Cut-off valve opening and closing is plug valve disc, sealing surfaces appear flat or cone, the valve disc make linear movement along the centerline of fluid.
Valve stem form of exercise, lifting lever (
The valve rod, hand wheel lifting)
And lift rotating lever (
The handwheel with the valve rod rotation movements, nut in the valve body)
By the only existing valve opened seated, does not allow for adjusting and throttling.
Cut-off valve belongs to compulsory sealed valve door, so the door is closed, the valve must be pressure on the valve disc, to force a sealing surface does not leak.
When media from the valve disc below to the valve 6, the operating force needed to overcome the resistance, is the valve stem and packing of the friction force and the thrust produced by medium pressure, close the valve door force than the valve door open force is large, so the diameter of the valve rod, otherwise it will occur the valve rod bending failure.
In recent years, from the seal gate valve, globe valve under the valve disc medium flow direction into the valve cavity, above under medium pressure at this moment, close the valve door is small, the force and the force of the valve door open, the diameter of the valve stem can be reduced accordingly.
At the same time, under the effect of medium, this form of gate valve is tight.
Valve door in China & other;
Order to & throughout;
Once, as the flow of the valve, shall be applied.
When the cut-off valve opens, the opening of the valve disc height, is 25% ~ 30% of nominal diameter, flow has reached maximum, said valve door has amounted to full open position.
So the cut-off valve in full open position, the valve disc to the trip to decide.
Globe valve has the following advantages: 1.
Simple structure, manufacture and maintenance more convenient.
Working stroke is small, opening and closing time is short.
Good sealing, sealing surface friction between the small, long service life.
Globe valve faults are as follows: 1.
Fluid resistance is big, open and closed when the required force is larger.
Do not apply to the medium with larger particles, viscosity, easy to coking.
Poor regulation performance.
The kinds of cut-off valve according to the position of the valve stem threads with external thread type, internal thread type.
According to the flow of medium, have straight-through type, straight and Angle.
Cut-off valve, the form of the seal packing seal globe valve and bellows seal globe valve.
Globe valve installation and maintenance should be paid attention to the following: 1.
The handwheel, handle operation of globe valves can be installed in any position.
The handwheel, handle and wei mechanism, does not allow for lifting.
The flow of medium should be consistent with the direction arrow shown in the valve body.