In hydrostatic transmissions with closed-loop circuits, significant temperature increases and pressure spikes can occur when shock valves activate at high pressure.
For example, if a shock valve opens with oil at 50 °C and a flow of 1 l/min, the temperature can rise by approximately 18 °C at a 300-bar pressure differential.
To protect the system, save energy that would otherwise be converted into heat, and reduce the need for cooling, pressure can be continuously relieved. A shuttle valve detects the highest pressure on drive side A or B and directs it to a pressure relief valve.
When the pressure relief valve reaches its setpoint, it offloads pressure to the actuator, which then reduces the pump displacement. This eliminates the need for the shock valves to open, as both flow and pressure are continuously regulated through pump displacement control.
In Bosch Rexroth’s A4VG pump, these shuttle valves are standard, but the solution can also be retrofitted to other pump brands and machines.
You can also use pressure sensors on drive sides A & B to control a proportional pressure relief valve. Based on the sensor readings, the actuator adjusts the pump displacement dynamically.
Want to learn more? Get in touch!
Fredrik Lamberg
Sales Engineer
fredrik.lamberg@hydnet.se
+46 70-316 40 81
Hydnet
EA Rosengrens gata 29
421 32 Västra Frölunda
+46 31 - 499 490
info@hydnet.se
