Manual valves are a type of valve commonly used in equipment and devices. They are operated by handles and handwheels. Generally speaking, clockwise rotation of the handle and handwheel is designated as the closing direction, and counterclockwise rotation is designated as the opening direction.
However, the opening and closing direction of some valves is opposite to the above, so you should check the opening and closing signs before operation.
For manual valves, the size of the handle and handwheel are designed according to normal manpower.
Operators are not allowed to use levers and long wrenches to open and close valves. At the same time, if the handle length and handwheel diameter are less than 320mm, only one person is allowed to operate; for handwheels with a diameter equal to or exceeding 320mm, two people are allowed to operate together, or one person is allowed to operate with the help of an appropriate lever (generally no more than 0.5m in length).
However, it is strictly prohibited to use levers or long wrenches to operate diaphragm valves and non-metallic valves, and it is not allowed to use excessive or excessive force to close the valve.
Some operators are accustomed to using levers and long wrenches to operate manual valves, thinking that the greater the closing force, the better, but this is not the case. This can cause premature damage to the valve and even cause an accident.
Practice has proven that, except for the impact handwheel, operating the valve too hard or too hard can easily damage the handwheel and handle, scratch the valve stem and sealing surface, or even crush the sealing surface. Secondly, if the handwheel or handle is damaged or lost, it should be replaced in time. It is not allowed to use an adjustable wrench as a substitute.
Valves such as gate valves and stop valves should be rotated 1/4 to 1/2 turns when closed or opened to the end (i.e. bottom dead center or top dead center) to make the threads more tightly sealed to facilitate inspection during operation and avoid twisting. Too tight and damage the valve.
Some of the larger diameter butterfly valves, gate valves and globe valves are equipped with bypass valves. The function of the bypass valve is to balance the pressure difference between the inlet and outlet and reduce the opening torque. When opening, the bypass valve should be opened first, and then the large valve.
Before opening the steam valve, the pipeline must be preheated and the condensate water must be discharged. Open slowly to avoid water hammer and damage to valves and equipment.
When opening and closing ball valves, butterfly valves, and plug valves, when the groove on the top surface of the valve stem is parallel to the channel, it indicates that the valve is in the fully open position; when the valve stem rotates 90 degrees to the left or right. When the groove is perpendicular to the channel, it indicates that the valve is in the fully closed position.
Some ball valves, butterfly valves, and plug valves are opened when the wrench is parallel to the channel, and closed when the wrench is vertical. The operation of three-way and four-way valves should be carried out according to the opening, closing and reversing marks. After the operation is completed, the movable handle should be removed.
For gate valves and throttle valves with scales, the fully open or fully closed indicating position should be checked and adjusted. Rising stem gate valves and globe valves should also remember their fully open and fully closed positions to avoid hitting the dead center when fully open. When the valve is fully closed, you can use the ruler and marks to find that the closing part has fallen off or is resisting foreign objects, so that you can troubleshoot.
Newly installed pipelines and equipment have a lot of dirt, welding debris, etc. inside. Dirt is easy to stick to the sealing surface of the normally open manual valve. The slightly open method should be used to allow the high-speed medium to wash away these foreign objects, and then close gently.
After some manual valves are closed, the temperature drops and the valve parts shrink, causing small gaps in the sealing surface and leakage. This should be done after closing and then closing again at the appropriate time.
Whether the valve is operated correctly or not directly affects the service life of the valve.
The process of operating the valve is also the process of inspecting and treating the valve. However, the following matters should be noted when operating the valve.
①High temperature valve. When the temperature rises above 200°C, the bolts will elongate due to heat, which may easily cause the valve to become loosely sealed. At this time, the bolts need to be "heat-tightened". It is not advisable to do it in the fully closed position of the valve during hot-tightening to avoid the valve stem from being pushed hard and making it difficult to open later.
② In seasons when the temperature is below 0°C, for valves that stop steam and water, be sure to open the valve seat plug to remove condensation and accumulated water to avoid freezing and cracking the valve. For valves that cannot remove accumulated water and valves that work intermittently, attention should be paid to thermal insulation.
③ The packing gland should not be pressed too tightly, and the valve stem should be operated flexibly (it is wrong to think that the tighter the packing gland is, the better, it will accelerate the wear of the valve stem and increase the operating torque). Without protective measures, packing cannot be replaced or added under pressure.
④ During operation, you must carefully analyze the causes of abnormal phenomena discovered through listening, smelling, seeing, touching, etc., and eliminate them in time if you need to solve them yourself; if you need a repairman to solve them, do not force yourself to make do, so as not to delay the repair opportunity.
⑤ Operators should keep special logs or record books to record the operation of various valves, especially some important valves, high temperature and high pressure valves and special valves, including their transmission devices. Their faults, treatment methods, replacement parts, etc. should be recorded.
These materials are very important to the operators themselves, repair personnel and manufacturers. Establishing a special log with clear responsibilities will help strengthen management.