Pilot Operated Safety Valve

Technical Summary

Nominal Size: 1” to 12”

Pressure Class: Class 150 to Class 2500

Temperature Range: -29°C to 538°C

Design Standards: API 526, ASME Section VIII, ASME B16.34

Set Pressure Range: As per system requirement

End Connections: Flanged / Butt Weld

Construction and Materials

Body and Pressure Retaining Parts

• ASTM A216 WCB
• ASTM A351 CF8M
• ASTM A217 WC6
• ASTM A217 WC9
• ASTM A182 F316

Internal Components

• Main Valve Disc: Stainless Steel / Hard faced (Stellite)
• Seat: Stainless Steel / Stellite faced
• Stem: ASTM A182 F316
• Pilot Assembly: Stainless Steel internals

Sealing System

• Seat Sealing: Metal to metal sealing with precision-machined seating surfaces
• Gasket: Spiral wound gasket with graphite filler

Functional Design

Pilot Operated Safety Valve uses system pressure through a pilot mechanism to keep the main valve closed until the set pressure is reached. When the system pressure exceeds the set point, the pilot opens and relieves pressure from the dome above the main piston or disc, allowing the main valve to lift quickly and discharge excess pressure.

This design provides tight sealing up to the set pressure, reduced simmer, and stable operation in systems with higher back pressure compared to conventional spring-loaded safety valves. It is suitable for applications requiring precise set pressure control, high relieving capacity, and minimal leakage.

Material and Grade

Standard Materials

Component	Material	Grade	Typical Application
Body	Carbon Steel	ASTM A216 WCB	General industrial and utility pressure relief service
Body	Stainless Steel	ASTM A351 CF8M	Corrosive and process media
Body	Alloy Steel	ASTM A217 WC6 / WC9	High temperature pressure relief service
Main Valve Disc & Seat	Stainless Steel with Stellite overlay	ASTM A182 F316	Wear resistance and tight sealing
Stem	Stainless Steel	ASTM A182 F316	Load transfer and corrosion resistance
Pilot Assembly	Stainless Steel	ASTM A182 F316	Accurate pressure sensing and control

Extended Materials (On Request)

• Hastelloy C276 for aggressive chemical service
• Inconel 625 / 718 for high temperature and severe pressure applications
• Duplex Stainless Steel (F51) for chloride-rich environments

Additional Information

Valve Type	Pilot Operated Safety Valve
Pressure Function	Overpressure protection
Operation	Pilot operated pressure relief
Back Pressure Performance	Suitable for applications with variable or higher built-up back pressure
Set Pressure Accuracy	High set pressure stability and repeatability
Installation	Vertical installation recommended
Service Media	Steam, gas, vapour, process fluids

End Connections

• Flanged as per ASME B16.5
• Butt weld as per ASME B16.25

Applications

• Oil and gas industry: high-capacity pressure relief in separators, pipelines, and gas handling systems
• Power generation: steam and utility pressure protection with stable set pressure control
• Refining and petrochemical industry: overpressure protection in process units with varying back pressure
• Chemical processing: pressure relief in corrosive and hazardous process systems
• Gas processing plants: high-performance relief with reduced leakage and stable operation
• General industrial systems: critical pressure protection where precise opening characteristics are required