
• Restricting valves, such as needle valves, can be installed as a last resort in the sense line to tune out instability in some regulator installations. The signal going to the regulator will be dampened but this will also lead to slower response. Caution: do not completely close off the valve or the sensed pressure will be blocked in and the regulator will fail to maintain pressure control.