Thermal/Pressure Relief Device – Drivetrain

PROBLEM SOLVED! How to Protect a System From Both Pressure and Thermal Excursions

Schrader Pacific was contacted by a drivetrain manufacturer that needed to protect a hydraulic part-time four-wheel drive axel against both overpressure and over-temperature.

Schrader Pacific developed an integrated valve with two relief modes, one utilizing a spring-loaded Pressure Relief Valve (PRV) and one utilizing a resetting Thermal Relief Device. In the event of a high-pressure excursion, the PRV opens, holding the torque transmission to the design limit. The TRD will trigger reducing system power in the case of a thermal excursion; after the operating temperature returns to the normal operating range, the TRD re-engages the drive.


  • Dual-purpose combination valve
  • Protection from over pressurization
  • Protection from thermal excursion

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