993K Wheel Loader Electrohydraulic System Caterpillar

Reference: For more information on the specifications for the hydraulic fan pump, refer to Specifications for your machine.

For any pump test, the pump flow at 5000 kPa (725 psi) will be larger than the pump flow at 20000 kPa (2900 psi) if the pump is operating at the same rpm. The pump flow is measured in L/min (US gpm).

The difference between the pump flow of two operating pressures is the flow loss.

Flow loss that is expressed as a percentage of pump flow is used as a measure of pump performance.

Table 1 shows the method of determining percent of flow loss.

Table 1

Method of determining flow loss(1)
	Pump flow at 5000 kPa (725 psi)	217.6 L/min (57.5 US gpm)
-	Pump flow at 20000 kPa (2900 psi)	196.8 L/min (52.0 US gpm)
	Flow loss	20.8 L/min (5.5 US gpm)

(1)	Values in the formula are not values for any specific pump, or for any specific pump condition. Refer to the specifications for the actual pump flow of a new pump at 5000 kPa (725 psi) and at 20000 kPa (2900 psi).

Table 2

Flow loss (L/min or US gpm)	×	100	=	Percent of flow loss
Pump flow at 5000 kPa (725 psi)

Table 3

20.8 L (5.5 US gal)	×	100	=	9.5%
217.6 L/min (57.5 US gpm)

Table 3 is an example of determining percent of flow loss.

Note: The values in the examples are not set values for any specific pump or for any specific pump condition. Refer to the specifications for the pump flow of a new pump at 5000 kPa (725 psi) and at 20000 kPa (2900 psi).

Test on the Machine

Install a flow meter. Operate the engine at high idle. Measure the pump flow at 5000 kPa (725 psi), and at 20000 kPa (2900 psi). Use these values in the Formula 1 in Table 4.

Table 4

	Formula 1
	Pump flow at 5000 kPa (725 psi)
−	Pump flow at 20000 kPa (2900 psi)	×	100	=	Percent of flow loss
	Pump flow at 5000 kPa (725 psi)

Test on the Bench

If the test bench can be run at 20000 kPa (2900 psi) and at full pump rpm, determine the percent of flow loss by using Formula 1 in Table 4.

If the test bench can not be run at 20000 kPa (2900 psi) or at full pump rpm, run the pump shaft at 1000 rpm.

Measure the pump flow at 5000 kPa (725 psi) and at 20000 kPa (2900 psi). Use these values in the top portion of Formula 2 in Table 4.

For the bottom part of the formula, run the pump shaft at 2000 rpm. Measure the pump flow at 5000 kPa (725 psi).

Table 5

	Formula 2
	Pump flow at 5000 kPa (725 psi)
−	Pump flow at 20000 kPa (2900 psi)	×	100	=	Percent of flow loss
	Pump flow at 5000 kPa (725 psi) and at 2000 rpm