A: ball valve
Ball valve is evolved from the plug valve, the plug body is a ball, a circular hole or passage through its axis, the ball valve only needs to rotate 90 degrees and a small turning moment can be closed tight ball valve design by The past is completely equal body cavity as a medium, is considered to be the most suitable for direct opening and closing use to the current throttle and control flow is a rapid change, the main features of the ball valve itself is compact, easy to operate and repair, For water, solvents, acids and natural gas and other general working medium, but also for poor working conditions of the medium, such as oxygen, hydrogen peroxide, methane and ethylene. Ball valve body can be a whole, it can be combined. Therefore, its application is quite extensive.
1). The working principle and realistic function of the ball valve
The working principle of the ball valve is by rotating the valve to make the valve unblocked or blocked. Ball valve switch is light, small size, can be made of large diameter, reliable sealing, simple structure, easy maintenance, sealing surface and the spherical surface is often closed, easy to be media erosion, widely used in various industries.
Ball valve is mainly used in the pipeline to cut off, distribute and change the flow direction of the medium. Has the following characteristics:
1. Fluid resistance is small, the resistance coefficient and the same length of the pipe section.
2. Simple structure, small size, light weight.
3. Tight and reliable, the current ball valve sealing surface material widely used plastic, good sealing, vacuum system has also been widely used.
4. Easy to operate, quickly open and close, as long as the full open to 90 degrees off, easy to remote control.
5. Easy maintenance, ball valve structure is simple, the seals are generally active, demolition and replacement are more convenient.
6. In the fully open or fully closed, the sealing surface of the ball and valve seat and media isolation, media will not cause erosion of the valve sealing surface.
7. Wide range of applications, the path from small to a few millimeters, up to a few meters, from high vacuum to high pressure can be applied.
2) The ball valve can be divided according to the structure:
1, floating ball valve
Ball valve ball is floating, under medium pressure, the ball can produce a certain displacement and squeeze the sealing surface at the outlet end, to ensure that the outlet end of the seal. Dynamic ball valve structure is simple, good sealing, but the ball to withstand the load of the working medium are all passed to the export seal, so to consider whether the seal material can withstand the working load of the ball medium. This structure is widely used in low pressure ball valve.
2, fixed ball valve
Ball valve ball is fixed, no pressure to move. Fixed ball valve with a floating valve seat, subject to media pressure, the valve seat to move so that the ring is pressed on the ball in order to ensure the seal. Usually with the ball on the lower shaft equipped with bearings, operating torque is small, suitable for high pressure and large diameter of the valve.
In order to reduce the operating torque of the ball valve and increase the reliability of the seal, in recent years there have been oil seal ball valves, both in the sealing surface injection of special lubricants to form a layer of oil film, which enhanced the tightness and reduced operating torque , More suitable for high pressure large diameter ball valve.
3, flexible ball valve
Ball valve ball is flexible. Sphere and seat ring are made of metal materials, sealing a large pressure, relying on the pressure of the media itself has reached the seal requirements, must impose external forces. This valve is suitable for high temperature and pressure medium.
Elastic ball is in the lower end of the ball wall to open a flexible groove, and to obtain flexibility. When closing the channel, the wedge-shaped head of the valve stem causes the ball to expand and press against the valve seat to seal. Before turning the sphere, the wedged head is released and the sphere then restores its original shape. This results in a small gap between the sphere and the seat, which can reduce the friction and operating torque of the sealing surface.
Ball valve can be divided according to their channel position through-type, three-way and right angle. The latter two ball valves are used to distribute the medium and change the flow of the medium.
3) Ball valve manual
1, Scope: This instruction manual applies to the electric (or pneumatic) ball valve with flange connection.
2, composed of: electric (or pneumatic) actuator (20) and the ball valve body part, which is connected by the bracket (18) and the connecting shaft (17).
3, the use of restrictions
4. Temperature and pressure limits
l The nameplate shows the maximum allowable operating pressure of the ball valve at maximum and minimum operating temperatures.
l Using PTFE or RTFE seat and seals, the operating temperature should be between -290C and 2000C. Other types of valve seat and seal operating temperature, should be KI factory inspection.
l Nominal pressure rating (PN) of the valve indicates the maximum working pressure of the valve at normal temperature. (Example: PN4, indicating a maximum operating pressure of (40 Bar) at an operating temperature of -90C to 380C).
l For the precautions of the electric or pneumatic actuator, refer to the corresponding instruction manual.
