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The properties of steel depend not only on the chemical composition but also on the metallographic structure. Through the process of heating, holding and cooling to get different metallographic structure and desired property is heat treatment. Common heat treatments include normalizing, quenching, tempering, and annealing. Normalizing treatment: The steel is heated to 30 ° C ~ 50 ° C above the AC3...
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Anti-static device is another basic and mandatory design for ball valve. During the operation of valve, the constant friction between ball and soft seat will generate static electricity. The spark caused by static electricity may ignite the inflammable fluid inside the valve and cause a potential fire hazard. To get rid of the hidden danger, an anti-static device is invented for ball valve. Like t...
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(6) Effect of surface hydrophilicity on sealing property The hydrophilicity of the surface affects the amount of leakage due to the characteristics of the capillary. When there is a thin film of oil on the sealing surface, it is necessary to increase the pressure of the water passing through the gap. Due to the good hydrophilicity of the metal surface, kerosene can easily penetrate the gap between...
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The blow-out proof stem is one of basic design features of ball valve. Ball valve stem is inserted from the valve body inside with integral T-type shoulder to provide blow-out proof effectively. It is internally inserted as a function of backseat to assure stem sealing safety. To describe it in details, the stem is sealed by o-rings & packing rings, and held in position by the stem housing whi...
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3. The influence of pressure difference before and after valve on sealing performance Theoretically, the pre- and post-valve pressure difference and leakage are proportional. However, the test proved that, under the same conditions, the increase in leakage is more than the increase in pressure difference. 4. The influence of sealing surface material and its treatment state on sealing performance T...
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Most of ball valves own the sealant injection system. In this article, we will explain why ball valve is installed with sealant injection fittings. Generally speaking, each ball valve has two sealant injection fittings. One is located at the stem area and the other seat area, like the picture shown below. The sealant injection system of ball valve plays a part as the emergency sealing or backup se...
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The factors affecting the sealing performance of the c are as below: A. sealing surface quality; b. sealing surface width; c. pressure difference; d. sealing surface material and its processing state; e. medium properties; f. surface hydrophilicity; g. the existence of sealing oil film ; h. the solid and structural characteristics of the closure. 1) Influence of sealing surface quality on valve se...
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Before we select an appropriate ball valve, there are many factors we need to take into consideration. Seat type is one of important perspectives. Soft Seated Ball Valve The seat ring in contact with the ball part is made of soft material, such as PTFE, RPTFE, Nylon, Devlon, Peek and so on. For floating ball valve, there is only one soft seat ring for one side seat. But for trunnion ball valve, th...
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(1) Soft sealing material A. Nitrile rubber (NBR). Nitrile rubber has excellent oil resistance; heat resistance is superior to natural rubber and styrene-butadiene rubber; air tightness and water resistance are better. Nitrile rubber can be divided into butyronitrile-18, butyronitrile-26 and butyronitrile-40. Nitrile rubber is suitable for petroleum products with a temperature of -60 ° C ~ +120 ° ...
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