The API 598 standard covers the inspection and testing for all valves and is heavily referenced in the industrial sector such as oil and gas industry. The standard specifies the hold time, allowable leakage, location, as well as the method of testing and inspection. Furthermore, API 598 references MSS-SP 55 for inspection of castings.
Standard Basic Information
Title: Valve Inspection and Testing | Edition: Tenth Edition | Date of Publish: October 2016
Status: ACTIVE | Next revision to be published 2020/2021
Organization: American Petroleum Institute
Work Group: Committee on Refinery Equipment (CRE) – Subcommittee on Piping and Valves (SCOPV)
- Normative References
- Terms and Definitions
- Inspection, Examination, and Supplementary Examination
- Pressure Tests
- Pressure Test Procedures
- Valve Certification and Retesting
- Annex A
API 598 Prescribed Testings
In general, the required testing per API 598 is pressure testing the valve to ensure pressure boundary integrity and verify that the seat can seal at both high and low pressure, with a visual inspection of casting per MSS-SP 55 prior to the pressure tests.
- High pressure: air, inert gas, kerosene, water, or a noncorrosive liquid with viscosity not higher than water.
- Low pressure: air or inert gas
- Iron Valves
- Shell Tests: Listed pressures
- Backseat and Closure Test
- Valves except check valves: 1.1 times of purchase specification
- Check Valves: Listed pressures
- Steel and Alloy Valves
- Shell Test: 1.5 times rated pressure at 38 °C (100 °F) rounded up to next 25 psig
- Backseat and Closure Test
- High pressure: 1.1 times rated pressure at 38 °C (100 °F)
- Low pressure: 80 ± 20 psig
|NPS||Shell (s)||Backseat (s)||Check Valve Closure (s)||Other Valves Closure (s)|
|2.5 to 6||60||60||60||60|
|8 to 12||120||60||120||120|
Allowable Leakage Rate
API 598 differentiates check valve from all other valves when it comes to allowable leakage rate. This is because check valve inherently relies on passive pressure force to seal, which causes it to be more difficult to seal depending on the force applied on the disc. The leakage rates have been tabulated and further discussed in the following pages.
API 598 standard is written with the mindset of testing new valves. The intention is to use a higher testing pressure to verify the integrity of the valves in a shorter testing duration. Thus, it’s important to understand that there are valve designs which may be damaged when over pressurized as specified per this standard’s high pressure testing, such as softer valve seats. As such, it’s important to work with the manufacture when specifying optional high pressure testing to avoid breaking a valve for the sake of testing for a pressure the valve is never intended to see.
For information on additional valve standards please see Standards Summaries.