CPM Hydraulic and Pneumatic Systems 2

Question 1

A hydraulic cylinder has a 4-inch bore and the system pressure is 1,000 psi. What is the approximate extension force?

Accepted Answer

12,566 lbf

Answer

Force = pressure × area = 1,000 psi × (π × 2² = 12.57 in²) ≈ 12,566 lbf.

Question 2

Why does a double-acting cylinder retract with less force than it extends at the same pressure?

Accepted Answer

The rod reduces the effective piston area on the rod side

Answer

The rod occupies part of the piston face, so the annular area on the rod side is smaller and gives less force.

Question 3

In a meter-out flow control circuit, where is the flow control valve placed?

Accepted Answer

In the line leaving the actuator, restricting exhaust flow

Answer

Meter-out restricts fluid leaving the actuator, which gives good control of overrunning loads.

Question 4

A gear pump makes a loud rattling, gravel-like noise and the reservoir oil looks normal. What is the most likely cause?

Accepted Answer

Cavitation from a restricted or clogged suction line

Answer

A restricted inlet starves the pump, forming vapor bubbles that collapse and cause a gravel-like noise.

Question 5

What is the main purpose of a pilot-operated check valve in a cylinder circuit?

Accepted Answer

To hold a load in position until pilot pressure opens it for reverse flow

Answer

A pilot-operated check blocks reverse flow to lock the load until pilot pressure unseats it.

CPM - Certified Plant Mechanic Practice Test