What is the difference between the open rod gate valve and the dark bar gate valve?

The valve according to the structure of the valve can be divided into: 1, the open bar gate valve: the stem nut in the valve cover or bracket, open and close the gate, with the rotating stem nut to achieve the rise and fall of the stem This structure is beneficial to the lubrication of the stem, the degree of opening and closing is obvious, so it is widely used 2, dark rod gate valve: the stem nut in the valve body, with the medium in direct contact When opening and closing the gate, use the rotary stem to achieve The advantage of this structure is that the height of the gate valve is always the same, so the installation space is small, suitable for large caliber or limited installation space gate valve Such structures should be fitted with an open-close indicator to indicate the degree of open-close The disadvantage of this structure is that the stem thread is not only unlubricated, but also directly subject to media erosion, easy to damage The main difference between the open bar gate valve and the dark bar gate valve: 1, the lift screw of the dark rod flange gate valve is only rotating and moving top less, exposed is only a rod, its nut is fixed to the gate plate, through the rotation of the screw to lift the gate, no visible door frame; The lift screw of the rod flange valve is exposed, the nut is close to the handwheel and is fixed (no rotation nor axial movement), by rotating the screw to lift the gate, the screw and the gate only relative rotation movement and no opposite axial displacement, the appearance of a door-shaped bracket 2, the dark rod valve can not see the screw, and the light bar can see the wire rod 3, the dark rod valve in the switch when the steering wheel and the stem is connected together relatively immobile, it is through the valve stem in the fixed point to drive the valve flap up lift and lower the gate to complete the opening and closing The open rod valve is to lift or lower the valve flap by the threaded drive of the stem and steering wheel To put it simply is that the open rod valve is the valve valve connected to the stem together to do up and down movement, the steering wheel is always at the fixed point.