Advantages and disadvantages of valves

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Valve Advantages and Disadvantages Gate Valve: Gate valve refers to a valve whose closing member (gate plate) moves along the vertical direction of the channel axis. It is mainly used to cut off the medium on the pipeline, that is, it is used fully open or fully closed. Generally, gate valves cannot be used to regulate flow. It can be applied to low temperature pressure or high temperature and high pressure, and can cast different materials of valves. However, gate valves are generally not used in pipelines transporting media such as mud. advantage: ①Small fluid resistance ； ②The torque required for opening and closing is small ； ③It can be used on ring network pipelines where the medium flows in both directions, which means that the flow direction of the medium is not restricted. ； ④When fully open, the sealing surface is less eroded by the working medium than the stop valve. ； ⑤The body structure is relatively simple and the manufacturing process is good. ； ⑥The structure length is relatively short. shortcoming: ①The overall dimensions and opening height are larger, and the required installation space is also larger. ； ②During the opening and closing process, the sealing surfaces rub against each other, resulting in greater wear and tear, and may even cause scratches at high temperatures. ； ③Generally, gate valves have two sealing surfaces, which adds some difficulties to processing, grinding and maintenance. ； ④Long opening and closing time. butterfly valve: Butterfly valve is a valve that uses a disc-type opening and closing part to rotate back and forth about 90° to open, close and adjust the fluid channel. advantage: ①Simple structure, small size, light weight, low consumption of consumables, can be used in large diameter valves ； ②Quick opening and closing, small flow resistance ； ③It can be used for media with suspended solid particles. It can also be used for powdery and granular media depending on the strength of the sealing surface. It can be used for two-way opening, closing and adjustment of ventilation and dust removal pipelines, and is widely used in gas pipelines and waterways in metallurgy, light industry, electric power, and petrochemical systems. shortcoming: ①The flow adjustment range is not large. When the opening reaches 30%, the flow rate will increase to more than 95%. ②Due to the limitations of the structure and sealing material of the butterfly valve, it is not suitable for use in high temperature and high pressure pipeline systems. The general working temperature is below 300℃ and below PN40. ③The sealing performance is worse than that of ball valves and globe valves, so it is used in places where sealing requirements are not very high. ball valve: It evolved from the plug valve. Its opening and closing part is a sphere. The sphere is rotated 90° around the axis of the valve stem to achieve opening and closing purposes. Ball valves are mainly used on pipelines to cut off, distribute and change the flow direction of media. Ball valves designed with V-shaped openings also have good flow regulation functions. advantage: ①Has the lowest flow resistance (actually 0) ； ②Because it will not get stuck during operation (when there is no lubricant), it can * Suitable for corrosive media and low boiling point liquids ； ③Able to achieve complete sealing over a wide pressure and temperature range ； ④It can achieve rapid opening and closing. The opening and closing time of some structures is only 0.05~0.1s to ensure that it can be used in the automation system of the test bench. When opening and closing the valve quickly, there is no impact in the operation. ⑤The spherical closing element can be automatically positioned at the boundary position ； ⑥The working medium can be sealed on both sides * ； ⑦When fully open and fully closed, the sealing surfaces of the ball and valve seat are isolated from the medium, so the medium passing through the valve at high speed will not cause erosion of the sealing surface. ； ⑧With its compact structure and light weight, it can be considered the most reasonable valve structure for cryogenic media systems. ； ⑨The valve body is symmetrical, especially the welded valve body structure, which can withstand the stress from the pipeline well. ； ⑩The closing parts can withstand the high pressure difference during closing. ⑾The ball valve with a fully welded body can be buried directly underground to prevent the valve internal parts from being corroded. The maximum service life can be up to 30 years. It is the most ideal valve for oil and natural gas pipelines. shortcoming: ①Because the most important seat seal material of the ball valve is polytetrafluoroethylene, it is inert to almost all chemical substances and has the comprehensive characteristics of small friction coefficient, stable performance, not easy to age, wide temperature range and excellent sealing performance. However, the physical properties of PTFE, including a high coefficient of expansion, sensitivity to cold flow and poor thermal conductivity, require that the valve seat seal must be designed around these properties. Therefore, when the sealing material hardens, the seal can * Sex is destroyed. Moreover, PTFE has a low temperature resistance level and can only be used below 180°C. Above this temperature, the sealing material will age. When considering long-term use, it is generally not used at 120°C. ②Its adjustment performance is worse than that of the stop valve, especially the pneumatic valve (or electric valve). globe valve: It refers to a valve in which the closing member (disc) moves along