How Should The Valve Be Maintained

1. Storage and maintenance of valves

The purpose of storage and maintenance is to prevent the valve from being damaged or reducing the quality during storage. In fact, improper storage is one of the important reasons for valve damage.

Valves should be kept in good order. Small valves should be placed on the shelf. Large valves can be placed neatly on the floor of the warehouse. They should not be stacked disorderly. Do not let the flange connecting surface directly contact the ground. This is not only for beauty, but also to protect the valve from being damaged. Due to improper storage or handling, the hand wheel is broken, the valve rod is crooked, and the fixing nut of the hand wheel and valve rod is loose and lost. These unnecessary losses should be avoided.

For valves that are not used for a short time, asbestos packing shall be taken out to avoid electrochemical corrosion and damage to the valve stem.

The inlet and outlet of the valve shall be sealed with wax paper or plastic sheet to prevent dirt from entering and affecting the valve.

Valves that can rust in the atmosphere shall be coated with anti rust oil and protected to prevent rust.

Valves placed outdoors must be covered with rain proof and dust-proof items such as linoleum or tarpaulin. The warehouse for storing valves shall be kept clean and dry.

2. Use and maintenance of valves

The purpose of use and maintenance is to prolong the service life of the valve and ensure reliable opening and closing.

The thread of the valve stem often rubs with the valve stem nut and needs to be coated with yellow dry oil, molybdenum disulfide or graphite powder for lubrication.

For valves that do not open and close frequently, the hand wheel should also be turned regularly to add lubricant to the stem threads to prevent biting.

For outdoor valves, a protective sleeve shall be added to the valve stem to prevent rain, snow, dust and rust. If the valve is a mechanical standby, the gearbox shall be lubricated on time.

Keep the valve clean.

Always adhere to and maintain the integrity of valve components. If the fixed nut of the hand wheel falls off, it shall be fully matched and cannot be used, otherwise the four sides on the upper part of the valve stem will be rounded, and the coordination reliability will be gradually lost, or even it will not be able to start.

Do not use the valve to carry other heavy objects, and do not stand on the valve.

The valve rod, especially despises the threaded part, should be wiped from time to time, and the lubricant that has been polluted by dust should be replaced with a new one, because the dust contains shadow debris, which is easy to wear the thread and valve rod surface, affecting the service life of the valve.

The valves put into operation shall be maintained once a quarter, once half a year after being put into operation, once a year after two years of operation, and the valves shall be maintained before winter every year. Conduct flexible valve operation and blowdown once a month.

3. Maintenance of packing

The packing is directly related to the key seal of whether there is external leakage when the valve is opened and closed. If the packing fails and causes external leakage, the valve is equal to failure. Especially for the valve of urea pipeline, due to its high temperature, the corrosion is relatively serious and the packing is easy to age. Strengthening maintenance can prolong the service life of the packing.

When the valve leaves the factory, due to temperature and other factors, leakage may occur. At this time, tighten the nuts on both sides of the packing gland in time, as long as there is no leakage, and then tighten it again in case of leakage in the future. Do not tighten it at one time, so as to avoid the loss of elasticity and sealing performance of the packing.

Some valve packing is equipped with molybdenum dioxide lubricating paste. When it is used for several months, the corresponding lubricating grease shall be added in time. When it is found that the packing needs to be supplemented, the corresponding packing shall be added in time to ensure the sealing performance.

4. Maintenance of transmission parts

In the process of opening and closing the valve, the original lubricating grease will be continuously lost. In addition, the influence of temperature, corrosion and so on will also make the lubricating oil continuously dry up. Therefore, the transmission part of the valve should be checked frequently. If it is found, it should be supplemented in time to prevent increased wear due to lack of lubricant, resulting in inflexible transmission or cartridge failure.

5. Maintenance of valve during grease injection

When the valve is greased, the problem of the amount of grease is often ignored. After the grease gun is oiled, the operator selects the connection mode between the valve and the grease injection, and then carries out the grease injection operation. There are two situations: on the one hand, the low amount of grease injection leads to insufficient grease injection, and the wear of the sealing surface is accelerated due to the lack of lubricant. On the other hand, excessive grease injection causes waste. The reason is that the sealing capacity of different valves is not accurately calculated according to the type and category of valves. The sealing capacity can be calculated according to the size and category of the valve, and then an appropriate amount of grease can be injected reasonably.

The pressure problem is often ignored during valve greasing. In the process of grease injection, the grease injection pressure changes regularly in peak and valley. The pressure is too low, the seal leaks or fails, the pressure is too high, the grease injection port is blocked, and the grease cherry blossom or sealing ring in the seal is locked with the valve ball and valve plate. Usually, when the grease injection pressure is too low, the injected grease mostly flows into the bottom of the valve cavity, which usually occurs in small gate valves. If the grease injection pressure is too high, on the one hand, check the grease injection nozzle and replace it if the grease hole is blocked. On the other hand, if the grease is hardened, use cleaning fluid to soften the failed sealing grease repeatedly and inject new grease for replacement. In addition, the sealing model and sealing material also affect the grease injection pressure. Different sealing forms have different grease injection pressure. Generally, the grease injection pressure of hard seal is higher than that of soft seal.

When filling the valve with grease, pay attention to the problem of valve opening and closing position. The ball valve is generally in the open position during maintenance, and it can be closed for maintenance under special circumstances. Other valves cannot be treated as open. The gate valve must be closed during maintenance to ensure that the grease fills the sealing groove along the sealing ring. If it is opened, the sealing grease will directly enter the flow channel or valve cavity, resulting in waste.

When the valve is greased, the problem of greasing effect is often ignored. During the grease injection operation, the pressure, grease injection volume and switch position are normal. However, in order to ensure the grease injection effect of the valve, it is sometimes necessary to open or close the valve, check the lubrication effect and confirm that the surface of the valve ball or ram is lubricated evenly.

During grease injection, pay attention to the problems of valve body blowdown and screw plug pressure relief. After the valve pressurization test, the gas and water in the valve chamber of the sealing chamber will rise due to the increase of ambient temperature. During grease injection, blowdown and pressure relief shall be carried out first to facilitate the smooth progress of grease injection. After grease injection, the air and water in the sealing cavity are fully replaced. Timely release the pressure in the valve chamber, which also ensures the safe use of the valve. After grease injection, the blowdown and pressure relief plugs must be tightened to prevent accidents.

During grease injection, also observe whether the valve diameter is flush with the seal ring seat. For example, for ball valve, if there is opening interference, the opening limiter can be adjusted inward to confirm that the diameter is straight. The adjustment of the limit should not only pursue the position of the opening or closing side, but also consider the whole. If the opening position is flush and the valve cannot be closed in place, the valve will not be closed tightly. Similarly, when adjusting the closing position, the corresponding adjustment of the opening position should also be considered. Ensure the right angle travel of the valve.

After grease injection, the grease injection port must be sealed. Avoid the entry of impurities or the oxidation of grease at the grease injection port. The cover shall be coated with anti rust grease to avoid rust. In order to operate the application next time.