What is the equal percentage trim on a valve?
What is the equal percentage trim on a valve?
Equal Percentage Trim in Control Valves
The valve position control system uses equal percentage trim which adjusts flow rates in proportion to valve movements instead of established volumetric changes. Equal percentage valves provide different valve characteristics from linear valves because they begin by providing gradual flow increases at low positions before showing a steeper increase at higher valve openings. Their unique characteristic makes equal percentage valves suitable for systems that experience changing pressure drops because they provide better control and operational efficiency.
Equal Percentage vs. Linear Control Valves
The shape of the valve characteristic curve expresses how valve position changes flow rate proportions. The response of equal percentage valves develops into an exponential increase of flow when the valve stem moves. The flow rate of linear valves follows a direct proportional relationship with their valve position.
Why Use Equal Percentage Valves?
Linear PID controllers must have linear processes for their optimal operation. The process response maintains consistency when controller output modifies by 10 percent throughout its operating area. The real-time behavior of a valve valve depends specifically on the operating pressure conditions of the system.
The actual pressure distribution across process equipment affects the original operational characteristics of the valve during normal operation. The actual installed characteristic of the valve deviates from its design targeting parameter. The use of an equal percentage valve usually becomes essential when achieving linear installed responses.
Equal percentage valves face incorrect use in systems that need linear valves for specific applications. Selection of the proper valve for a specific application demands thorough knowledge about the relationships among valve features and system pressure control mechanisms.