Emerson Process Management’s Fisher VBL booster incorporates a fixed deadband, internal soft seats, and an integral bypass restriction that combine to eliminate the positioner problems. The enhanced booster design is for applications where a valve positioner alone cannot provide the stroking speed needed to meet rapidly changing process conditions and demands. The new design features internal soft seats that yield tight shutoff to reduce unnecessary air consumption and eliminate saturation of positioner relays. The booster also has bypass restriction that enables fast actuator response. The restriction also allows tuning valve response to follow slow signal changes or provide on/off control. This capability does not impact booster deadband. The booster features an aluminum body with 1/4 NPT input and 1/2 NPT connections. Internal diaphragms, upper and lower valves, and o-rings are of HNBR. Maximum input signal pressure is 10.3 bar (150 PSIG) with an input to output ratio being fixed at 1-to-1.