Inspection and Testing Regulations for Valves

1. Valve Inspection

1) Manufacturers shall conduct visual inspections on all valve bodies, covers, and seals castings to ensure compliance with MSS SP-55 specifications.

2) Manufacturers must inspect each valve to ensure compliance with this standard and procurement specifications.

3) All inspections shall be conducted according to written procedures established in accordance with the relevant standards.

2. Inspection Content (Refer to SH3518 Regulations)

1) The valve body should have a manufacturer's label with markings such as model, nominal pressure, nominal bore, and manufacturer's name.

2) Quality Certificate: Includes manufacturer's name, date of manufacture, product name, model and specifications, nominal pressure, nominal diameter, applicable medium and temperature, standard referenced, inspection conclusion and date, factory number, and signatures of inspectors and responsible personnel.

3) Valves required to undergo low-temperature sealing tests should be accompanied by a manufacturer's certificate of low-temperature sealing test approval.

4) The MT and RT of cast steel valves are agreed upon by both parties. If inspection is required, the manufacturer shall inspect according to the standards specified in the contract and issue a report.

5) For stainless steel valves requiring intergranular corrosion testing as per design documents, the manufacturer should provide a test certificate of compliance.

6) Valve外观 inspection.

The valve should be set to the following positions during transportation:

■Gate valves, stop valves, throttle valves, regulating valves, butterfly valves, and bottom valves—should be in the fully closed position.

Check valves, globe valves—should be in the fully open position.

The diaphragm valve should be set to the closed position, but not too tightly.

The check valve's valve disc should be closed and secured.

Valves must be free from damage, missing parts, corrosion, or label detachment. The valve body must be clean.

Valves should have protective caps at both ends, with handles or handwheels that operate smoothly and easily.

Valves should have a smooth and flat surface when cast, free of cracks, shrinkage holes, sand holes, blow holes, burrs, etc. (For valves that are forged, the surface should be free of cracks, laminations, spots, shouldered areas, etc.).

The check valve's valve disc or core should operate smoothly and accurately, free of eccentricity, displacement, or tilt.

Spring-loaded safety valves should have a lead seal, and lever safety valves should have a heavy hammer positioning device.

Valves lined with rubber, enameled steel, or plastic should have a smooth and even inner surface. The lining should be firmly bonded without cracks or bubbles, and should be tested with an electric spark generator.   Surface inspection of the liner did not reveal any punctures, deemed合格.

The valve flange sealing surface must meet the requirements and should not have radial scratches.

Valve Calibration

7) Inspection and Testing of Valve Drive Assembly

Valves utilizing gear and worm drive mechanisms.

The worm and worm gear should mesh well, operate smoothly, and have no binding or excessive wear.

Clean the meshing surface of the gears and bearings in the opening mechanism, and apply new lubricating oil.

Valves with closed mechanisms should be sampled at a rate of 10% and not less than one, with all parts complete and internally clean without any debris. The drive components should be free of burrs, and all gaps and mating surfaces should meet specifications. If any issues are found, the drive mechanism of the batch of valves should be inspected.

Check the cover and replace the lubricating oil if it is found to be deteriorated.

Valves equipped with chain wheel mechanisms should have the center plane of the chain frame aligned with the chain wheel. Check the chain's operation at the working position, ensuring smooth movement without falling off the track. The chain must not have defects such as open links, weld failure, rust, or mismatched pitch between the chain wheel and the chain links.

Valves driven by air or hydraulic pressure should be tested for opening and closing by using air or water as the medium, based on the working pressure of the piston. In case of necessity, the valves should undergo a sealing test.

The electric valve's transmission should not only be cleaned and inspected but also the concentricity of the coupling should be rechecked. Then, after powering on, check and adjust the valve's limit device in both fully open and fully closed positions, performing at least three trials. The electric system should operate reliably with accurate indication.

The electromagnetic valve should be powered on for opening and closing tests, which should not be less than three times. If necessary, a sealing test should be conducted on the valve while it is in the closed position.

Valves equipped with mechanical interlock devices should be tested and adjusted on a mock-up frame at the installation location. The two valves should operate in a coordinated manner, be easy to work with, and have accurate positioning.

8) Valve Additional Inspections and Tests

The welding bevels of the welding joints for the valves with butt joints should be inspected by MT or PT according to the following specifications.

Welding bevels of steel with a minimum tensile strength of ≥540 MPa and Cr-Mo low-alloy steel should be inspected.

Non-austenitic stainless steel bevels designed for temperatures ≤ -29℃ should be randomly inspected at a rate of 5%.

Alloy steel valves should be re-inspected for material quality using PM1 (or other methods), and marked accordingly. Valves that do not meet the requirements must not be used.

Before installation of alloy steel valves and valves for highly toxic, flammable medium pipelines, a spot check should be conducted on the valve body, sealing surface, and materials of gaskets and fillers with special requirements, as specified in the "Valve Specification" in the design documents. At least one item should be checked per batch. If any item fails the inspection, the batch of valves shall not be used.