Open Circuit Pump with Piston Motor

  • Danfoss continues to lead the industry with groundbreaking fan drive technologies like our reverse displacement motor (RDM). By occasionally changing the airflow direction, accumulations of debris can be dislodged from the vehicle’s radiator to help ensure efficient cooling system performance. When used in radiator cooling fan applications, the Danfoss RDM uniquely incorporates the external shift valve within the motor itself, eliminating the directional control valve, and either simplifying or completely eliminating the HIC block. With fewer components in the hydraulic circuit, the RDM frees up space in the engine compartment to create additional opportunities for innovation. RDM technology also eliminates the heat generated by traditional reversing systems — and by drawing less engine power, leaves more of that power for work functions.

    Design advantages like this help combat the challenges brought on by today’s harder-working, hotter-running Tier 4-compliant engines, where emission control equipment takes up more under-hood space than ever before. Building on our proven efficiency and reliability, the compact Danfoss RDM motor is technology that’s helping Danfoss engineer tomorrow.

    Danfoss offers a wide range of efficient fan drive systems. Below are the benefits and critical considerations you need to take into account as you determine the right system for your specific needs.


    • Increased efficiency due to variable flow and piston motor technology
    • Fan speed independent of engine speed
    • Fails to full fan speed
    • Motor speed sensors available
    • Higher motor pressure, power and life ratings
    • Less engine power consumption

    Critical considerations:

    • Back pressure required for axial piston motors
    • No ZERO speed capability
    • Larger reservoir capacity required for high flows
    • Motor thrust load capability must be calculated


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