API 598-Valve Test Standard and Test Time

Main test items and requirements

Shell Test

Purpose: To verify the strength and sealing of the valve body and valve cover.
Test pressure: Generally 1.5 times the nominal pressure of the valve (such as 800-pound valves calculated at 1.5 times the rated pressure)
Test medium: Water, kerosene or non-corrosive liquid, temperature not exceeding 52°C.
Duration: Depending on the valve specification (NPS), the shortest is 60 seconds (≤NPS 2″) to 300 seconds (≥NPS 14″).
Leakage requirements: No visible leakage or surface wetting is allowed.

Backseat Test

Applicability: All valves with upper sealing structure (except bellows sealed valves).
Test pressure: the same as the shell test pressure or 110% of the design pressure difference.
Duration: the same as the shell test time.
Leakage requirement: no visible leakage.

Low-Pressure Seal Test

Test pressure: 0.5-0.7 MPa (60-100 psi), or 1.1 times the nominal pressure.
Test medium: air or inert gas, suitable for small size or low pressure valves.
Duration: at least 1 minute (usually 60 seconds).
Leakage requirement: no visible leakage is allowed for non-metallic sealing valves;

High-Pressure Seal Test

Test pressure: 1.1 times the nominal pressure, or 110% of the design pressure difference.
Test medium: water, kerosene or gas (buyer’s consent required).
Duration: at least 5 minutes (usually 300 seconds).
Leakage requirement: the same as the low-pressure seal test, but the leakage rate is slightly higher.

High-pressure gas shell test

Applicable conditions: only performed when specified in the order.
Test pressure: 110% of the design pressure and must be performed after the hydraulic shell test.
Leakage requirements: No visible leakage is allowed.