4) Installation
1, remove the cover on both sides of the flange, the valve is fully open the state for flushing and cleaning.
(2) Pre-installation should be carried out according to the provisions of the signal (electrical or gas) machine test (to prevent vibration due to transport use of performance, qualified before installation (wiring according to the electric actuator circuit diagram.
3. Flush and remove residual contaminants from clean pipelines (these materials may damage the seat and ball) before preparing for connection to the pipe.
4, during the installation, please do not use the valve actuator part of the crane as a lifting point to avoid damage to the implementing agencies and accessories.
5, this type of valve should be installed in the pipe horizontal or vertical direction.
6, the pipeline near the installation point may not have droop or bear the phenomenon of external force, you can use pipe brackets or support to eliminate the deviation of the pipeline.
7. After connecting with the pipe, cross-fasten the flange connecting bolts with the specified torque.
5) Operation and use
1, before operation must confirm the pipeline and the valve has been washed over.
2, the valve operation according to the size of the input signal actuator driven stem rotation is completed: forward rotation 1/4 (900), the valve is off. The valve opens when rotated 1/4 turn (900) in the reverse direction.
3, when the implementing agency direction arrow parallel with the pipeline, the valve is open; the arrow and the pipeline perpendicular to the direction, the valve is closed.
6) Maintenance
Having a long service life and a maintenance-free period will depend on several factors: normal operating conditions, maintaining a consistent temperature / pressure ratio, and reasonable corrosion data
Precautions:
â— Ball valve in the closed state, there is still pressure within the body of fluid
â— Before servicing, relieve line pressure and keep the valve in the open position
â— Before maintenance, disconnect the power or air supply
â— Before maintenance, remove the actuator from the bracket
(1), the packing should be locked again
If there is micro-leakage at the filler culvert, the valve stem nut must be locked again
Be careful not to lock too tight, usually locked 1/4 turn ~ 1 turn, the leak will stop.
(2), replace seat and seal
A), disassembly
The valve is half-open position, flushing, clear the body of dangerous substances may exist inside and outside
Close the ball valve, remove the connecting bolts and nuts on both flanges and remove the valve completely from the pipe.
(20), connecting bracket (18), lock washer (14), stem nut 13), butterfly shrapnel (12) ), Stem packing (9)
Remove the cap connection bolts (5) and nuts, separate the cap from the valve body, and remove the cap gaskets (16).
Make sure the ball (3) is in the "off" position, which allows it to be easier to remove from the valve body and then remove the valve seat.
Push the stem (6) downwards through the hole in the body until it is completely removed, then remove the O-ring (8) and stem underfill (7)
CAUTION: Exercise caution to avoid scratching the stem surface and the stuffing box sealing area of ​​the valve body
B), reassemble
Cleaning and inspection Remove the parts, it is strongly recommended to replace the valve seat cover and gaskets and other seals with spare parts package
Assemble in the reverse order of disassembly.
With the specified torque, cross-lock the flange connecting bolts (5)
With the specified torque, lock the stem nut (13)
After installing the actuator, input the corresponding signal to rotate the valve core by rotating the valve stem to open and close the valve.
If possible, please pressure-seal the valve and test the performance according to relevant standards before reassembling the pipe.
Second: butterfly valve
Butterfly valve opening and closing member is a disc-shaped butterfly plate, rotating around the axis of its own axis in the valve body to achieve opening and closing or regulating valve called butterfly valve fully open to the fully closed valve is usually less than 900, the butterfly valve and the butterfly itself Self-locking force, in order to disc positioning, to install a worm reducer on the stem. With a worm gear reducer, not only can make the disc self-locking ability to stop the disc in any position, but also to improve the valve performance.
Industrial butterfly valve features high temperature, high pressure range, the valve nominal diameter, the valve body made of carbon steel, the valve ring using a metal ring instead of rubber ring. Large high temperature butterfly valve welded steel manufacturing, mainly for high temperature medium smoke duct and gas pipelines.
A: The advantages of butterfly valve are as follows:
1, quick and easy opening and closing, effort, fluid resistance, you can often operate.
2, simple structure, small size, light weight.
3, you can transport the mud, the liquid accumulated in the pipe port at least.
4, under low pressure, can achieve a good seal.
5, adjust the performance.
