Advantages and Structural Characteristics of Flanged Ball ...

1. What are the advantages of flanged ball valves?

Flanged ball valve is a relatively new type of ball valve, and its own structure has some unique advantages, such as no friction to the switch, small wear on the seal, and small opening and closing torque.

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The flanged ball valve is equipped with a multi-turn electric actuator, and the medium can be adjusted. It is widely used in petroleum, chemical industry, urban water supply and drainage, etc. Ball valve and gate valve belong to the same type of valve, the difference is that the closing part of the flanged ball valve is a sphere, which rotates around the center line of the valve body to open and close.

Ball valves are mainly used to cut off, distribute and change the flow direction of the medium in the pipeline. A flanged ball valve is defined as a valve whose opening and closing member (ball) is driven by a valve stem and rotates around the stem axis.

The ball valve flange type and gate valve belong to the same type of valve, the difference is that its closing part is a ball that rotates around the centerline of the valve body to open and close.

The three-piece ball valve is a new type of valve that has been widely used in recent years. The ball valve is mainly used to cut off, distribute and change the flow direction of the medium in the pipeline. The V-shaped opening ball valve also has a good flow adjustment function.

Flanged ball valve has the following advantages:

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

2. Simple structure, small size and light weight.

3. Tight and reliable. At present, the sealing surface material of flange type valve is widely made of plastic with good sealing performance, and it is also widely used in vacuum system.

4. Easy to operate, quick to open and close, just rotate 90° from fully open to fully closed, which is convenient for remote control.

5. Easy maintenance, simple structure of ball valve, generally movable sealing ring, easy disassembly and replacement.

6. When fully open or fully closed, the sealing surface of the ball and the valve seat is isolated from the medium, and the sealing surface of the valve will not be eroded when the medium passes through.

7. Wide range of applications, from a few millimeters to several meters in diameter, from high vacuum to high pressure.

&#;. Structural characteristics of flanged ball valve

1. No friction when opening and closing. This function completely solves the problem that the traditional valve affects the sealing due to the friction between the sealing surfaces.

2. Top installation structure. The valve installed on the pipeline can be directly inspected and maintained online, which can effectively reduce the downtime of the device and reduce the cost.

3. Single valve seat design. It eliminates the problem that the abnormal increase of medium pressure in the valve cavity affects the safety of use.

4. Low torque design. The specially designed valve stem can be easily opened and closed with a small handle.

5. Wedge-shaped sealing structure. Through the mechanical force provided by the valve stem, the ball wedge is pressed against the valve seat to seal the valve, so that the sealing performance of the valve is not affected by the change of pipeline pressure difference, and reliable sealing performance is guaranteed under various working conditions.

6. Self-cleaning structure of sealing surface. When the ball tilts away from the valve seat, the fluid in the pipeline passes through the sealing surface of the ball evenly at 360 degrees, which not only eliminates the local scouring of the valve seat by the high-speed fluid, but also washes away the accumulation on the sealing surface of the flanged ball valve. for self-cleaning purposes.

Overview of gate valves&#;

Gate valves are one of the most common types of valves in the isolation category. They can be found in every refinery, chemical plant, power station, and industrial production facility, and can be manufactured in sizes ranging from DN6 to . gate valves are chosen for the primary purpose of fluid shutoff. It is for this reason that gate valves are often referred to as "cut-off" or "blocking" valves.

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Gate valves are generally used in the fully open or fully closed operation. When fully open, the pressure drop through the gate valve is very small; when fully closed, the pressure sealing performance is very good. Due to the fit of the gate and seat ring, there is almost no leakage when the gate valve is closed. However, in the case of very low back pressure (generally not less than 0.34 bar, 1 bar = 105 Pa), some leakage may occur.

Another advantage of gate valves is that they usually open and close very slowly, a feature that prevents fluid water hammer effects from damaging the piping system.

The main limitation of gate valves is that they cannot be used in throttling conditions. When gate valves are used in dry throttling service, the fluid often has a high flow rate near the seat, which can cause erosion. Also in the partially open state, the gate will swing under the impact of the medium, which will cause damage to the seal. Usually, gate valves are more prone to seat and gate seal surface wear than globe valves, and the repair of such wear is difficult to be accomplished by means of grinding and polishing.

Because the structural characteristics of the gate valve are very suitable for large-scale devices, its application range is expanding, and to high temperature and high-pressure development. The maximum diameter of the gate valve has reached DN, in the ammonia plant has been a large number of high-pressure gate valve PN320, for oil and gas drilling wellhead gate valve working pressure up to 138MPa. manufacturing a high-temperature and high-pressure gate valve is the key to solving the problem of wedging the gate plate due to temperature changes, as well as ensuring its reliable sealing performance. To this end, the gate and seat sealing structure should be studied and improved. Resilient seats and resilient floating seats have begun to be applied to enable the gate valve to achieve inlet sealing, outlet sealing, or double sealing of import and export.

Composition of gate valve&#;

Gate valve, also called the gate valve, mainly consists of the valve body, bonnet, gate, stem, seat and seal packing, and other parts.

The gate valve is the opening and closing member (gate), driven by the valve stem, along the seat (sealing surface) to do a linear movement of the valve. Generally, the gate valve can not be used to regulate the flow, only a cut-off device can be used, either completely open or completely closed. Among the various types of valves, the gate valve is the most widely used one. It is suitable for both normal temperature and pressure conditions, as well as high and low temperature and high and low-pressure conditions, and can be applied to a variety of different media through the selection of different materials.

The advantages of the gate valve:

&#;Small fluid resistance. Gate valve body's internal media channel is straight, the media flow through the gate valve does not change its flow direction, so the fluid resistance is small.

&#; structure length (the distance between the two ends connected to the pipe) is small. As the gate is disc-shaped, is placed vertically in the body of the valve, and the globe valve flap (also disc-shaped) is placed parallel to the body of the valve, so compared with the globe valve, its structure length is smaller. Such as the PN16, and DN150 globe valve, the structure length of 480mm, while the same parameters of the gate valve structure length are only 350mm.

&#; opening and closing less effort. When opening and closing the gate movement direction is perpendicular to the direction of media flow, while the shut-off valve flap is usually closed in the direction of movement and seated in the opposite direction of media flow, and therefore must overcome the force of the medium. Therefore, compared with the shut-off valve, the opening, and closing of the exposition valve is more labor-saving.

&#; Media flow direction is not restricted. The medium can flow from both sides of the gate valve in any direction through the gate valve and can achieve the purpose of connection or cut off. Easy to install, suitable for the flow direction of the medium may change in the pipeline.

&#; When fully open, the sealing surface is subject to minimal erosion of the working medium.

&#;The structure of the body is relatively simple, and the manufacturing process is good.

Disadvantages of the gate valve:

&#;Sealing surface is easy to produce abrasions. When opening and closing the gate and the valve seat in contact with the relative sliding between the two sealing surfaces, under the action of the medium thrust easy to produce abrasion, thus destroying the sealing performance, and affecting the service life.

&#; more parts, the structure is more complex, manufacturing and maintenance are more difficult, compared with the cost of the globe valve are higher.

&#; shape size and opening height are larger, and the space required for installation is larger.

&#;Generally gate valves have two sealing pairs, which adds some difficulties to processing, grinding, and maintenance.

&#; The operating stroke is large, and the opening and closing time is long. Since the gate needs to be completely lifted to the top of the seat channel when opening, and all the gate needs to fall down to block the seat channel when closing, so the opening and closing stroke of the gate is large, and the opening and closing time is long.

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