Safety and relief valves are the last line of defence against overpressure, automatically opening to relieve excess pressure and protect equipment, personnel, and the environment. AQ Process Systems sources and exports spring-loaded, pilot-operated, and balanced bellows safety valves certified to international codes.
We supply safety valves for steam boilers (ASME Section I, IBR), pressure vessels (ASME Section VIII), and process applications (API 520/526). Sizes from 1/2" to 12" in carbon steel, stainless steel, and alloy materials with set pressures from 0.5 barg to 400+ barg.
All safety valves are supplied set, tested, and sealed with certification documentation including the set pressure, popping pressure, blowdown, and capacity test results. We also offer valve testing, recertification, and repair services.
| Product | Specification | Description |
|---|---|---|
| Spring-Loaded Safety Valves | ||
| Conventional Safety Valves | 1/2", 8" | ASME I / VIII | Flanged | Standard spring-loaded safety valves for steam, air, gas, and liquid overpressure protection, open-bonnet or closed-bonnet designs. |
| Balanced Bellows Safety Valves | 1", 8" | API 526 | Back-pressure compensation | Bellows-balanced safety valves compensating for downstream back-pressure, maintaining set pressure accuracy regardless of discharge conditions. |
| Low-Lift Safety Valves | Boiler safety | IBR certified | Pop-action | Low-lift safety valves for steam boiler protection, IBR and ASME Section I certified with full-lift pop action. |
| Pilot-Operated Relief Valves | ||
| Pilot-Operated Relief Valves (PORV) | 1", 12" | API 520/526 | Gas or liquid service | Pilot-operated safety valves, using a pilot valve to control the main valve opening. Higher capacity and tighter shutoff than spring-loaded types. |
| Modulating Pilot-Operated Valves | Proportional opening | Process applications | Modulating PORVs that open proportionally to overpressure, reducing valve chatter and product loss in process applications. |
| Specialty | ||
| Thermal Relief Valves | 1/2", 2" | Low-flow | Blocked-in liquid protection | Small thermal relief valves protecting against hydraulic expansion in blocked-in liquid-filled piping and equipment. |
| Vacuum Relief Valves | 2", 24" | Atmospheric protection | Vacuum relief valves preventing vessel collapse from internal vacuum, weight-loaded or spring-loaded designs. |
A safety valve opens rapidly (pops) when the set pressure is reached, used for compressible fluids (steam, gas, air). A relief valve opens proportionally to overpressure, used for incompressible fluids (liquid). A safety relief valve (SRV) can function as either, depending on the application. The terminology is defined in API 520 and ASME PTC 25.
Our safety valves carry ASME Section I (boilers), ASME Section VIII (pressure vessels), API 526 (standard dimensions), PED (European Pressure Equipment Directive), IBR (Indian Boiler Regulations), and CRN (Canada). Certification is selected based on the jurisdiction and application code requirements.
Yes. Pilot-operated relief valves (PORVs) use a small pilot valve to sense process pressure and control the opening of the main valve. Advantages over spring-loaded types include: higher capacity (full bore opening), tighter shutoff (up to 98% of set pressure), and immunity to back-pressure effects. Preferred for high-pressure gas and process applications.
Yes. All safety valves are supplied set, tested, and sealed to the customer-specified set pressure. Test documentation includes set pressure, popping/reseating pressure, blowdown, and capacity verification. Valves are locked and lead-sealed after testing to prevent tampering.
Testing intervals depend on the applicable code and jurisdiction. Typical intervals are annually for boiler safety valves, every 3-5 years for process safety valves, and as required by the plant's Risk Based Inspection (RBI) programme. We can advise on the testing requirements for your specific application and jurisdiction.
Share your valve specification, size, pressure class, material, end connections, we respond within 24 hours.