B: The shortcomings of the butterfly valve are as follows:
1, the use of pressure and operating temperature range.
2, poor sealing.
C: Butterfly valve structure:
Butterfly valve can be divided according to the structure of the bias plate, vertical plate, inclined plate and lever. According to the sealing form can be divided into more sealed and hard seal two. Rubber seals are generally used rubber ring seal, hard seal is usually used metal ring seal. According to the connection type can be divided into flange connection and the clamp connection; According to the transmission can be divided into manual, gear transmission, pneumatic, hydraulic and electric several.
D: butterfly valve installation and maintenance should note the following:
1, in the installation, the valve to stop in the closed position.
2, the opening position should be determined by the rotation angle of the disc.
3, with bypass valve butterfly valve, open the bypass valve should be opened before.
4, should be installed according to the manufacturer's installation instructions, the weight of the butterfly valve, should be set up a solid foundation. Three: stop valve
Closing valve opening and closing pieces of plug-shaped flap, the sealing surface was flat or tapered surface, the valve flap along the fluid center line for linear motion. Stem movement form, lifting rod (stem lift, hand wheel does not lift), there are lifting rotary rod (hand wheel with the stem rotating together, the nut is located in the valve body). Globe valve only applies to fully open and fully closed, does not allow for regulation and throttling.
Stop valves are forced to seal the valve, so the valve is closed, the pressure must be applied to the valve flap to force the sealing surface does not leak. When the medium from the bottom of the valve into the valve six, the operating force needed to overcome the resistance is the stem and packing friction and the pressure generated by the media thrust, off the valve force than the valve opening force, so the valve The diameter of the rod should be large, otherwise it will happen to the top of the valve stem failure. In recent years, since the self-sealing valve appears, the cut-off valve of the media flow to change over from the top of the valve into the valve cavity, then under medium pressure, the valve closing force is small, and open the valve force, the valve stem The diameter can be reduced accordingly. At the same time, in the medium, this form of valve is also more stringent. China's valve "three to" have provided that the flow of the valve, all from top to bottom.
When the valve is open, the valve opening height, 25% to 30% of the nominal diameter, the flow has reached its maximum, indicating that the valve has reached the fully open position. Therefore, the full-stop position of the valve, valve stroke should be determined.
Globe valve has the following advantages:
1, the structure is simple, more convenient to manufacture and maintain.
2, small work schedule, opening and closing time is short.
3, good sealing, sealing surface friction, longer life expectancy.
The shortcomings of the globe valve are as follows:
1, fluid resistance, the required force to open and close larger.
2, does not apply to the particles with a larger viscosity, easy to coking medium.
3, adjust the performance is poor.
The type of stop valve by the position of the threaded stem is externally threaded type, the female type. By media flow points, there are straight-through, DC and angle. Globe valve by sealing form points, there are packing seal globe valve and bellows seal valve.
Globe valve installation and maintenance should note the following:
1, handwheel, the handle of the globe valve can be installed in any position on the pipeline.
2, hand wheel, handle and Wei moving mechanism, do not allow lifting.
3, the flow of medium should be consistent with the arrow direction shown by the valve body.
Four: gate valve
Gate valve (gate valve) is the gate opening and closing pieces, the direction of movement of the gate and fluid perpendicular to the gate valve can only be fully open and fully closed, can not be adjusted and throttling. The gate has two sealing surfaces. The two sealing surfaces of the most commonly used gate valves form a wedge. The wedge angle varies from valve to valve, typically 50, with a 2 ° 52 'medium temperature. Wedge gate valve gate can be made as a whole, called the rigid gate; can also be made to produce a small amount of deformation of the gate, to improve its technology to make up for the sealing surface angle in the process of deviation Shuren called elastic gate.
1. Gate valve is closed, the sealing surface can only rely on medium pressure to seal, that is, rely on media pressure to the sealing surface of the gate to the other side of the valve seat to ensure that the sealing surface of the seal, which is self-sealing. Part of the gate valve is forced seal, that is, when the valve is closed, it must rely on external force to force the gate to the valve seat to ensure the sealing surface of the seal.
