Figs. WH 182 and WH 183
General
(p1) Delivery rate curve per pump as a function of pressure with two pumps operating
(p2) Delivery rate curve as a function of pressure with only one pump operating
(N1) Prescribed hydraulic power of the variable double pump in kW and HP
(N2) Attainable delivery curve with available 3-spring total capacity controller
At pressure p = 0 bar to cut-in, both pumps have maximum delivery rate (l/min)
A further pressure increase, depending on operating resistance, causes the pumps to pivot back against the spring force until, blocked by a fixed stop, they deliver the maximum output. If the pressure should continue to rise, the main relief valve opens and the minimum flow returns to the oil tank.
Increasing pressure - pumps pivot back - flow reduced
Decreasing pressure - pumps pivot out - flow increased
The values of the pump delivery diagram were obtained at a tank pilot pressure of 0.2 bar (20 kPa) and an oil temperature of 60°C and take the pilot-control pump into consideration.
Instructions for Measuring Hydraulic Pump Delivery (Flow) Rates
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Make reference to WARNING on first page of TESTING AND ADJUSTING Section. |
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NOTE: Measure at 60°C oil temperature and tank pilot pressure of 0.2 bar (20 kPa).
A prerequisite for the measurement of the delivery rate is that both hydraulic circuits can be subjected to pressure simultaneously and by stages. Suitable measuring instruments fitted with throttle valves can be purchased for this purpose. Measuring instruments without throttle valves may also be used, if the following procedure is observed:
1. Connect a measuring turbine (flow meter) between pump and control unit of one hydraulic circuit and connect a digital display unit.
2. Connect a pressure gauge to the hydraulic circuit that is to be checked.
3. Reset the main relief valves on each control unit all the way back.
4. Run engine at full speed and cut in and hold one actuator on each circuit. (Retract bucket cylinder and push-shovel cylinder against stop.)
5. Set both main relief valves at 80 bar (8000 kPa), note down the delivery rate reading. The pressure at both main relief valves is now raised uniformly and in stages of 10 bar (1000 kPa) (or more) until the maximum pressure of 300 bar (30 000 kPa) has been reached. Note down delivery rate reading for each stage. Check engine speed while measuring. The engine must run at rated speed between cut-in and cut-out of the pumps.
6. Remove the measuring turbine (flow meter) and, if necessary, connect it on the other circuit between the pump and control unit. Connect the digital display unit and proceed as described in Steps 2 to 5.
7. Compare the readings with Pump Delivery Diagrams on the preceding pages.