Sedelon Valve Knowledge Science - Common Failures and Preventive Measures of Valves

Valve in a period of working time to continuously maintain and complete the given functional requirements, so that the given parameter value to maintain in the specified range of this performance is called trouble-free, when the performance of the valve is damaged will produce failure.

1. Stuffing box leakage

This is often seen in factories.

The reasons for the leakage of the stuffing box are as follows:

①The packing is incompatible with the corrosiveness, temperature and pressure of the working medium;

②The installation method is wrong, especially when the whole packing is placed in a spiral, it is most 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;

⑦The operation is too violent.

The method to eliminate packing leakage is:

①Correct selection of packing;

②Fill in the correct way;

③If the valve stem is unqualified, it should be repaired or replaced, and the surface finish should be at least ▽5, and more importantly, it should reach ▽8 or above, and there are no other defects;

④Take protective measures to prevent rust, and those that have been rusted should be replaced;

⑤Bending of the valve stem should be straightened or updated;

⑥After the packing has been used for a certain period of time, it should be replaced;

⑦The operation should be stable, open slowly and close slowly to prevent sudden temperature changes or medium impact.

2. Leakage of closing parts

Usually, the leakage of the stuffing box is called external leakage, and the closing part is called internal leakage. Leakage of closing parts, inside the valve, is not easy to find.

The leakage of closing parts can be divided into two types: one is the leakage of the sealing surface, and the other is the leakage of the root of the sealing ring.

The causes of leakage are:

①The sealing surface is not well ground;

②The sealing ring is not tightly matched with the valve seat and valve disc;

③The connection between the valve disc and the valve stem is not firm;

④The valve stem is bent and twisted, so that the upper and lower closing parts are not centered;

⑤Close too fast, the sealing surface is not in good contact or has long been damaged;

⑥ improper material selection, can not withstand the corrosion of the medium;

⑦Use globe valve and gate valve as regulating valve. The sealing surface cannot withstand the erosion of high-speed flowing medium;

⑧Some media will gradually cool down after the valve is closed, so that the sealing surface will appear slits, and erosion will also occur;

⑨Threaded connection is used between some sealing surfaces and valve seat and valve disc, which is easy to generate oxygen concentration difference battery 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.

The preventive measures are:

①Before use, you must carefully test the pressure and leak, and find the leakage of the sealing surface or the root of the sealing ring, and then use it after treatment;

②It is necessary to check in advance whether the various parts of the valve are in good condition. Do not use the valve that the valve stem is bent or twisted or the valve disc and the valve stem are not connected securely;

③The valve should be closed firmly, not violently. If you find that the contact between the sealing surfaces is not good or there is obstruction, you should immediately open it for a little while to let the debris flow out, and then close it carefully;

④When choosing a valve, not only the corrosion resistance of the valve body, but also the corrosion resistance of the closing parts should be considered;

⑤ In accordance with the structural characteristics of the valve and correct use, the components that need to adjust the flow should use the regulating valve;

⑥For the case where the medium is cooled and the temperature difference is large after closing the valve, the valve should be closed tightly after cooling;

⑦When the valve seat, valve disc and sealing ring are connected by thread, PTFE tape can be used as the packing between the threads, so that there is no gap;

⑧A filter should be added in front of the valve for the valve that may fall into impurities.

Correct use of the valve and timely maintenance of the valve can prolong the service life of the valve.

Sedelon valves are always fully inspected before the valve leaves the factory, providing customers with high performance and high quality valves.