The development and working principle of ball valve

The ball valve only needs to be rotated 90 degrees and a small turning torque to close tightly. The fully equal valve body cavity provides a small, straight-through flow path for the medium. It is generally considered that the ball valve Zui is suitable for direct opening and closing, but recent developments have designed the ball valve to have throttling and control flow. The main features of the ball valve are its compact structure, easy operation and maintenance, suitable for general working media such as water, solvent, acid and natural gas, and also suitable for medium with harsh working conditions such as oxygen, hydrogen peroxide, methane and ethylene. The ball valve body may be integral or combined.

The working principle and realistic effect of the ball valve

The ball valve works by rotating the valve to make the valve unblocked or blocked. The ball valve switch is light in weight, small in size, can be made into a large diameter, reliable in sealing, simple in structure, convenient in maintenance, and the sealing surface and the spherical surface are often closed, and is not easily eroded by the medium, and is widely used in various industries.

The ball valve and the plug valve are the same type of valve, only the closing member of which is a ball, and the ball rotates around the center line of the valve body to open and close a valve.

The ball valve is mainly used in the pipeline to cut, distribute and change the flow direction of the medium. Ball valve is a new type of valve widely used in recent years, which has the following advantages:

1. The fluid resistance is small, and its resistance coefficient is equal to the pipe length of the same length.

2. The structure is simple, small in size and light in weight.

3. It is compact and reliable. At present, the sealing surface material of the ball valve is widely used in plastic and has good sealing performance. It has also been widely used in vacuum systems.

4. The operation is convenient, the opening and closing is rapid, and the rotation is 90° from full opening to full closing, which is convenient for long-distance control.

5. The maintenance is convenient, the ball valve has a simple structure, and the sealing ring is generally movable, and the disassembly and replacement are relatively convenient.

6. When fully open or fully closed, the sealing surface of the ball and the valve seat is isolated from the medium, and the medium does not cause erosion of the sealing surface of the valve.

7. Wide range of applications, from small to a few millimeters, up to a few meters, from high vacuum to high pressure can be applied.

Ball valves have been widely used in petroleum, chemical, power generation, paper, atomic energy, aviation, rocket and other departments, as well as people's daily lives.

The ball valve can be divided according to the structure:

First, the floating ball valve

The ball of the ball valve is floating. Under the action of the medium pressure, the ball can generate a certain displacement and press against the sealing surface at the outlet end to ensure the sealing of the outlet end.

The floating ball valve has a simple structure and good sealing performance, but the load of the ball subjected to the working medium is all transmitted to the outlet sealing ring, so it is necessary to consider whether the sealing ring material can withstand the working load of the spherical medium. This structure is widely used in medium and low pressure ball valves.

Second, fixed ball valve

The ball of the ball valve is fixed and does not move after being pressed. The fixed ball valve has a floating valve seat. After the medium pressure, the valve seat moves, so that the sealing ring is pressed against the ball to ensure the seal. Usually mounted on the upper and lower shafts of the ball, the operating torque is small, suitable for high pressure and large diameter valves.

In order to reduce the operating torque of the ball valve and increase the reliability of the seal, oil seal ball valves have appeared in recent years, and the special lubricating oil is injected between the sealing faces to form an oil film, which enhances the sealing performance and reduces the operating torque. It is more suitable for high pressure and large diameter ball valves.

Third, the elastic ball valve

The ball of the ball valve is elastic. Both the ball and the seat ring are made of metal material, and the sealing pressure is very large. The pressure of the medium itself cannot meet the sealing requirements, and an external force must be applied. This valve is suitable for high temperature and high pressure media.

The elastic sphere is made by opening an elastic groove at the lower end of the inner wall of the sphere to obtain elasticity. When the passage is closed, the wedge of the valve stem is used to open the ball and press against the seat to seal. Before the ball is rotated, the wedge head is loosened, and the ball is restored to its original shape, so that a small gap occurs 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, three-way and right-angle types according to their channel positions. The latter two ball valves are used to distribute the medium and change the direction of the medium.

Ball valve instruction

1. Scope: This manual applies to electric (or pneumatic) ball valves at flanged ends.

2. Composition: It consists of an electric (or pneumatic) actuator (20) and a ball valve body part connected to the bracket (18) and the connecting shaft (17).

3, use restrictions

Temperature and pressure limits

l The nameplate shows the large operating pressure of the ball that is allowed under the small operating temperature of Zui Da and Zui.

l Use PTFE or RTFE seat and seals, operating temperature should be between -290C and 2000C. Operating temperatures for other types of seats and seals are subject to inspection by the KI facility.

l The nominal pressure rating (PN) of the valve indicates the large working pressure of the valve at normal temperature. (Example: PN4.0, indicating that the operating temperature of zui at -290C to 380C is 40 Bar (4.0 MPa)).

