Taboo 16
Manual valve opening and closing, excessive force
Consequence: the valve will be damaged if it is light, and the safety accident will be caused if it is heavy
Measures: manual valve, its handwheel or handle, is designed according to common manpower, considering the strength of sealing surface and necessary closing force. Therefore, it is not allowed to move with long lever or long wrench. Some people are used to using the wrench, should pay strict attention, do not use too much force, otherwise it is easy to damage the sealing surface, or break the handwheel and handle. Open and close the valve, the force should be stable, not impact. Some parts of high-pressure valves with impact opening and closing have considered the impact force and the general valve can not wait. For steam valve, before opening, it shall be heated in advance and condensed water shall be removed. When opening, it shall be as slow as possible to avoid water hammer. When the valve is fully opened, turn the hand wheel back a little, so that the threads are tight to avoid looseness and damage. For open stem valves, remember the valve stem position when fully open and fully closed to avoid hitting the top dead center when fully open. It is convenient to check whether it is normal when it is fully closed. If the valve office falls off, or a large sundry is embedded between the valve core seals, the valve stem position will change when the valve is fully closed. When the pipeline is used for the first time, there is a lot of dirt inside, so the valve can be slightly opened. The high-speed flow of the medium can be used to wash it away, and then it can be slightly closed (it can’t be closed quickly or violently to prevent the residual impurities from damaging the sealing surface). It can be opened again. Repeat for many times, clean the dirt, and then put into normal operation. When the valve is normally opened, there may be dirt on the sealing surface. When it is closed, the above method shall be used to wash it clean, and then it shall be formally closed. If the handwheel and handle are damaged or lost, they should be immediately matched, and can not be replaced by a flexible wrench, so as to avoid damaging the four sides of the valve stem and failing to open and close, resulting in accidents in production. For some media, when the valve is closed and cooled to shrink the valve, the operator should close it again at a proper time to keep the sealing surface free of fine seams. Otherwise, the media flows through the fine seams at a high speed and easily erodes the sealing surface. During operation, if it is found that the operation is too laborious, the reasons shall be analyzed. If the packing is too tight, it can be loosened properly. If the valve stem is skewed, the personnel shall be informed to repair it. For some valves, when they are closed, the closing parts are heated and expanded, which makes it difficult to open; if they must be opened at this time, they can loosen the bonnet thread for half a circle to eliminate the stress of the valve stem, and then move the hand wheel.
Taboo 17