Valves are widely used in various industries, but valve failures are also common during the application process. Once a valve malfunctions, it can be very difficult to repair in the later stages, so preventive maintenance and after-sales service from the valve manufacturer are important during the use of the valve.
The following are common faults and preventive measures of valves:
1. Leakage of stuffing box
In factories, it is common to see phenomena such as running, emitting, dripping, and leaking at valve locations.
The reasons for leakage are as follows:
The corrosiveness, temperature, and pressure of material A are not compatible with the working medium;
The filling method is incorrect, especially when the entire packing is placed in a spiral manner, which is most likely to cause leakage;
The machining accuracy or surface smoothness of the valve stem is insufficient, or there is ovality or scoring;
The valve stem has developed pitting corrosion or rusted due to lack of protection in the open air;
The valve stem is bent;
The filler has been used for too long and has aged;
The operation process is too aggressive.
The method to eliminate packing leakage is:
Correct selection of fillers;
Fill according to the correct method;
If the valve stem processing is not qualified, it should be repaired or replaced. The minimum surface smoothness should reach ▽ 5, and more importantly, it should reach ▽ 8 or above, and there should be no other defects;
Take protective measures to prevent rusting, and replace those that have already rusted in a timely manner;
The bent valve stem should be straightened or updated;
After a certain period of use, the filling material should be replaced;
Attention should be paid to smooth operation, slow opening and closing, to prevent temperature fluctuations or medium impact.
3. Valve stem lifting failure
The reasons for the malfunction of valve stem lifting are:
Excessive force caused damage to the threads;
Lack of lubrication or lubricant failure;
C valve stem bending and twisting;
The surface smoothness is insufficient;
The fitting tolerance is not accurate and the bite is too tight;
The valve stem nut is tilted;
Improper material selection, for example, if the valve stem and valve stem nut are made of the same material, it is easy to bite;
The thread is corroded by the medium (referring to valves with hidden stem or stem nuts at the lower part);
The outdoor valve lacks protection, and the valve stem thread is covered with dust and sand, or corroded by rain, dew, frost, and snow.
Preventive methods:
Carefully operate, do not use excessive force when closing, and do not reach the top dead center when opening. After opening enough, reverse the handwheel one or two turns to ensure that the upper side of the thread is tightly fitted, so as to prevent the medium from pushing the valve stem upward and impacting it;
Regularly check the lubrication condition and maintain normal lubrication status;
Do not use long levers to open and close valves. Workers who are accustomed to using short levers should strictly control their force to prevent twisting and bending of the valve stem (referring to valves directly connected to the handwheel and valve stem);
Improve processing or repair quality to meet regulatory requirements;
The material should be corrosion-resistant, suitable for working temperature and other working conditions;
Do not use the same material as the valve stem for the valve stem nut;
When using plastic as the valve stem nut, it is necessary to verify the strength, not only considering good corrosion resistance and low friction coefficient, but also considering the strength issue. If the strength is not enough, do not use it;
Outdoor valves should be equipped with valve stem protective sleeves;
I keep the valve open and regularly turn the handwheel to prevent the valve stem from rusting.
