AT Rack-and-Pinion Pneumatic Actuator

AT Rack-and-Pinion Pneumatic Actuator – Product Manual
I. Product Overview
The AT pneumatic actuator is a rack-and-pinion piston-style drive unit designed specifically for quarter-turn valves. It utilizes a symmetrical dual-piston transmission structure powered by clean compressed air, converting the linear motion of the pistons into 90° rotational torque. It is designed to pair with quarter-turn valves—such as pneumatic ball valves, butterfly valves, plug valves, and dampers—to enable automated on/off switching and proportional control.
The product is available in two main types: double-acting (AT-D) and single-acting spring-return (AT-S). It features a compact design, uniform output force, smooth operation, and a long service life. With standardized dimensions, it fully complies with international interface standards such as ISO 5211, NAMUR, and DIN 3337. It supports the integration of accessories such as solenoid valves, limit switches, valve position feedback units, smart positioners, and manual override mechanisms. It is widely used in automated pipeline control systems across industries including chemicals, water treatment, power generation, HVAC, oil and gas, and explosion-proof environmental protection applications.
II. Model Designation
2. AT: Rack-and-pinion pneumatic actuator

1. D: Double-acting; bidirectional air supply drives switching; no springs
2. S: Single-acting; built-in springs; automatic reset upon air loss (fail-safe)
   III. Structure and Working Principle
   The AT actuator employs a symmetrical dual-piston and precision rack-and-pinion transmission structure. When the air supply enters the cylinder, it drives the pistons on both sides to move linearly in synchronization; the racks drive the central pinion to rotate, producing a standard 0°–90° angular stroke to operate the valve.

• Double-acting: Air is alternately supplied to and exhausted from both sides; the air supply controls the switching action throughout the entire cycle, making it suitable for stable, high-frequency operating conditions.
• Single-acting: Air supply opens the valve, while spring force closes it upon exhaust; automatic reset occurs upon loss of air or power, meeting plant safety interlock requirements. IV. Product Structural Features

1. Balanced output via symmetrical dual pistons: Symmetrical dual-direction transmission ensures stable torque output without eccentricity or vibration; smooth opening and closing actions effectively protect valve sealing surfaces.
2. High-precision adjustable mechanical stops: External stop screws at both ends allow for precise fine-tuning (±5°) of fully open and fully closed positions, eliminating issues such as incomplete closure, failure to reach the full travel position, and excessive leakage.
3. High-strength hard-anodized cylinder body: The aluminum alloy cylinder undergoes hard-anodizing treatment, offering wear resistance, scratch resistance, aging resistance, and dimensional stability; the smooth inner wall minimizes friction, ensuring effortless operation.
4. High-quality sealing system: Utilizes aging-resistant NBR, HNBR, and FKM (fluororubber) seals to ensure excellent airtightness and zero internal or external leakage; suitable for high- and low-temperature conditions as well as frequent, long-term cycling.

• Standardized modular interfaces: Output shaft, flange, air ports, and accessory interfaces fully comply with international standards, ensuring high interchangeability, universal accessory compatibility, and easy maintenance.

1. Intrinsically safe explosion-proof design: Purely pneumatic mechanical structure eliminates electrical sparks, providing inherent explosion protection suitable for various flammable and explosive chemical processing environments.
2. Compact size with high torque: Compact design minimizes space requirements while offering a wide torque output range, making it suitable for the vast majority of small, medium, and large-bore quarter-turn valves. V. Material Specifications
3. Cylinder Body: Hard-anodized aluminum alloy

• Piston, Rack, Pinion: High-strength precision alloy

1. Output Shaft: High-strength stainless steel
2. End Caps, Fasteners: Corrosion- and rust-resistant treatment
3. Seals: Standard NBR; optional high-temperature FKM or low-temperature HNBR

• Return Springs: High-toughness precision springs (for single-acting models)
  VI. Technical Parameters

1. Operating Air Pressure: Double-acting 0.2–0.8 MPa; Single-acting 0.3–0.8 MPa
2. Maximum Pressure Rating: 1.0 MPa

• Output Angle: 0°–90° (adjustable range ±5°)
• Output Torque Range: Full specification coverage from 3 Nm to 10,000 Nm

1. Operating Temperature: Standard -20°C to +80°C; High-temp version up to 160°C; Low-temp version down to -40°C
2. Operating Medium: Clean, dry compressed air (40μm filtration grade)
3. Protection Class: IP67

• Control Method: Pneumatic on/off, 4–20mA proportional control

2. Mounting Standards: ISO5211, NAMUR, DIN3337

• Accessories: Solenoid valves, air preparation units (FRL), limit switches, valve position feedback, smart positioners, manual override mechanisms
  VII. Applicable Operating Conditions
  ✅ Applicable Scenarios
• Automated on/off control for fluid pipelines in chemical, petrochemical, and fine chemical industries
• Valve actuation for water treatment, sewage, and environmental desulfurization/denitrification systems

1. HVAC, district heating, air conditioning, and water supply/drainage circulation systems
2. Explosion-proof automated pipelines for gas, oil/gas, and flammable/explosive media
3. Process systems requiring remote DCS control, automatic interlocking, and fail-safe reset
4. Indoor and outdoor standard operating conditions; equipment requiring frequent opening/closing cycles
   ❌ Inapplicable Conditions
5. Direct immersion in strong acids or alkalis; highly corrosive gaseous environments (upgrading to a corrosion-resistant model with stainless steel pistons is recommended).
6. Operating conditions exceeding rated temperature or pressure parameters.
   VIII. Standards
7. Design and Manufacturing: ISO 5211, DIN 3337, and NAMUR international standards.
8. Protection Rating: IP67.
9. Explosion-proof Rating: Compatible with Ex d IIC T6 explosion-proof components.
   IX. Installation and Usage Instructions

• Before installation, verify that the actuator torque specifications match the valve and confirm the operating direction aligns; do not use a low-torque actuator to drive a high-load valve.
• The air supply must be clean and dry; an air service unit (filter-regulator-lubricator) must be installed upstream to prevent water, oil, or impurities from entering the cylinder and causing jamming or air leaks.

2. Before supplying air, fine-tune the limit screws at both ends to calibrate the fully open and fully closed positions, preventing over-travel impacts that could damage the valve seat and gears.
3. Double-acting models rely on air supply switching for operation; single-acting models automatically reset upon loss of air pressure, serving as a safety feature for process protection.
4. Periodically check for air leaks, screw tightness, and seal aging; for equipment out of service for extended periods, perform monthly no-load cycling maintenance.

• For high- or low-temperature applications, replace seals with temperature-appropriate versions; do not use standard seals outside their rated temperature range.
  X. Product Advantages Summary
  The AT piston-type rack-and-pinion pneumatic actuator features a mature, stable design, ample torque, precise operation, and exceptional versatility. It supports high-frequency cycling, offers high adjustment precision, and boasts a long maintenance-free service life. With standard international interfaces compatible with 99% of pneumatic ball and butterfly valves on the market, it is the most versatile, cost-effective, and stable quarter-turn pneumatic drive unit for industrial automated pipeline control systems.