SAEL
Fisher Controls International
VBL Volume Booster
The Fisher 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 is used to improve stroking speed. If precision valve control is required, the use of a positioner is recommended. 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).
Connectors and piping can be installed with the VBL volume booster for diagnostic testing
IEC 61508 SIL 3
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