HIPPS Shutdown Valve

A HIPPS (High Integrity Pressure Protection System) shutdown valve is a safety-critical valve that isolates process sections within milliseconds of detecting overpressure, achieving SIL 3 or SIL 4 safety integrity as an alternative to conventional pressure relief for protecting pipelines and vessels from overpressure without venting product.

Working Principle

HIPPS is an instrumented safety system that detects overpressure using redundant pressure sensors (typically 2-out-of-3 voting) and commands a fast-acting valve to close before the pressure exceeds the design limit. The shutdown valve must close within a specified response time (typically 1-2 seconds) to prevent overpressure from reaching downstream equipment. The valve is typically a trunnion ball valve with a spring-return hydraulic actuator capable of closing against full differential pressure within the required time. The entire system (sensors, logic solver, valve, actuator) must achieve SIL 3 per IEC 61508/61511, requiring redundant components, diagnostic coverage, and regular proof testing. HIPPS eliminates the need for conventional pressure relief (safety valves, rupture discs) on the protected equipment, avoiding product loss, emissions, and flare system loading.

Key Components

Trunnion ball valve (API 6D), fast-acting spring-return hydraulic actuator, redundant pressure transmitters (2oo3 voting), safety-certified logic solver (SIL 3), solenoid valves, position switches, partial stroke testing system.

Types & Variants

Common Materials

Valve: API 6D trunnion ball, ASTM A216 WCB or A217 LCC body. Ball: F6a with tungsten carbide coating. Seats: metal (tungsten carbide or Stellite overlay). Actuator: spring-return hydraulic with accumulator, qualified per API 6D Appendix B. Pressure transmitters: SIL 3 certified, 0.075% accuracy. Logic solver: SIL 3 certified safety PLC.

Applicable Standards

• IEC 61508 (functional safety of E/E systems)
• IEC 61511 (functional safety for process industry)
• API 6D (pipeline valves)
• API 17D (subsea, if applicable)
• ISA 84 (process safety, reference)
• ISO 15848-1 (fugitive emissions)

Industrial Applications

• Pipeline overpressure protection (replaces safety valves)
• Compressor discharge overpressure protection
• Wellhead flowline overpressure protection
• Subsea pipeline HIPPS
• Process vessel overpressure without flaring
• Multi-phase pipeline overpressure

Advantages & Disadvantages

Selection Guide

• HIPPS must be designed as a complete system (sensors, logic solver, valve, actuator) — piecemeal specification does not achieve SIL 3
• Perform SIL verification (PFD calculation) per IEC 61508 to confirm the system meets the required SIL
• Partial stroke testing at least quarterly is mandatory per IEC 61511 for SIL 3 HIPPS
• 2-out-of-3 voting on pressure sensors provides the best balance of safety (low PFD) and availability (few spurious trips)
• Ensure the actuator can close the valve within the required response time at the maximum differential pressure with margin for seat breakout friction

Practical Tips

• A HIPPS that replaces a safety valve on a pipeline can save millions in product loss and flare system cost over the project life — but only if the proof testing is maintained. An untested HIPPS has unknown reliability and may not protect when needed
• The most common HIPPS failure is solenoid valve stiction — the solenoid sticks closed from lack of exercise. Quarterly partial stroke testing exercises both the solenoid and the main valve, preventing this silent failure

FAQ