1、 Valve characteristics
Service characteristics: it determines the main service performance and service range of the valve. The service characteristics of the valve include: the category of the valve (closed-circuit valve, regulating valve, safety valve, etc.); Product type (gate valve, globe valve, butterfly valve, ball valve, etc.); Materials of main parts of the valve (valve body, bonnet, valve rod, valve disc and sealing surface); Valve transmission mode, etc.
Structural characteristics: it determines some structural characteristics of valve installation, repair, maintenance and other methods. The structural characteristics include: the structural length and overall height of the valve, and the connection form with the pipeline (flange connection, threaded connection, clamp connection, external thread connection, welded end connection, etc.); Form of sealing surface (insert ring, threaded ring, surfacing, spray welding, valve body); Valve stem structure (rotating rod, lifting rod), etc.
2、 Valve selection basis
① The purpose, operating conditions and operation control mode of the selected valve.
② Nature of working medium: working pressure, working temperature, corrosion performance, whether it contains solid particles, whether the medium is toxic, whether it is flammable or explosive, viscosity of the medium, etc.
③ Requirements for valve fluid characteristics: flow resistance, discharge capacity, flow characteristics, sealing grade, etc.
④ Requirements for installation dimension and overall dimension: nominal diameter, connection mode and connection dimension with pipeline, overall dimension or weight limit, etc.
⑤ Additional requirements for reliability, service life of valve products and explosion-proof performance of electric devices.
