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Analysis of commonly used valves in China

Time:2016-07-06  Views:7013

Butterfly valve

The butterfly valve butterfly plate installed on the diameter of the pipe direction. Cylindrical channels in butterfly valve body, disc disc around the axis of rotation, rotation Angle for 0 ° ~ 90 °, rotate to 90 °, the valve is fully open.

Butterfly valve has simple structure, small volume, light weight, only by a few parts. And only need to rotate 90 ° can rapid opening and closing, simple operation, at the same time, the valve has good flow control characteristics. Butterfly valve in the fully open position, the butterfly plate thickness is medium flows through the body when the only resistance, thus produced by the valve pressure drop is small, it has good flow control characteristics. Butterfly valves have a seal and metal seal two kinds of seal type. Elastic sealing valve, sealing ring can be embedded in the body?or?attached to the butterfly plate peripheral.

Using metal seal valve generally live longer than elastic sealing valve, but it is hard to be completely sealed. Metal sealing can adapt high working temperature, elastic seal has the defect of being limited by the temperature. If required butterfly valve used as flow control, mainly is the right choice of the size and type of valve. The structure and principles of butterfly valve is especially suitable for production of large diameter valves. Butterfly valve not only in the oil, gas, chemical industry, water treatment and other general industrial used widely, but also applied to the cooling water system of thermal power plants.

Commonly used butterfly valve, which has two kinds of the wafer butterfly valve and flanged butterfly valve. Wafer butterfly valve with stud connection in place between two pipe flanges and flanged butterfly valve is a valve with flange, bolts on the valve flange connection on the pipe flange on both ends. The strength of the valve performance is the ability to under medium pressure valve. Within the valve is under pressure of mechanical products, and therefore must have sufficient strength and rigidity, so as to ensure the long-term use without cracking?or?deformation.

Ball valve

Ball valve is made up of cock. It has the same rotate 90 degrees to action, different is the cock body is ball, a round hole?or?channel through its axis. Spherical and opening ratio should be such, that is when the ball rotate 90 degrees, in the inlet and outlet should be completely present spherical, thereby blocking flow.

Ball valve just has to rotate 90 degrees operation and small rotational torque can be closed tight. Full equality of the valve body cavity for medium resistance is very small, straight flow channel. Usually do think most suitable direct ball valve open and close, but recent development has put a ball valve designed to make it with throttling and control flow. Ball valve itself is the main characteristics of compact structure, easy operation and maintenance, and is applicable to water, solvent, acid and gas, such as general work medium, but also is suitable for the working conditions of media, such as oxygen, hydrogen peroxide, methane and ethylene. Ball valve body can be a whole, also can be combined.

Globe valve

The cut-off valve stem and valve seat sealing surface vertical axes. Open?or?close the valve stem travel relatively short, and very reliable cutting action, makes this valve very suitable for used as medium cut?or?adjust and throttling.

Cut-off valve disc once in an open position, it is no longer the contact between the seat and clapper sealing surfaces, and have a very reliable cutting action, close to the valve is very suitable for used as medium cut?or?adjust and throttling.

Once stop valve is fully open, it will no longer have a contact between the seat and clapper sealing surfaces, and thus its sealing surface mechanical wear and tear is small, because most of the cut-off valve seat and valve disc is easy to repair?or?replace the whole valve sealing components without removed from the pipeline, for the valve and pipeline welding into one occasion is very applicable. Flow direction of medium through the valve changed, so stop valve flow resistance was higher than that of other valves.

Commonly used globe valve has the following kinds: 1) the Angle type globe valve; Only need to change in Angle type cut-off valve, fluid direction at a time, so that through this valve pressure drop is smaller than conventional structure of the valve. 2) once-through globe valve; In once-through?or?y-shaped cut-off valve, the valve port from the mainstream way into a diagonal lines, so that the flow state damage than conventional cut-off valve, and pressure loss across the valve and the corresponding small. 3) the plunger valve: this form of cut-off valve is normal variant of globe valve. In the valve, the valve disc and seat is usually designed on the basis of the principle of plunger. Disc polishing pillars plug connected to the stem, the seal is set in the column inserting two elastic sealing ring. Two elastic sealing ring with a set of rings is separated, and through the bonnet nut of load on the valve cover pressed around the plunger seal. Elastic sealing ring can be replaced, can use a variety of materials, the valve is mainly used in the "on"?or?"off", but with a special form of plunger?or?special thimble, can also be used to adjust flow.

