The ball valve can be closed tightly only by rotating 90 degrees and a small rotating torque. The completely equal inner cavities of the valve body provide a direct flow channel with little resistance for the medium. Generally speaking, the ball valve is most suitable for direct opening and closing, but the ball valve has been designed in recent development to make it have the function of throttling and controlling flow. The main features of ball valve are compact structure and convenient operation and maintenance. Suitable for general working media such as water, solvent, acid, natural gas, etc., and also suitable for media with harsh working conditions such as oxygen, hydrogen peroxide, methane and ethylene. Ball valve body can be integrated or combined.
Working principle and practical function of ball valve
The working principle of ball valve is to make the valve unblocked or blocked by rotating the valve. Ball valve switch is light in weight, small in volume, can be made into large caliber, reliable in sealing, simple in structure, convenient in maintenance, and the sealing surface and spherical surface are often closed, so it is not easy to be eroded by media, and is widely used in various industries.
Ball valve and plug valve belong to the same type of valve, only its closing part is a sphere, and the sphere rotates around the center line of the valve body to realize opening and closing.
Ball valve is mainly used to cut off, distribute and change the flow direction of medium in pipeline. Ball valve is a new type of valve widely used in recent years. It has the following advantages:
1. The fluid resistance is small, and its resistance coefficient is equal to that of the same length pipe section.
2. Simple structure, small volume and light weight.
3. Close and reliable. At present, plastic is widely used as the sealing surface material of ball valve, which has good sealing performance and has been widely used in vacuum system.
4. Convenient operation, rapid opening and closing, only 90-degree rotation from full opening to full closing, convenient for remote control.
5. Convenient maintenance, simple ball valve structure, movable sealing ring and convenient disassembly and replacement.
6. When fully opened or closed, the sealing surfaces of the ball and the valve seat are isolated from the medium, and when the medium passes through, it will not cause corrosion of the valve sealing surface.
7. Wide application range, from small diameter to several millimeters to several meters, from high vacuum to high pressure.
Ball valves have been widely used in petroleum, chemical industry, power generation, paper making, atomic energy, aviation, rockets and other departments, as well as people's daily lives.
Ball valves can be divided into the following structural forms:
I. Floating ball valve
The ball of the ball valve is floating. Under the action of medium pressure, the sphere can produce a certain displacement and press it on the sealing surface of the outlet end to ensure the sealing of the outlet end.
The floating ball valve has simple structure and good sealing performance, but the load of the ball bearing the working medium is all transferred to the outlet sealing ring, so it is necessary to consider whether the sealing ring material can bear the working load of the ball medium. This structure is widely used in medium and low pressure ball valves.
Second, the fixed ball valve
The ball of the ball valve is fixed and does not move after being pressed. Ball valves with fixed balls all have floating seats. After being pressed by the medium, the valve seat moves, so that the sealing ring is pressed tightly on the sphere to ensure sealing. Bearings are usually installed on the upper and lower shafts of the ball, which has small operating torque and is suitable for high-pressure and large-caliber valves.
In order to reduce the operating torque of ball valves and increase the reliability of sealing, oil-sealed ball valves have appeared in recent years. Special lubricating oil is injected between the sealing surfaces to form an oil film, which not only enhances the sealing performance, but also reduces the operating torque, and is more suitable for high-pressure large-caliber ball valves.
Third, the elastic ball valve
The ball of the ball valve is elastic. Both the ball and the seat sealing ring are made of metal, and the sealing pressure is very high. The pressure of the medium itself can not meet the sealing requirements, and external force must be applied. This valve is suitable for high temperature and high pressure medium.
The elastic sphere obtains elasticity by opening an elastic groove at the lower end of the inner wall of the sphere. When the channel is closed, the wedge-shaped head of the valve stem is used to make the ball expand and press the valve seat to realize sealing. Before rotating the ball, loosen the wedge head, and the ball will return to its original state, so that there is a small gap between the ball and the valve seat, which can reduce the friction and operating torque of the sealing surface.
Ball valves can be divided into straight-through type, three-way type and right-angle type according to their channel positions. The latter two kinds of ball valves are used to distribute the medium and change the flow direction of the medium.
Ball valve description
1. Scope: This manual is applicable to electric (or pneumatic) ball valves with flanged ends.
2. Composition: composed of electric (or pneumatic) actuator (20) and ball valve body, connected by bracket (18) and connecting shaft (17).
3. Use restrictions
Temperature and pressure limits
The nameplate shows the maximum allowable working pressure of the ball valve at the highest and lowest working temperatures.
L PTFE or RTFE seats and seals shall be used, and the working temperature shall be between-290 C and 2000C C.. The working temperature of other types of seats and seals should be checked by KI factory.
L The nominal pressure rating (PN) of the valve can indicate the maximum working pressure of the valve at room temperature. (For example, PN4.0 means that when the working temperature is-290 C ~ 380 C, the maximum working pressure is 40 Bar(4.0MPa).
