Wholesale China Electrical Testing And Compliance Factories Pricelist – Valve Inspection – EC

I. Quality Requirement

The relevant requirements for valve quality have been set forth in standards.

①The chemical component and mechanical property of the valve’s main materials conform to requirements in relevant material standards.

②The shape and size error of the valve castings meet the regulations in drawings.

③The non-processed surface of the valve castings shall be flat, smooth and free from adhering sand, oxide skin, pore, sand inclusion, cracks or other defects. The typecasting sign shall be clear, and the sprue and riser shall keep in level with castings surface after cleaning.

④All valve parts shall be connected firmly and free from loose.

⑤The results of pressure test and sealing performance test for valve conform to requirements of relevant test standards.

⑥The valve operation shall be under nominal pressure and designated differential pressure, and starting and stopping valve shall be free from clamping.

⑦It has the certain operation times and service life.

⑧It‘s featured by better flow capacity (meaning the pressure loss at valve is smaller after passing through it).
II. Test and Inspection Method

1、Castings Quality

The castings shape and size shall conform to the requirement of technical drawings and regulations from demander. The minimum wall thickness of valve parts, structural length error, abrasion displacement allowance of gate plate shall not lower than requirements in product technical standard and product drawings. The surface of rough valve and pressured shell of finished valve product shall be no cracks, cold shut, sand inclusion, pore and other defects. The adhering sand, sprue, riser and oxide skin on castings surface shall be cleaned off.

2、Pressure Test

The pressure test is the most basic test for valve. Each valve shall be carried out for pressure test before delivering from factory. The test pressure and time duration follow the regulation in GB/ T13927, and test items cover shell test and sealing test. If any of back sealing structure on valve, it’s required to conduct back seal test. During the test process, the external force that may affect test result shall not be applied to valve. The test pressure shall keep constant during the process of pressure holding and testing.

The shell test for valve is a kind of pressure test for whole valve shell connected by valve body and cover. Its purpose is to check the compactness between valve body and cover, namely the anti-pressure capacity of whole shell including connection of valve body and cover.

The sealing test is to check the performance of on-off parts and valve sealing pair, and can be divided into high-pressure liquid sealing test and low-pressure air sealing test.