Gate valves

Gate valve is used as a cut-off media, through the entire circulation when fully open, the medium run minimal pressure loss. Gate valves are normally applied to don't need to often open/close, and keep the gate full open?or?full close condition. Is not suitable for use as regulating?or?throttling. For the high-speed flow medium, ram in local open conditions can cause the vibration of the gate, and vibration and possible damage of disc and seat sealing surface, and the throttling can make gate medium of erosion. From the structure form, the main difference is adopted in the form of packing element. According to the form of sealing element, often the gate valve is divided into several different types, such as: parallel double parallel wedge gate valve, gate valve, gate valve, wedge double disc brake, etc. The most common form is wedge gate valve and parallel gate valve.

This type of valve's role is only allowed to medium flows in one direction, the direction and stop the flow. This valve is normally automatic work, in a direction of flow of fluid pressure and valve opening; In the opposite direction of fluid flow, the fluid pressure since the overlap of the disc and the disc on the seat, thereby cutting off flow. The check valve is belong to this type of valve, which includes swing check valve and lift check valve. Swing check valve with the humble hinge institutions, there is also a disc freely like door on the tilt of the seat surface. In order to ensure that each disc to seat the appropriate location, in valve design hinge agencies, so that the disc with enough space of a swing, and real, comprehensive, and the valve seat contact. All disc can be made from metal, can 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 conditions, almost unimpeded fluid pressure, so the pressure drop across the valve is relatively small. Lift check valve on the disc is located in the body of the valve seat sealing surface. In addition to this check valve can be freely valve movements, like the rest of the cut-off valve, fluid pressure from the valve seat sealing surface lift, medium return led to the disc back to seat, and cut off the flow. According to the conditions of use, valve can be all-metal structure, it can also be embedded in disc shelves rubber mat?or?rubber ring form. Like a cut-off valve, fluid through the lift check valve channel is narrow, so the lift check valve through the pressure drop than the swing check valves are bigger, and swing check valves are very few restrictions

In the process of production, in order to make the medium parameters such as pressure, flow conforms to the requirement of technological process, need to install the regulator to adjust the above parameters. The main working principle of regulating mechanism, it is by changing the valve disc and the circulation between disc and seat area, achieve the purpose of regulating the parameters. Belong to this type of valve are collectively referred to as control valves, which are divided into depending on the medium power driven itself is called self drive type control valve, such as pressure reducing valve, regulator valve and so on, all that lead up to driving (such as electricity, compressed air and fluid dynamics) called him drive type control valve, such as electric control valve, pneumatic control valve and hydraulic regulator, etc.

Electric valve

Electric valve is a common way of driving valve, often call this kind of drive of drive valve electric device, the characteristics of the valve electric actuator are as follows: 1) rapid opening and closing, can greatly shorten the time needed for opening and closing the valve; 2) can greatly reduce the labor intensity of operators, especially suitable for high pressure, large diameter valves; 3) suitable for installation in manual operation?or?difficult to close position, easy to realize remote operation, and the installation height with unlimited; 4) for the automation of the whole system; 5) than air and hydraulic power source is easy to get the wire laying and maintenance than compressed air and hydraulic pipeline is much simpler.

Valve electric actuator faults is a complex structure, use more difficult in damp places, when used in explosive medium, need to adopt and isolation measures.

The valve electric actuator driven by valve type, can be divided into two major categories of Z type and Q type. Z type valve electric actuator output shaft can roll out a lot of laps, suitable for driving gate valve, globe valve, diaphragm valve, etc.; Q type valve electric actuator output shaft can rotate 90. , and is suitable for driving plug valves, ball valves and butterfly valves, etc. According to its protective type are normal, flameproof (B), heat resistance (R) and integrative type (i.e. outdoor, anti-corrosion, explosion-proof, expressed in S).

Valve electric device generally by the actuator (reducer), the time control mechanism, the motor, the torque limit institutions, manual, electric switching mechanism, opening indicator, etc.

Pneumatic and hydraulic valve

Pneumatic and hydraulic valve is a certain pressure of air, water?or?oil as the source of power, using cylinder?or?hydraulic cylinder and the piston movement to drive the valve, the general pneumatic air pressure is less than 0.8 MPa, hydraulic pressure?or?oil pressure is 2.5 MPa ~ 25 MPa.?or?diaphragm valve; Back to the transformation of gas and liquid driving device used to drive device used to drive the ball valve, butterfly and plug valves. Driving force of the hydraulic device, suitable for driving large diameter valves. If used to drive the plug valves, ball valves and butterfly valves, must transform the reciprocating movement of the piston rotary movement. In addition to adopt cylinder?or?the piston of hydraulic cylinder to drive, don't have driven by pneumatic membrane, because of its stroke and the driving force is small, so it is mainly used for the regulator.

Manual valve

Manual valve is one of the most basic way of driving the valve. It includes using the handwheel, handle?or?wrench direct drive and driven by transmission mechanism, two kinds. When the valve is rev torque is larger, can through the gear?or?worm gear drive, to achieve the purpose of ellipsis. Gear transmission points straight tooth cylindrical gear and taper gear transmission. Gear reduction ratio is small, be applicable to the gate and globe valves, worm gear deceleration is larger, apply to cock shem, ball valve and butterfly valve.

