Electric pinch valves are now used in many jobs such as power stations, petrochemicals, steel metallurgy, food processing and water treatment, especially in large companies that require active control. Electric valves create clear conditions for remote control of valves, and also make it possible to automate and intelligentize production systems. However, electric valves (such as electric wedge gate valves and globe valves) often have the appearance of improperly closed electric operation during use, which brings trouble to valve users and operators, and seriously affects the service life of the valve. When valves such as wedge gate valves, globe valves, and sealed butterfly valves are closed, they rely on the occurrence of satisfactory sealing surface specific pressure on the valve sealing surface to ensure the sealing, and the sealing surface specific pressure depends on the operating torque of the valve. This type of valve is a torque control valve. In production practice, this kind of electric valve often shows the appearance of medium leakage after the electric operation is closed. To this end, manual operation is required to close the valve. In case of accidents, in order to ensure that the valve is closed tightly, it is usually necessary to use an extra-long afterburner to close the valve forcefully.
Such operating conditions can not end the remote control of the valve and the automation of the system, but also increase the labor intensity of the operator and shorten the service life of the valve. Because the valve is not closed tightly, the leaking medium will flush the valve sealing surface at a high speed, which will surely cause rapid damage to the sealing surface. Use the afterburner to close the valve forcefully, and the closing torque cannot be controlled, and it is inevitable to harm the valve sealing surface. The electric operation of the valve is not tight, but manual afterburner can be closed, which is a manifestation of the short closing torque of the valve. The obvious question is related to the control system of electric equipment. Control method The current valve electric equipment is usually equipped with two sets of stroke control and torque control systems, which are based on "stroke as control and torque as protection". This is only applicable to stroke control type valves. For valves that require stroke control, during normal operation, the stroke is used to control the fully open and fully closed positions of the valve. If the stroke control fails, there is over-torque protection to maintain the operation of the valve and avoid damage to the valve. Then the safety of the valve and the production system is guaranteed.
For the torque control valve, in the existing system, the stroke system has no protective effect. If the torque control fails or the value changes, the operating torque of the valve will increase rapidly in an instant, but there is no other protection method. Therefore, this control system is not complete. Even with a suitable control system, after the electric equipment and valve device, the control parameters need to be accurately debugged and set. Normally, when the electric equipment leaves the factory, the rated output torque has been verified. However, the verified torque only indicates the working capability of the electric equipment, and is not equivalent to the torque required for valve closing. The torque required to close the valve is not only related to the specification and model of the valve, but also related to the medium, pressure and temperature of the valve's practical work. The user may adjust and set it from scratch. However, most valve users (including many valve manufacturers) do not have the method of torque checking and cannot set a reasonable torque value.
Moreover, after the valve has been operated for a period of time and repaired, the factory-set torque of the electric equipment has been changed, and it is necessary to set it from the beginning. In the case of the short torque measurement method, the valve user can only adjust the valve opening indication according to the valve fully open and fully closed position, and set the stroke switch action in the fully open and fully closed position to ensure that the stroke control can work normally. Then, on the basis of the valve closing and the stroke closing switch action, the valve is manually closed, and when the closing torque is felt to increase to a certain extent, the torque switch action is adjusted. The effect of this setting must be that the opening and closing of the valve is still only controlled by the travel switch. The closing torque of the valve cannot be guaranteed, so the tightness of the closing is difficult to guarantee.