Detailed explanation of fireball valve

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Detailed explanation of ball valve

what is a ball valve

ball valve is a valve that uses a ball with a circular channel as the opening and closing part, and the ball rotates with the valve stem to realize the opening and closing action. The opening and closing part of the ball valve is a sphere with holes, which rotates around the axis perpendicular to the channel, so as to achieve the purpose of opening and closing the channel. Ball valves are mainly used to open and close pipelines and equipment media

the main advantages of the ball valve are as follows:

1. It is suitable for regular operation, and the opening and closing is fast and light

2. Low fluid resistance

3. Simple structure, relatively small size, light weight and easy maintenance

4. Good sealing performance

5. No, you should fully understand the product before using any experimental machine. Due to the limitation of installation direction, the flow direction of media can be arbitrary

6, no vibration, low noise

classification of ball valves:

ball valves can be divided into floating ball valves, fixed ball valves, elastic ball valves and oil sealed ball valves according to their structural forms; According to the channel, it can be divided into direct energy type, angle type and three-way type, and the three-way type can be divided into T-shape and L-shape. According to the connection method, it can be divided into three types: threaded connection, flange connection and welding

the following matters should be paid attention to in the installation and maintenance of ball valve:

1. The position of valve handle rotation should be reserved

2. It cannot be used as throttling

3. The ball valve with transmission mechanism should be installed vertically

what is the cut-off method

stop valve

the opening and closing parts of the stop valve are plug-shaped disc, the sealing surface is flat or conical, and the disc moves in a straight line along the center line of the fluid. The movement form of the valve rod includes lifting rod type (the valve rod is lifted and the handwheel is not lifted), and lifting rotating rod type (the handwheel rotates and lifts with the valve rod, and the nut is set on the valve body). The stop valve is only applicable to full open and full close, and adjustment and throttling are not allowed

the stop valve is a forced sealing valve, so when the valve is closed, pressure must be applied to the valve disc to force the sealing surface not to leak. When the medium enters valve VI from below the valve disc, the resistance to be overcome by the operating force is the friction between the valve rod and the packing and the thrust generated by the pressure of the medium. The force to close the valve is greater than the force to open the valve, so the diameter of the valve rod should be larger, otherwise the valve rod bending fault will occur. In recent years, since the emergence of self sealing valves, the medium flow direction of the stop valve has changed from the top of the valve disc to the valve cavity. At this time, under the action of medium pressure, the force to close the valve is small, while the force to open the valve is large, and the diameter of the valve rod can be reduced accordingly. At the same time, under the action of medium, this type of valve is also relatively tight. Although the market share of each enterprise is different, it has been stipulated that the flow direction of stop valves should be from top to bottom

when the stop valve is opened, when the opening height of the valve disc is 25% - 30% of the nominal diameter, the flow has reached the maximum, indicating that the valve has reached the full open position. Therefore, the full open position of the stop valve should be determined by the stroke of the valve disc

the stop valve has the following advantages:

1, simple structure, convenient manufacturing and maintenance

2. Small working stroke and short opening and closing time

3. Good sealing performance, small friction between sealing surfaces and long service life

the disadvantages of the stop valve are as follows:

1. The fluid resistance is large, and the force required for opening and closing is large

2. It is not suitable for media with particles, high viscosity and easy coking

3. Poor regulation performance

the types of stop valves can be divided into external thread type and internal thread type according to the position of valve stem thread. According to the flow direction of the medium, there are straight through type, direct current type and angle type. Stop valves are divided into packing seal stop valves and bellows seal stop valves according to the sealing form

installation and maintenance of stop valve one of the important characteristics of rock mechanical properties should pay attention to the following:

1. The stop valve operated by hand wheel and handle can be installed at any position of the pipeline

2. Handwheel, handle and servo mechanism are not allowed to be used for lifting under the effect of load friction body

3. The flow direction of medium should be consistent with the arrow direction shown on the valve body

pipe fittings

common accessories include tee, elbow, reducer, straight, steel pipe, flange, gasket, etc

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