Valve Selection Procedure
Valve selection is a important activity of a material engineer or process engineer. Key to valve selection is as follows:
A. First determine type of conveyed fluid : Gas, Liquid, Slurry or Powder.
B. Determine nature of fluid :
- Substantially neutral : not noticeably acid or alkanline, such as various oils, nitrogen, air, gas, drinking water etc.
- Corrosive – markedly acid, alkaline or otherwise chemically reactive.
- Hygienic – materials for food, drug, cosmetic or other industries.
- Slurry – suspension of solid particles in a liquid can have an abrasive effect on valves etc. Non-abrasive slurries such as wood-pulp slurries can choke valve mechanisms.
C. Determine required operation
- ‘On/Off” – Fully open or fully closed.
- Regulating – including close regulation (throttling)
D. Other factors affecting choice
- Stem operation method.
- Closing time required e.g. quick closing.
- Availability of valve
- Special installation problems – such as welding valves into lines. Welding heat will sometimes distort the body and affect the sealing of small valves.