Hydraulic Pumps, Actuators and Testing Service

Question 1

Why don’t variable displacement motors reach a zero-displacement position?

Answer 1

The motor will hydrostatically lock and stall (free wheel) in the zero position

Question 2

Leaking piston seals in a differential cylinder result in __________, _________ and _________

Answer 2

• Increased cylinder cycle times
• cylinder drifting in the extension direction,
• pressure intensification when in the hold position

Question 3

Pressurized oil is allowed to flow past the piston to the ____________

Answer 3

rod side of a ram type cylinder

Question 4

What does a cylinder rod wiper do?

Answer 4

Prevent contamination from entering the cylinder

Question 5

When does the quick drop valve provide regeneration?

Answer 5

When the full lower position is used

Question 6

One factor that does not influence motor torque generation is _____

Answer 6

Inlet flow rate

Question 7

Most motors have a drain line that carries ______ to _______.

Answer 7

Motor leakage oil to the reservoir

Question 8

What is the function of a spool valve on a gerotor motor?

Answer 8

Direct the flow of oil to and from the valleys in the gerotor element

Question 9

As pumps outlet pressure increases, the pumps internal leakage ___________

Answer 9

Increases

Question 10

Oil that gathers in the case of an axial piston pump comes from ________

Answer 10

Internal leakage

Question 11

What is the most common cause of pitted erosion on internal surfaces?

Answer 11

Cavitation

Question 12

What are the three ways a pump can lack in lubricaion?

Answer 12

1. Improper oil used
2. Low reservoir oil level
3. Severe aeration (possibly over speeding)

Question 13

What are the four tasks that should be done when a pump is installed to ensure the system is clean enough?

Answer 13

1. Oil may need to be changed or filtered
2. Change the filters
3. Reservoir cleaned thoroughly and completely
4. system flush

Question 14

The hydraulic pump converts mechanical energy into ________ energt

Answer 14

hydraulic

Question 15

What are the four start up procedures that should be done after a new motor is installed?

Answer 15

1. Back off system pressure controls
2. Operate motor at no load and check for leaks or unusual noise
3. Apply load to the motor and warm up the oil, adjust system pressure controls
4. Perform operational tests to confirm machine is working correctly

Question 16

The two types of radial piston pumps are __________and __________

Answer 16

Rotating cam and rotating piston

Question 17

What is mechanical efficiency?

Answer 17

The amount of power required to overcome the internal friction of the pump.

Question 18

What is volumetric