The globe valve, also known as the globe valve, is one of the mandatory sealing valves. The valve stem is used to lift 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 a cut-off valve that is widely used in chemical production. The globe valve is mainly used for the control of water, steam, compressed air and other pipelines in actual production, but it is not suitable for materials with high viscosity and easy crystallization.
The structure of the globe valve is relatively complicated, but the actual operation is simple and labor-saving, and it has a good performance in regulating the flow and cutting off the channel. The globe valve has a compact structure and obvious features. The top of the valve is provided with a handwheel and a valve stem, and a thread and a stuffing box sealing section are provided in the middle.
The main way of judging the opening and closing state of the valve when the globe valve is in use is to observe the height of the valve stem exposed from the valve cover, so as to control the operation of the valve. There may be a gap in the connection between the valve stem and the bonnet, which is prone to medium leakage, which can be solved by packing sealing. The stem thread of the small globe valve is set in the valve body, so it is often in contact with the medium for a long time in 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 keep the fluid in the pipeline from low in and high out, that is, flowing through the valve seat port from bottom to top. The purpose of this installation is to reduce the fluid resistance in the valve body, thereby reducing the valve opening and closing force, and at the same time, it can keep the valve stem and stuffing box from contacting the medium when the valve is closed, thereby reducing damage and leakage.
Precautions for the use of globe valve:
1. The globe valve should be checked for leakage before opening to determine whether the valve has no leakage defects and whether the stuffing box has no leakage defects.
2. If the valve stem operation of the globe valve cannot be done by hand, it can be replaced by a special F wrench. However, if the F wrench still cannot be opened, do not use the extended wrench to forcibly open and close it to avoid damage to the valve and even safety. the occurrence of the accident.
3. When the globe valve is used in the medium pressure steam pipeline, the condensed water needs to be removed before opening, and then the pipeline is preheated with steam, and the preheating pressure is kept between 0.2 and 0.3MPA. The purpose of this is to avoid the temperature . If the seal is damaged due to sudden changes in pressure, the pressure can be adjusted to the required level after it is determined that the state is stable.
The structure is simple, and the manufacture and maintenance are relatively convenient. The working stroke is small, and the opening and closing time is short. Good sealing performance, small friction between sealing surfaces, and long service life. The disadvantages of globe valves are as follows:
The fluid resistance is large, and the force required to open and close is large. Not suitable for media with particles, high viscosity and easy coking. Poor adjustment performance.
The types of globe valves are 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, direct-current type and angle type. The globe valve is divided into sealing form, including packing seal globe valve and bellows seal globe valve.
The above is the working principle, structure and use of the globe valve. I hope it will be helpful to everyone. Please collect it and forward it.