For any pump test at a given rpm, the pump flow at 690 kPa (100 psi) will be larger than the pump flow at 6900 kPa (1000 psi) .
The difference between the pump flow of the two operating pressures is the flow loss.
Flow loss is used as a measure of pump performance when the flow loss is expressed as a percent of pump flow.
| Percent of flow loss | |
|---|---|
| [(A - B) ÷ C] × 100 = D | |
| A | Pump flow at 690 kPa (100 psi) |
| B | Pump flow at 6900 kPa (1000 psi) |
| C | Pump flow at 690 kPa (100 psi) |
| D | Percent flow loss |
| Example | |
| [(A - B) ÷ C] × 100 = D | |
| A | 217.6 L/min (57.5 US gpm) |
| B | 196.8 L/min (52.0 US gpm) |
| C | 217.6 L/min (57.5 US gpm) |
| D | Percent of flow loss |
| [(217.6 L/min (57.5 US gpm) - 196.8 L/min (52.0 US gpm)) ÷ 217.6 L/min (57.5 US gpm)] × 100 = D | |
| D = 9.6 percent | |
If the percent of loss is more than 10 percent for the machine test or 15 percent for the bench test, the pump performance is not good enough.
Note: The numbers in the formula are only examples. These numbers are not values for any particular pump nor for any particular pump condition. See Specifications, "Piston Pump (Steering)" for the pump flow of a new pump at 690 kPa (100 psi) and at 690 kPa (100 psi) .
Machine Test
- Install a 4C-9437 Flow Measuring Tool .
- Start the engine.
- Run the engine at high idle.
- Measure the pump flow at 690 kPa (100 psi) and 6900 kPa (1000 psi) .
- Use the values that were measured in Step 4 in Table 1 .
Bench Test
If the bench test can be run at 6900 kPa (1000 psi) and at full rpm, determine the percent flow loss.
If the bench test cannot be run at 6900 kPa (1000 psi) and at full rpm, use the following procedure:
- Run the pump shaft at 1000 rpm.
- Measure the pump flow at 690 kPa (100 psi) and 6900 kPa (1000 psi) .
- Use the measurements from Step 2 for the values of A and B in Table 1 .
- To determine the value of C, use Steps 4.a through 4.b .
- Run the pump shaft at 2000 rpm.
- Measure the pump flow at 690 kPa (100 psi) .
- Use the measurement from Step 4.b for the value of C in Table 1 .