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Butterfly Valve Selection Rules

Jul 18, 2017

  Butterfly valve selection rules

  Functional use:

  Butterfly valve refers to the closure (disc or butterfly plate) for the disc, around the valve shaft rotation to achieve the opening and closing of a valve, the main cut off and throttling on the pipeline. Butterfly valve opening and closing parts is a disc-shaped butterfly plate, in the valve body around its own axis of rotation, so as to achieve the purpose of opening or closing or adjustment. Butterfly valve fully open to the whole is usually less than 90 °, butterfly valve and butterfly rod itself does not have self-locking ability, in order to butterfly plate positioning, to install the worm on the stem reducer. The use of worm reducer, not only can make the disc with self-locking ability, so that the butterfly plate to stop at any position, but also improve the valve operating performance. Industrial special butterfly valve features high temperature, suitable pressure range is also high, the valve nominal diameter, the valve body made of carbon steel, valve plate ring with metal ring instead of rubber ring. Large-scale high-temperature butterfly valve made of steel plate welding, mainly used for high-temperature medium of the smoke duct and gas pipeline.

  Selection rule:

  Stem diameter: on the multi-turn class stem valve. It can not be assembled into electric valves. Therefore, if the electric butterfly valve device allows passage of the largest stem diameter can not pass through the valve stem of the valve. The inner diameter of the hollow shaft of the electric device must be greater than the stem diameter of the stem valve. For the local rotary valve and multi-turn valve in the dark bar valve, although not consider the stem diameter through the problem, but should also take into account the choice of stem diameter and keyway size, so that after assembly to work properly.

  Operating Torque: The operating torque is the most important parameter for selecting the valve motor. The electric butterfly valve movement process can be controlled by the stroke, the torque or the axial thrust. As the operating characteristics and utilization of the valve electric device depends on the type of valve, the device work standard and the position of the valve on the pipeline or equipment, the valve electric butterfly valve device is the indispensable equipment to realize the valve program control, automatic control and remote control. Therefore, the correct choice of valve electric device, to prevent the occurrence of overload (working torque is higher than the control torque) is essential. Usually, the correct choice of valve electric butterfly valve device basis.

  The output torque of the electric device shall be 1.2-1.5 times the maximum torque of the valve operation.

  Electric butterfly valve operation thrust: valve electric device host structure there are two: one is not configured thrust plate. The output torque is converted to the output thrust by the stem nut in the thrust plate. Direct output torque; the other is to configure the thrust plate.

  Number of revolutions of the output shaft: The number of turns of the output shaft of the valve motor is related to the nominal diameter of the valve, the stem pitch and the number of thread heads. H for the valve opening height, according to M = HZS calculation (M for the electric device should meet the total number of turns. S for the stem drive thread pitch, Z for the stem thread head number.