Pressure reducing regulator - A “proportional only” control device that controls and responds to changes in its OUTLET pressure due to flow changes.
Back pressure regulator - A “proportional only” control device that controls and responds to changes in its INLET pressure.
Differetial pressure regulator - A “proportional only” control device that maintains a CONSTANT DIFFERENTIAL PRESSURE between a reference pressure and the pressure of the controlled fluid.
External piloted regulator - A “proportional + reset” control device that uses a piston or diaphragm actuated main valve controlled by a separate external pilot regulator that uses the flowing fluid as its power source.
Pressure loaded regulator - A regulator using a fixed volume and pressure of compressible fluid as a spring and set point reference to accomplish pressure reduction or back pressure regulation. Sometimes called a Dome Loaded Regulator.
Minimum controllable flow - The lowest flow at which a steady regulated condition of the controlled variable can be maintained.
Setpoint - The value of regulated pressure at the MINIMUM controllable flow.
Lockup - The pressure deviation from setpoint pressure when the regulator is fully closed.
Flow coefficient (Cv) - The regulator capacity in GPM of H2O at 20°C at one psi pressure drop at full rated travel. Refer to ISA S75.01 and S75.02 for Testing Procedures and Sizing Equations.
Specific Gravity - The ratio of the weight of a given volume of a fluid to the weight of an equal volume of water (liquids) or air (gases) at “standard” conditions.