This advanced valve actuator ensures reliable performance with automatic valve closure when actuator pressure is released. Designed for safety, it features a metal back seal on the bonnet and stem for secondary sealing during stem packing failure, along with a test port and hole for easy diagnostics. A back-pressure valve releases excess pressure in the actuator, while the increased piston dimension enables operation under low pneumatic pressure. The top shaft doubles as a position indicator for switch status, and the nitrided actuator cylinder and piston surfaces provide enhanced corrosion resistance for long-lasting durability.