What is the difference between butterfly valve and ball valve

Update:2019-05-15      From:Tongling Wusong Valve Co.,Ltd

The biggest difference between the two is that the butterfly valve open and close the member is a plate, the ball valve is a ball.

Ball valve from the plug valve evolved. It has the same 90-degree lift, except that the plug is a sphere with a circular through-hole or through its axis. The ratio of the spherical surface to the channel opening should enable the spherical surface to exist completely at the inlet and outlet to intercept the flow when the ball rotates 90 degrees. The ball valve only needs to rotate 90 degrees, the rotary torque is small may close tightly. Completely equal valve body cavity for the medium provides a small and straight flow path. Ball valves are generally considered to be most suitable for opening and closing, but recent developments have designed ball valves to control flow and control flow. The main characteristics of the ball valve is compact structure, easy operation and maintenance, suitable for water, solvent, acid, natural gas and other general working medium, also suitable for oxygen, hydrogen peroxide, methane and other harsh conditions. And ethylene. The ball valve body may be integral or combined.

Working principle and practical effect of ball valve

Ball valves open or block by rotating the valve. Ball valve switch light and small, can be made into a large diameter, reliable sealing. Simple structure, easy maintenance, sealing surface and sphere often closed, not easy to be eroded by medium, widely used in all walks of life.

Ball valves and plug valves are of the same type, except that the closing member is the ball and the ball rotates around the center line of the valve body to open and close the valve.

Ball valve is mainly used for cutting, distributing and changing the flow direction of medium in pipeline. Ball valve is a new valve widely used in recent years, with the following advantages:

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

2. Simple structure, small size and light weight.

3. Compact and reliable structure. At present, ball valve sealing surface material is widely used in plastic, sealing performance is good. It is also widely used in vacuum systems.

4, easy to operate, fast to open and close, fully open and fully close 90° rotation, convenient for remote control.

5, easy maintenance, simple structure of ball valve, sealing ring can be moved, easy to remove and replace.

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

7. Wide range of application, from a few millimeters to a few meters, from high vacuum to high vacuum can apply 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 life.

Ball valves can be divided into:

One, float valve

The ball of the ball valve is floating. Under the action of medium pressure, the ball can produce a certain displacement and pressure on the sealing surface of the outlet end, to ensure that the outlet end is sealed.

The float ball valve is simple in structure and has good sealing performance. However, it is necessary to consider whether the sealing ring material can bear the working load because all the load of the ball bearing the working medium is transferred to the outlet sealing ring. Spherical medium. This structure is widely used in middle and low pressure ball valves.

Two, fixed ball valve

The ball of the ball valve is fixed and does not move when pressed. Fixed ball valve has a floating seat. After medium pressure, the seat moves to press the sealing ring against the ball to ensure seal. Usually mounted on the upper and lower shaft of the ball, the operation torque is small, suitable for high pressure and large diameter valve.

In order to reduce the operating torque of ball valve and improve the reliability of seal, oil seal ball valve has appeared in recent years. Special lubricating oil is injected between the sealing surface to form an oil film and enhance the tightness. Performance and reduced operating torque. It is more suitable for high pressure and large diameter ball valve.

Three, elastic ball valve

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

An elastic ball is made by opening an elastic groove at the bottom of the inner wall of the ball to obtain elasticity. Stem wedges are used to open the ball and press against the seat to seal when the channel is closed. Before the ball rotates, loosen the wedge head and return the ball to its original shape, creating a small gap between the ball and the seat that reduces friction and operating torque on the sealing surface.

Ball valves can be divided into straight - through, three - way and right Angle according to the location of the channel. The latter two ball valves are used to distribute media and change the direction of media.

Ball valve that

1. Scope: this manual is applicable to electric (or pneumatic) ball valves with flanged ends.

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

3. Use restrictions

Temperature and pressure limits

The nameplate shows the maximum allowable operating pressure of the ball valve at the highest and lowest operating temperatures.

PTFE or RTFE seats and seals can be operated at temperatures ranging from -19 ° c to 200 ° c. The operating temperature of other types of seats and seals shall be checked by KI facilities.

The rated pressure class (PN) of the valve represents the maximum working pressure of the valve at room temperature. (for example: PN40, representing the maximum working pressure of 40 bar when operating at -290 ° c to 380 ° c).

For instructions on electric or pneumatic actuators, see their respective instructions.

4, the installation

1) remove the protection cover on both sides of the flange end and flush when the valve is 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). After passing the test, it can be installed on the circuit (wiring according to the electric actuator circuit diagram).

3) flush and remove residual impurities (materials that may damage seats and balls) from the piping prior to installation.

