How to deal with valve internal leakage
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A common problem encountered with domestic valves is that they do not close tightly after being opened twice, resulting in internal leakage. Please give us your advice on how to avoid this.
Please list what material pipeline it is used for and where it is located, so that everyone can refer to it and come up with ideas.
This problem usually occurs on gate valves and is generally a problem with the material of the sealing surface. If the valve seat sealing surface and the gate sealing surface are made of the same material, for example, D507 (that is, 13% Cr) is used, and their hardness is roughly the same, the sealing surface of the gate will be strained during the opening and closing process, resulting in loose sealing and internal leakage. It appears more often on stainless steel valves such as 304 and 316 whose sealing surfaces are made of body material. Especially for valves with oil and grease removal requirements, they are more likely to be strained. The current common practice in the industry is to use 5# or 8# internal parts to increase the hardness of the sealing surface, or to ensure that there is a hardness difference of greater than or equal to 50HB between the two sealing surfaces through heat treatment and other means. Debris in the medium is also one of the causes of seal leakage. Globe valves and check valves basically do not have the phenomenon mentioned by the original poster. Ball valves should consider the smoothness of the ball, the hardness of the valve seat, and the cleanliness of the medium. This post was last edited by yunfly on 2007-12-23 08:30 ]
Our catalytic cracking unit and the inlet and outlet valves of the slurry pump are often worn out. The reason is that the bottom of the fractionation tower contains a catalyst, which washes away the valve core. Every time the pump is inspected, it cannot be closed tightly. This time we are going to replace the valve. “Yunfei, please give me a recommendation, and I’m going to add double valves to the inlet and outlet of the pump, just in case.
Worker M gave me the problem. I am really not good at recommending valve brands. I have remained silent on all the posts about brand recommendations in the forum. Without the saying “silence is golden”, there is really no guarantee of the reliability of the recommended brands. I don’t understand the catalytic cracking process and I don’t understand what catalyst you use, so the legal department provides specific help. But one thing is certain, the valve material selected must have high resistance to corrosion and erosion. Ask other students to continue to help.
Our current production process is similar to what Mr. M said. What we use is to pass hydrogen into the reactor and then add a catalyst to reduce it to obtain the reductant. Our catalyst is alkaline corrosion. We are now using valves from Jiu0 Valve Factory, which are made of carbide (Y type). The effect now is pretty good. In the past, we used valves from Beijing Valve Factory. The situation was similar to what Mr. M said. It leaked after being switched on and off a few times. If possible, Mr. M could give it a try.~
To add, we mostly use ball valves, I don’t know about the others.
The impact of media containing solid particles similar to catalytic devices on valves does exist. Therefore, it is necessary to consider the selection and operation, for example: Selection: Select valves with the same diameter as the pipeline, such as ball valves, plug valves, etc., to reduce the possibility that the gate valve will easily accumulate solids in the valve channel and cannot be closed.: Reduce debris entering the valve, fully open the gate valve to avoid erosion and wear caused by throttling, inject flushing medium into the valve channel, etc.
The ball valve must be fully open and fully closed, otherwise this situation will easily occur. If it is left in a half-open state for a long time, it will easily cause damage to the spherical surface and cause internal leakage. In addition, the sealing surface of the stop valve must be made of soft material.[The seal is still a hard seal, sometimes there will be leakage.
If the valve has slight internal leakage, it can be opened and closed several times to increase the fluid flow rate, wash away impurities on the sealing surface, and inject sealing grease. If the internal leakage is serious, the pipeline must be stopped and the valve repaired. If it cannot be repaired, a new valve must be replaced. The key is to strictly control quality during the design, procurement, and installation processes to prevent substandard products from being installed, so as to nip problems in the bud.
The cause of internal leakage may be corrosion. I think it can only be repaired, not replaced with new valves. Our factory has replaced many valves, all for this reason.
Pay attention to purging to prevent debris from getting stuck on the sealing surface or damaging the sealing surface. At the same time, if the pressure difference is too large, causing erosion and corrosion, you can choose another valve such as a throttle valve. Find out in detail the reasons why the valve is easily damaged, and targeted solutions will be effective.
If the internal leakage is caused by the medium wearing out the valve core, it is difficult to fix. It is usually dismantled and polished to repair.
The oil slurry inlet and outlet valve must be fully open and fully closed, and cannot be only half-open during operation, otherwise it will wear out faster.
Flush? corrosion? Abrasion? It must be clearly distinguished! What about flushing? Just increase the opening, reduce the diameter, and increase the hardness of the material! What about corrosion? Just choose a higher level of corrosion-resistant material! What about abrasion? Increase the opening, reduce the diameter, and choose ceramic or dual-phase steel!