Safety Valve Certification Explained

Introduction

Safety valve certification in Australia is primarily derived from the interaction between AS 1210 and AS 1271.

AS 1210 applies to the protected pressure equipment and establishes the requirement for adequate certified relieving capacity. AS 1271 applies to the safety valve and provides the Australian basis for valve performance, capacity rating and certification.

These requirements are best understood as two connected parts. The protected vessel or system must have adequate certified relieving capacity for the nominated duty, and the safety valve must have a recognised capacity basis with the individual valve tested and documented against the applicable acceptance criteria.

Together, these standards define separate parts of the same certification chain.

1. AS 1210 and the Protected Equipment

AS 1210 is the Australian pressure vessel standard. In relation to safety valves, its function is to ensure that the protected equipment has adequate overpressure protection.

This requirement is addressed through AS 1210:2010 Section 8.6, which sets out the required discharge capacity of pressure-relief devices. In practical terms, the installed pressure-relief device must have sufficient relieving capacity for the applicable overpressure condition. The valve selected for the duty must therefore have a certified relieving capacity suitable for the required flow case.

AS 1210 then links this equipment requirement to the valve certification basis. AS 1210:2010 Section 8.6.5 requires the capacity of safety valves and relief valves selected to meet Section 8.6 to be certified in accordance with AS 1271 and adjusted as necessary for the fluid being relieved.

AS 1210:2010 Section 8.7 separately sets out the pressure-setting requirements for pressure-relief devices installed on pressure equipment.

The result is that AS 1210 establishes what the protected equipment requires, but it does not normally certify the safety valve itself. The safety valve’s capacity must be supported by AS 1271 or another recognised equivalent basis.

2. AS 1271 and the Safety Valve

AS 1271 is the Australian standard for safety valves and related fittings for boilers and unfired pressure vessels. It covers the valve itself, including design, construction, testing, capacity rating and certification.

The relevant AS 1271 certification and performance requirements include:

• Set pressure tolerance: AS 1271:2003 Section 3.4.2(a)
• Lift: AS 1271:2003 Section 3.4.2(b)
• Adjustable blowdown: AS 1271:2003 Section 3.4.2(c)
• Non-adjustable blowdown: AS 1271:2003 Section 3.4.2(d)
• Blowdown for incompressible fluids: AS 1271:2003 Section 3.4.2(e)
• Capacity rating, classification and certification: AS 1271:2003 Section 3.5
• Method of rating: AS 1271:2003 Section 3.5.1
• Classification of rated capacity: AS 1271:2003 Section 3.5.2
• Certification: AS 1271:2003 Section 3.5.3
• Other certification, including previous testing and overseas testing: AS 1271:2003 Section 3.5.4
• Manufacturer records and retained capacity records: AS 1271:2003 Section 2.5.6

These clauses show that AS 1271 deals with both valve performance characteristics and the certification of rated capacity. The certified capacity established under AS 1271 is then used as the capacity basis when demonstrating compliance with the AS 1210 relieving capacity requirements for the protected equipment.

3. Manufacturer Capacity Certification and International Type Testing

Most safety valves supplied in Australia are manufactured overseas. Their relieving capacity is therefore typically established through capacity testing and certification conducted under recognised international standards and international type-testing programs.

This is permitted within the Australian certification pathway where the alternative basis is recognised, documented and applicable to the valve being supplied. AS 1210:2010 Section 8.1 allows pressure-relief devices, where appropriate, to comply with AS 1271 or an equivalent basis. AS 1210:2010 Section 8.6.5 then requires the capacity of safety valves and relief valves selected to meet the required discharge capacity provisions of Section 8.6 to be certified in accordance with AS 1271 and adjusted as necessary for the fluid being relieved.

AS 1271:2003 Section 3.5.4 provides the valve-side mechanism for this. It allows capacity certification to be supported by previous testing, including testing conducted outside Australia, provided the certification is supported by documentation and sufficient information to prove that the test results apply to the valves under consideration.

This means an internationally type-tested valve does not normally need to be flow-tested again in Australia simply because it is being supplied into the Australian market. The requirement is that the capacity basis must be recognised, documented and applicable to the valve and intended duty.

Common recognised sizing, selection, capacity or certification bases include:

• ASME Section I: boiler safety valve code basis
• ASME Section VIII: pressure vessel safety valve code basis
• API 520: pressure relief valve sizing and selection basis
• ISO 4126: international safety valve performance and capacity basis
• AD 2000-Merkblatt A2: German pressure equipment safety valve sizing and capacity basis

These standards and certification systems do not all perform the same function. Some provide sizing and selection methodologies, while others establish valve performance requirements, rated relieving capacity certification, discharge coefficients, or the basis for the manufacturer’s certified capacity data.

