Electric gate valves are also divided into two types, one is open rod gate valve, the other is dark rod gate valve.
1) open rod gate valve. The handwheel (or other driving device) is fixed to the stem nut. When the handwheel (or other driving device) rotates the stem nut, the stem moves up and down, thus driving the gate valve to move up and down while the pipe is opened and closed.
When open-bar gate valve is opened, the stem extends from the top of handwheel, which can directly show the opening degree of electric gate valve. Valve stem trapezoid thread on the upper half of the stem, no direct contact with the medium, no corrosion of the medium, and lubrication. Therefore, it is suitable for corrosive medium, dirty medium and high temperature steam medium gate valve. The opening and closing degree of the valve can be seen directly from the thread, easy to operate is one of its advantages. The disadvantage is that the thread leakage, easy to adhere to the dust in the air, accelerated thread wear, so should be installed indoors as far as possible. However, it is still widely used.
(2) dark rod gate valve. The handwheel (or other driving device) is fixed to the stem, and the screw thread of the electric butterfly valve stem is fixed to the top of the gate plate. When the handwheel (or other driving device) rotates, the stem thread drives the gate plate up and down. The stem can only rotate. The advantage is that the stem does not rise when opened and the required installation space is small. Therefore, it is often used as a gate valve of the main channel, or where the installation space is limited. Since the stem does not move up or down, it cannot display the degree of opening through the extension length of the stem as the open stem gate valve does, so an opening indicator should be installed.
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