A pilot operated safety relief valve uses system pressure to keep the main valve tightly closed, while a small pilot valve continuously senses the pressure. When the set pressure is reached, the pilot vents the dome above the main piston and the main valve opens to relieve the overpressure, either fully for snap action or in proportion to the overpressure for modulating action. Once system pressure drops, the pilot closes and the main valve reseats tightly.
Because line pressure loads the seat instead of a spring, the valve maintains excellent tightness right up to the set point, allowing the process to run closer to its maximum operating pressure. The design also tolerates high back pressure, offers precise set pressure repeatability, and delivers large relieving capacity from a compact body. Compatible accessories include pilot supply filters, backflow preventers, remote sensing lines, and field test connections.
- Pilot controlled operation with system pressure keeping the main valve closed for superior seat tightness
- Operating ratio up to 95% of set pressure, reducing unnecessary leakage and product loss
- Snap acting or modulating pilot selectable to suit the process and system dynamics
- Tight shutoff soft seat, with metal seat option for high temperature and abrasive service
- Stable operation with high back pressure and low blowdown, helping prevent chatter
- Remote sensing option for installations with high inlet pressure drop
- Compact, high capacity design with a wide choice of body materials
- NACE MR0175 compliant configurations available for sour service
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