For matters needing attention of electric or pneumatic actuators, please refer to the corresponding instructions.
4. Device
1), remove the protective covers on both sides of the flange end, and rinse and clean with the valve fully open.
2) Before installation, the whole machine should be tested according to the specified signal (electricity or gas) (to prevent vibration caused by transportation from affecting performance), and it can be installed online only after it is qualified (the wiring should conform to the circuit diagram of electric actuator).
3) Before preparing to connect with the pipeline, the residual impurities in the pipeline must be cleaned and removed (these substances may damage the valve seat and ball).
4) When installing, do not use the actuator part of the valve as a lifting point to avoid damaging the actuator and accessories. .
5) This valve should be installed in the horizontal or vertical direction of the pipeline.
6) The pipeline near the installation point shall not sag or bear external force, and the deviation of the pipeline can be eliminated by pipeline bracket or support.
7) After connecting with the pipeline, please cross-lock the flange connecting bolts with the specified torque.
4, operation and use
1), before operation, make sure that the pipes and valves have been washed clean.
2) The operation of the valve drives the valve stem to rotate according to the input signal of the actuator: when the valve rotates forward 1/4 turns (900), the valve is closed. When the valve rotates in the reverse direction 1/4 turns (900), the valve opens.
3) When the directional arrow of the actuator is parallel to the pipeline, the valve is in an open state; When the indicating arrow is perpendicular to the pipeline, the valve is closed.
5. Maintenance
Long service life and maintenance-free period will depend on the following factors: normal working conditions, harmonious temperature/pressure ratio and reasonable corrosion data.
Note: ● When the ball valve is closed, there is still pressurized fluid in the valve body.
● Release the pipeline pressure and keep the valve in the open position before maintenance.
● Please disconnect the power supply or air supply before maintenance.
● Remove the actuator from the bracket before maintenance.
1), the package should be locked again.
L If there is slight leakage at the packing culvert, the stem nut must be locked again (13).
I'm careful not to lock it too tightly. At ordinary times, when the lock 1/4 is turned to 1, the leakage stops.
2) Replace the valve seat and seal.
A) disassembly
L Keep the valve in the half-open position, flush and remove the possible dangerous substances inside and outside the valve body.
L Close the ball valve, remove the connecting bolts and nuts on the two flanges, and then completely remove the valve from the pipeline.
Disassemble the drive device-actuator (20), connecting bracket (18), stop washer (14), stem nut (13), butterfly spring plate (12) and GNAN (1/) in turn.
Remove the connecting bolts (5) and nuts of the valve body cover, separate the valve cover from the valve body, and remove the valve cover gasket (16).
L make sure that the valve ball (3) is in the "closed" position, which can be easily taken out of the valve body, and then take out the valve seat.
L Gently push the valve stem (6) down from the hole of the valve body until it is completely taken out, and then take out the O-ring (8) and packing (7) under the valve stem.
Note: Please be careful to avoid scratching the surface of the valve stem and the sealing part of the stuffing box of the valve body.
B) reassembly
L clean and check the removed parts. It is strongly recommended to replace seals such as seat and bonnet gasket with spare parts kit.
L assemble in the reverse order of disassembly.
L Cross-lock the flange connecting bolts (5) with the specified torque.
Tighten the stem nut with the specified torque (13).
L after installing the actuator, input the corresponding signal, and rotate the valve stem to drive the valve core to rotate, so as to realize the opening and closing of the valve.
If possible, before reassembling the pipeline, please carry out pressure sealing test and performance test on the valve according to relevant standards.
Model representation method:
Like the previous valve Q 1 1S- 16C, "s" is the old method, and "s" stands for plastic package pay. Now it is represented by "F", which stands for tetrafluoroethylene or polytetrafluoroethylene material.
Classification and characteristics of ball valves
Ball valves are divided into O-type ball valves and V-type ball valves. O-type ball valve adopts floating structure, the ball core is precision cast, the surface is plated with hard chromium, the valve seat is made of reinforced PTFE material, the orifice has the same diameter as the pipeline, the flow capacity is large, the flow resistance is small, and there is no leakage when it is closed. Generally used as an on-off valve, especially suitable for high viscosity, fibrous and granular media. V-shaped ball valve adopts fixed structure, with V-shaped notch on the ball core, which can realize proportional adjustment and approximate equal percentage of flow characteristics.
According to different process equipment, pneumatic or electric actuators can be selected to form pneumatic ball valves and electric ball valves respectively, in which pneumatic ball valves must be equipped with valve positioners to realize proportional adjustment, and electric ball valves must be equipped with electronic electric actuators or servo amplifiers to realize proportional adjustment.
From the material, it is divided into: carbon steel ball valve, stainless steel 304 ball valve, 3 16 ball valve and copper ball valve.
In application, it can be divided into: high pressure ball valve and low pressure ball valve.
High pressure ball valve: mainly used in petroleum, natural gas, hydraulic oil, construction machinery and other industries.
Low pressure ball valve: mainly used for corrosive pipes such as water!