The Structure of The Globe Valve

The globe valve is a valve that uses the valve stem to move the valve head.thereby changing the distance between the valve disc and the valve seat to achieve opening and closing control.

The globe valve is the most widely used shut-off valve in chemical production. In actual production, the globe valve is used primarily to control pipelines such as water, steam, and compressed air, but it is not suitable for materials with high viscosity and easy to crystallize.

The structure of the globe valve is relatively complex, but the actual operation is simple and labor-saving. It has good performance in regulating flow and cutting off channels. The opening and closing speed is slow and the water hammer phenomenon rarely occurs.

The globe valve has a compact structure and a more obvious appearance. The top of the valve is equipped with a handwheel and a valve stem, and the middle is equipped with a thread and a stuffing box sealing section.The main way to judge the opening and closing state of the globe valve when it is in use is to observe the height of the valve stem exposed from the valve cover to control the operation of the valve. There may be a gap in the part where the valve stem and the valve cover are connected, which is prone to medium leakage.

This can be solved by packing seals. The valve stem thread of a small globe valve is set in the valve body, so it is more in contact with the medium for a long time during use and is easily corroded by the medium.

The installation of the globe valve should refer to the direction of the fluid, and pay attention to keeping the pipeline fluid low inlet and high outlet, that is, flowing from bottom to top through the valve seat.

The globe valve  has the following advantages.

Simple structure, convenient manufacturing, and maintenance. Small working stroke, short opening and closing time. Good sealing, small friction between sealing surfaces, and long service life.

The disadvantages of the globe valve are as follows.

1.The fluid resistance is large, and the force required for opening and closing is large. It is not suitable for media with particles, high viscosity, and easy cooking. The adjustment performance is poor.

2.The types of globe valves are divided into external thread type and internal thread type according to the position of the valve stem thread. According to the flow direction of the medium, there are straight-through types, direct current types, and angle types. According to the sealing form, the globe valve is divided into packing seal globe valve and bellows seal globe valve.

When using the globe valve,the following three points should be noted.

1. Before opening the globe valve, a leakage check should be carried out to determine whether the valve and the stuffing box have no leakage defects.

2. If the valve stem of the globe valve cannot be operated manually, a special F wrench can be used instead. However, if the F wrench still cannot be opened, do not use an extended wrench to force opening and closing to avoid damage to the valve or even safety accidents.

3. When the globe valve is used in a medium-pressure steam pipeline, condensate must be removed before opening, and then the pipeline must be preheated with steam. The preheating pressure is maintained between 0.2 and 0.3 MPA. The purpose of this is to avoid damage to the seal caused by sudden changes in temperature and pressure. After confirming that the state is stable, the pressure can be adjusted to the required level.

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