subject: Plumbing [print this page] Valve has the following advantages: simple structure, manufacture and maintenance more convenient. Working stroke is small, open and close a short time. Sealing, the sealing surface between the friction force is small, longer life expectancy.
Valve defects are as follows: fluid resistance large force required to open and close more. Does not apply with particles, viscosity, easy to medium coke. Regulation poor performance.
Valve stem threads according to the type of location points are male, and internal threaded. Divided by the flow medium, with straight-through, DC type, and roles. The form of points by sealing stop valve, a packing seal valves and bellows sealed stop valve.
Cut-off stop valve structure: the structure of cut-off stop valve in the form of a straight-through, DC and right-angle type. Straight-through processing is the most common structure, but its resistance to most fluids. DC-type fluid resistance small, more used to contain solid particles or viscosity of the fluid. By forging multi-angle-type body for small pass through the higher pressure of the stop valve.
Valve Installation and Maintenance of the following: hand wheel, lever operated valves can be installed in any position in the pipeline. Handwheel, handle and William move, to allow for lifting use. Medium as shown in the flow direction of the arrow should be consistent with the body.
First, the channel under the direction of stop valve closing, divided into: straight-through valve.Is compression fittings very important?DC-type valve: the DC-type or Y-shaped cut-off valve, the valve body and the main channel flow into a slash, so the damage flow state is smaller than the conventional cut-off valve, so the pressure losses through the valve corresponding small. Angle-type valve: the roles valve, the fluid just changed one direction, so that the pressure drop through the valve structure than conventional globe valves. Plunger-type valve: This form of cut-off valve is a variant of conventional valves. In the valve, the valve disc and seat are usually designed based on the plunger principle. Polished into a flap valve connected between the plunger and valve stem seal is set in the plunger on the realization of the two elastomeric seals. Two elastic rings separated by a ring, and through the valve cover nut load exerted on the valve cover seals around the plunger pressure prison. Elastic ring can be replaced, you can use variety of materials, the valve is mainly used for "open" or "off", but with a special form of plunger or special ring can also be used to adjust flow.
Next, the valve stem can be divided into position on the thread: the thread stem stop valve: valve stem of the thread outside the body. The advantage is that stem from media erosion, ease of lubrication, more common use of such structures. Next thread stem valve: valve stem in the valve body threads. This structure stem threads and direct contact with media, vulnerability to erosion, and can not be lubricated. Such structure for small caliber and high temperature areas.
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Stop valve he opening and closing parts are plug-shaped disc, leaving it flat or cone seal, stop valve flap along the centerline of the fluid in a straight line. Stem form of exercise has lifting rod (stem down, hand the wheel does not lift), also rotating rod down (with hand wheel rotation and stop valve lift, nut located on the body). Valve is only applicable to fully open and fully closed, does not allow for adjustment and throttle.
Valve is mandatory sealed valves, so the valve closes, the disc must exert pressure to force the sealing surface does not leak. When the media entered the bottom of the valve flap valve 6:00, operating force required to overcome the resistance, is the stem and the packing of the friction and pressure from the media generated by the thrust, power off the valve to open the valve than the force, Therefore, larger diameter valve stem, or stem occurs curved roof failure. In recent years, the emergence of self-sealing valve, globe valve replaced by medium flow on the top flap valve into the valve chamber, then under the medium pressure, force off valve is small, and open the valve of the force, stem diameter can be reduced. Meanwhile, the role of the media, this form of valve is also more closely. China Valves "three to" have the provisions of the flow valves, all with top-down.
