Incorporating a fixed deadband, internal soft seats and an integral bypass restriction, the VBL pneumatic volume booster has an enhanced performance capability that is important in applications where a valve positioner alone cannot provide the stroking speed needed to meet rapidly changing process conditions and demands. Its new booster design features internal soft seats that yield tight shutoff to reduce unnecessary air consumption and eliminate saturation of positioner relays. The VBL booster is compact and lightweight, and has an aluminum body. Its internal diaphragms, valves and O-rings are made from HNBR (hydrogenated nitrile butadiene rubber). — Emerson Process Management, Chanhassan, Minn.