What should the setting of the hot oil relief shuttle valve in a hydrostatic transmission be compared to the main replenishing relief valve?

The correct setting for the hot oil relief shuttle valve in a hydrostatic transmission is lower than the setting of the main replenishing relief valve. This configuration is crucial for proper operation of the hydraulic system.

The hot oil relief shuttle valve serves as a safety mechanism that helps manage oil temperature. If the oil temperature rises too high, the valve opens to allow excess flow, preventing overheating. By setting it lower than the main replenishing relief valve, the system ensures that the hot oil relief valve responds first during instances of pressure buildup due to thermal expansion or other factors, ensuring that the oil is relieved before it can reach potentially damaging pressures.

In contrast, the main replenishing relief valve is designed to maintain system pressure and allow for appropriate fluid replenishment. Those two functions must be complementary: the hot oil relief must allow system relief to occur before the pressures reach the threshold of the replenishing valve, thereby preventing damage or inefficiencies in the system. This relationship between the two valves is central to maintaining both the safety and efficiency of the hydraulic system in a hydrostatic transmission.