API Standard 598

API Standard 598

API Standard 598, from the American Petroleum Institute, provides industry standards for valve ratings and valve leakage. The standard is currently in the 9th edition, which was released in 2009.

Scope

API 598 covers the inspection, examination, and testing requirements for resilient-seated, nonmetallic-seated, and metal-to-metal-seated gate, glove, plug, ball, check, and butterfly valves. It is relevant to examination and testing by the valve manufacturer, supplementary examinations performed at the valve manufacturer’s plant, and pressure tests performed at either the plant or another mutually agreed-upon facility.

Tests

API 598 specifies the following tests and examinations:

TEST	PURPOSE
Visual examination	Assure compliance with all applicable standards for all valve bodies, bonnets, covers, and closure elements
Shell tests	Validate the soundness of the pressure containing structures within the valve
Shell test High-pressure pneumatic shell test
Backseat tests	Verify leakage through the stem or shaft to the seal
Low-pressure backseat test High-pressure backseat test
Closure tests	Verify leakage through the closure mechanism
Low-pressure closure test High-pressure closure test Double block and bleed high-pressure closure test

Testing requirements

• Shell tests are required for all gate, globe, plug, check, floating ball, and butterfly and trunnion mounted ball valves.
• Backseat tests are required for all gate and globe valves.
• Closure tests are required for all gate, globe, plug, check, floating ball, and butterfly and trunnion mounted ball valves, with the type (low- or high-pressure) depending on the valve size and class.

Test fluids

TEST	TEST FLUID
Shell High-pressure backseat High-pressure closure	Air, inert gas, kerosene, water, or a noncorrosive liquid with a viscosity less than or equal to that of water (5°C to 50°C [41°F to 122°F], unless otherwise specified by the purchaser)
Low-pressure backseat Low-pressure closure	Air or inert gas

A full copy of API 598, with complete testing procedures and specifications, can be purchased from the American Petroleum Institute.