Hydraulic Horsepower Testing Caterpillar

Problem:

It may be necessary to complete a hydraulic horsepower test during the diagnosis of machine performance. A consistent test procedure is required for the accurate measurement of hydraulic horsepower.

Solution:

A hydraulic horsepower test procedure has been developed. The test will measure the hydraulic horsepower at the boom cylinders. The following is a list of test instruments, instrument installation, test procedures, and data worksheets for conducting the test:

Required Test Instruments:

The flow meters must be capable of measuring the flow rates listed in Chart A. Do not use the temperature display on the flow meter. Use service code 14 displayed on the machine monitor to measure the hydraulic oil temperature. The pressure gauges listed in Chart B should be certified for reasonable accuracy.

Test Instrument Installation:

1. Install the two 60 000 kPa (8700 psi) gauges. Install one gauge to the top pump discharge quick disconnect fitting. Install the second gauge to the bottom pump discharge quick disconnect fitting. Both fittings are located on the pump.

2. Install the 6000 kPa (870 psi) gauge to the power shift quick disconnect fitting located on the pump.

3. Install the 250 kPa (36 psi) gauge to the inlet manifold for measurement of engine boost pressure. The measurement of engine boost pressure is optional.

4. Install the tachometer or test equipment normally used to measure engine speed, if not using the display on the machine monitor.

5. Remove the boom cylinder hose assemblies from the boom cylinder tube assemblies. Install caps on the boom cylinder tubes. If using only one flow meter, install plugs in one hose assembly supplying the piston end of one of the boom cylinders, and in one hose assembly supplying the rod end of one of the boom cylinders. Connect the flow meter(s) to the boom cylinder lines so that the line to the piston end is connected to the incoming side of the flow meter(s), and the line to the rod end to the out going side of the flow meter(s).

Test Procedure:

1. Obtain a fuel sample and determine the API rating. Use the correction factor listed in Chart C in order to calculate the corrected hydraulic horsepower. Interpolate a correction factor if the exact fuel rating is not listed.

2. Determine the machine configuration. Non-standard machine configurations will have increased parasitic loads that will reduce the net power transferred to the two implement pumps. The net power reduction will decrease the hydraulic horsepower output.

3. The temperature range of the oil when performing the test at the low pressure point should be 50° to 55°C (120° to 130°F).

4. The temperature range of the oil when performing the test at the high pressure point should be 50° to 57°C (120° to 135°F).

5. The hydraulic oil temperature will warm up quickly while doing this test. It is recommended that the collection of data begin when the temperature reaches 50°C (120°F).

6. Hydraulic horsepower will be measured at two points on the hydraulic horsepower curve. The high pressure point value for all models will be the same. The low pressure point value (the pressure point slightly above the pressure at which the pump destrokes) will be a different value depending on the model.

7. Set the monitor to: POWER MODE (indicator light on), BOOM PRIORITY during the test.

8. Set the throttle control to: DIAL SPEED 10.

9. Load the hydraulic pumps by doing a full BOOM UP. Close the flow meter(s) to load the pumps to 6900 kPa (1000 psi) (close the flow meters evenly if using two, but this is not necessary as long as the flow being measured is below the maximum flow capability of the flow meter). If using two flow meters, the flow of each flow meter will be added together to equal total flow.

10. Load the top and bottom pumps by loading the flow meter to the pressure listed on the data worksheet for the first test point. Record the data and calculate the corrected hydraulic horsepower.

11. Load the top and bottom pumps by loading the flow meter to the pressure listed on the data worksheet for the second test point. Record the data and calculate the corrected hydraulic horsepower. Chart D lists the corrected minimum hydraulic horsepower specifications for the first and second test points.

12. The length of the test is approximately 1 hour including installation and returning the machine to its normal condition.

Calculated hydraulic horsepower is equal to the averaged top and bottom pump pressures, multiplied by the total flow, with the result divided by the constant (all models) 1714. The corrected hydraulic horsepower equals the calculated hydraulic horsepower multiplied by the correction factor. From the example data sheet:

(2900+2850) / 2 = 2875

2875 x 115.6 = 332,350

332,350/1714 = 193.9

193.9 x 1.011 = 196

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