Product Overview
The OMS-245, OMS-305, and OMS-395 are the flagship medium-to-large displacement models in the Danfoss OMS series of disc valve orbital hydraulic motors, engineered for heavy-duty applications in construction machinery, agricultural equipment, and drilling rigs. With geometric displacements of 245.0, 305.0, and 395.0 cm³/rev respectively, these motors deliver continuous speeds up to 300, 240, and 190 rpm (intermittent up to 908 rpm) and continuous output torques of 720, 825, and 865 N·m, achieving complete drop-in interchangeability with Danfoss OMS series originals in mounting flange, output shaft, and port configurations.
Each motor features a Geroler (roller gerotor) gear set with a disc valve plate optimized through hydrodynamic design, effectively reducing flow pulsation in the pressure transition zone. The output shaft is supported by tapered roller bearings capable of simultaneously accommodating substantial axial and radial loads. Every unit undergoes 100% simulated load testing before shipment, with protocols covering output torque verification at rated pressure, volumetric efficiency measurement at multiple speed points, internal leakage testing, and noise assessment.
Technical Specifications
Basic Specifications
Model: OMS-245 / OMS-305 / OMS-395
Motor Type: Disc Valve Orbital Motor (Geroler)
Gear Set Type: Geroler (roller gerotor)
Mounting Flange: 2-Bolt Standard Flange (BC Ø106.38 mm, Pilot Ø82.55 mm) or 4-Bolt
Shaft Type: Ø32 mm Cylindrical / 14T Involute Spline / Tapered
Port Size: G 1/2 (main), G 1/4 (drain)
Seal Material: NBR standard, FKM optional
OMS-245 Performance Data (245.0 cm³/rev)
Geometric Displacement: 245.0 cm³/rev
Max. Speed (Continuous): 300 rpm
Max. Speed (Intermittent): 360 rpm
Max. Pressure Drop (Continuous): 200 bar
Max. Pressure Drop (Intermittent): 270 bar
Max. Torque (Continuous): 720 N·m
Max. Torque (Intermittent): 870 N·m
Max. Output (Continuous): 14.5 kW
Max. Flow (Continuous): 75 L/min
Weight: Approx. 11.6 kg
OMS-305 Performance Data (305.0 cm³/rev)
Geometric Displacement: 305.0 cm³/rev
Max. Speed (Continuous): 240 rpm
Max. Speed (Intermittent): 290 rpm
Max. Pressure Drop (Continuous): 200 bar
Max. Pressure Drop (Intermittent): 270 bar
Max. Torque (Continuous): 825 N·m
Max. Torque (Intermittent): 1,000 N·m
Max. Output (Continuous): 15.0 kW
Max. Flow (Continuous): 75 L/min
Weight: Approx. 12.3 kg
OMS-395 Performance Data (395.0 cm³/rev)
Geometric Displacement: 395.0 cm³/rev
Max. Speed (Continuous): 190 rpm
Max. Speed (Intermittent): 240 rpm
Max. Pressure Drop (Continuous): 160 bar
Max. Pressure Drop (Intermittent): 210 bar
Max. Torque (Continuous): 865 N·m
Max. Torque (Intermittent): 1,020 N·m
Max. Output (Continuous): 11.0 kW
Max. Flow (Continuous): 75 L/min
Weight: Approx. 12.6 kg
Materials & Construction
Housing: High-strength cast iron
Gear Set: Carburized and hardened alloy steel, surface hardness HRC 58-62
Valve Plate: Powder metallurgy bimetal composite
Bearings: Tapered roller bearings (axial + radial load capable)
Shaft Seal: High-pressure shaft seal, no drain line required for high return pressure
Key Technical Advantages
1. High-Speed Capability with Optimized Torque Density
The OMS-245/305/395 series offers significant high-speed advantages among large-displacement orbital motors of comparable size. Through optimized gear set tooth profile parameters and enlarged valve plate flow passages, these motors achieve higher permissible speeds while maintaining large displacement output. The OMS-245 reaches a continuous speed of 300 rpm with intermittent capability up to 360 rpm, substantially exceeding conventional orbital motors of equivalent displacement. This makes the series particularly suitable for drilling rig rotation drives and travel drive systems requiring rapid response and high-speed output.