1, gate valve,

Gate valve is also called the gate door, its characteristic is more closely, commonly used in water pipes and hot water heating pipe, due to unfavorable blocking foreign body after gate six door open, so is used as a heating tube of drain valve and small boiler, such as transverse vertical water tube boiler drain valve. The valve need not on the steam pipe, because the pressure is high, will be under pressure because of the single side gate valve and difficult to open it.

Gate valves are suitable for the work under the state of full open?or?close, appropriate adjust flow with it. If the gate is for a long period of work under the state of the switch, the sealing face of gate can become imprecise due to erosion by the medium.

2, cut-off valve and throttle valve

Globe valve and throttle the two valve is generally referred to as the ball valve in the past. Although the cut-off valve is used to truncate the steam, water channel, throttle valve is mainly used to adjust flow, but is indistinguishable from the appearance, different places only lies in the valve core. By the end of the valve core is flat, and throttle valve core is conical.

Copper valve core of the cut-off valve, regardless of the steam, water pipe can be used. By adding leather money on valve core, rubber?or?plastic thermal cut-off valve door) (also known as skin money section, it will only be used for water?or?low temperature hot water pipes,?or?leather, rubber,?or?plastic money losing rigor goes bad.

3, cock and ball valves

Cock to also call Ming check watergate, commonly known as the heart valve, is also called the test a small cock in the past, is a kind of quick opening valve, according to its distribution situation is straight through, three general formula, four general formula, etc. Cock is connected to the valve stem and valve core, valve core is truncated cone, it opened a rectangular hole, the hole is small cock is round. When the grooves on the top of the stem?or?handle is parallel to the direction of the import and export of cock valve fully open, the vertical for all valves.

Ball valve is a variation of cock, actually, like cock, it is by changing the Angle of the valve core is at the beginning of the valve. Ball valve of the valve core is a sphere, the sphere with cylindrical holes, sphere fluorine plastic hot ring on both sides of the line, as the seat, sealing ring.

Cocks and valves are quickly open the valve, small resistance and large flow. But its sealing surface wears, switch power is bigger, easy to get stuck, so not suitable for high temperature and high pressure.

Cock and ball valve specifications for 15 mm (1/2 in) ~ 50 mm (2 in). Cock can also be used in the switch line in media as a throttle valve; Ball valve is used only for switch tube medium, should not be used as throttle valve, in order to avoid losing rigor valve long time scour by the medium.

4, non-return valve (check valve)

Non-return valve and check valve, also known as single flow valve, can according to the valve before the valve pressure difference and automatically open, after the purpose is to automatically control the direction of liquid flow, making it flow in one direction, and prevent the reverse flow. Check valve is used in the feed line, installed with the direction of the strict, must not installed backwards.

Lift check valve. The valve valve core of the upper guide rod, guide rod and the valve core can lift freely along the guide sleeve on the bonnet, from left to right of fluid flow, namely the pressure, the valve core when fluid flow down to the valve core seat, pathway is truncated.

Rolled plate check valve, also known as the swing check valve, slightly with principle and lift.

The above two kinds of check valve installed in a horizontal line.

Spring loaded non-return valve, the valve is the development of the lift.

Ordinary lift check valve can be installed in the pipeline and the lifting of check valve spring can not restricted by the direction. Whether in the flat to the pipe, vertical pipe and pipe are used into a certain way.

The lifting of check valve spring. The valve's specifications for 15 mm (1/2 in) ~ 50 mm (2 in).

Bottom valve. Specially in the pump suction inlet of a one-way valve, also known as bottom of navarre, shower, etc.

5, straight valve and Angle valve

Straight valve is a kind of special radiator valve, can be used for the entrance of the gas heating radiator and water heating with heat exchanger of exports, at the entrance. Right Angle valve import and export into 90. Right Angle. Commonly known as eight valve heating system with the right Angle valve. Dedicated to the radiator, the gas heating when used for cooling the steam inlet of place, when water heating can be used in the inlet and outlet of the radiator, adjust the action of steam?or?water.

6, pressure reducing valve

Medium pressure reducing valve to reduce the pipe, make the medium pressure in accordance with the needs of the production. Commonly used pressure reducing valve piston, bellows type pressure reducing valve, tympanic membrane type and spring type, etc.

Pressure reducing valve should be installed in horizontal pipe runs erect, cover with vertical, horizontal pipeline installation direction arrow pay attention to the body. Pressure reducing valve on both sides of the valve should be device. High and low pressure pipe has been provided with a pressure gauge, and at the same time set the low pressure system safety valve. The purpose of these device is convenient and reliable to adjust and control the pressure, is especially important for low voltage system to ensure safe operation.

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