SAN-EI Air Motor
DM Series – Radial Piston Type Air Motor
The DM Series air motor is a radial piston type pneumatic motor manufactured by SAN-EI SEIKI SEISAKUSHO Co., Ltd. (Japan). It is designed for applications requiring low speed, high torque, and long service life.
Compared with vane type air motors, the DM series provides strong starting torque and stable operation under heavy load, making it suitable for equipment such as hoists, winches, and other industrial machinery requiring powerful drive performance.
1 Structure and Working Principle
The DM series adopts a radial piston structure.
Mechanical principle
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Multiple pistons are arranged radially around the crankshaft.
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Compressed air pushes each piston outward.
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The piston force is transmitted to the crankshaft through connecting rods.
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A rotary valve synchronized with the crankshaft distributes compressed air to each cylinder.
This mechanism converts compressed air energy into rotational motion of the motor shaft.
The radial piston design provides higher torque output than vane-type motors, especially at low rotational speeds.
2 Main Features
Low Speed – High Torque
The DM series provides large torque in the low-speed range, making it ideal for equipment that requires strong starting force.
Durable and Long Service Life
These motors have been used in industrial applications for many years and are known for their durability.
Multiple Configuration Options
The motor can be supplied with optional equipment such as:
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Brake units
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Gear reducers
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Control valves
This flexibility allows adaptation to different industrial systems.
Strong Engine Braking
When used in a meter-out speed control circuit, the motor can provide strong engine braking capability.
Flexible Installation
Two mounting options are available:
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Base mounting
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Flange mounting
3 Lubrication System
The DM series uses an oil-bath lubrication system for internal moving parts.
Advantages:
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Stable lubrication performance
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Reduced wear on sliding components
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Longer service life
A line lubricator is normally not required, but it is recommended for:
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continuous operation
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infrequent operation
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vertical installation (shaft downward)
4 Installation Notes
SAN-EI provides several operational recommendations:
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The motor should normally be installed horizontally.
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If vertical installation is required, consultation with the manufacturer is recommended.
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Flexible piping should be used for air supply and exhaust connections.
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Oil levels must be checked regularly using the oil gauge.
For motors equipped with brakes, a center-open type control valve must be used to ensure proper brake release.
5 DM Series Models and Specifications
Specifications below are based on 0.5 MPa air pressure.
| Model | Output | Speed | Torque | Air Consumption |
|---|---|---|---|---|
| DM1 | 0.64 kW | 1300 rpm | 4.7 Nm | 0.7 m³/min |
| DM3 | 1.4 kW | 1250 rpm | 10.9 Nm | 1.7 m³/min |
| DM9 | 3.1 kW | 1000 rpm | 30.0 Nm | 3.4 m³/min |
| DM220 | 6.0 kW | 645 rpm | 89.0 Nm | 4.8 m³/min |
| DM36 | 9.7 kW | 630 rpm | 148.0 Nm | 7.5 m³/min |
| DM45 | 14.2 kW | 800 rpm | 170.0 Nm | 14.0 m³/min |
From these specifications it can be seen that the DM series covers a wide range of torque and power outputs, from small machines to heavy-duty industrial equipment.
6 Typical Applications
The DM series is commonly used in industries requiring high torque pneumatic drives.
Hoisting Equipment
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Air hoists
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Winches
Marine Equipment
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Deck machinery
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Mooring equipment
Mining and Heavy Industry
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Conveyors
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Drilling equipment
Industrial Machinery
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Mixers
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Agitators
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Large industrial drive systems
Because air motors use compressed air instead of electricity, they are suitable for explosive or hazardous environments.
7 Advantages Compared with Electric Motors
Air motors like the DM series provide several benefits:
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Safe in explosive atmospheres
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No risk of electrical spark
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Overload protection (motor slows or stops safely)
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Instant start and stop
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High torque at low speed
These advantages make them popular in chemical plants, offshore facilities, and hazardous industrial areas.
| 型式 | 出力［kw］ | 回転数［rpm］ | トルク［N-m］ | 空気消費量［㎥/min(nor)］ |
|---|---|---|---|---|
| DM1 | 0.64 | 1300 | 4.7 | 0.7 |
| DM3 | 1.4 | 1250 | 10.9 | 1.7 |
| DM9 | 3.1 | 1000 | 30.0 | 3.4 |
| DM220 | 6.0 | 645 | 89.0 | 4.8 |
| DM36 | 9.7 | 630 | 148.0 | 7.5 |
| DM45 | 14.2 | 800 | 170.0 | 14.0 |