Knife gate valve troubleshooting

First, knife-type gate valve closure leakage:

Leakage of the stuffing box is often called an external leak. Leakage of the closure is called endoleak. Leakage of the closure is present in the valve. It is not easy to detect. Leakage of closures can be classified into two categories; one is leakage at the sealing face; the other is leakage at the root of the seal. The causes of leaks are:

1. The seal surface of the knife gate valve is not well ground;

2, seals and valve seats, valve office do not tie tightly;

3, valve office and valve stem connection is not reliable;

4. The valve stem is bent and twisted so that the upper and lower closing parts are not aligned.

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

6, improper material selection, can not stand the corrosion of the media;

7. The cut-off valve and gate valve are used for adjustment, and the sealing surface cannot withstand the impact of high-speed flowing medium;

8, some media, gradually cooled after the valve is closed, so that the sealing surface appears a thin seam, there will be erosion;

9, some seals and valve seats, valve between the use of threaded connections, easy to produce oxygen concentration battery, corrosion loose;

10, due to welding slag, rust, dust and other impurities embedded in the production system or a mechanical part off the plug valve plug, so that the knife-type gate valve can not be closed.

Second, knife gate valve packing leakage:

1. The corrosiveness, temperature and pressure of the filler and working medium are not suitable;

2. The loading method is wrong, especially the entire packing is put into the spare screw, which is most likely to cause leakage;

3, valve stem machining accuracy or surface finish is not enough, or oval, or nicks;

4. The valve stem has pitted or rusted due to lack of protection in the open air;

5, valve stem bending;

6, filler has been used for too long has been aging.

7, the operation is too fierce.

Third, knife-type valve stem lifting failure:

1, too much damage to the thread;

2, lack of lubricant or lubricant failure;

3, valve stem bending;

4, the surface finish is not enough;

5, with inaccurate tolerances, too tight bite;

6, stem nut tilt;

7. Improper material selection; for example, the stem and the stem nut are the same material, which is easy to bite;

8, thread wave dielectric corrosion (refer to the dark rod valve or valve stem in the lower valve);

9, the lack of protection of open-air valves, valve stem thread full of dust sand, or rain, frost, snow and other rust.

Fourth, other:

1, the valve body cracking: generally caused by freezing. When the weather is cold, the knife gate valve must have thermal insulation and heating measures.

2, hand wheel damage: impact or long lever due to violent operation. It can be avoided as long as the operator or other concerned person pays attention.

3. Fracture of packing glands: When the packing is pressed, the force is not uniform, or there is a defect in the gland. Press the packing tightly and rotate the screws symmetrically. When manufacturing, it is necessary not only to pay attention to large parts and key parts, but also to secondary parts such as glands, otherwise it will affect the use.

4. Failure of connection between valve stem and gate plate: The knife-type gate valve adopts many types of connection between the rectangular head of the valve stem and the T-shaped groove of the gate plate. The T-shaped groove is sometimes not machined, thus making the stem of the valve rod wear faster. Mainly from the manufacturing side to solve. However, the use of units can also be T-line groove processing, so that she has a certain degree of finish.