Inspection scope
If no other additional items are specified in the order contract, the buyer’s inspection should be limited to the following:
a) In compliance with the regulations of the order contract, use nondestructive inspection tools and methods to inspect valves during the assembly process.
b) The visual inspection of the valves’ castings should be in accordance with JB/T 7929.
c) "Mandatory" and "optional" pressure tests.
d) Other additional inspections.
e) Review processing records and nondestructive inspection records (including the specified radiographic inspection records).
Note: All inspections should be carried out in accordance with the written procedures established in the corresponding standards.
The inspection
The valve manufacturer should conduct a visual inspection on all of the castings of valves’ bodies, bonnets and sealing elements to safeguard its compliance with JB/T 7929.
The valve manufacturer should inspect each valve to ensure compliance with applicable standards and related product standards.
General requirements for pressure testing
1. For special-structured valves that allow emergency sealing grease to be injected into the sealing surface or packing parts (except for lubricated plug valves), the injection system should be empty and inoperative during the test.
2. When testing with liquid, make sure the cavity's air is drained.
3. Before conducting a valve shell test, the valve must not be painted nor covered with any coatings that could conceal surface defects. Phosphating or similar chemical treatments used to protect the valve’s surface are allowed, but they mustn’t cover defects like leaks, air holes or blisters.
4. When performing sealing tests on gate valves, plug valves and ball valves, the body’s cavity between the bonnet and the sealing surface should be filled with a medium. Then you should apply pressure to it in order to test the pressure and avoid the gradual filling of the above parts with medium and pressure during the test, while also avoiding seal leakage.
5. When conducting a sealing test, no external force should be applied at neither ends of the valve that has an effect on the leakage of the sealing surface. The operating torque used to close the valve should not exceed the closing moment of force (torque) of the valve's design.
EC provides professional valve inspection services throughout China. Contact us if you need to accurately assess the quality of your products.
Post time: Jul-09-2021