Valves and flow control
Safety valve
Relief of excess pressure to protect piping or equipment
Specialist selection guide
What should be reviewed before selecting this valve?
A safety valve is the final mechanical layer of overpressure protection. Selection must be based on the relieving scenario, set pressure, back pressure, fluid phase, required capacity and discharge system. Approximate sizing or line size alone is not acceptable.
Technical selection path
- 1
Define the credible overpressure scenario and relieving rate
- 2
Specify set pressure, allowable accumulation and back pressure
- 3
Include gas, vapour or liquid phase in sizing
- 4
Evaluate conventional spring, balanced-bellows or pilot-operated design
- 5
Design inlet and outlet piping, reaction forces and safe discharge
Key strengths
- Independent automatic overpressure protection
- Design options for gas, vapour and liquid
- Testable and certifiable relieving capacity
Selection limitations
- Sizing requires validated process calculations
- Back pressure and discharge piping directly affect performance
- Setting and repair require a qualified authorised facility
Typical applications
Where can this option be considered?
- Pressure-vessel and equipment protection
- Boiler and steam systems
- Process piping and equipment with overpressure scenarios
Reference standards
A standard does not replace the project specification
ASME B16.34Pressure-temperature ratings, materials, construction, testing and marking requirements for industrial valvesAPI 598Valve inspection, shell pressure testing and seat leakage testingAPI 520Sizing, selection and installation of pressure-relieving devicesAPI 526Flanged steel pressure-relief valves and standard dimensionsAPI 527Seat tightness of pressure-relief valves
Common technical questions
Concise answers before enquiry
Must safety-valve size match the line size?
No. Required orifice area comes from relieving-capacity calculations, after which standard inlet-outlet sizes, pressure loss and discharge piping are checked.
What is the difference between set and operating pressure?
Operating pressure is the normal process condition; set pressure is the defined point at which the valve begins to operate within standard tolerance and must coordinate with equipment limits.
Can a safety valve be adjusted in the field?
Adjustment, sealing and testing must follow regulations and project procedures through qualified personnel and facilities; unauthorised alteration is hazardous.
Final protection against calculated overpressure scenarios
Set pressure, relieving capacity, back pressure and certified testing
Initial review sheet
Technical attributes to review
Final values must come from project specifications, calculations and manufacturer data. This table defines the information scope.
FamilyManual and mechanical valves
Main groupValves and flow control
Materials to evaluateCarbon steel, Stainless steel, Alloy steel, Cast and ductile iron, Bronze and brass, Special alloys
Connections to evaluateFlanged, Butt-weld, Socket-weld, Threaded, Wafer and lug
Typical mediaProcess liquids, Gas, Steam, Water, Corrosive fluids
Relevant industriesOil and gas, Refining, Petrochemical, Power generation, Water and utilities
Reference standardsASME B16.34 · ASME B16.10 · API 6D · API 600 · API 602 · API 609 · API 598
Enquiry checklist
Include this information with your request
Valve duty
Class and design pressure
Temperature and fluid
Body, trim and seat materials
End connection and face-to-face
Leakage class
Before substitution
A matching name does not guarantee interchangeability
Installation dimensions, pressure rating, wetted materials, sealing design, construction standard, testing and documentation must be checked independently.
Adjacent types
Other options in this family
Final technical approval is required
This page is educational and intended for initial screening. Final selection must be approved against project requirements, actual service conditions and manufacturer documentation.
Send request for review