The test method of Level III is the same as that of Level IV. However, the allowable leakage is 0.1% of the rated flow of the valve. Level III is usually used as a pressure balanced dual channel, double seat regulating valve without continuous pressure balance seal, such as O-ring is higher than the standard of ordinary level. The test method of Level II is the same as that of Level II, and the allowable valve seat leakage is 10% of the rated flow of the valve. Like Level III, this level is usually used as a double channel, double seat valve and pressure balance valve without continuous pressure balance seal. Level I When the valve to be tested is designed according to the basic type, the Level I standard allows some amendments to Level II, III or IV, and the test may not be conducted after the agreement between the supplier and the demander is reached.

1、 The application scope of internal thread pneumatic ball valve The internal thread pneumatic ball valve and butt welding pneumatic ball valve are applicable to various pipelines with PN1.0~4.0MPa, operating temperature of - 29~180 ℃ (the sealing ring is reinforced polytetrafluoroethylene) or - 29~300 ℃ (the sealing ring is aligned polystyrene), and are used to cut off or connect the medium in the pipeline. Different materials can be used for water, steam, oil, nitric acid, acetic acid and other media.