What time explaining the operation of the valve torque

by:AIRWOLF     2020-05-21
What time explaining the operation of the valve torque shows many directional valves, such as cut-off valve, throttle valve, relief valve, check valve, etc. , if the flip back, will affect the use effect and service life ( Such as throttle valve) Or simply doesn't work ( Such as pressure reducing valve) And even dangerous, Such as check valve) 。 There direction mark on the general valve, the valve body; One thousand no, should according to the working principle of the valve, the correct recognition. Stainless steel gate valves are not inversion ( The handwheel down) , otherwise, it will make the medium to long term retained in the valve cap space, easy to corrosion stem, and taboo by some technical requirements. Replacement of packing at the same time is extremely convenient. Rising stem stainless steel gate, do not install in the ground, or corrosion due to damp the leakage of the valve stem. Lift check valve installation to ensure that its disc vertical, in order to lift flexible. Swing check valve installation to ensure the pin level, flexible to swing. Relief valve to vertical installed in horizontal pipe runs, all directions don't tilt. Stainless steel gate valve operating torque explain: & middot; When gate opening in more than 10% of the axial force of the gate valve, gate valve operating torque changed little. When the gate opening is lower than 10%, due to the throttle fluid, increased the gate valve pressure difference before and after. The differential pressure effect on the disc, the valve lever larger axial force is needed to drive the gate, so in this range, the operation of the valve torque change is larger. Flexible disc gate valves, close to closing the required operating torque is bigger than the rigid disc. · Gate is closed, because of the sealing surface sealing way is different, can produce different situations. For automatic seal gate valves ( Including flat gate valve) In the valve is closed, the sealing surface of the disc is right for valve seat sealing surface, is a gate in the full open position. But this position under the condition of valve operation is unable to monitor, so in actual use, is the gate to dead point position as the gate valve seated position. Thus, automatic sealing gate location is fitted according to the location of the damper ( The trip) To determine. For mandatory seal gate valves, closed must be make the ram pressure to the valve seat. The pressure can ensure the sealing surface between disc and seat sealing strictly, is forced to seal gate valve sealing force. The sealing force due to stem nut with self-locking will continue to do. Obviously, in order to provide sealing force to ram, stem nut transmission torque than the torque in the process of valve operation. Thus, for mandatory seal gate valves, seated position by the stem nut torque size to determine. · Gate valve is turned off, because the media or the change of environmental temperature, thermal expansion of the gate valve components will lead to pressure between disc and seat, reflect on the stem nut, for the open gate difficult again. So, open the gate valve torque than shutoff gate valves required torque required, in addition, for a pair of sealing surface contact each other, the static friction coefficient is larger than the kinetic friction coefficient between them, to make them from static state to produce relative motion, to exert greater force to overcome the static friction force. Due to changes in temperature, pressure, between the sealing surface to overcome the static friction force is bigger, so that the open gate, the torque exerted on the stem nut sometimes will increase a lot.
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