Copyright Goodheart-Willcox Co., Inc.
144 Hydraulic Systems for Mobile Equipment
Cylinder Drift
Cylinder drift occurs when a rod leaks down over an extended period of
time. Several different types of valves can cause this problem if the valves are
leaking or malfunctioning:
• Thermal-relief valves.
• Cylinder port relief valves.
• Pilot-operated check valves.
• Counterbalance valves.
• Lift check valves.
• Secondary poppet valves.
The operation of these valves will be detailed in Chapter 7 and Chapter 9.
Figure 6-28. The portion of the control valve highlighted in yellow connects the cylinder’s return oil back into the
cylinder’s inlet during regeneration.
Figure 6-27. A differential cylinder can be extended faster when the DCV routes the return back into the cylinder’s inlet.
Decreasing
volume
Increasing
volume
Larger area
Smaller
area