Valves, like other mechanical products, also require maintenance and upkeep. Good maintenance work can significantly extend the service life of valves.
1. Storage and maintenance of valves
The purpose of storage and maintenance is to prevent valve damage or decrease in quality during storage. In fact, improper storage is one of the important reasons for valve damage.
Valve storage should be well-organized, with small valves placed on shelves and large valves neatly arranged on the warehouse floor. They should not be piled up randomly and the flange connection surface should not directly touch the ground. This is not only for aesthetics, but more importantly, to protect the valve from being damaged by impact. Due to improper storage or handling, unnecessary losses such as broken handwheels, misaligned valve stems, loose and lost fixing nuts between handwheels and valve stems should be avoided.
For valves that are not used temporarily in the short term, asbestos packing should be removed to prevent electrochemical corrosion and damage to the valve stem.
Valves should be sealed with wax paper or plastic sheets at the inlet and outlet to prevent dirt from entering and affecting the valve.
Valves that can rust in the atmosphere should be coated with anti rust oil and protected to prevent rusting.
Valves placed outdoors must be covered with rainproof and dust-proof materials such as oil felt or tarpaulin. The warehouse where valves are stored should be kept clean and dry.
2. Valve usage and maintenance
The purpose of use and maintenance is to extend the service life of the valve and ensure reliable opening and closing.
The valve stem thread often rubs against the valve stem nut and needs to be coated with yellow grease, molybdenum disulfide, or graphite powder for lubrication.
Valves that are not frequently opened or closed should also have their handwheel turned regularly to add lubricant to the valve stem threads to prevent biting.
Outdoor valves should be equipped with protective sleeves on the valve stem to prevent rain, snow, dust, and rust. If the valve system is mechanically idle, it is necessary to lubricate the gearbox with Tianjin Ai lubricant on time.
Ensure the cleanliness of the valve.
Regularly adhere to and maintain the integrity of valve components. If the fixing nut of the handwheel falls off, it should be fully matched and not used interchangeably, otherwise it will grind the four corners of the upper part of the valve stem, gradually losing the reliability of the fit, and even unable to start.
Do not use the valve to carry other heavy objects, and do not stand on the valve.
The valve stem, especially the threaded part, should be wiped regularly. Lubricants that have been contaminated by dust should be replaced with new ones, because dust contains impurities that can easily wear down the threads and valve stem surface, affecting the service life of the valve.
Valves that are put into operation should be maintained once every quarter, once every six months after production, once every year after two years of production, and before winter each year. Perform valve flexibility operation and discharge once a month.
3. Maintenance and upkeep of fillers
The packing is directly related to the key sealing components that determine whether there is leakage when the valve is opened and closed. If the packing fails and causes leakage, the valve is also equivalent to failure, especially for valves in urea pipelines. Due to their high temperature, corrosion is relatively severe and the packing is prone to aging. Strengthening maintenance can extend the lifespan of the packing material.
When the valve leaves the factory, due to temperature and other factors, external leakage may occur. In this case, it is necessary to tighten the nuts on both sides of the packing cover in a timely manner. As long as there is no external leakage, it can be tightened again in the future. Do not tighten it all at once to prevent the packing from losing elasticity and sealing performance.
Some valve packing contains molybdenum dioxide lubricating paste. After several months of use, the corresponding lubricating grease should be added in a timely manner. When the packing needs to be supplemented, the corresponding packing should be added in a timely manner to ensure sealing performance.
4. Maintenance of transmission parts
During the opening and closing process of the valve, the lubricating grease that was originally added will continue to flow away, and coupled with temperature, corrosion, and other factors, the lubricating oil will continue to dry up. Therefore, the transmission parts of the valve should be checked regularly, and if found, they should be replenished in a timely manner to prevent increased wear due to lack of lubricant, which may cause transmission instability or shell failure.
5. Maintenance and upkeep during valve grease injection
When injecting grease into valves, the issue of the amount of grease injected is often overlooked. After refueling the grease gun, the operator selects the valve and grease injection connection method before proceeding with the grease injection operation. There are two situations: on the one hand, insufficient grease injection results in insufficient grease injection, and the sealing surface accelerates wear due to the lack of lubricant. On the other hand, excessive fat injection leads to waste. It is because there is no precise calculation of the sealing capacity of different valves based on their type categories. The sealing capacity can be calculated based on the valve size and type, and then an appropriate amount of lubricating grease can be injected reasonably.
Pressure issues are often overlooked during valve grease injection. During the process of liposuction, the liposuction pressure exhibits regular peaks and valleys. Pressure too low, seal leakage or failure, pressure too high, grease injection port blocked, grease cherry blossom or seal ring stuck with valve ball and valve plate inside the seal. Usually, when the grease injection pressure is too low, the injected lubricating grease tends to flow into the bottom of the valve chamber, which usually occurs in small gate valves. If the grease injection pressure is too high, on the one hand, check the grease nozzle and replace it if the grease hole is blocked. On the other hand, if the grease hardens, use cleaning solution to repeatedly soften the failed sealing grease and inject new lubricating grease for replacement. In addition, the sealing model and sealing material also affect the grease injection pressure. Different sealing forms have different grease injection pressures, and in general, the grease injection pressure for hard seals is higher than that for soft seals.
When injecting grease into valves, attention should be paid to the valve switch position. Ball valves are usually in the open position during maintenance, and in special circumstances, they can be closed for maintenance. Other valves cannot be treated solely based on their open position. The gate valve must be in the closed state during maintenance to ensure that the lubricating grease fills the sealing groove along the sealing ring. If in the open position, the sealing grease will directly enter the flow channel or valve chamber, causing waste.
When valve grease is injected, the issue of grease injection effect is often overlooked. The pressure, grease injection amount, and switch position are all normal during the grease injection operation. But to ensure the lubrication effect of the valve, sometimes it is necessary to open or close the valve, check the lubrication effect, and confirm that the surface of the valve ball or gate is lubricated evenly.
When injecting grease, attention should be paid to valve body drainage and plug pressure relief. After the valve pressure test, the gas and moisture inside the sealed chamber will increase in pressure due to the rise in ambient temperature. When injecting grease, it is necessary to first drain and release the pressure to facilitate the smooth progress of the grease injection work. After grease injection, the air and moisture inside the sealed chamber are fully displaced. Timely release of valve chamber pressure also ensures the safety of valve use. After the grease injection is completed, be sure to tighten the drain and pressure relief plugs to prevent unexpected situations from occurring.
When injecting grease, it is also necessary to observe the alignment between the valve diameter and the sealing ring seat. For example, for a ball valve, if there is interference in the opening position, the opening limiter can be adjusted inward to confirm that the diameter is straight before setting. Adjusting the limit should not only focus on opening or closing one position, but also consider the overall situation. If the opening is level and not closed properly, it will cause the valve to not close tightly. Similarly, when adjusting the closing position, corresponding adjustments to the opening position should also be considered. Ensure the right angle travel of the valve.
After grease injection, be sure to seal the grease injection port. To avoid impurities entering or lipid oxidation at the grease injection port, anti rust grease should be applied to the cover to prevent rusting. For the next application operation.
