Cylinder Drift Causes

Cylinder drift occurs when the piston moves unintentionally while the control valve is in neutral. Common causes include:

• Internal cylinder leakage: Worn piston seals allowing fluid to bypass
• Directional valve leakage: Spool wear or contamination
• Check valve leakage: Seat damage or debris
• Counterbalance valve issues: Incorrect setting or wear

Drift Rate Calculation

Drift Rate = Drift Distance / Time

From drift rate, we can calculate internal leakage:

Leakage = Drift Rate x Piston Area

Acceptable Drift Limits

Industry guidelines for acceptable drift vary by application:

• Precision positioning: < 0.1 mm/min
• General industrial: < 1 mm/min
• Heavy duty: < 5 mm/min
• Mobile equipment: < 10 mm/min

Diagnostic Procedure

1. Apply load and measure drift with valve in neutral
2. If drift occurs, disconnect return line - if drift stops, valve is leaking
3. If drift continues with disconnected return, cylinder is leaking internally
4. Check oil temperature - high temp increases leakage