The legend of gate valve and stop valve
When the valve is installed, the medium can enter from the bottom of the valve core and enter the two way from the top. Medium from the spool into the advantages of the valve closed when the packing is not under pressure, can extend the service life of the packing, and can be pressure in front of the valve in the case of replacement of packing work. Medium from the spool into the bottom of the shortcomings of the valve driving torque is larger, about 1.05~1.08 times above the entrance, the stem by the axial force of large, easy to bend the stem. To this end, the media from below to enter the way, generally only applicable to small caliber manual stop valve, to the valve closed, the media acting on the spool of force is not greater than 350kg limit. Electric cut-off valve is generally used to enter the media from the top way. The disadvantage of the medium entering from the top is just the opposite of the way it is entered below.Compared with the gate valve, the utility model has the advantages of simple structure, good sealing performance, and convenient manufacture and maintenance. The disadvantage is that the liquid resistance is large, and the opening and closing force is large. Gate and globe valves are fully open closed type valve, cut off or connected as the medium use, not as a control valve.The range of application of stop valves and gate valves is determined by their characteristics. In the smaller passages, the cut-off valve is used when required for better shutoff; in the steam pipe and the large diameter water supply pipe, the gate valve is generally used because of less fluid resistance.
Compared with the cut-off valve, the main advantage is that the flow resistance is small, the flow resistance coefficient of ordinary gate valve is about 0.08~0.12, while the ordinary cut-off valve resistance coefficient is about 3.5~4.5. Opening, closing force is small, the medium can flow in two directions. The disadvantage is that the structure is complex and the height is large. The sealing surface is easy to wear. The sealing surface of the valve must be forced to close the valve to achieve sealing, in the same caliber, work pressure and the same drive device, the drive valve torque is 2.5~3.5 times the gate valve. This point should be noticed when adjusting the torque control mechanism of the electric valve.The sealing surface of the stop valve contacts each other only when the valve is completely closed, and the relative sliding amount between the valve core and the sealing surface is very small, so that the wear of the sealing cover is very small. The sealing surface of the valve cover, mostly due to the spool and sealing surface before the debris, or because of the closed state is not tight, causing the medium of high-speed erosion caused by.
The working principle is different. The stop valve is an upward stem type, and the handwheel rotates and rises with the stem. Valve is hand wheel rotation, stem upward movement. Flow is not the same, the gate valve requires full open, the cut-off valve is not the same. The gate valve has no inlet and outlet direction requirements, and the cut-off valve has the required inlet and outlet!Gate valve and stop valve are shut-off valve, is the most common two valves.From the exterior, the gate valve is shorter than the cut-off valve, especially the bar valve needs a higher height space. Valve sealing surface has a certain degree of self sealing capacity, its spool depends on the media pressure tight contact with the valve seat sealing surface, to achieve tight leakage. Wedge gate valve spool angle is generally 3~6 degrees, when forced to shut down excessive or temperature changes of the valve core is easy to die. Therefore, high temperature and high pressure wedge gate valve, in the structure have taken certain measures to prevent spool stuck. The valve in the opening and closing valve and valve seat sealing surface contact and mutual friction is always so easy to wear sealing surface, especially in close off the valve, the valve before and after the great pressure, sealing surface wear is more serious.
