Globe and Ball Valves

The ball valve uses a ball with a circular passage as the opening and closing part, and the ball rotates to open and close the valve with the valve stem. The opening and closing part of the ball valve is a holed sphere, 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 pipes and equipment media.

The main advantages of the ball valve are as follows:

1, suitable for frequent operation, opening and closing quickly and lightly.

2, fluid resistance is small.

3, simple structure, relatively small size, light weight, easy maintenance.

4, good sealing performance 5, not limited by the installation direction, the flow of the media can be arbitrary.

6, no vibration, low noise.

Ball valve classification:

The ball valve can be divided into floating ball valve, fixed ball valve, elastic ball valve and oil seal ball valve according to the structural form. According to the channel, it can be divided into straight energy type, angle type and tri-type, etc. The three-type can be divided into T-shaped and L-shaped two. Species. According to the connection, workers can be divided into three types: threaded connection, flange connection and welding type.

Ball valve installation and maintenance should pay attention to the following matters:

1, to leave the valve handle rotation position 2, can not be used as throttling.

3, ball valve with transmission mechanism should be installed upright.

The shut-off valve closing valve is a plug-shaped valve flap, the sealing surface is flat or tapered surface, the valve flap along the centerline of the fluid for a straight line. The valve stem is in the form of a lifting rod (the stem moves up and down, the hand wheel does not lift), and there is also a lifting and rotating rod type (the hand wheel rotates and lifts together with the valve stem, and the nut is arranged on the valve body). Shut-off valves are only suitable for full opening and full closing and do not allow adjustments and throttling.

The shutoff valve is a forced seal type valve, so when the valve is closed, pressure must be applied to the valve flap to force the seal surface not to leak. When the medium enters valve 6 from below the valve flap, the resistance to be overcome by the operating force is the friction force of the stem and packing and the thrust generated by the pressure of the medium. The force of closing the valve is greater than the force of opening the valve, so the valve The diameter of the rod must be large, otherwise a failure of the stem bending may occur. In recent years, after the emergence of the self-sealing valve, the medium flow of the stop valve has been changed from above the valve flap into the valve chamber. At this time, under the pressure of the medium, the force to close the valve is small, and the force to open the valve is large. The diameter can be reduced accordingly. At the same time, this type of valve is also tighter under the influence of the medium. China's valve "three to give" has stipulated that the flow of the stop valve, shall be adopted from top to bottom.

When the stop valve is opened, the opening height of the valve flap is 25% to 30% of the nominal diameter, and the flow rate has reached the maximum, indicating that the valve has reached the fully open position. Therefore, the fully open position of the stop valve should be determined by the stroke of the disc.

Globe valves have the following advantages:

1, simple structure, manufacturing and maintenance more convenient.

2, the work schedule is small, opening and closing time is short.

3, good sealing, low friction between the sealing surface, long life.

The disadvantages of the globe valve are as follows:

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

2, does not apply to particles, viscosity, easy to coke the medium.

3, poor regulation performance.

The type of globe valve is divided into male thread type and female thread type according to the position of the stem thread. According to the flow direction of the media, there are straight-through, direct-flow, and angled. The shut-off valve is divided according to the form of the seal. There are packing seal cut-off valve and bellows sealed shut-off valve.

For the installation and maintenance of globe valves, please note the following:

1. The handwheel and handle operated stop valve can be installed anywhere on the pipe.

2. Handwheels, handles and vigor mechanisms shall not be used for hoisting.

3, the direction of flow of the medium should be consistent with the direction of the arrow shown in the valve body.

Fittings accessories.

The usual accessories are three-way, elbow, size, straight, steel pipe, flange, gasket and so on.