4. Australian Workshop Certification and Verification Scope

In Australia, a workshop certificate for a safety valve is normally an AS 1271-based individual valve test certificate.

This certificate has a different function from a manufacturer’s capacity certificate. The workshop certificate confirms the tested condition of the specific valve at the time of testing. It does not, by itself, establish or verify the valve’s inherent design attributes such as certified relieving capacity, coefficient of discharge, full rated flow, full lift or blowdown performance.

For routine workshop certification, the primary test item is the valve’s observed opening pressure compared with the nominated set pressure or CDTP, assessed against the AS 1271 pressure setting tolerance.

Where specified, seat leakage may also be tested and recorded to API 527.

A typical AS 1271-based workshop certificate may therefore confirm:

• Valve identification
• Nominated set pressure or CDTP
• Observed opening pressure
• Assessment against AS 1271 pressure setting tolerance
• Reference gauge or calibrated instrument
• Date of test
• Test result
• Seat leakage result where API 527 is specified

Routine workshop certification is therefore generally best regarded as confirming only the characteristics actually verified during the test, typically opening pressure and, where specified, seat tightness.

5. Workshop Testing Limitations

A standard Australian workshop test rig is normally configured to apply pressure to the valve, observe the opening pressure, and confirm seat tightness where required. It is not normally configured as a flow-capacity or full-performance test facility.

This distinction is important because lift, blowdown and rated capacity are performance characteristics that depend on the valve operating under suitable flow conditions. API RP 576:2017 Section 5.4 notes that functional testing and blowdown measurement require similar media properties and sufficient flow capacity to fully cycle the valve. It also notes that, because test facility volume is limited, it is usually impractical to obtain a specific blowdown value on a maintenance shop test block.

API RP 576:2017 Annex A.1 makes the same practical distinction. It explains that shop test blocks are used to determine set pressure and tightness, but do not duplicate field conditions exactly. It also notes that the amount of liquid or gas a shop test block can discharge is limited, and that it is not generally practical to measure relieving capacity or blowdown on a shop test block.

ASME PTC 25:2018 also separates routine bench testing from performance testing. ASME PTC 25:2018 Section 9 treats set pressure, blowdown and lift as computed operational characteristics only where those characteristics are actually tested and supported by suitable recorded data. ASME PTC 25:2018 Section 10 also requires a test report to contain sufficient supporting information to prove that the objectives of the test have been met. This would require adherence to a specific testing methodology to demonstrate compliance and verify that the stated performance characteristics have been properly assessed.

For this reason, a standard workshop certificate should not state or imply that certified relieving capacity, coefficient of discharge, full rated flow, full lift or blowdown performance have been verified unless the test facility, test medium, flow capacity, instrumentation and documented method are suitable for those characteristics and the applicable fluid service.

6. Summary

Safety and relief valve certification in Australia is primarily derived from the interaction between AS 1210 and AS 1271. AS 1210 establishes the pressure equipment requirement for adequate certified relieving capacity, while AS 1271 provides the Australian basis for safety valve performance, capacity rating and certification.

The valve’s certified capacity is used to demonstrate that the selected valve can satisfy the AS 1210 relieving capacity requirement for the protected equipment. This capacity is normally supported by manufacturer certification, recognised international type testing, or another accepted certification basis recognised through AS 1271.

AS 1271 also defines the primary valve acceptance criteria, including set pressure tolerance, lift, blowdown requirements and capacity certification requirements. These criteria establish the performance basis against which the valve design and individual valve testing are considered.

An AS 1271-based workshop certificate serves a more specific function. It normally confirms that the individual valve has been tested against the nominated set pressure or CDTP and assessed against the AS 1271 pressure setting tolerance. Where specified, seat tightness may also be verified using API 527. It does not commonly establish or re-establish certified relieving capacity, coefficient of discharge, full lift or blowdown performance unless those characteristics have been specifically tested using suitable equipment and documented methods.

The practical distinction is that the manufacturer’s type-tested capacity certification confirms the rated performance of the valve design, while workshop certification considers the tested condition of the individual valve and its calibration. Together, these documents demonstrate both that the valve design is suitable for the application and that the individual valve has been correctly tested for service.