Prevention is key to preventing internal leakage in valves
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Internal leakage of a valve refers to the situation where the valve loses some or all of its ability to prevent fluid flow, allowing fluid to pass from one end of the valve to the other inside the valve even when it is fully closed. The cause of internal leakage is the failure of the internal seal due to corrosion, wear, scaling, deformation, or other issues affecting the sealing surfaces of the valve core or seat. If a valve develops internal leakage, it is usually rendered unusable and must be replaced. Therefore, preventing internal leakage in valves is of primary importance. (1) Alloy materials with better corrosion and wear resistance. (2) Try to avoid keeping the valve in a position between fully open and fully closed; under the condition that process requirements are met, the valve should either be fully open or fully closed. To reduce the erosive wear of the valve core caused by the fluid. (3) Excessive force should be avoided when closing the valve; after closing the gate valve with sufficient force, the valve stem should be turned slightly (1/8 to 1/4 turn) to relieve the load on it. This allows the valve stem to expand slightly, preventing it from getting stuck or damaging the valve, without affecting its sealing performance. (4) Valves that have been out of use for a long time should generally be kept in an fully open position, provided that the production conditions permit it. This prevents corrosive substances from accumulating at the valve and causing corrosion. Or, in winter, the medium gathered at the valves freezes and expands, damaging the valves. After the shutdown period from 2000 to 2002, during the preparation to restart the two atmospheric and vacuum distillation units, it was found that over 80% of the valves with internal leakage issues identified were closed valves. Among them, the spools of the four valves on the constant-pressure vapor and oil line were almost completely destroyed due to corrosion by acidic water generated by the volatilization of the medium in the tower. The valves closed on the steam lines also suffer from internal leaks or other failures, mostly due to water freezing and expanding. (5) Valves in high-temperature and high-pressure areas should be opened and closed slowly to avoid rapid increases in temperature and pressure. When conditions permit, the valves in high-temperature and high-pressure areas are placed in the fully open position before being put into use. Avoid the impact on valves caused by rapid changes in temperature and pressure during operation. This post was last edited by chinazwr on 2009-1-2 07:48.]
I would like to ask how prevention can be achieved? If there are no physical or chemical testing devices to analyze the components, how can it be determined whether a valve is of satisfactory quality?
It’s true what you say, but how can one generally ensure full on and full off?
The sealing performance of valves used in the chemical industry is very important; for ordinary gate valves, special sealing measures are required between the valve body and the valve disc to prevent powder particles and corrosive substances from damaging the valve body
Float-type ball valves can sometimes be reused after replacing the seals. This is the case for ball valves of the Q41F-16P type with different inner diameters
The summary is good, but it’s inaccurate in some places； 1 The throttle valve is used for adjustment throughout the entire process ； It’s best for the shut-off valve to be either fully closed or fully open. 2 After fully closing, rotating by 1/8~1/4 is simply to relieve the stress in the handwheel and the upper threaded sleeve
There are many reasons for internal leakage in valves, mainly internal factors such as incorrect selection, poor quality, unreasonable design, and substandard sealing materials, as well as external factors such as harsh operating conditions, improper opening and closing, installation scratches, and rough or incorrect handling. If it’s not a genuine seal damage. Internal leakage can be resolved simply by tightening and adjusting the valve. If it is a genuine seal damage, the best solution is of course to stop the machine, replace the seal or the valve. If it cannot be stopped/failed to stop, repair must be carried out online while under pressure; there is a certain success rate for such repairs, and even professional teams cannot guarantee a 100% successful fix. In companies with advanced technology, once online repair is successful, the valve can be opened and closed freely, and its functional performance returns to its original state. If you want relevant information, please send me a message within the platform so we can all improve together.