Valve Assembly and Testing in the Manufacturing Shop

ted wang
Jun 5
2 min read

Factory acceptance testing (FAT) of valves verifies that each valve meets the specified requirements before shipment to the project site. Understanding the manufacturing and testing process helps purchasers and inspectors verify quality and identify deficiencies early.

Manufacturing Process Overview

Raw material receiving inspection: chemical analysis, mechanical properties verification, PMI (positive material identification)
Casting or forging inspection: visual examination, dimensional check, non-destructive testing
Machining: body, bonnet, trim, and seat machining to dimensional tolerances
Assembly: installation of seats, trim, packing, and other internal components per procedures
Testing: hydrostatic, seat leakage, operational, and special tests per applicable standards

Hydrostatic Shell Test

ASME B16.34 requires all valves to be hydrostatically tested to 1.5 times the Class 150 (or applicable class) 100 deg F rating. The test pressure is held for a minimum duration with no leakage permitted through body, bonnet joints, or packing.

Seat Leakage Test

Seat leakage is tested per API 598 or ASME FCI 70-2 at the specified test pressure. Test medium is water for most valves; gas testing may be required for specific services. Leakage allowances depend on valve size and leakage class specified.

Special Tests

Low-pressure gas test: typically 80-100 psi nitrogen, verifying Class VI (bubble-tight) leakage for on/off valves
Fire-safe test: API 607 fire test for quarter-turn valves
Cryogenic test: per BS 6364 for LNG and low-temperature service valves
Fugitive emission test: ISO 15848 or API 624/641 for low-emission valves
Anti-static test: verifies electrical continuity between stem and body

Third-Party Inspection

Purchasers may appoint a third-party inspector to witness and certify tests at the manufacturer's works. Inspection and test plans (ITP) define the hold points, witness points, and review points for each type of test. Inspection records form part of the valve documentation package.