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U20-3, U25-3 WSM
C.Testing
a. Pump flow
(1) Hydraulic oil tank
(3) Tester
Pump discharge side
(1) To control valve (P1)
(3) To control valve (P3)
(2) Pump
(4) Control valve
(2) To control valve (P2)
(4) To pilot filter
1) Measuring procedure
1. Connect the tester to the pump outlet. Be
careful not to confuse the tester's pipe
connections.
2. Open the tester's loading valve. Start the
engine.
3. Set the engine to the maximum rpm.
4. Gradually close the loading valve. Apply the
rated load pressure (test pressure) to the
pump.
5. Measure the discharge flowrate and pump rpm
(engine rpm).
6. Calculate the volumetric efficiency and judge
the performance.
2) Checking the pump performance
To inspect the pump performance, apply the
specified pressure to the pump discharge side.
Measure the discharge rate at the specified
rpm to check the volumetric efficiency.
Volumetric efficiency =
Discharge rate at rated load
Theoretical discharge rate (calculated value)
Notes
1. The pump's volumetric efficiency is
proportional to the pump rpm and inversely
proportional to the load pressure. During the
test, keep the engine at its maximum rpm.
2. The volumetric efficiency is the ratio of the
discharge rate per pump turn (cc/rev) to the
theoretical discharge rate (calculated value).
The main relief set pressure is used as the
rated load.
3. The discharge rate under rated load must be
converted to that per pump turn. This is
because the pump usually runs at lower rpm.
Discharge rate under rated load
Discharge rate at rated load (L/min) × 1000
(cc/rev) =
Pump rpm at rated load (rpm)
4. The volumetric efficiency must be satisfied to
accept the pump for its performance.
5. The hydraulic oil temperature must be 50±5°C.
IV-S-29
Hydraulic system (Service section)
× 100(%)
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