Gate valves can be divided according to the construction of the valve stem:
1. Rising stem gate valve:
Open stem gate valve: stem nut in the bonnet or bracket, open and close the gate, and rotate the stem nut to achieve the stem lift. This structure is favorable to the lubrication of the valve stem, and the degree of opening and closing is obvious, so it is widely used.
Usually, there are trapezoidal threads on the lifting stem, through the nut at the top of the valve, and the guide groove on the valve body, the rotary motion into a linear motion, that is, the operating torque into the operating thrust.
The opening and closing parts of the open stem gate valves are the gate, the movement direction of the gate is perpendicular to the direction of the fluid, and the rising stem gate valve can only be used for full open and full close, not for regulating and throttling.
A little bit of rising stem gate valve:
① The whole package rubber:
Rising stem soft seal gate valve gate using the whole package of rubber, it’s good coverage performance and precise geometry, to ensure reliable sealing, life.
② Light weight:
The valve body is made of ductile iron, light weight, and easy to install.
③ Flat bottom valve seat:
The bottom adopts the same flat-bottomed valve seat design as the water pipe, which does not produce debris siltation and makes the sealing more reliable.
④Corrosion resistance:
The inner cavity of the gate valve is coated with non-toxic epoxy resin to prevent corrosion and rust, which can be used not only for drinking water but also for sewage systems.
2. No rising stem gate valve:
No rising stem gate valve is also called rotary stem gate valve (also called dark stem wedge gate valve). Stem nut in the valve body, in direct contact with the medium. Open and close the gate, with a rotating stem to achieve.
The opening and closing parts of the no rising stem gate valves are the gate, the movement direction of the gate is perpendicular to the direction of the fluid, and the gate valve can only be fully open and fully closed, can not be regulated and throttled.
Valve stem nut on the gate, handwheel rotation drives the valve stem rotation, and make the gate lift, usually in the bottom end of the valve stem has trapezoidal threads, through the bottom end of the valve threads, and the valve on the valve flap guide groove, the rotary motion into a straight line, that is, the operating torque into the operation of the thrust.
The main difference between a rising stem gate valve and no rising stem gate valve:
1. The lifting screw of the concealed stem gate valve is only rotating without upward and downward movement, and the exposed one is only a rod, and its nut is fixed on the gate plate, and the rotation of the screw lifts the gate plate, and there is no visible gate frame.
The rising stem gate valve lifting screw is exposed, the nut is close to the handwheel and is fixed (not rotating or axial movement), through the rotation of the screw to lift the gate, the screw, and the gate only relative rotary motion without relative axial displacement, the appearance of a gate-shaped bracket.
2. No rising gate valves can not see the screw, while the rising stem gate valves can see the screw.
3. No rising stem gate valve in the switching disc and valve stem is connected to the relative immobility, it is through the valve stem at a fixed point of rotation to drive the valve flap up and down to complete the opening and closing of the gate. The rising stem gate valve is through the stem and the steering wheel of the threaded drive to lift or lower the valve flap. To put it simply, the rising stem gate valve is the valve flap together with the valve stem to do up and down movement, the steering wheel is always at a fixed point.
