Butterfly valves selection:Determine the application conditions
media characteristics ：
Fluid type (gas, liquid, particle/corrosive medium, etc.).
The temperature, viscosity and corrosiveness of the medium (such as acid, alkali, oil, steam, etc.).
Working pressure and temperature range:
Determine the maximum working pressure (PN/Class) and temperature (high, normal or low).
Metal sealing butterfly valves should be selected for high temperature medium, and low temperature brittleness of materials should be paid attention to.
Flow control requirements:
Whether the flow needs to be adjusted or only used for opening and closing (switch type).
Selection of structural types
Classified by valve plate structure:
Centerline butterfly valves: the valve plate and the valve stem are concentric, the structure is simple, suitable for low pressure, normal temperature, no strict sealing requirements (such as water supply system).
Double eccentric butterfly valves: the sealing performance is better than the central type, suitable for medium pressure and medium temperature working conditions.
Triple-offset butterfly valves: the sealing surface is metal to metal, high temperature and high pressure, suitable for harsh working conditions (such as steam, oil and gas pipeline).
By connection mode:
Clamp type: compact structure, suitable for space limited pipeline.
Flange: easy to install and disassemble, good sealing, suitable for high pressure large diameter pipeline.
Welding: used for high pressure or special media (such as chemical pipeline).
Material selection
Valve body material:
Cast iron (low pressure room temperature, such as gray cast iron, ductile cast iron).
Carbon steel (medium and high pressure, e.g. WCB).
Stainless steel (corrosive media, e.g. 304/316).
Special alloy (high temperature, strong corrosion working condition).
sealing material ：
Rubber (EPDM, NBR, etc.): used for water, air and other non-corrosive media.
Polytetrafluoroethylene (PTFE): corrosion resistant, high temperature resistant, suitable for chemical media.
Metal sealing (stainless steel, alloy): high temperature and high pressure resistant, used for triple eccentric butterfly valves.
Nominal bore (DN) and pressure class
Piping diameter: match the inner diameter of the pipe to avoid excessive flow rate resulting in wear or noise.
Pressure rating: Select according to the maximum working pressure of the system (e.g. PN10, PN16, Class150, etc.).
How to operate
Manual operation: suitable for small diameter (DN≤300) or occasions that do not require frequent operation.
Electric actuator: used for automated control or remote operation (requires matching torque).
Pneumatic actuators: suitable for explosion-proof environments or rapid opening and closing requirements (e.g., compressed air systems).
Hydraulic actuators: used for high torque, large diameter valves (e.g., hydropower stations).
Sealing class requirements
Leakage level (e.g. ISO 5208 standard):
Centerline butterfly valves are usually Class VI (allowing slight leakage).
Triple eccentric butterfly valves can be Class V or zero leakage (metal hard seal).
Special sealing requirements: such as food grade, vacuum sealing, fire protection design, etc.
Installation and maintenance
Installation space: flange spacing should be reserved for wafer-type butterfly valves, and bolt operation space should be considered for flange type.
Maintenance convenience: the structure of the center line butterfly valves is simple and easy to maintain, and the three eccentric butterfly valve has a long life but complex maintenance.
Flow direction: some butterfly valves have flow direction restrictions (such as double eccentric, triple eccentric type).
Industry standards and certification
standard specification ：
National standard (GB), American standard (API 609, ANSI), European standard (EN), Japanese standard (JIS).
Industry certification:
Fire protection (FM/UL), drinking water (NSF), explosion-proof (ATEX), petrochemical (API), etc.
Economic evaluation
Under the premise of meeting the performance, the initial purchase cost, maintenance cost and life cycle cost are comprehensively compared.
For example, the three eccentric butterfly valve has high initial cost, but long service life, suitable for long-term operation in harsh working conditions.
Typical selection examples
Water treatment system (at room temperature and pressure): central line butterfly valve (EPDM seal) + cast iron valve body.
Chemical pipeline (corrosive medium): flanged three eccentric butterfly valve (316 stainless steel body +PTFE seal).
Steam system (high temperature and high pressure): three eccentric metal sealing butterfly valves + electric actuator.
Notes
Avoid butterfly valves for high viscosity media (e.g. asphalt) or media containing a large number of solid particles (easy to block).
Large diameter butterfly valve needs to check the strength of the valve stem and actuator torque.
In the throttling condition, cavitation and vibration risks should be considered.
Through the systematic analysis of the above steps, the selection of butterfly valve can be ensured to meet the actual needs, taking into account performance, reliability and economy.
