Issues that need to be paid attention to when using manual valves
Release time：
2021-11-12 11:01
Manual valves are control components in pipeline fluid transportation systems that are used to change the channel cross-section and medium flow direction. They have functions such as diversion, cut-off, adjustment, throttling, check, diversion, or overflow pressure relief. Valves used for fluid control, with nominal sizes ranging from extremely small instrument valves to industrial pipeline valves with sizes up to 10m.
1、 Opening and closing of manual valves:
1. Manual valves are the most widely used valves, and their handwheels or handles are designed according to ordinary manual labor, taking into account the strength of the sealing surface and the necessary closing force. Therefore, it is not possible to use a long lever or a long wrench to move the board. Some people are accustomed to using a wrench and should be strictly careful not to use too much force, otherwise it may damage the sealing surface or break the handwheel or handle.
2. When opening and closing the valve, the force should be steady and not impact. Some components of high-pressure valves with impact opening and closing have considered that this impact force cannot be equivalent to that of ordinary valves.
3. For steam valves, prior to opening, they should be preheated and condensed water should be drained. When opening, they should be opened as slowly as possible to avoid water hammer.
4. After the valve is fully opened, the handwheel should be turned back a little to tighten the threads tightly to avoid loosening and damage. For rising stem valves, it is important to remember the 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 stem falls off or there are large debris embedded between the valve core seals, the position of the valve stem will change when fully closed.
5. When the pipeline is first used, there is a lot of internal dirt. The valve can be slightly opened, and the high-speed flow of the medium can be used to flush it away. Then, it can be gently closed (not quickly closed or forcefully closed to prevent residual impurities from damaging the sealing surface), and then opened again. Repeat this process multiple times to flush out the dirt before putting it into normal operation.
6. Normally open valves may have dirt sticking to their sealing surfaces. When closing, the above method should also be used to flush them clean and then officially close them tightly.
7. If the handwheel or handle is damaged or lost, it should be immediately equipped and cannot be replaced by a flexible wrench to avoid damaging the valve stem and causing accidents during production due to poor opening and closing.
8. Some media cool down after manually closing the valve, causing the valve to contract. The operator should close it again at an appropriate time to ensure that there are no gaps on the sealing surface. Otherwise, the media can flow through the gaps at high speed and easily erode the sealing surface.
9. When operating, if it is found that the operation is too laborious, the reason should be analyzed. If the packing is too tight, it can be relaxed appropriately. If the valve stem is tilted, personnel should be notified for repair. Some valves, when in a closed state, experience thermal expansion of the closing part, causing difficulty in opening; If it is necessary to open at this time, the valve cover thread can be loosened by half a turn to one turn to eliminate the stress on the valve stem, and then the handwheel can be turned.
2、 Precautions:
1. High temperature valves above 200 ℃ must be tightened again due to being installed at room temperature. After normal use, the temperature increases, the bolts expand due to heat, and the gap increases. This is called "hot tightening", and operators should pay attention to this work, otherwise leakage may occur.
2. When the weather is cold and the water valve is closed for a long time, the accumulated water behind the valve should be drained. After the steam valve stops, the condensate should also be discharged. The bottom of the valve is like a plug, which can be opened for drainage.
3. Non metallic valves, some are hard and brittle, some are
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