The most common valves used in chemical processing are ball valves, butterfly valves, diaphragm valves, and check valves.
Valves are essential to the operation of any piping system that transports liquid. They range from the simple manual control valve with an on/off flow switch to the sophisticated actuated valve controlled by a computer-based programmable logic controller (PLC) that can proportion flowrate based on a variety of criteria. Choosing the right valve requires engineers to consider several factors. This article outlines how to select the best valve for an application, and discusses the advantages and disadvantages of each type.
Valve Material compatibility
In general, the first step in valve selection is choosing the appropriate material. Usually, valves are made of the same material as the piping in which they are installed. Operating pressure, operating temperature, chemical compatibility, ease of installation, cost, and product availability all factor into material selection. Of these factors, chemical compatibility is the most important in Rubber Sealing.
Metal piping systems have advantages such as high working pressures and temperatures, and traditional joining techniques. However, the chemical industry is increasingly turning to plastic systems because they offer better chemical resistance. The most common materials for plastic piping include polypropylene, polyethylene, polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), poly viny Iidene fluoride (PVDF), and acrylonitrile butathene styrene (ABS). Most materials suppliers and many equipment manufacturers provide chemical resistance and compatibility guides for material selection.
The term “wetted surface” is often used to refer to those parts of the valve (or other equipment) that come in contact with the process fluid. Most valves contain seals that are exposed to the fluids, and these must also be carefully selected for compatibility with the process. Seal materials range from simple rubber to synthetic compounds such as ethylene propylene rubber (EPDM) and fluorine rubber (FPM).