What are the advantages of closed hydraulic system
What is closed hydraulic system? As the name suggests, the loop is a closed hydraulic system, which is called a closed hydraulic system. 1、 Any hydraulic system must be safety protection components, closed system is no exception, there must be a safety valve. Since the high and low pressure oil circuit of closed system can be switched, a safety valve should be set on a and B oil circuit respectively. 2、 Any hydraulic component has internal leakage. On the one hand, oil film lubrication is formed between the moving pairs to lubricate the components; on the other hand, internal oil drainage 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 housing of the pump motor. 3、 The existence of internal oil drain requires that the closed circuit should have a corresponding oil supply circuit to ensure the stable and normal operation of the closed circuit; the oil supply circuit here is a typical open hydraulic system. About oil replenishment (1) There are two types of make-up pumps: internal and external. Built in to the main pump is usually behind the internal gear pump (save space); external make-up pump some gear pump, some plunger pump (mostly constant pressure variable pump). In the closed system of construction machinery, the built-in make-up pump is mostly used; in industry, the external make-up pump is mostly used. (2) The displacement of make-up pump is about 20% of that of main pump; (3) According to experience, in order to avoid air suction in closed system, the instantaneous oil filling pressure should not be less than 8 bar. Therefore, in some closed systems, due to bad working conditions, in order to make full oil filling, it is usually necessary to add an accumulator. 4、 In the control loop of closed system, the change of oil flow direction in closed system is realized by controlling the swash plate of pump to cross the zero position. Generally, the control oil is supplied by the make-up pump. 5、 The oil tank of closed circuit is small (compared with open circuit, it only needs to match with hydraulic oil pump), so the heat dissipation effect of the system is not good. In order to accelerate the heat exchange of the system, flushing valve will be added in the closed system when necessary.