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Direct action Pneumatic Diaphragm Actuators

XM-D series is a direct-acting pneumatic diaphragm actuator with a multi-spring structure. It is lightweight, compact, has high performance and can exert great output force.The core working logic of the direct action pneumatic diaphragm actuator is as follows: when the signal pressure in the diaphragm chamber increases, the diaphragm pushes the actuator rod downward for extension; when the signal pressure decreases, the built-in spring resets the rod upward for retraction. The rod stays at the upper retracted position when air supply fails.

Combination with positioner provides high accuracy position control.

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Product Definition

Combination with positioner provides high accuracy position control.

Core Features

Stable Action Logic: The signal pressure is positively and linearly correlated with the rod stroke; higher pressure brings longer extension stroke, with intuitive and reliable control logic for conventional regulation working conditions.

Optimized Safety Adaptation: Automatic spring reset and rod retraction upon air failure. Matched with air-to-close valves to keep the valve normally open, ensuring continuous medium flow and preventing pipeline overpressure and material cutoff.

Compact & Reliable Structure: Adopts multi-spring coaxial layout with uniform stress distribution and excellent axial stability. No complex transmission parts, achieving ultra-low failure rate.

Wide Compatibility: Compatible with electro-pneumatic positioners, solenoid valves, limit switches and other accessories, suitable for various linear-stroke control valves such as single-seat valves and sleeve valves.

Technical Parameters

Model	XM-D21, XM-D27, XM-D35, XM-D45S, XM-D-45L, XM-D65S, XM-D65L
Material	Ductile iron / carbon steel
Action type	Direct action: Air to valve shut
Color	Grey
Air Supply	300kPa G; 340kPa G; 400kPa G
Air Connection	Rc1/4 (Φ650: Rc3/8)
AMB Temp	Standard: -10°C to +70°C; High temperature: 0°C to +100°C; Low temperature: -40°C to +40°C

Technical Advantages

High Precision Regulation: Constant effective diaphragm area ensures high stroke linearity and small hysteresis. Zero calibration function improves valve regulation accuracy significantly for precise process control.

Strong Output Thrust: The optimized multi-spring structure provides larger output thrust under the same volume, meeting the driving requirements of medium and low pressure, large-diameter control valves.

Low Operation & Maintenance Cost: Simple integral structure with few parts. Only diaphragms and seals are wearable parts, which are easy and low-cost to replace with minimal routine maintenance.

Fast Response Speed: Sensitive pneumatic transmission and rapid spring reset enable quick response to system signal changes, suitable for dynamic regulation conditions.

FAQ

Q: What is the core operation of the Direct Action pneumatic diaphragm actuator? Which type of valve is it suitable for?

When the signal pressure increases, the rod extends downward; when the pressure decreases or air supply fails, the rod resets upward. It is normally matched with air-to-close valves to realize fail-open protection, avoiding process material cutoff and pipeline overpressure.

Q: Can the Direct-Acting Pneumatic Diaphragm Actuator be changed to be used in reverse mode?

It cannot be modified directly in conventional conditions. Direct-acting and reverse-acting actuators have different diaphragm air intake and spring installation structures. Professional reverse-acting components or dedicated models are required for mode switching; unauthorized modification is prohibited to avoid safety risks.

Q: What are the reasons for the poor adjustment accuracy and inaccurate stroke of the direct action pneumatic diaphragm actuators?

Main causes include positioner calibration deviation, aging and leaking diaphragm, fatigue and uneven stress of springs, and rod jamming caused by dust accumulation. Solutions: recalibrate the positioner, replace aging diaphragms and seals, clean the rod, and replace fatigued springs.

Q: What should I do if the valve fails to open automatically after the air supply is cut off?

Prioritize checking whether the spring is stuck or invalid, the rod is blocked by foreign matters, and residual pressure exists in the air circuit. Clean foreign matters, replace invalid springs, and exhaust residual air pressure to restore normal fail-reset function.

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