expanding gate valve|Common faults and solutions for knife gate valves

1. Leakage of closing parts of knife gate valve: The leakage of stuffing box is usually called external leakage, and the leakage of closing parts is called internal leakage. The leakage of closing parts is in the valve and is not easy to find. The leakage of the closure can be divided into two categories; one is the leakage of the sealing surface; the other is the leakage of the root of the seal. The reasons for the leakage are:
1. The sealing surface of imported pneumatic knife gate valve is not well ground;
2. The seal ring is not tightly matched with the valve seat and valve office;
3. The valve office and the valve stem are not firmly connected;
4. The valve stem is bent and twisted to make the upper and lower closing parts misaligned;
5. The closing is too fast, the sealing surface is in poor contact or has long been damaged;
6. Improper selection of materials can not withstand the corrosion of the medium;
7. The imported stop valve and imported gate valve are used for adjustment, and the sealing surface cannot withstand the impact of high-speed flowing medium;
8. Some media gradually cool down after the inlet valve is closed, causing fine cracks on the sealing surface, which will also cause erosion;
9. Threaded connections are used between some sealing rings and valve seats and valve seats, which can easily produce oxygen concentration difference batteries and corrode loose;
10. Due to welding slag, rust, dust and other impurities embedded, or mechanical parts in the production system fall off and block the valve core, the knife gate valve cannot be closed tightly.

2. Leakage of stuffing box of imported electric knife gate valve:
1. The packing is not compatible with the corrosiveness, temperature and pressure of the working medium;
2. The filling method is wrong, especially if the whole packing is spared and screwed in, it is most likely to cause leakage;
3. The processing accuracy of the valve stem or the surface finish is not enough, or there is ellipse, or there are notches;
4. The valve stem has been pitted or rusted due to lack of protection in the open air;
5. The valve stem is bent;
6. The filler has aged after being used for too long.

3. Imported knife gate valve stem lifting failure:
1. The thread is damaged due to excessive operation;
2. Lack of lubricant or lubricant failure;
3. The valve stem is bent and twisted;
4. The surface finish is not enough;
5. Inaccurate fit tolerances and bite too tightly;
6. The stem nut is tilted;
7. Improper material selection; for example, the stem and stem nut are made of the same material, which is easy to bite;
8. Corrosion of thread wave medium (referring to dark stem valve or valve with stem in the lower part);
9. The open-air valve lacks protection, and the valve stem thread is covered with dust and sand, or is rusted by rain, dew, frost, and snow.

4. Others:
1. Valve body cracking: generally caused by freezing. When the weather is cold, the knife gate valve must be insulated and heated.
2. Handwheel damage: caused by impact or strong operation of the long lever. It can be avoided as long as the operator or other relevant personnel pay attention.
3. The packing gland is broken: the pressure is uneven when the packing is pressed, or the gland is defective. To compress the packing, rotate the screws symmetrically and not skew. Attention should be paid not only to large and key parts during manufacturing, but also to minor parts such as glands, otherwise the use will be affected.
4. The connection failure between the valve stem and the gate: the knife gate valve adopts a large number of connection forms between the long square head of the valve stem and the T-shaped groove of the gate. The T-shaped groove is sometimes not processed, so the long square head of the valve stem wears faster. Mainly from the manufacturing aspect to solve. But the user can also make up the T-row grooves to give her a certain smoothness.