Does your application require a valve that is able to throttle efficiently? When choosing a valve it is important to consider the throttling service required. Not all valves are good choices for throttling service, but knowing some valve basics will ensure that you make the right choice.
A throttling valve has a closure element designed to give the valve the ability to start and stop flow as well as stop along any position of the valve's travel. This ability regulates the process flow-rate as well as the downstream pressure of the system. By restricting the flow, certain physical effects can often occur. These effects include increased velocities immediately downstream of the device and possible cavitation (think of folding over a garden hose and the sound it makes).
Globe and angle valves are often used in throttling service, and both respond well to this type of service. Be sure to select the most suitable disc materials for the intended service. Some valves, such as soft seated valves, may not provide satisfactory service.
Ball and butterfly valves provide alternative choices. However, standard commercial and plumbing valves are commonly supplied with soft seating materials which can become damaged at elevated pressure drops. Also, due to their round openings, they do not offer the precise control required for some systems. An alternative would be to consider
Milwaukee Valve's Flow Control ball valve
Gate valves, designed to operate fully open or fully closed, are never recommended for throttling. Throttling a gate valve will cause damage to the wedge and/or seat rings, and prevent the valve from shutting off effectively, even after a very short period of time on the throttling position.