Valves have a wide range of applications in various industries, but in the application process, valve failure is also very common. Once the valve fails, it is very troublesome in the later maintenance, so preventive maintenance during the use of the valve and the after-sales service of the valve manufacturer are very important.
The following are common failures and preventive measures of valves:
Valve stem lifting failure
The reasons for valve stem lifting failure are:
a. Too much operation damages the thread;
b Lack of lubrication or lubricant failure;
c The valve stem is bent and twisted;
d The surface finish is not enough;
e The fit tolerance is not accurate and the bite is too tight;
f The stem nut is inclined;
g Improper selection of materials, for example, the stem and stem nut are made of the same material, which is easy to bite;
h The thread is corroded by the medium (referring to the dark stem valve or the valve with the stem nut at the bottom);
i The open-air valve lacks protection, and the thread of the valve stem is covered with dust and sand, or is corroded by rain, dew, frost, and snow.
Methods of prevention:
a. Operate carefully, don't use violent force when closing, do not reach the top dead center when opening, turn the handwheel one or two turns after opening enough to make the upper side of the thread tightly, lest the medium push the valve stem upward impact;
b Frequently check the lubrication conditions and maintain normal lubrication status;
c Do not use long levers to open and close the valve. Workers who are accustomed to using short levers should strictly control the force and measure to prevent twisting the valve stem (referring to the valve with the hand wheel and the valve stem directly connected);
d Improve the quality of processing or repair to meet the requirements of the specification;
e The material should be corrosion resistant and adapt to the working temperature and other working conditions;
f The stem nut should not be made of the same material as the stem;
g When using plastic as the stem nut, check the strength, not only consider the good corrosion resistance and small friction coefficient, but also the strength issue, do not use it if the strength is not enough;
h The open-air valve should be equipped with a stem protection sleeve;
i For normally open valves, turn the handwheel regularly to prevent the valve stem from rusting.