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

5) such valves shall be installed in the horizontal or vertical direction of the pipeline.

6) the pipes near the installation point should not sag or bear external force. Pipe supports or brackets may be used to eliminate deviations from the pipe.

7) after connecting with the pipe, cross tighten the flange connection bolts with the specified torque.

4. Operation and use

1) confirm that pipes and valves have been flushed before operation.

2), valve operation according to the size of the input signal of the actuator to drive stem rotation: when forward rotation 1/4 turn (900), the valve closes. When 1/4 turn (900) in opposite direction, valve opens. 3) when the actuator direction arrow is parallel to the pipe, the valve opens; When the indicating arrow is perpendicular to the pipe, the valve closes.

5, maintain

The long service life and maintenance-free time depend on several factors: normal working conditions, a harmonious temperature/pressure ratio, and reasonable corrosion data.

Note:

● when the valve body is closed, there is still pressurized fluid inside the ball valve.

● release line pressure and keep valve in open position prior to service

● disconnect power or air supply before maintenance

● before maintenance, the actuator is separated from the bracket

1), the packaging is re-locked

If there is a minor leak in the packing culvert, the stem nut (13) must be locked again.

Be careful not to lock too tightly. Usually lock 1/4 turn to 1 turn. Leakage will stop.

2) replace the valve seat and sealing ring.

A) demolition

Place valve in half-open position, flush and remove potentially hazardous material inside and outside the valve.

Close ball valve, remove connecting bolts and nuts from both flanges, and remove valve completely from line.

Remove drive unit - actuator (20), connection bracket (18), lock washer (14), stem nut (13), butterfly shrapnel (12), Glam (11), wear plate (10), stem packing (9)

Remove body cover coupling bolt (5) and nut, separating cover from body, and remove cover washer (16).

Make sure the ball (3) is in the "off" position so it can be easily removed from the body and then removed from the seat.

Push stem (6) down through the hole in the body until completely removed, then remove o-ring (8) and stem (7) below the spool

Note: be careful not to scratch body surfaces and body packing seals

B) reassemble

Remove and inspect removed parts, and it is strongly recommended to replace seals, such as seat and cover gaskets, with spare parts kits.

Assemble in the reverse order of disassembly.

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

Lock stem nut with specified torque (13)

After installing the actuator, input the corresponding signal and rotate the valve core by rotating the stem to open and close the valve.

If possible, perform a pressure seal test and performance test on the valve in accordance with relevant standards before returning to the pipe.

The butterfly valve means the closing member (valve or disc) is the disc valve that rotates around the valve shaft to open and close, primarily for pipe cutting and throttling. The butterfly valve opening and closing member is a disc-shaped butterfly plate that rotates around its own axis in the valve body to open and close or adjust. From fully open to fully closed, butterfly valves are usually less than 90°. Butterfly valves and rods have no self-locking capability. In order to locate the butterfly plate, a worm gear reducer is added on the valve stem. The use of worm gear reducer not only makes the disk with self-locking ability, but also can stop the disk in any position and improve the operation performance of the valve.

Industrial butterfly valve is characterized by high temperature resistance, applicable pressure range is high, the nominal diameter of the valve is large, the body is made of carbon steel, the valve plate seal ring is made of metal ring rather than rubber ring. Large high temperature butterfly valve is made of steel plate welding, mainly used for high temperature medium flue and gas pipeline.

The advantages of butterfly valve are as follows:

1, easy to open and close, labor saving, low fluid resistance, frequent operation.

2. Simple structure, small size and light weight.

3, can transport mud, the minimum amount of liquid accumulation in the pipe mouth.

4. Good sealing can be achieved at low pressure.

5. Good adjustment performance.

The disadvantages of butterfly valve are as follows:

1, use pressure and operating temperature range around the small.

2. Poor tightness.

Butterfly valve according to the structure can be divided into bias plate, vertical plate, inclined plate and lever type. According to the sealing form, it can be divided into two types: relative sealing type and hard sealing type. Soft seal type is usually sealed with rubber ring, hard seal type is usually sealed with metal ring.

According to the type of connection, can be divided into flange connection and clamping connection; According to the transmission mode, can be divided into manual, gear transmission, pneumatic, hydraulic and electric.

Installation and maintenance of butterfly valve should pay attention to the following matters:

1. The disc should stop at the closed position during installation.

2. The opening position should be determined according to the rotation Angle of the disc.

3. For butterfly valve with bypass valve, open the bypass valve before opening.

4. Install according to the manufacturer's installation instructions. Heavy duty butterfly valves shall be provided with a solid foundation.