Pressure and flow are the two basic parameters of a hydraulic pump and two of the most basic parameters in a hydraulic system. Let's take a look at the main performance parameters of the hydraulic pump.
With regard to stress, there are three concepts that are often mentioned:
A. Working pressure: The output pressure of the hydraulic pump when it is actually working is called the working pressure. The working pressure depends on the size of the external load of the hydraulic system and the pressure loss on the drain line, regardless of the flow rate of the hydraulic pump.
B. Rated pressure: The highest pressure of continuous operation of the hydraulic pump under normal working conditions according to the test standard. Generally, the working pressure must not exceed the rated pressure. The general rated pressure will be marked on the nameplate.
C. Maximum allowable pressure: The maximum pressure value that allows the hydraulic pump to operate briefly, according to the test specification, when the rated pressure is exceeded. Above this pressure, the leak of the pump will increase rapidly. The rated pressure must not exceed the maximum allowable pressure. Once exceeded, the pump will leak.
2. Displacement and flow
Cars often have 1.6 displacements and 2.0 displacements. This is actually the volume of gasoline consumed by the engine rotating one revolution, which is very similar to the hydraulic pump displacement concept.
Displacement refers to the volume of oil that can be discharged by one revolution of the hydraulic pump without leakage. This is a parameter related to the mechanical structure of the hydraulic pump. Its size is only related to the geometry of the sealed working cavity in the hydraulic pump. The size is related to the number.
In terms of mechanical structure, some displacements are constant, that is, quantitative pumps, and some displacements are variable, that is, variable pumps.
Note: The general dosing pump has better sealing performance, less leakage, and higher efficiency at high pressure.
The flow rate is the volume of liquid discharged per unit time (L/min), and there is theoretical flow rate Qth, actual flow rate Qac, rated flow rate Qn.
The theoretical flow refers to the flow value obtained without considering the leakage, so Qth=qn, where q is the displacement of the pump (L/r) and n is the rotation speed of the pump (r/min)
The actual flow is considered for this part of the leakage, Qac=Qth-△Q. In the formula, △Q represents the leakage loss of the pump, and the oil will leak from the high pressure zone to the low pressure zone when the pump is running.
The rated flow rate Qn (L/min) refers to the flow rate that the hydraulic pump must guarantee under normal working conditions according to the test standards (such as at rated pressure and rated speed). Usually marked on the nameplate. In theory, the output flow will be slightly lower than the rated flow value.