Opening and closing of manual valves

Common manual valves include ball valves, gate valves, globe valves, butterfly valves, plug valves, etc. They are widely used valves, and their handwheels or handles are designed according to ordinary human labor, considering the strength of the sealing surface and the required closing force. Therefore, it cannot be pulled with a long lever or wrench. Some people are accustomed to using wrenches and should be strictly careful not to apply too much force, otherwise it is easy to damage the sealing surface or break the handwheel and handle.

When opening and closing the valve, the force should be steady to avoid impact. Some components of high-pressure valves with impact opening and closing have already considered that this impact force cannot be equivalent to that of general valves.

For steam valves, they should be preheated and condensed water should be drained before opening. When opening, they should be opened as slowly as possible to avoid water hammer.

After the valve is fully opened, the handwheel should be turned back slightly to tighten the threads tightly to prevent loosening and damage.

For open stem valves, remember the position of the valve stem when fully open and fully closed to avoid hitting the dead center when fully open, and to facilitate checking whether it is normal when fully closed. If the valve disc falls off or large impurities are embedded between the valve core seals, the position of the valve stem will change when fully closed. The normal bellows globe valve adopts a concealed rod type and is equipped with a positioning block, so this situation will not occur.

When the pipeline is first used, there are many impurities inside. It is necessary to flush the steam pipeline clean, then slightly open the valve, use the high-speed flow of the medium to wash it away, and then gently close it (do not close quickly or abruptly to prevent residual impurities from damaging the sealing surface), and then open it again. Repeat this process multiple times, flush out the impurities, and then put it back into normal operation.

Normally open valves may have debris adhering to the sealing surface. When closing, use the above method to flush it clean before closing it tightly.

If the handwheel or handle is damaged or lost, it should be immediately equipped and cannot be replaced with a flexible wrench to avoid damaging the valve stem, causing ineffective opening and closing, and leading to accidents in production.

Some media may cool down after the valve is closed, causing the valve to contract. The operator should close it again at an appropriate time to leave no gaps on the sealing surface. Otherwise, the medium will flow through the narrow gaps at high speed, which can easily erode the sealing surface.

When operating, if it is found that the operation is too difficult, the reason should be analyzed. If the packing is too tight, it can be relaxed appropriately. If the valve stem is skewed, personnel should be notified for repair. Some valves, when in the closed state, have their closing components expand due to heat, causing difficulty in opening; If it is necessary to open at this time, loosen the valve cover thread by half a turn to one turn, eliminate the stress on the valve stem, and then turn the handwheel.

Precautions

1. Valves with temperatures above 200 ℃ are installed at room temperature. However, after normal use, the temperature increases, causing the bolts to expand and the gap to widen. Therefore, they must be tightened again, which is called "hot tightening". Operators should pay attention to this work, otherwise leakage may occur.

2. When the weather is cold and freezing, especially for outdoor valves, the accumulated water in the pipelines and valves should be drained to prevent freezing damage to the pipelines and valves.

3. Non metallic valves, some are hard and brittle, while others have lower strength. When operating, the opening and closing force should not be too strong, especially not too forceful. Also pay attention to avoiding object collisions.

4. When using a new valve, do not press the packing too tightly to prevent leakage, in order to avoid excessive pressure on the valve stem, accelerate wear, and make opening and closing difficult. It is recommended to use Guangzhou Weiyuan bellows globe valve, as the bellows sealing switch is easier.

For working conditions that require adjusting the opening height to simply control flow, pressure, or temperature, it is recommended to use Way's adjustable corrugated pipe globe valve S25FGB-N or S16FGBH-N. If a direct steam equipment front-end pipeline globe valve is used, manual flow adjustment is often required, such as in the feed industry's granulator and puffing machine modulators, and in the grain and oil industry's distillation lines, conditioning towers, stripping towers, deodorization towers, etc.