Valve knowledge: Operating torque characteristics of cut-off valves and ball valves daily maintenance of check valves

Valve knowledge: Operating torque characteristics of cut-off valves and ball valves daily maintenance of check valves

The operating torque characteristic curve of the cut-off valve is high in the middle and low on both sides. The reason for this situation is that, when the cut-off valve is in the central position, the liquid is blocked by the butterfly plate, circumvent the butterfly plate liquidity, will be produced on both sides of the butterfly plate swirling current, the butterfly plate produces a front-end water moment, the moment is driven to cancel the butterfly plate. With the opening or closing of the butterfly plate, the influence of the swirling flow caused by the liquid on both sides of the butterfly plate is getting smaller and smaller, until the operating torque characteristic diagram of the subsiding ball valve is very similar to that of the cut-off valve, the main reason is also because of the influence of the fluid in the sphere caused by the inflow change.
(a) The operating characteristics of the cut-off valve
The operating torque characteristic curve of the cut-off valve is high in the middle and low on both sides.
The reason for this situation is that, when the cut-off valve is in the central position, the liquid is blocked by the butterfly plate, circumvent the butterfly plate liquidity, will be produced on both sides of the butterfly plate swirling current, the butterfly plate produces a front-end water moment, the moment is driven to cancel the butterfly plate. With the opening or closing of the butterfly plate, the influence of the liquid on the two sides of the butterfly caused by the vortex flow is smaller and smaller, until the cyclone subsides, at this time the friction resistance of the butterfly plate is also smaller and smaller, resulting in the high center, low characteristics of the two sides of the diagram. The actual operating torque in the opening process of the gate valve is larger than that in the closing process. The main reason is that the hydrodynamic torque caused by the liquid on the butterfly plate is always towards the closing Angle.
The very large actual operating torque of the non-hermetically sealed stop valve occurs in the central position, while the very large actual operating torque of the hermetically sealed stop valve occurs when the gate valve is closed, mainly because of the additional forced sealing torque.
The valve seat of the cut-off valve only for rotary motion, its disc and seat itself is not locked strength. In order to make the disc accurate positioning (terminating at the specified point), one method requires an additional reducer with locking strength on the seat. After the additional planetary reducer, the angular speed can be increased to dozens of turns, while the actual operating torque is relatively reduced. This allows some actual operating characteristics of the cut-off valve (such as total turns and actual operating torque) to be close to other gate valves, which is conducive to the application of electric devices.
For the forced closure of the cut-off valve, its closing position should be determined by the actual operating torque rising to the standard value.
(2) Valve operating characteristics Valve operating torque characteristics:
The operating torque characteristic diagram of the ball valve is very similar to that of the cut-off valve, the main reason is also because of the influence of the fluid flow caused by changes in the inflow in the sphere. The effects of the cyclone flow gradually decrease with the opening or closing of the valve.
Ball valve from opening to closing, valve seat rotation direction is 90%, ball valve to set mechanical limit. The beginning or closing part of the ball valve should be determined by the direction of rotation of the valve seat, so the ball valve is positioned according to the travel arrangement.
Daily maintenance of clamp check valve valve daily maintenance flange ball valve storage should be waterproof, moisture-proof, waterproof, and the flange cover tightly, stored more than 12 months of gate valve, application should be retested to ensure stable quality. If a small leak is found on the filling material during use, the valve stem nut can be slightly tightened until the leak is terminated, not tightened again. General flange ball valve are using tetrafluoride (PTFE) as rubber seals, flange ball valve surface for metal spray welding. If the pipe ball valve needs to be cleaned, be careful to avoid damaging the seal ring and leakage during disassembly.
Flange ball valve should be waterproof, moisture-proof, waterproof when stored, and the flange cover is tight, stored more than 12 months of gate valve, application should be retested to ensure quality stability. If a small leak is found on the filling material during use, the valve stem nut can be slightly tightened until the leak is terminated, not tightened again. General flange ball valve are using tetrafluoride (PTFE) as rubber seals, flange ball valve surface for metal spray welding. If the pipe ball valve needs to be cleaned, be careful to avoid damaging the seal ring and leakage during disassembly.
Flange ball valve applicator
1, the factory nameplate indicates that the flange ball valve is allowed to operate at a very large temperature compared to the minimum operating temperature of the King Kong grade.
2, flange ball valve with PTFE or RTFE material high pressure gate valve and hydraulic seals, the working temperature needs to be in the middle of -290C to 2000C. The operating temperature of other types of high pressure gate valves and hydraulic seals shall be checked by KI factory.
3, the nominal diameter of the valve class (PN), can indicate that the valve in the standard temperature state is very large pressure. (For example: PN4.0, indicating that the operating temperature of -290C ~ 380C after a very large pressure of 40 Bar(4.0MPa)).
Clamp check valve ball valve daily maintenance class
One, floating ball valve
Ball valve ball is floating up and down, under the influence of material working pressure, the ball can produce a certain offset and tight on the inlet end surface, to ensure that the outlet end sealing. Floating ball valve structure is simple, compact structure, but the ball assumes the load of all the media to the inlet and outlet sealing ring, so we should understand the rubber sealing ring can withstand the ball medium work load. This structure is used for medium and low pressure ball valves.
Two, fixed ball valve
Ball valve ball is constant, after the force will not be moved. Fixed ball valves come with fluctuating high pressure gate valves. After the material working pressure, the high pressure gate valve is moved, so that the sealing ring is firmly pressed on the ball to ensure the tightness. Generally in and ball cloth, the lower shaft is equipped with rolling bearings, small control torque, suitable for high pressure and small caliber valve body. In order to reduce the operating torque of the ball valve and increase the reliability level of the seal, the skeleton sealed ball valve has appeared in recent years. It is not only betting special grease between the surface to form a layer of oil slick, which improves the tightness and reduces the actual operating torque. It is more suitable for the ball valve with high pressure and small diameter.
Three, elastic ball valve
The ball of a ball valve is tensioned. Ball and high pressure gate valve seal ring are made of metal composite materials, sealing pressure is very large, dependent on the material’s own pressure has exceeded the requirements of the closure, the need to increase the external force. This gate valve is suitable for ultra-high pressure and high temperature substances. Elastic sphere to open a malleable groove under the sphere cavity, and get elastic force. When the safety channel is turned off, the ball is opened with the wedge head of the piston rod and the high pressure gate valve is jammed to achieve sealing. Before rotating the ball, first loosen the wedge head, the ball with the return to normal prototype, so that the ball and the valve block in the middle of the gap, can reduce the actual operation torque of friction surface.
Classify the daily maintenance of pinch check valve ball valve according to the safe passage position
Ball valve in accordance with its safety channel position can be divided into direct connection, three way or right Angle. The latter two ball valves are used to distribute materials and change the flow of media. Ball valve installation and maintenance need to pay attention to the following matters: 1. Leave the rotating part of the valve handle. 2. Can not be used as a throttle valve. Ball valves with transmission devices should be assembled straight.
Daily maintenance of clamp check valve ball
Cleaning flange ball valve, to comprehensively clean the residual dust, oil stains and other appendages, such as warm water can not be cleaned up, can not destroy the oil circuit board and parts under the premise, targeted with alcohol and other cleaning agents. Flange ball valve cleaning after the cleaner completely evaporated before installation. Flange ball valve body still residual part of the material, also under a certain working pressure. Before the maintenance of the ball valve, it is necessary to turn off the ball valve before the emergency cut off the valve, open the ball valve that must be repaired, and completely release the flange ball valve oil circuit plate internal structure working pressure.