In the production and piping process of coal chemical workshop, stop valve is often used. Here is to analyze its working principle and operation. Today, we will understand it together.
Globe valve, also known as cut-off valve, is one of the most widely used valves. It is popular because the friction between the sealing surface in the opening and closing process is small, more durable, the opening height is not large, easy to manufacture, convenient maintenance, not only suitable for low and medium pressure, but also suitable for high pressure. Globe valve is a forced sealing valve, so when the valve is closed, pressure must be applied to the disc to force the sealing surface not to leak.
Cut-off valve working principle: the valve plays an cut off in its line in the medium and the important role of throttle, cut-off valve, as a kind of extremely important truncated class valves, which exert torque on the valve stem seal, valve stem in axial direction to the pressure on the disc, the valve sealing surface and the valve seat sealing surface fit closely, prevent leakage of medium along the gaps between the sealing surface.
The sealing of the globe valve is composed of the valve disc sealing face and the valve seat sealing face. The stem drives the valve disc to move vertically along the center line of the valve seat. In the process of opening and closing the globe valve, the opening height is small, it is easy to adjust the flow, and it is convenient to manufacture and maintain, and the pressure is applicable to a wide range.
Compared with the industrial production of another kind of commonly used cut-off valve – gate valve, from the structural point of view, the globe valve is simpler than the former, easy to manufacture and maintenance. In service life, cut-off valve sealing surface is not easy to wear and scratches, in the process of opening and closing the valve disc with no relative sliding between _ seat sealing surface, thus less wear and scratches on the sealing surface, so to improve the service life of the seal globe valves in the process of the full close disc stroke is small, its height relative to other smaller valve. The disadvantage of the globe valve is that the opening and closing moment is large and it is difficult to realize the fast opening and closing. Because the flow channel in the valve body is tortuous and the fluid flow resistance is large, the fluid power loss is large in the pipeline.
For globe valves, not only must be able to install and maintain, but also to operate.
1, open and close the globe valve, the force should be stable, not impact. Some impact opening and closing of the high pressure globe valve components have taken into account this impact force and the general globe valve can not be equal.
2. When the globe valve is fully open, the handwheel should be reversed a little, so that the threads are tight, so as to avoid loosening and damage.
3. When the pipeline is used for the first time, there are many internal dirt, so the cut-off valve can be opened slightly, washed away by the high-speed flow of the medium, and then closed gently (not closed quickly or violently, so as to prevent the residual impurities from hurting the sealing surface), opened again, repeated many times, washed clean dirt, and then put into normal work.
4. Normally open the globe valve, there may be dirt on the sealing surface. When it is closed, the above method should also be used to wash it clean, and then officially close.
5. If the handwheel and handle are damaged or lost, they should be equipped immediately, and can not be replaced by the movable plate hand, so as to avoid damaging the valve stem four sides, and failing to open and close, so as to cause accidents in production.
6, some media, cooling after the cut-off valve is closed, so that the valve contraction, the operator should be closed again at the appropriate time, so that the sealing surface does not leave a thin seam, otherwise, the medium from the thin seam high-speed flow, it is easy to erosion the sealing surface.
7. If it is found that the operation is too laborious, the reasons should be analyzed. If the packing is too tight, it can be relaxed properly. If the valve stem is skewed, the personnel should be notified to repair. Some globe valves, in the closed state, the closing parts of thermal expansion, resulting in opening difficulties; If it must be opened at this time, loosen the bonnet thread half turn to one turn to relieve stem stress, then pull the handwheel.
Post time: Mar-24-2021