Gate valve is widely used in the pipeline a valve, the main play and cut off the media role. Does not apply to regulate the flow of media, but according to the height of the stem to determine the size of the flow rate (such as fire with a seat sealing valve with opening and closing scale). Gate valve compared to other valves, the pressure, temperature, diameter and other requirements of the scope of the wider. Gate valve according to the different internal structure can be divided into: wedge single gate type, elastic gate type, double gate type, parallel gate type. According to the different stem holder can be divided into: Ming rod valve and dark rod gate valve. Gate valve main performance advantages are: 1, the valve fluid resistance is small, because the gate valve body is straight through, the flow of the medium does not change direction, so compare the other valve flow resistance is smaller. 2, the sealing performance is better than the cut-off valve, opening and closing than the cut-off valve labor-saving. 3, wide range of applications, except for steam, oil and other media, but also for containing granular solids and viscous media, but also for the valve to do vent valve and low vacuum system to use. 4, the gate valve is a dual flow valve, not restricted by the flow direction of the medium, it is suitable for medium may change the flow direction of the pipeline, but also easy to install. Gate valve's main performance shortcomings are: 1, shape design size, starting and closing a long time. The valve plate needs to be lifted to the upper part of the valve cavity when the valve is opened, and the valve plate needs to be completely thrown into the valve seat when the valve is closed. Therefore, the valve plate has a large opening and closing stroke and a long time. 2, because the gate valve plate and valve seat sealing surface in the process of opening and closing there is friction, so easy to scratch the sealing surface, the sealing performance and service life are affected, and not easy to repair. Several different structure of the gate valve performance comparison: (1) wedge single gate valve a, the structure is simpler than the elastic gate valve b, at higher temperatures, the sealing performance is not as good as the elastic gate valve or double gate valve. c, suitable for high temperature coking medium. (2) elastic gate valve a, it is a special form of wedge single gate valve. Compared with the wedge gate valve, at high temperature, the sealing performance is good, the gate is not easy to get stuck after heating; b, suitable for steam, high temperature oil products and hydrocarbon media, and is suitable for frequent switching parts. c, does not apply to easy caking medium. (3) double gate valve a, the sealing performance is better than the wedge gate valve, when the sealing surface of the tilt angle and seat with the valve is not very accurate, still has good sealing performance. b, the gate seal surface wear, the bottom of the spherical top center metal pad can be used after replacement, generally do not have to surfacing and grinding sealing surface, which is a single gate and elastic gate does not have the advantages. c, suitable for steam, high temperature oil and hydrocarbon media, and applies to the frequent switch parts. d, does not apply to easy caking medium. (4) parallel gate valve a, sealing performance worse than other forms of gate valve. b, suitable for lower temperature and pressure medium. c, gate and valve seat sealing surface processing and maintenance than other forms of gate valve simple. Ming rod valve and the difference between the dark rod gate valve: gate valve is up and down through the stem of the drive gate opening and closing, Ming rod gate drive screw thread in the top of the stem bracket, so you can determine the gate opening and closing of the valve stem Position, while the drive thread is also easy to maintain daily lubrication, while fluid erosion, the disadvantage is the installation of larger space requirements. Dark bar gate valve drive thread in the body, saving the stem bracket space, so the entire valve height decreases. On the need to clearly open and close the position, the valve cover can be installed above the opening and closing scale, suitable for the bottom of the gutter (such as underground dark bar gate valve), ditch and other small space, or dust content of the place. Gate valve can also be based on different materials, different pressures, different seals, different connections, divided into different gate valve type.
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