Created on:2021-04-06 08:42

Main parameters and common problems of hydraulic pump

Main parameters and common problems of hydraulic pump

 

main parameter

The main parameters of hydraulic pump are pressure, speed, displacement and flow, power and efficiency.

(1) Pressure

① Working pressure p the output pressure of hydraulic pump is called working pressure. During the operation of the hydraulic pump, the working pressure changes with the load (pressure adaptation) (Fig. f), that is, the greater the load, the greater the working pressure of the pump; otherwise, the working pressure of the pump is smaller; or the pressure control valve or constant pressure pump is stable at one or several set values (single-stage pressure regulation or multi-stage pressure regulation) (Fig. g and Fig. h); for the proportional control pressure system In general, the pump pressure will change with the input signal (current) of the proportional pressure control valve (Fig. I).

1FGHI.jpg

② Rated pressure PN under normal working conditions, according to the test standard can continue to operate the highest pressure, known as the hydraulic pump rated pressure, rated pressure is also known as the nominal pressure. This pump structure is more than the rated pressure, leakage and other factors.

③ According to the test standard, the maximum allowable pressure Pmax, which exceeds the maximum allowable pressure for short-term operation of rated pressure, is called the maximum allowable pressure of hydraulic pump (referred to as the maximum pressure).

④ Pressure difference △ p the pressure difference between the discharge port and the suction port of the pump is called the pressure difference of the hydraulic pump. Usually, the inlet pressure of the pump is very low, which is close to zero, so in many cases, the outlet working pressure P of the pump can be used to replace it.

The legal unit of measurement of hydraulic system and component pressure (working pressure, rated pressure, maximum pressure, etc.) in China is pa (PA, N / m2). When the pressure is high, it is expressed by MPa (MPA) (1MPa = 106 PA). The pressure shall conform to the pressure series specified in GB / T 2346-2003 (table below).

 

Nominal pressure series of fluid transmission system and components MPa

one

1.25

1.6

2.0

2.5

3.15

4.0

5.0

6.3

8.0

10.0

12.5

16.0

20.0

25.0

31.5

35.0

40.0

45.0

50.0

63.0

80.0

100

125

160

200

250

 

The pressure units used in China before include kgf / cm2 (kgf / cm2), bar (bar), engineering atmospheric pressure, water column height or mercury column height, while LBF / in2 (LBF / in2) has been used in the United States. In order to facilitate the use of imported technology and equipment, the conversion relationship of these pressure measurement units is given

l kgf/cm2≈1 bar=105Pa

1 standard atmospheric pressure = 1.01325 × 105Mpa = 10.33m water column height = 760mm mercury column height

1 Engineering atmospheric pressure = l kgf / cm2 = 98066.5 pa

1 LBF / in2 = 6894.757293 PA = 0.068 engineering atmospheric pressure

In engineering, the pressure is usually divided into several different levels (the table below) for the design, production and use of hydraulic components and systems including hydraulic pump and hydraulic motor.

 

Pressure classification of hydraulic components and systems

压力等级

低压

中压

中高压

高压

超高压

压力范围

≤2.5

>2.5~8

>8~16

>16~32

>32

 

 

(2) Rotational speed

① Rated speed NN is the highest speed that can run normally for a long time under rated pressure, which is called the rated speed of hydraulic pump.

② The maximum speed nmax under the rated pressure, which exceeds the rated speed to allow short-term operation, is called the maximum speed of the hydraulic pump.

③ The minimum speed Nmin is the minimum speed allowed for normal operation, which is called the minimum speed of hydraulic pump.

The common legal unit of measurement of speed (rated speed, maximum speed, minimum speed, etc.) is R / min (RPM). Sometimes the angular velocity W is used to express the speed of the pump, and the unit of W is rad / S (radians per second) [1R / min = (π / 30) rad / S].

Home    Article    Main parameters and common problems of hydraulic pump