Pressure retention in the inner chamber of the ball valve (floating ball)
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In ball valves (floating ball type), pressure is maintained in the internal chamber; the floating ball achieves sealing through pressure. The company has been manufacturing ball valves, and it uses dual-pressure application for this purpose. The valve inspectors at Shanghai Tianxiang Company, who are responsible for inspecting goods for foreign clients, have consistently demanded that pressure be maintained inside the chamber, which has led to conflicts with the company’s technical, production, and quality control teams. Who is right after all?
Ball valves (floating ball type) can only be pressure-tested on one side; pressure testing must be carried out separately on both sides. The medium-chamber pressure retention test is applicable to fixed ball valves. The testing methods are different.
Is this description complete? During the sealing test of a floating ball valve, the middle chamber must be under pressure. The pressure application procedure is as follows: open the valve partially, apply pressure, close the valve, maintain the pressure on the inlet side, release pressure on the outlet side, and check for any leaks ； Similarly, look at the other side. However, it is inappropriate to use pressurization in a single middle cavity with pressure relief at both ends as a criterion for determining sealing.
Observe the pressure application method for maintaining pressure in the cavity: Valve opened – Valve pressurized – Valve closed – Valve removed from the pressure applicator – Water filled into one end of the valve – Valve opened, with a sound indicating pressure release heard.
For pressure retention in the middle cavity, as a TPA, around 2008, I encountered this in an \"iron casting valve manufacturing plant\" – the factory carried out such tests on the gate valves it produced itself
Many manufacturers in Wenzhou use the method of pressurizing the internal chamber in order to improve the efficiency of pressure testing. I asked a senior engineer about this, and he said that although this method does not conform to the sealing principle of floating ball valves, if there are no leaks on either side of the internal chamber when under pressure, then there will be no leaks even during normal pressure testing. I wonder whether this inspector is deliberately asking for this approach to be used
Sometimes: According to API 598, there is no leakage during pressure testing on both sides, but leakage occurs when maintaining pressure in the middle chamber, which leads to rework and delivery delays
Is there any risk? Because, are some spheres drilled to relieve pressure in the central cavity?
This method won’t work for drilling spheres; I’ve never encountered such a situation before. It is quite common for there to be no leaks when testing each side separately, but leaks to occur in the central chamber. In the case of our company’s soft-seal ball valves, increasing the compression of the sealing ring is usually used to improve the success rate of pressure tests; however, this increases the force required to open and close the valve. More reputable companies will precision-machine the sealing rings, which also helps a lot. A newbie who has been in the field for not long; I’m not sure if what I’m saying is correct{:1_90:}
The pressure retention in the middle cavity is satisfactory； Does testing the valve on both sides cause leakage?
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