AT251U S12 A AIR TORQUE Pneumatic Actuator

The AT251U S12 A AIR TORQUE is a heavy-duty, rack-and-pinion pneumatic actuator designed for precise quarter-turn automation of industrial ball, butterfly, and plug valves. Built with a hard-anodized extruded aluminum body and high-alloy steel springs, the AT251U S12 A AIR TORQUE delivers failsafe spring-return operation in demanding process control loops.

Certified to SIL 3 safety integrity level and ATEX explosion-proof standards, the AT251U S12 A AIR TORQUE actuator features standard ISO 5211 valve mounting interfaces and NAMUR VDI/VDE 3845 solenoid and limit switch connections. Its dual bi-directional stroke adjustment stop bolts allow precise travel limit tuning from -5° to +15° in both open and closed positions.

Key Features of the AT251U S12 A AIR TORQUE Actuator

• Spring Return Failsafe Design (S12 Set): High-tensile alloy steel springs with epoxy coating ensure fail-safe spring action upon air supply loss

• Hard Anodized Aluminum Body: Extruded aluminum housing with Coating A hard anodization for superior wear and corrosion resistance

• Electroless Nickel Plated Steel Shaft: Heavy-duty ENP steel drive pinion provides high resistance to mechanical stress and oxidation

• Bi-Directional Travel Adjustment: Dual external end-stop screws allow ±10° rotation adjustment in both fully open and closed positions

• Standardized Interfaces: Full compliance with ISO 5211 for direct valve mounting and NAMUR VDI/VDE 3845 for ancillary automation accessories

• High Safety & Ex Compliance: Certified under SIL 3 (IEC 61508) and ATEX 94/9/EC for safe deployment in hazardous Zone 1 and 2 explosive atmospheres

Technical Specifications

Package Contents

• 1 × AT251U S12 A AIR TORQUE Spring Return Pneumatic Actuator

• Visual Position Indicator Cap

• Technical Operations & Wiring Manual