2. Geroler Gear Set with High Volumetric Efficiency
All three models utilize a Geroler (roller gerotor) gear set manufactured to micron-level tolerances. The engagement between roller pins and cycloidal gear profile is hydrodynamically optimized to minimize internal leakage, achieving volumetric efficiency above 95%. Stable torque output is maintained at low speeds without stick-slip, ensuring smooth operation across the entire speed range.
3. Disc Valve Design for Low-Noise Operation
The valve plate is fabricated from powder metallurgy bimetal composite, combining wear resistance with self-lubricating properties. Progressive throttling in the valve transition zone effectively reduces pressure shock and flow pulsation during commutation, lowering operating noise by 3-5 dB(A) compared to conventional designs. The OMS-395 demonstrates particularly effective noise control at large displacement operating conditions, making it suitable for noise-sensitive industrial applications.
4. Tapered Roller Bearings for Extended Service Life
The output shaft is supported by tapered roller bearings capable of simultaneously accommodating substantial axial and radial loads. Bearing preload is precisely controlled during assembly to prevent axial displacement at high speeds and excessive bearing stress under heavy loads. The high-strength cast iron housing provides excellent rigidity, preventing elastic deformation at peak pressure and ensuring long-term gear mesh precision.
5. 100% Simulated Load Testing & Batch Consistency
Every OMS-245, OMS-305, and OMS-395 undergoes 100% simulated load testing on a dedicated test bench before shipment. Test protocols cover output torque verification at rated pressure, volumetric efficiency measurement at multiple speed points, internal leakage testing, overspeed validation, and noise assessment. All test data is archived and traceable, ensuring each motor’s performance matches its published specifications.
Application Areas
Oil & Gas Drilling Rigs: Rotary table drive, winch drive, mud pump drive
Construction Machinery: Loader travel drive, rotary drilling rig swing drive, road roller drive
Agricultural Machinery: Combine harvester travel drive, sugarcane harvester cutter drive
Material Handling: Forklift drive, heavy-duty conveyor drive, winch drive
Municipal Vehicles: Street sweeper drive, snow removal vehicle drive
Industrial Machinery: Injection molding machine rotary drive, automatic rotary indexing tables
Expert Maintenance Tips
1. Mounting Fit and Bolt Torque
Before installation, verify that the flange spigot (2-bolt flange: Pilot Ø82.55 mm, BC Ø106.38 mm) and machine mounting bore conform to H8/f7 tolerance fit. Tighten mounting bolts in diagonal sequence in 2-3 stages to the specified torque. All port connections must use O-ring seals; recommended tightening torque for G 1/2 main ports is 40-50 N·m. Due to its larger displacement, the OMS-395 requires that the machine mounting base has sufficient rigidity to withstand the reaction torque generated by motor output.
2. Case Drain Piping
The OMS series is equipped with a G 1/4 case drain port that must be piped separately to the reservoir—never connected in parallel with the main return line. Case drain back pressure should be maintained below 0.5 bar. While the high-pressure shaft seal allows operation with elevated return pressure when the drain line is properly connected, routine inspection of drain flow is recommended. A significant increase in drain flow may indicate wear in the shaft seal or valve plate.
3. System Flushing and Oil Cleanliness
After initial installation or motor replacement, operate at 200-400 rpm under no load for 10-15 minutes to purge air. System oil cleanliness should meet NAS 9 or ISO 18/15 or better. A 10 μm return-line filter is recommended. ISO VG 46 or VG 68 anti-wear hydraulic oil is recommended, with viscosity maintained between 20-75 mm²/s. For the OMS-305 and OMS-395, flushing flow should reach at least 1.5 times the motor’s rated flow due to their larger displacement.
4. Storage and Extended Shutdown
For long-term storage, install port plugs to prevent contamination and fill the motor with clean hydraulic oil. Store at temperatures between -20°C and +50°C, away from direct sunlight and moisture. Motors stored for more than 6 months should undergo an internal leakage check before installation.
