Medium used as a cut-off valve in the full-time through the entire flow, this time the pressure medium to run minimal loss. Valve is usually applied to less frequent open and close, but also to maintain full-or full-closed gate of the working conditions. Does not apply to the use of a regulator or throttling. For high-speed flow of medium, open the gate in local conditions can cause the vibration of the gate, but they may damage the vibration damper and the valve seat sealing surface, while the throttling damper will suffer erosion of the medium. From a structural form, the main difference is that the sealing component used in the form of. According to the form of sealed components, often divided into several different types of valve, such as: wedge gate valve, parallel-type valve, parallel Shuangzha plate gate valve, wedge gate, etc. Shuangzha board. The most common form of wedge gate valves and parallel-type valve.
Valve
As the valve stem and valve seat sealing surface perpendicular to the axis. Valve stem to open or close the trip is relatively short, and has very reliable cutting action, makes this valve ideally suited as a medium and cutting off or regulate the use of. Cut-off valve when the valve flap in the open position, and its valve seat and valve sealing surface is no longer between the contacts and has a very reliable cutting action, and combine this valve is suitable as a medium to cut off or adjust and cutting use.
Once the cut-off valve is turned on, its seat and the valve between the valve sealing surface is no longer in contact, so it's a smaller sealing surface mechanical wear, as most of the cut-off valve seat and valve flap is easier to repair or replace When sealing element is not required to remove the entire valve from the pipeline to which the valve and pipeline welding for the occasion into one is very applicable. Medium through such valve when the flow direction changed, so a higher cut-off valve of the flow resistance in other valves.
Commonly used cut-off valves are the following: 1) Angle type globe valve; in angle-type stop valve, the fluid simply by changing a direction, so that through this valve on the pressure drop than the conventional structure of small cut-off valve. 2) DC-type cut-off valve; in the DC-type or Y-shaped cut-off valve, the valve of the flow channel and mainstream Road into a slash, so that movement of the state extent of the damage is smaller than the conventional cut-off valve, so the pressure loss through the valve is also the corresponding smaller. 3) The plunger-type valve: This form of cut-off valve is a variant of conventional cut-off valve. In the valve, the valve flap and valve seats are usually based on the plunger principle of design. Polished into a flap valve stem is connected with the plunger, the plunger seal is on the two sets of flexible seals achieved. Two elastic rings separated by a ring, and through a valve cover nut the load exerted on the valve cover seals around the plunger pressure prison. Elastic ring can be replaced, you can use a variety of material, the valve is mainly used for "open" or "off", but with a special form of plunger or special rings can also be used to adjust flow.
Butterfly
Butterfly valve butterfly plate installed in the direction of the pipe diameter. Cylindrical channel in the valve body, the disc-shaped butterfly plate around the axis of rotation, rotation angle of 0 ° ~ 90 ° between the rotation to 90 ° when the valve is fully open state license.
Butterfly simple structure, small size, light weight, only by a small number of parts. And just rotate 90 ° to quickly open and close, easy to operate, while the flow control valve has a good feature. Butterfly in the fully open position, the butterfly plate thickness is only when the medium flows through the valve body resistance through the valve so the pressure drop generated by small, it has good flow control characteristics. There are shells and metal sealing butterfly valve seal two kinds of sealed type. Elastic sealing valves, seals can be mounted on the body or attached to the butterfly board peripheral.
Metal sealed valves generally higher than those elastic sealing valve long life, but it is difficult to achieve completely sealed. Metal seal can adapt to a higher operating temperature, flexible seal is affected by temperature limit has flaws.
If you require the use of flow control valve as the main choice is the right size and type of valve. Butterfly structure principle is particularly suitable for production of large-diameter valves. Butterfly not only in oil, gas, chemicals, water treatment, etc. are widely used in general industry, but also applied to thermal power plant cooling water systems.
Commonly used in butterfly valves are wafer type butterfly valve and flange type butterfly valve two kinds. Right clip-on butterfly is double-headed bolts to connect the valve between the two pipe flanges, flange type butterfly valve is a valve with a flange on, with bolts at both ends of the valve on the pipe flange connection method Lan on.
Ball
Evolved from the stopcock valve. It has the same movement rotated 90 degrees to mention only difference is that cock body is a sphere, a circular through-hole or channel through its axis. The sphere and the ratio of openings should be such that when the ball rotated 90 degrees, in the import and export of office should be fully rendered sphere, thus cutting off the flow.
Just use the rotary valve 90-degree rotation of the operation and a small torque can be closed tightly. The body cavity of full equality for the media to provide a little resistance, through the flow channel. Generally considered the most suitable valve opening and closing done directly used, but the recent development has been designed to give it a throttle valve and control the flow purposes. The main features of valve is its own compact, easy operation and maintenance for water, solvents, acids, and natural gas work in general media, but also applies to poor working conditions of media, such as oxygen, hydrogen peroxide, methane and ethylene and so on. Ball valve can be integral, it can be modular.
Selection of valves to prevent backflow by media
This type of valve is the role of media in one direction only allows movement, but also to prevent the direction of flow. Usually the valve is automatically work, the fluid flow in one direction under pressure, valve flap open; fluid flow in the opposite direction from the fluid pressure and valve flap valve flap from the coincidence of acting on the valve seat and thus cut off the flow. Check them belonging to this type of valve, which includes Swing check valve and lift check valve. Swing Check Valve with ordinary hinge, there is a door the same as the free flap valve leaning tilt seat surface. In order to ensure that the flap valve seat face every time to reach a suitable position, the valve flap design in the hinge body to valve flap has enough to swing space, and make a real flap valve, comprehensive engagement with the valve seat. Valve flap can all be made of metal can also be embedded in the metal on leather, rubber, or synthetic coverage, depending on the use of performance requirements. Swing check valve in the fully open position, the fluid pressure virtually unimpeded, so the pressure drop through the valve is relatively small. Check the valve lift valve is located in the valve body on the valve seat sealing surface. In addition to this valve flap valve is free to lift, the other part of the same as the cut-off valve, the fluid pressure valve from the valve seat sealing surface of valve lift, medium return valve flap led to a seat on the back, and cut off the flow. According to conditions of use, the valve flap can be all-metal structure can also be rack mounted in the valve flap rubber mat or rubber ring form. The same as the cut-off valves, fluid channels through the lift valve is narrow, so that by elevating the pressure drop valve Swing check valve than the bigger, and the flow of Swing Check Valve restrictions on rarely.
Medium parameters chosen by regulating valve
In the production process, in order to make media pressure, flow and other parameters meet the process requirements, need to install the adjusting mechanism to adjust these parameters. Regulating the organization's main working principle is to change the valve by valve flap and valve seat between the flap and the circulation area, to achieve the purpose of regulating the above parameters. Such valves are referred to as control valves, which are divided into relying on power-driven media itself is called self-drive-type control valve such as valves, regulator valve, all leading up power-driven (such as electricity, compressed air and fluid power) as he was driving control valve, such as the electric control valve, pneumatic control valve and hydraulic control valve and so on.
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