API 598 Standard Summary

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)


  1. Scope
  2. Normative References
  3. Terms and Definitions
  4. Inspection, Examination, and Supplementary Examination
  5. Pressure Tests
  6. Pressure Test Procedures
  7. Valve Certification and Retesting
  8. Annex A
  9. Bibliography

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.

Pressure Testing

Test Media

  • High pressure: air, inert gas, kerosene, water, or a noncorrosive liquid with viscosity not higher than water.
  • Low pressure: air or inert gas

Test Pressures

  • 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

Test Duration

NPSShell (s)Backseat (s)Check Valve Closure (s)Other Valves Closure (s)
2.5 to 660606060
8 to 1212060120120

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.

Important Notes

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 access to API 598 standard, please check. IHS | Techstreet |

For information on additional valve standards please see Standards Summaries.

Other Standards