1989/09/25 Caterpillar

As the product line expands and becomes more complex, keeping current on technical information can be a major challenge. Beginning with this issue, a new feature, called "What's Your Answer?", will occasionally appear in Service Magazine. This feature will consist of a number of service-related questions. Fundamentals will be included as well as current topics of interest. Along with allowing you to match wits with other service experts in your workplace, the quiz can help sharpen and maintain your technical knowledge. If you have difficulty with some questions, see your service or training manager for help. Specific references will be cited after each quiz for further information on the topic covered.

What's Your Answer? - Hydraulics

NOTE: The correct answers can be found elsewhere in this issue.

1. Which symbol represents a unidirectional, variable displacement pump?

2. What two factors affect the amount of fluid pressure required to lift a load?

a) Maximum fluid pressure and the area on which that pressure is exerted.

b) Input force and the resulting fluid pressure.

c) Input force and the area on which the input force is applied.

d) Resisting force of load and the area on which fluid exerts pressure to support the load.

3. The following symbol represents what type of valve?

a) Nonadjustable relief valve.

b) Adjustable relief valve.

c) Pressure reducing valve.

d) Flow divider valve.

4. Hydraulic pump displacement is calculated by measuring which of the following?

a) The volume of fluid pumped during one revolution of the pump.

b) The average pressure during one revolution of the pump.

c) The volume of fluid pumped in one minute.

d.) None of the above.

5. TRUE or FALSE: I.S.O. symbols make it easy to distinguish between the different types of pumps (gear, vane, piston).

6. TRUE or FALSE: In a variable displacement piston pump, when the swashplate angle is increased, displacement is increased.

7. TRUE or FALSE: A gear-type pump is classified as a variable displacement pump.

8. TRUE or FALSE: Vane and piston-type pumps are always fixed displacement pumps.

9. TRUE or FALSE: Hydraulic motors convert mechanical energy to into fluid energy.

10. TRUE or FALSE: Vane type pumps will self compensate for wear.

11. TRUE or FALSE: A charge pump supplies flow to the outlet of a larger pump to prevent cavitation.

12. TRUE or FALSE: A simple relief valve is kept open during normal operation by a force exerted by the spring in the valve body.

13. TRUE or FALSE: Compound or pilot operated valves are designed to enable the main valve to respond to short duration pressure surges.

14. TRUE or FALSE: In a hydraulic system, valves have no control over pressure.

15. Two types of control valves are:

a) Positive and non-positive

b) Parallel and Series

c) Open and Closed Center

d) None of the above

16. How can fluid flow rate through a hydraulic system be reduced?

a) Decrease cross-sectional area of all lines and hoses in the system.

b) Increase pump output.

c) Increase cross-sectional area of all lines and hoses in the system.

d) Reduce fluid flow from the pump

17. Pressure is usually measured in:

a) Feet per second, meters per second

b) Gallons per minute, liters per minute

c) Pounds per square inch, (kPa)

d) Hose diameter

18. Which valve maintains a set difference in pressure between lines or circuits?

a) Flow divider valve

b) Differential valve

c) Make-up valve

d) Check valve

19. Which valve limits system pressure by dumping full pump flow at a set pressure?

a) Check valve

b) Quick drop valve

c) Relief valve

d) Pressure reducing valve

20. Which valve will provide a predetermined maximum flow rate to one circuit and bypass excess flow to another circuit?

a) Make-up valve

b) Flow control valve

c) Flow divider valve

d) Flow bypass valve

21. Auxiliary pressure used to actuate or control hydraulic pressure is:

a) Signal Pressure

b) Pilot Pressure

c) Cracking Pressure

d) System Pressure

22. The pressure at which a pressure actuated valve begins to pass fluid is:

a) Signal Pressure

b) Pilot Pressure

c) System Pressure

d) Cracking Pressure

23. This type of pump is used in most load sensing hydraulic systems:

a) Positive displacement pump

b) Variable displacement pump

c) Non-positive displacement pump

d) Negative displacement pump

24. This controls system hydraulic flow by adjusting a piston pump swashplate angle or an unloading valve:

a) Signal Pressure

b) System Pressure

c) Pilot Pressure

d) Cracking Pressure

25. The outside diameter of a spool valve which controls and limits the amount of flow through the valve:

a) Lands

b) Poppet

c) Sleeve

d) Limiter

Answers: 1.b, 2.d, 3.c, 4.a., 5.F, 6.T, 7.F, 8.F, 9.F, 10.T, 11.F, 12.F, 13.F, 14.F, 15.c, 16.d, 17.c, 18.b, 19.c, 20.b, 21.b, 22.d, 23.b,d, 24.a., 25.b