Valve bellowsThe opening and closing part is a plug-shaped valve disc, the sealing surface is flat or conical, and the valve disc moves linearly along the center line of the fluid. The movement form of the valve stem can be divided into the lifting rod type (the valve stem is lifted, the handwheel is not lifted) and the lifting rotating rod type (the handwheel rotates with the lifting of the valve stem, and the nut on the valve body). The bellows stop valve is only suitable for full opening and full closing, and no adjustment or throttling is allowed. Such valves should normally be installed horizontally in the pipeline. The hand wheel and handle operated bellows shut-off valve can be installed in any position of the pipeline. Do not use handwheels, handles and lifting mechanisms for lifting. The flow direction of the medium should be consistent with the direction of the arrow shown on the valve body.

Valve bellows, also known as globe valve, is a very wide range of valves. It is popular because of the low friction between the sealing surfaces during the opening and closing process, relatively durable, small opening height, easy to manufacture, and easy to maintain. It is not only suitable for medium and low pressure, but also for high pressure. The closing principle is to make the sealing surface of the valve clack and the sealing surface of the valve seat with the pressure of the valve stem to prevent the flow of the medium. The valve bellows only allows one-way flow of the medium and has directionality during installation. Its structure length is greater than the gate valve, fluid resistance. Long-term operation, sealing reliability is not strong. There are three types of valve bellows: straight-through, right-angle and straight-through tilt globe valves. When the valve bellows is opened, when the opening height of the valve disc is 25% ~ 30% of the nominal diameter, the flow has reached a large value, indicating that the valve has reached the fully open position. Therefore, the fully open position of the stop valve should be determined according to the stroke of the valve disc. The valve bellows 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 the valve body from the lower part of the valve disc, the resistance overcome by the operating force is the friction between the valve stem and the packing and the thrust generated by the medium pressure. The force to close the valve is greater than the force to open the valve, so the diameter of the valve stem is larger, otherwise the valve stem will bend. In recent years, since the emergence of self-sealing valves, the medium flow direction of the stop valve has been transferred from the top of the valve disc to the valve chamber. At this time, under the medium pressure, the force to close the valve is small, and the force to open the valve is large, and the diameter of the valve stem can be reduced accordingly. At the same time, under the action of the medium, this type of valve is also relatively tight. China's "three supply" provisions, the flow of the valve should be from top to bottom.

When the valve bellows is opened, when the opening height of the valve disc is 25% ~ 30% of the nominal diameter, the flow has reached a large value, indicating that the valve has reached the fully open position. Therefore, the fully open position of the stop valve should be determined according to the stroke of the valve disc. The electric gate valve is sensitive, safe and reliable. Many plants with high control requirements are specially equipped with compressed air stations for pneumatic instrument control elements. Electric needs electricity. And its flow can be controlled. The structure is simple, and the manufacturing and maintenance are relatively convenient. Small working stroke, short switching time. Good sealing performance, low friction on the sealing surface and long service life. The disadvantages of the valve bellows are as follows: the fluid resistance is large, and the force required to open and close is large. It is not suitable for medium with particles, high viscosity and easy coking. Poor regulation performance. According to the position of the valve stem thread, the type of valve bellows is divided into external thread type and internal thread type. According to the flow direction of the medium, there are straight-through type, DC type and angle type. Globe valve according to the sealing form is divided into packing valve bellows and bellows seal globe valve.