Butterfly valve is suitable for flow regulation. Because the pressure loss of butterfly valve in pipeline is relatively large, which is about three times that of gate valve, the influence of pressure loss on pipeline system should be fully considered when selecting butterfly valve, and the firmness of butterfly plate under the pressure of pipeline medium should also be considered when closing. In addition, the working temperature limit of elastic valve seat material at high temperature must be considered.
The butterfly valve has small structural length and overall height, fast opening and closing speed and good fluid control characteristics. The structural principle of butterfly valve is most suitable for manufacturing large-diameter valves. When the butterfly valve is required to control the flow, the most important thing is to correctly select the size and type of the butterfly valve so that it can work correctly and effectively.
Usually, in throttling, regulating control and mud media, short structure length and fast opening and closing speed (1/4 rpm) are required. Low pressure cut-off (small pressure difference), butterfly valve is recommended.
Butterfly valves can be used in places with two-position adjustment, necking channel, low noise, cavitation and gasification, and a small amount of leakage to the atmosphere and abrasive media.
When the butterfly valve is used under special working conditions, or requires strict sealing, or under severe wear and low temperature (cryogenic) and other working conditions, it is necessary to use a special butterfly valve with specially designed metal seal and three eccentric or two eccentric adjusting devices.
The mid-line butterfly valve is suitable for pipelines with fresh water, sewage, seawater, salt water, steam, natural gas, food, medicine, oil products, various acids and alkalis, etc., which require complete sealing, zero leakage during gas test, long service life and working temperature of-10℃ ~150℃.
Soft sealing eccentric butterfly valve is suitable for bidirectional opening and 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.
Metal-to-metal wire sealing double eccentric butterfly valve is suitable for urban heating, gas supply, water supply and other gas, oil, acid and alkali pipelines as regulating and throttling devices.
Metal-to-metal tri-eccentric butterfly valve is not only used as the program control valve of large PSA gas separation device, but also widely used in petroleum, petrochemical, chemical, metallurgical, electric power and other fields. It is a good substitute for time gate valve and globe valve.
Selection principle of butterfly valve:
1. Because the pressure loss of butterfly valve is larger than that of gate valve and ball valve, it is suitable for pipeline system with lax pressure loss requirements.
2. Because the butterfly valve can be used to adjust the flow, it is suitable for the pipeline that needs to adjust the flow.
3. Due to the limitation of butterfly valve structure and sealing material, it is not suitable for high temperature and high pressure pipeline system. Generally, the working temperature is below 300℃ and the nominal pressure is below PN40.
4. Because the butterfly valve has a short structural length and can be made into a big mouth, it is more appropriate to choose a butterfly valve with a short structural length or a big mouth valve (such as DN 1000 or above).
5. Because the butterfly valve can only be opened or closed by rotating 90o, it is appropriate to choose the butterfly valve in the occasion with the requirement of quick opening and closing.
Ball valve applicable occasions:
Because the material of valve seat sealing ring of ball valve is usually rubber, nylon and PTFE, its service temperature is limited by the material of valve seat sealing ring. The cut-off function of ball valve is accomplished by the mutual compression of metal balls between plastic valve seats under the action of medium (floating ball valve). Under the action of certain contact pressure, the seat sealing ring is deformed elastically and plastically in some areas. This deformation can compensate the manufacturing accuracy and surface roughness of the ball and ensure the sealing performance of the ball valve.
Because the valve seat sealing ring of ball valve is usually made of plastic, the fire resistance and fire prevention performance of ball valve should be considered when choosing the structure and performance of ball valve, especially in petroleum, chemical industry, metallurgy and other departments, when using ball valve in equipment and pipeline systems with flammable and explosive media, more attention should be paid to fire resistance and fire prevention.
Generally, the ball valve is recommended to be used in pipeline systems with two-position adjustment, strict sealing performance requirements, mud, wear, necking channels, rapid opening and closing action (1/4 to open and close), high pressure cutoff (large pressure difference), low noise, cavitation and gasification, small atmospheric leakage, small operating torque and small fluid resistance.
Ball valve is also suitable for light structure, low pressure cut-off (small pressure difference) and corrosive medium pipeline system.
Ball valves can also be used in cryogenic equipment and piping systems.
In the oxygen pipeline system of metallurgical industry, ball valves that have been strictly degreased must be used.
When the main pipeline in oil and gas pipeline needs to be buried underground, it needs full-diameter welded ball valves.
When the performance needs to be adjusted, the ball valve with special structure with V-shaped opening should be selected.
In petroleum, petrochemical, chemical, electric power and urban construction, metal-to-metal sealed ball valves can be used in pipeline systems with working temperatures above 200℃.
Selection principle of ball valve:
1, the main oil and gas pipelines and pipelines need to be cleaned and buried, and all-pass and all-welded ball valves are selected; When buried, choose all welded or flanged ball valves; Branch pipe, choose flange connection, welding connection, full-diameter or reduced-diameter ball valve.
2. Flanged ball valves should be used for product oil pipelines and storage equipment.
3. Floating ball valves with flange connection and internal thread connection are selected for urban gas and natural gas pipelines.
1. In the oxygen pipeline system of metallurgical system, the flange-connected fixed ball valve which has been strictly degreased should be selected.
2, low temperature medium piping system and device, appropriate chooses low temperature ball valve with valve cover.
3. In the pipeline system of the catalytic cracking unit of the oil refining unit, the lifting rod ball valve can be selected.
4. In the devices and piping systems of corrosive media such as acid and alkali in the chemical system, stainless steel ball valves made of austenitic stainless steel with PTFE as the seat sealing ring should be selected.
5. Metal-to-metal sealed ball valves can be used for piping systems or devices of high-temperature media in metallurgical systems, power systems, petrochemical plants and urban heating systems. 6. When it is necessary to adjust the flow, worm gear, pneumatic or electric V-shaped opening adjusting ball valve can be selected.