Introduce the advantages and disadvantages of globe valves and precautions for installation and maintenance

The opening and closing part of the globe valve is a plug-shaped disc, the sealing surface is flat or conical, and the disc moves linearly along the centerline of the fluid. The movement form of the valve stem includes a lifting rod type and a lifting rotary rod type. The stop valve is only suitable for full opening and full closing, and does not allow adjustment and throttling.

The globe valve is a forced sealing valve, so when the valve is closed, pressure must be applied to the disc to force the sealing surface not to leak. When the medium enters the valve 6 from the bottom of the disc, the resistance overcome by the operating force is the friction between the valve stem and the packing and the thrust produced by the medium pressure. The force to close the valve is greater than the force to open it, so the diameter of the valve stem should be larger, otherwise the valve stem will bend. In recent years, since the appearance of the sealing valve, the medium flow direction of the globe valve has changed from the top of the valve plate to the direction of the valve cavity. Under the action of medium pressure, the force to close the valve is small, but the force to open the valve is large, so the diameter of the valve stem can be reduced accordingly. At the same time, under the action of the medium, this valve is also tight.

When the stop valve is opened, when the opening height of the disc is 25% - 30% of the nominal diameter, the flow has reached the upper limit, indicating that the valve has reached the fully open position. Therefore, the fully open position of the globe valve should be determined according to the stroke of the disc.

Globe valves have the following advantages:

1. Simple structure, easy manufacture and maintenance.

2. The working stroke is small and the opening and closing time is short.

3. The sealing performance is good, the friction between the sealing surfaces is small, and the service life is long.

The disadvantages of globe valves are as follows:

1. The fluid resistance is large, and the force required to open and close is also large.

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

3. Poor regulatory performance.

he type of globe valve is divided into external thread type and internal thread type according to the position of the stem thread. According to the flow direction of the medium, there are straight-through type, DC type and angle type. The sealing forms of the globe valve include packing seal globe valve and bellows seal globe valve.

Globe valve structure:

The structural forms of the stop valve body are straight-through, straight-through and right-angle. The straight-through type is a common structure, but its fluid resistance is very large. One-pass fluid resistance is small, and it is mostly used for fluids with solid particles or high viscosity. Right-angle valve bodies are mostly forged, suitable for globe valves with smaller diameters and higher pressures.

The installation and maintenance of the globe valve should pay attention to the following items:

1. Handwheel and handle operated globe valves can be installed anywhere in the pipeline.

2. Do not use handwheels, handles and moving mechanisms for lifting.

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

Globe valves are mainly used for cut-off in pipelines. Globe valves have the following advantages:

1. In the process of opening and closing, the friction of the sealing surface is smaller than that of the gate valve, and it has wear resistance.

2. The opening height is small.

3. Usually there is only one sealing surface, which is easy to repair due to its good manufacturing process.