What are the functions of valves in a piping system? 

Essentially, valves play a vital role in increasing efficiency, improving quality control and ensuring process safety and reliability. A primary consideration in valve selection is the desired function of the valve. Valves are included in piping systems for one or more of the following reasons

• Starting or stopping fluid flow. 
• Throttling flow rates in piping systems. 
• Pressure regulation. 
• Regulation of fluid temperature in piping systems. 
• Redirecting flow from one path to another.
• Restricting flow to balance the system or prevent overpressure. 
• Prevent reverse flow of fluid. 
• Stopping the flow if the system fails. 
• Improving safety by reducing pressure or vacuum in a piping system.

Basically, a valve is a mechanical device used in fluid systems to direct, separate, mix, or control fluid flow or pressure by improving passage through pipes. Normally when the valve is in the open position, the passage flows at a lower pressure than when it is unobstructed. By partially or completely obstructing the passage through the valve, the flow can be reduced as well as completely stopped.