Valves
Valve functions can be defined as on/off service (shut off), throttling service (flow control through partial opening), and the prevention of reverse flow (backflow). The mediums controlled by valves are liquids and gases, including plain water, corrosive fluids, steam, toxic gases, and other fluids with widely-varying characteristics. Valves must be able to withstand the pressure and temperature variations of the system in which they are used.
Because there is a different valve for each application and operating environment, it is required that a valve's performance match the specific service requirements. Operating problems can be avoided if care is taken to select the correct valve for the intended service. Manufacturers' recommendations regarding the handling, installation, operation, and maintenance procedures should be followed to avoid future operating problems.
Several valve types are presented here to aid users in selecting the correct valve for proper operation. In abnormal or unusual circum-stances, the need for special considerations and precautions should be recognized and special references consulted.
Valve List
| Title | Purpose | Description |
| Angle | on/off | Angle valves are almost identical to globe valves in seat design and operation. Angle valves... |
| Backflow Preventer | directional, protection | Backflow preventers protect against reversed flow caused by backpressure or backsiphonage.... |
| Balancing | throttle | Balancing valves are used in hydronic systems to adjust and proportion the flow through various... |
| Ball | on/off, throttle | A ball valve uses a ball as the opening/closing device and operates with a one-quarter (90°)... |
| Butterfly | on/off, throttle | A butterfly valve has a wafer-shaped body with a thin rotating disc as the closing device. Like... |
| Check | directional | Check valves automatically check or prevent the reversal of flow. Basic types of check valves... |
| Diaphragm | on/off, throttle | Diaphragm valves are comprised of three parts: body, diaphragm, and bonnet. The diaphragm is... |
| Gate | on/off | The term gate valve refers to the wedge shaped disc that is lifted out of the main flow chamber... |
| Globe | throttle | Globe valves are so-called because old-style globe valves had a globular shape. Some modern... |
| Plug | on/off, throttle | A plug valve uses a tapered cylindrical plug that fits a body seat of corresponding shape. When... |
| Pressure Balancing | mixing, protection | A pressure balancing valve is a type of anti-scald valve that is used in domestic hot and cold... |
| Thermostatic Mixing | mixing, protection | Thermostatic mixing valves are used in domestic hot and cold water systems and in hydronic... |