For the notes on electric or pneumatic actuators, refer to their respective instructions.

4, installation

1) Remove the protective cover on both sides of the flange end and rinse it with the valve fully open.

2) Before installation, the whole machine test should be carried out according to the specified signal (electricity or gas) (to prevent the use of vibration due to transportation). After passing the test, it can be installed on the line (wiring according to the electric actuator circuit diagram).

3) Before installing the pipe, flush and remove the remaining impurities in the pipe (these materials may damage the seat and the ball).

4) During installation, please do not use the actuator part of the valve as a lifting point for lifting to avoid damage to the actuator and accessories. .

5) This type of valve should be installed in the horizontal or vertical direction of the pipe.

6) The pipe near the installation point should not have the phenomenon of drooping or bearing external force. Pipe brackets or supports can be used to eliminate the deviation of the pipeline.

7) After connecting with the pipe, cross-tighten the flange connection bolt with the specified torque.

4 , operation and use

1) Confirm that the pipeline and valve have been flushed before operation.

2), the operation of the valve according to the size of the input signal of the actuator to drive the rotation of the valve stem: when the forward rotation of 1/4 turn (900), the valve is closed. The valve opens when the 1/4 turn (900) is rotated in the opposite direction.

3) When the actuator direction indicator arrow is parallel to the pipeline, the valve is open; when the indicator arrow is perpendicular to the pipeline, the valve is closed.

5, maintenance

With a long service life and maintenance-free period, it will depend on several factors: normal working conditions, maintaining a harmonious temperature/pressure ratio, and reasonable corrosion data.

Note: ● When the ball valve is closed, there is still a pressurized fluid inside the valve body.

● Before the repair, release the line pressure and keep the valve in the open position

● Disconnect power or air supply before maintenance

● Before the maintenance, the actuator is separated from the bracket

1), the packing is relocked

l If the micro-leakage occurs in the packing culvert, the stem nut (13) must be locked again.

l Be careful not to lock too tightly, usually lock 1/4 turn to 1 turn, the leak will stop.

2), replace the valve seat and seals.

A), disassembly

l Put the valve in the half-open position, flush and remove dangerous substances that may exist inside and outside the valve.

l Close the ball valve, remove the connecting bolts and nuts on the flanges on both sides, and then completely remove the valve from the line.

l Disassemble the drive unit-actuator (20), connecting bracket (18), lock washer (14), stem nut (13), butterfly shrapnel (12), Glam (11), wear-resistant piece (10), stem packing (9)

l Remove the body cover connecting bolt (5) and nut, separate the bonnet from the valve body, and remove the bonnet gasket (16).

l Confirm that the ball (3) is in the “OFF” position, which makes it easier to remove it from the valve body and then remove the seat.

l Push the valve stem (6) down from the hole in the valve body until it is completely removed, then remove the O-ring (8) and the stem under the packing (7)

Note: Please be careful to avoid scratching the stem surface and the sealing body of the valve body packing

B ), reassembly

l Cleaning and inspection of the removed parts, it is strongly recommended to replace the seals such as the seat and bonnet gasket with spare parts packages.

l Assemble in the reverse order of disassembly.

l Cross-tighten the flange connection bolts (5) with the specified torque.

l Lock the stem nut (13) with the specified torque

l After installing the actuator, input the corresponding signal to rotate the spool through the rotary valve stem to open the valve to the open and closed positions.

l If possible, perform pressure sealing test and performance test on the valve according to relevant standards before returning the pipe.

Model representation method:

Like the previous valve Q11S-16C, the "S" is an older method, and the "S" stands for a plastic seal. It is now represented by "F". It stands for PTFE or PTFE.

Classification and characteristics of ball valves

The ball valve has an O-type ball valve and a V-type ball valve. O-type ball valve adopts floating structure, the core is precision casting, the surface is hard chrome-plated, the valve seat is made of reinforced PTFE material, the flow port is the same as the pipe diameter, the circulation capacity is great, the flow resistance is very small, no when closed Leakage, generally used as an on-off valve, is especially suitable for high-viscosity, fiber-containing, granular media; V-type ball valve adopts a fixed structure, and a V-shaped slit is opened on the core to achieve proportional adjustment, and the flow characteristics are approximately equal percentage.

According to different process equipment, pneumatic or electric actuators can be selected to form pneumatic ball valves and electric ball valves respectively. Among them, pneumatic ball valves must be equipped with valve positioners for proportional adjustment. For electric ball valves, electronic electric actuators must be selected for proportional adjustment. Servo amplifiers, etc.

From the material, it can be divided into: carbon steel ball valve, stainless steel 304 ball valve, 316 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 oil, natural gas, hydraulic oil, engineering machinery and other industries

Low-pressure ball valve: mainly used in corrosive pipelines such as water!