signal amplifier / charge / high-accuracy / electronic
The VBL volume booster is used in conjunction with a positioner on a throttling control valve to increase stroking speed.
The booster incorporates fixed deadband, soft seat construction, and an integral bypass restriction to eliminate positioner saturation problems that can occur with volume boosters that do not have these features. Adjustment of the integral bypass restriction is necessary for system stability. This adjustment does not affect the deadband of the volume booster, but does permit the control valve to respond to small input signal changes without sacrificing steady-state accuracy. It also allows the booster to deliver high-volume output for fast stroking when large, rapid input signal changes occur.
The volume booster, when used in conjunction with a positioner/actuator, is used only to improve stroking speed. It is not recommended for other applications requiring a high-accuracy, instrument-type volume booster. If the volume booster is to be used only with an actuator, for on-off control, the integral bypass restriction on the booster must be closed (turned fully clockwise).