Danfoss OMH BMH Series Orbital Hydraulic Motor | BMH-200 BMH-250 BMH-315 BMH-400 BMH-500

The BMH Series low-speed high-torque (LSHT) orbital hydraulic motors manufactured by Chengyuan Hydraulic are heavy-duty, high-efficiency fluid power drive components engineered to match global Danfoss OMH industrial standards. Purpose-built for high-load mobile machinery, demanding industrial drive systems, and severe outdoor operations, this premium series comprehensively replaces and scales traditional multi-stage configurations. The specific engineering layout directly targets the prominent displacement array: BMH-200, BMH-250, BMH-315, BMH-400, and BMH-500. Featuring an advanced Geroler gear set coupled with a specialized shaft distribution fluid design, the monoblock motor housing is poured from high-tensile ductile cast iron. This architectural composition guarantees an exceptional torque-to-weight ratio alongside immense radial and axial shock load capacities. Every single BMH orbital motor undergoes 100% digital test-bench validation under full-load master-slave circuit configurations, minimum-speed indexing anti-stiction checks, high-backpressure shaft seal retention runs, and full volumetric efficiency tracking prior to dispatch to match original performance curves, delivering proven 100% original-place interchangeable compatibility.

Technical Specifications :

• Core Product Framework: Danfoss OMH / BMH Series Shaft Distribution Low Speed High Torque Orbital Hydraulic Motors

• Displacement Family Matrix: BMH-200 / BMH-250 / BMH-315 / BMH-400 / BMH-500

• Geometric Volumetric Displacements:

  • BMH-200 Profile: 203.2 $cm^3/rev$

  • BMH-250 Profile: 255.9 $cm^3/rev$

  • BMH-315 Profile: 316.1 $cm^3/rev$

  • BMH-400 Profile: 406.4 $cm^3/rev$

  • BMH-500 Profile: 489.2 $cm^3/rev$

• Maximum Allowable Continuous Pressure Drop:

  • BMH-200 / BMH-250 Tier: 16 MPa (160 bar / 2320 psi)

  • BMH-315 Tier: 14 MPa (140 bar / 2030 psi)

  • BMH-400 Tier: 12.5 MPa (125 bar / 1812 psi)

  • BMH-500 Tier: 11 MPa (110 bar / 1595 psi)

• Maximum Intermittent & Peak Pressure Drop Thresholds:

  • Intermittent operation bounds reach up to 15 ~ 19 MPa; transient peak impulses tolerate up to 18 ~ 22.5 MPa.

• Maximum Continuous Mechanical Torque Output:

  • Scales progressively from 425 N·m on the BMH-200 up to 830 N·m on the BMH-500 (with maximum intermittent peaks topping at 1170 N·m).

• Maximum Continuous Operating Speeds:

  • BMH-200 Parameters: Continuous rotation up to 365 rpm

  • BMH-500 Parameters: Continuous rotation up to 155 rpm

• Maximum System Fluid Input Flow Rate: Continuous rating set at 75 L/min; intermittent max transients handle up to 90 L/min.

• Mounting Interface & Input Shaft Formats: Standard 4-bolt or 2-bolt oval rhombic flange patterns; output drive options cover parallel keyed cylindrical shafts (Ø32mm / Ø35mm), tapered shaft ends, and involute splined layouts.

• Component Net Weight Range: Approx. 10.5 kg to 13.0 kg (23.1 to 28.6 lbs) depending on displacement and shaft execution.

Key Technical Advantages:

• High-Strength Ductile Iron Housing to Prevent Structural Breathing: The main housing block of the BMH motor is poured from high-grade structural ductile iron instead of commercial gray iron castings. This prevents structural distortion or micro-breathing when system pressure spikes to 25 MPa. This robust architecture secures internal alignment, limits internal fluid bypass, and delivers high fatigue endurance in abrasive outdoor operations.

• Low-Friction Geroler Gear Set for Low Start-Up Pressure: The central power generation unit utilizes an advanced Geroler geometry equipped with precision-ground rolling alloy steel pins. By replacing traditional fixed sliding-contact teeth with a dynamic rolling interface, boundary friction during cold starts and low-speed transitions drops by over 35%. This design delivers low start-up pressure thresholds and smooth torque transition without mechanical stuttering.

• Optimized Driver-Linker and Balanced Shaft Distribution System: The heavy-duty drive link (the “dog bone” shaft) is machined from a high-chromium steel alloy, featuring precision-cut internal splines and case-hardened tooth profiles. Paired with a flow-optimized shaft distribution grid, this mechanism balances radial and axial forces hydrostatically during high-torque runs, significantly reducing noise and wear.

• Multi-Stage High-Pressure Shaft Seal (HPSS) for Series Circuit Flexibility: The front journal bearing layout integrates an imported, multi-stage triple-lip high-pressure shaft seal assembly. This design allows the motor enclosure to handle backpressures up to 17.5 MPa during continuous running without an external case drain line. This structural safeguard enables multiple BMH motors to be plumbed directly in series or parallel circuits without risking seal blowout or external leakage.

Application Areas:

• Heavy Agricultural & Forestry Platforms: Main feed-header conveyors on combine harvesters, logging processors, and high-torque grab rotators on forestry timber cranes.

• Plastics & Industrial Machine Tools: Mold height adjustment mechanisms on heavy injection molding machinery, automated rotary assembly tables, and drive assemblies on industrial floor scrubbers.

• Construction & Road Infrastructure Equipment: Hydrostatic wheel drives for compact road milling attachments, active power sweeping brush swivels, and heavy-duty portable hydraulic sawmills.

Expert Maintenance Tips:

• Route the External Case Drain (Port T) Directly to Tank for High-Duty Operation: Although the integrated HPSS shaft seal handles high backpressures, it is highly recommended to route an independent line from the G 1/4 drain connection (Port T) directly back to the reservoir below the oil level when running continuous high-load cycles or series configurations. Keeping the casing under minimal pressure ensures continuous flushing and lubrication of the front bearings, extending shaft seal wear life by up to two times.

• Enforce Minimum Inlet Volumetric Flow to Prevent Low-Speed Stiction: Because heavy-displacement units like the BMH-400 and BMH-500 drive heavy rotating components, ensure the active input flow into the valve ports does not fall below 10 L/min during system configuration. Dropping below this baseline under high resistive loads can push the friction pairs into the boundary stiction zone, leading to “jerking” or low-speed crawling that degrades the Geroler surfaces over time.

• Enforce the 6-Second Limit on Intermittent Pressure Peaks During Stall Conditions: In high-load attachment or machine-tool clamping setups, if the motor stalls against a solid resistance, the differential pressure must not exceed the intermittent threshold (15–19 MPa) for more than 6 cumulative seconds per operating minute. Extended stall periods generate rapid, localized fluid shear heat that quickly degrades oil viscosity, risking bimetallic seizure or scoring on the distribution surfaces.