2. Gate valve gate with the stem for linear motion, called lifting rod gate valve (also known as rod gate valve). Usually on the lifting rod
A trapezoidal thread through the valve at the top of the nut and the guide groove on the body, the rotary motion into a linear motion, that is, the operating torque into the thrust .3 open the valve, when the gate lift height equal to the valve pass At 1: 1 diameter, the fluid path is completely clear, but this position can not be monitored during operation. The actual use is based on the top of the valve stem as a sign, that is, an open position, as its fully open position. To consider the temperature change lock phenomenon, usually in the open to the top position, and then back 1 / 2-1 lap, as a fully open valve position. Therefore, the valve fully open position, according to the gate position (ie travel> to determine.
4. Some gate valve, the stem nut is located in the gate, the hand wheel rotates the stem to rotate, leaving the rake to enhance, this valve is called rotary rod valve or dark rod gate valve.
5. Gate valve advantages:
(1) fluid resistance is small, the sealing surface of the media by the brush and erosion of small, more open and close effort.
(2) The flow of medium is unrestricted, does not disturb the flow, does not reduce the pressure.
(3) Simple body, short structure length, good manufacturability and wide range of application.
6. Gate valve shortcomings are as follows:
(1) between the sealing surface easily lead to erosion and abrasion, maintenance more difficult.
(2). Large size, open the need for a certain space, open and close a long time. The structure is more complex
7. Zhaku wide variety
According to the sealing surface configuration can be divided into wedge gate valve and parallel gate valve, wedge gate valve can be divided into: single gate type, double gate type and elastic gate type; parallel gate type gate valve can be divided into single gate Plate and double gate type. According to the thread position of the stem division, can be divided into Ming rod valve and dark rod gate valve two.
8. Gate valve installation and maintenance should note the following:
1, hand wheel, handle and transmission are not allowed to start lifting, and no collision.
2, double gate valve should be mounted vertically (ie stem in a vertical position, the hand wheel at the top).
3, with bypass valve gate valve should be opened before opening the bypass valve (to balance the pressure difference between import and export and reduce the opening force).
4, with the gear valve, according to the instructions of the product installation instructions.
5, if the valve is often used switch, lubrication at least once a month.
Five: pressure reducing valve
Reducing valve (valve) is the use of control valve body opening and closing parts of the opening to regulate the flow of media, the media pressure is reduced, with the help of the role of post-valve pressure regulator opening and closing parts, the valve pressure Keep within a certain range, and in the valve body or after the injection of cooling water, the media temperature is reduced, this valve is called decompression valve. The characteristic of this valve is to keep the outlet hearing pressure and temperature within a certain range under the condition that the inlet pressure is constantly changing.
According to the structure can be divided into film, spring film, piston, lever and bellows; according to the number of seats can be divided into single-seat and two-seater; according to the different positions of the valve can be divided into positive role And the reaction type.
Pressure reducing valve is an essential part of the pneumatic control valve, the main role is to depressurize the pressure of the gas source and stabilized to a fixed value, so that the control valve can obtain stable air source power for regulation and control.
1. The basic performance of the valve
(1) Regulating range: It refers to the adjustable range of pressure reducing valve output pressure P2, in this range requires the required accuracy. Regulating the pressure range and the main spring stiffness.
(2) Pressure characteristics: It refers to the flow rate g is set value, due to input pressure fluctuations caused by the output pressure fluctuations. The smaller the output pressure fluctuation, the better the characteristics of the pressure reducing valve. The output pressure must be lower than the input pressure - the setting will not substantially change with the input pressure.
(3) flow characteristics: it refers to the input pressure - timing output pressure with the output flow g changes in the holding capacity. When the flow rate g changes, the output pressure changes as small as possible. The lower the general output pressure, the smaller it fluctuates as the output flow changes.
2. Pressure reducing valve installation and maintenance
When installing the valve, according to the requirements of the selected type of valve and pressure regulator accuracy, and then select the maximum output flow rate of its path. When determining the air pressure of the valve, it should be greater than the maximum output pressure 0.1MPa. Pressure relief valve is generally installed in the water after the scrubber, mist eliminator or setter before, and be careful not to import and export reversed; also need to be aware that the valve should not use the knob to relax, in order to avoid the diaphragm often Pressure deformation and affect its performance.
Pressure relief valve installation and maintenance should note the following:
1, in order to facilitate the operation and maintenance, the valve is generally installed upright in the horizontal pipe.
2, the installation should pay attention to the flow direction of the medium in the pipeline and the direction of the arrow shown on the same break.
3, in order to prevent overpressure valve pressure, should be at least 4M at the valve outlet to install a pressure reducing valve.
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