What are the advantages of closed hydraulic systems

What are the advantages of closed hydraulic systems

What is a closed hydraulic system? As the name implies, a closed hydraulic system is called a closed hydraulic system. Today, I will take you to see what features it has.

1. Any hydraulic system must have safety protection components, and closed systems are no exception. They must have safety valves. Since the high and low pressure oil circuits of the closed system can be switched, a safety valve should be installed on the A and B oil circuits.

2. Any hydraulic component has internal leakage. On the one hand, the internal oil drain is to form an oil film between the moving pairs to lubricate the components; on the other hand, the internal oil drain can bring the heat generated during the operation of the components back to the oil tank to cool the components. Therefore, there will be a drain pipe connected to the oil tank on the pump motor housing.

3. The existence of internal oil leakage requires the closed circuit to have a corresponding oil supplement circuit to ensure the stable and normal operation of the closed circuit; the oil supplement circuit here is a typical open hydraulic system.

Regarding refueling, remind friends to understand the following points:

(1) There are two types of charge pumps that provide supplementary oil: built-in and external. The internal gear pump (saving space) is usually built into the main pump; some of the external charge pumps are gear pumps or plunger pumps (mostly constant pressure variable pumps). Closed systems on construction machinery mostly use built-in charge pumps; in industry, they are mostly external charge pumps.

(2) The displacement of the charge pump is generally about 20% of the displacement of the main pump;

(3) According to experience, in order to prevent the closed system from cavitation, the instantaneous replenishment pressure cannot be lower than 8bar. Therefore, in some closed systems due to poor working conditions, in order to fully replenish the oil, it is usually necessary to add an accumulator .

Fourth, the control loop in the closed system, the flow direction of the oil in the closed system is changed by controlling the pump swash plate to cross the zero position. Under normal circumstances, the control oil is provided by the charge pump.

5. The oil tank of the closed circuit is small (compared to the open circuit, it only needs to be matched with the hydraulic oil pump), so the heat dissipation effect of the system is not good. In order to accelerate the heat exchange of the system, when necessary, the closed system will Increase flush valve.