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There are many types of valves, each with its own advantages and disadvantages. The following examples illustrate the advantages and disadvantages of several major valves, including gate valves, butterfly valves, ball valves, globe valves, and plug valves. We look forward to helping you.
Gate valve
Gate valve refers to a valve whose closing member (gate) moves in the vertical direction of the channel axis. It is mainly used to cut off the medium on the pipeline, i.e., fully open or fully closed. Generally, gate valves cannot be used to adjust flow. It can be applied to low temperature and high pressure as well as high temperature and high pressure, depending on the different materials of the valve. However, gate valves are generally not used in pipelines that transport media such as mud.
advantage:
① Low fluid resistance;
② The torque required for opening and closing is small;
③ It can be applied to a loop network pipeline where the medium flows in two directions, in other words, the flow direction of the medium is not limited;
④ When fully open, the sealing surface is less eroded by the working medium than the stop valve;
⑤ The mold structure is very simple, and the production and manufacturing process performance is good;
⑥ The construction length is relatively short.
Disadvantages:
① The overall size and opening height are large, and the installation space is also large;
② During the opening and closing process, the sealing surface is relatively rubbed, causing great friction damage, and even easily causing scratching at high temperatures;
③ Generally, gate valves often have two sealing surfaces, adding some difficulties to production, processing, grinding, and maintenance;
④ Long opening and closing time.
butterfly valve
Butterfly valve is a valve that uses a disc type opening and closing member to reciprocally rotate 95 ° up and down to open, close, and adjust the fluid channel.
advantage:
① Simple structure, small size, light weight, low consumption, not used in large diameter valves;
② Fast opening and closing, small flow resistance;
③ A substance that can be used to carry solid particles, and can also be used for powdery and particulate matter depending on the strength of the sealing surface. Suitable for dual opening and closing and adjustment of ventilation and dust removal pipelines, widely used in fuel pipelines and waterways in metallurgical industry, light industry, electric power engineering, petrochemical equipment and system software.
Disadvantages:
① The flow adjustment range is not large, and when it is opened to 30%, the flow will increase to about 96%;
② Due to the construction and sealing material limitations of butterfly valves, they are not suitable for use in high-temperature and high-pressure pipeline systems. Generally, the operating temperature is below 400 ℃ and below PN40;
③ Relativity of sealing characteristics is weaker than that of ball valves and globe valves, so the requirements for sealing performance are not very high.
ball valve
The ball valve is evolved from a plug valve. Its opening and closing member is a ball, which is used to rotate 95 ° around the center line of the valve stem to maintain the purpose of opening and closing. Ball valves are mainly used in pipelines to disconnect, distribute, and change the direction of material flow. Gate valves designed with V-shaped openings also have excellent flow adjustment functions.
advantage:
① Low flow resistance (specifically 0);
② Because it is not easy to get stuck during work (when there is no lubricant), it can be reliably used in corrosive substances and low melting point liquids;
③ Fully sealed within a wide range of working pressure and temperature;
④ It can maintain rapid opening and closing, and the opening and closing time of some structures is only 0.05~0.5s to ensure that it can be used in the automation system of the test bench. When quickly opening and closing the valve, the actual operation has no impact;
⑤ The spherical closure can fully automatically and accurately locate the boundary position;
⑥ The medium has reliable sealing performance on both sides during operation;
⑦ During full opening and full closing, the convex surfaces of the ball and valve seat are isolated from the medium, so high-speed corrosion of the convex surface is not easily caused by the substance of the valve;
⑧ Compact and lightweight, it can be felt that this is an effective valve structure for ultra-low temperature material systems;
⑨ The valve body is symmetrical, especially in the construction of welded valve bodies, which can very well bear the stress originating from the pipeline;
⑩ The closing element can bear the high pressure difference when closing The ball valve with a fully welded valve body can be directly buried in the ground, preventing the valve internals from corrosion, and has a long service life of 30 years. It is an ideal valve for crude oil and gas pipelines.
Disadvantages:
① As the key valve seat sealing ring material for ball valves is ptfe, it is often plastic for almost all chemical substances, and has comprehensive characteristics such as low friction resistance, stable characteristics, not easy to embrittle, wide range of temperature applications, and high-quality sealing properties. However, the physical characteristics of ptfe include a high coefficient of linear expansion, sensitivity to cold flow, and poor thermal conductivity. It is stipulated that the design concept of valve seat sealing must revolve around this feature. Therefore, when the sealing material hardens, the reliability of the seal is severely damaged. Moreover, the high temperature resistance level of ptfe is relatively low, and it can only be used under conditions below 180 ℃. Beyond this temperature, the rubber seal will become brittle. Considering long-term use, it is usually not used at 130 ℃.
② Its regulating characteristics are somewhat inferior to those of shut-off valves, especially in pneumatic (or electric) valves.
Globe valve
Stop valve: refers to a valve whose closing member (valve flap) moves along the valve seat axis. According to this type of movement of the valve disc, the transition of the valve seat opening is in direct proportion to the valve disc stroke. Because the valve stem opening or closing stroke of this type of valve is relatively short and has a very reliable cutoff effect, and because the change in the valve seat opening is directly proportional to the stroke of the valve disc, it is suitable for flow adjustment. Therefore, this type of valve is very often used for shutoff or adjustment as well as throttling.
advantage:
① During the entire process of opening and closing, the friction force between the valve flap and the valve body protrusion is smaller than that of the gate valve, so it is wear-resistant.
② The opening height to width ratio is usually only 1/4 of the safety channel of the valve seat, which is much smaller than the gate valve;
③ Generally, there is only one sealing surface on the valve body and disc, so the production and manufacturing process performance is relatively good, which is conducive to maintenance;
④ Because its filler is usually a compound of asbestos and high-purity graphite, it has a high temperature resistance rating. Generally, steam valves use globe valves.
Disadvantages:
① Because the medium varies according to the flow direction of the valve, the low flow resistance of the stop valve is also higher than that of most different types of valves;
② Due to the long travel schedule, the opening speed is slower than the ball valve.
Plug valve
Plug valve: Refers to a rotary valve with a plunger shaped shut-off member. Through 95 ° rotation, the passage port on the valve plug and the passage port on the valve body are connected or separated to achieve opening or closing. The valve plug can be cylindrical or conical in shape. Its basic principle is similar to that of ball valves. Ball valves are developed based on plug valves, which are mainly used for oil and gas field exploration and also for petrochemical industry.
advantage:
1. For frequent operation, fast and lightweight opening and closing.
2. Low fluid resistance.
3. Simple, relatively small in size, light in weight, and convenient for maintenance.
4. Good sealing performance.
5. Restricted by the installation orientation, the inflow of material can be arbitrary.
6. No vibration, low noise.
Disadvantages:
1. The cover is too large, resulting in a large torque and insufficient flexibility.
2. Due to the influence of body weight, the caliber size is limited.
3. In specific applications, if large size valves are used, the inverted plug structure must be used, which can easily affect the sealing effect.
