Valve leakage mainly includes two kinds of leakage of stuffing box and leakage of closing parts.
The main reasons for stuffing box leakage are:
①The packing is not compatible with the corrosiveness, temperature and pressure of the working medium;
②The filling method is wrong, especially when the whole packing is placed in a spiral, it is more likely to cause leakage;
③The machining accuracy or surface finish of the valve stem is not enough, or there is ovality, or there are nicks;
④The valve stem has been pitted, or rusted due to lack of protection in the open air; ⑤The valve stem is bent; ⑥The packing has been used for too long and has aged;
The main reasons for the leakage of closing parts are:
①The sealing surface is not well ground; ②The sealing ring is not tightly matched with the valve seat and the valve disc; ③The valve disc and the valve stem are not firmly connected; Surface contact is not good or has long been damaged; ⑥ improper material selection, can not withstand the corrosion of the medium; ⑦ use globe valve and gate valve as regulating valve. The sealing surface cannot withstand the erosion of the high-speed flowing medium; ⑧ Some media gradually cool down after the valve is closed, causing the sealing surface to have slits and erosion; 9. Threaded connection is used between them, which is easy to produce oxygen concentration cells and corrode loose; ⑩The valve cannot be closed tightly due to the embedding of impurities such as welding slag, rust, dust, or mechanical parts in the production system that fall off and block the valve core.