the centerline of the valve seat. According to this movement form of the valve disc, the change of the valve seat opening is proportional to the valve disc stroke. Because the valve stem of this type of valve has a relatively short opening or closing stroke and is very reliable, * It has a cut-off function, and because the change of the valve seat opening is proportional to the valve disc stroke, it is very suitable for adjusting the flow rate. Therefore, this type of valve is very suitable for shutting off or regulating as well as throttling. advantage: ①During the opening and closing process, because the friction between the valve disc and the valve body sealing surface is smaller than that of the gate valve, it is wear-resistant. ②The opening height is generally only 1/4 of the valve seat channel, so it is much smaller than the gate valve ； ③Usually there is only one sealing surface on the valve body and valve disc, so the manufacturing process is relatively good and it is easy to maintain. ④Since its filler is generally a mixture of asbestos and graphite, it has a higher temperature resistance level. Generally, stop valves are used for steam valves. 5+7m = Disadvantages: ①Due to the change in the flow direction of the medium through the valve, the minimum flow resistance of the stop valve is also higher than that of most other types of valves ； ②Due to the longer stroke, the opening speed is slower than that of the ball valve. Hp` \/%ts Plug valve: It refers to a rotary valve with a plunger-shaped closing member. Through 90° rotation, the channel port on the valve plug is connected or separated from the channel port on the valve body, thereby opening or closing the valve. The shape of the valve plug can be cylindrical or conical. Its principle is basically similar to that of a ball valve. The ball valve is developed on the basis of the plug valve. It is mainly used in oil field mining and also in the petrochemical industry. Diaphragm valve: It refers to a flexible membrane or combined diaphragm installed in the valve body and valve cover, and its closing member is a compression device connected to the diaphragm. The valve can be in the shape of a weir, or it can be a pipe wall that leads directly to the flow channel. +5+ ! Advantages: ①The operating mechanism is separated from the medium passage, which not only ensures the purity of the working medium, but also prevents the possibility of the medium in the pipeline impacting the working parts of the operating mechanism. There is no need to use any form of separate sealing at the valve stem unless it is used as a safety device in controlling harmful media. ； ②Since the working medium only contacts the diaphragm and the valve body, both of which can be made of a variety of different materials, the valve can ideally control a variety of working media, especially suitable for media with chemical corrosion or suspended particles. ③The structure is simple, consisting of only three parts: valve body, diaphragm and valve cover assembly. The valve is easy to quickly disassemble and repair, and diaphragm replacement can be completed on site and in a short time. v}d#L2.p Disadvantages: ①Due to the limitations of the valve body lining process and diaphragm manufacturing process, the manufacturing process of larger valve body lining and larger diaphragm is difficult, so the diaphragm is not suitable for larger pipe diameters and is generally used on pipelines with DN ≤ 200mm. ②Due to the limitations of the diaphragm material, diaphragm valves are suitable for low pressure and low temperature situations. Generally no more than 180℃ ； ③The adjustment performance is relatively poor and can only be adjusted within a small range (generally when it is closed to 2/3 of the opening, it can be used for flow adjustment). safety valve: It refers to being used as an overpressure protection device on pressure vessels, equipment or pipelines. When the pressure in the equipment, container or pipeline rises above the allowable value, the valve automatically opens and then discharges the entire amount to prevent the equipment, container or pipeline and pressure from continuing to rise. ； When the pressure drops to a specified value, the valve should automatically close in time to protect the safe operation of equipment, containers or pipelines. steam trap: In transporting steam, compressed air and other media, some condensed water will form. In order to ensure the working efficiency and safe operation of the device, these useless and harmful media should be discharged in time to ensure the consumption and use of the device. It has the following functions: ①Quickly removes condensation water generated ； ②Prevent steam leakage ； ③Exclude air and other non-condensable gases. Pressure reducing valve: It is to reduce the inlet pressure to a required outlet pressure through adjustment, and according to * The energy of the medium itself makes the outlet pressure automatically maintain a stable valve. Check valve: Also known as counterflow valve, check valve, back pressure valve and one-way valve. These valves are * It is an automatic valve that automatically opens and closes due to the force generated by the flow of the medium itself in the pipeline. Check valves are used in pipeline systems. Their main functions are to prevent the backflow of media, the reverse rotation of pumps and drive motors, and the release of container media. Check valves may also be used on lines supplying auxiliary systems where the pressure may rise above the system pressure. It can be mainly divided into swing type (rotating according to the center of gravity) and lift type (moving along the axis).