Hydraulic Oil Foaming: Causes, Hazards and Solutions

1. Hazards of Hydraulic Oil Foaming

Unstable cylinder movement, jitter and slow response

Abnormal pump noise and cavitation, accelerating pump wear

Rising oil temperature, aging seals and oil leakage

Oil emulsification, oxidation and shortened service life

2. Main Causes & Solutions

2-1  Air Inhalation (Most Common)

Causes: Loose suction pipe joints, aging seals, low oil level, return oil splashing on the oil surface.

Solutions:

Tighten pipe connectors and replace damaged seals

Refill hydraulic oil to standard liquid level

Keep the return pipe below the oil surface to avoid splashing

2-2  Poor Hydraulic Oil Quality

Causes: Inferior oil, mixed different oil types, failed anti-foam additives, water contamination.

Solutions:

Never mix different hydraulic oils

Replace deteriorated or emulsified oil

Add qualified anti-wear hydraulic oil

2-3 Overhigh Oil Temperature

Causes: Blocked cooler, long-term overload operation, sustained overflow pressure.

Solutions:

Clean the air cooler or water cooler regularly

Avoid long-time pressure holding without working

2-4  Unreasonable Oil Tank Structure

Causes: Small tank volume, no partition, short oil circulation distance.

Solutions: Add internal baffles to separate return oil and suction oil, extend defoaming time.

2-5 Blocked Filter Elements

Causes: Dirty filter leads to poor oil circulation and negative pressure air intake.

Solutions: Replace suction filter and return filter regularly.

2-6 Mechanical Component Wear

Causes: Worn hydraulic pump, stuck valve spool and unstable system pressure.

Solutions: Inspect pump pressure, clean manifold blocks and replace damaged parts.

3. Simple Inspection Steps

Check and replenish hydraulic oil

Inspect the suction pipeline for air leakage

Confirm the return pipe is under the oil level

Check oil quality (no emulsification)

Clean cooler and replace filters

Check hydraulic pump and valve blocks

4. Daily Maintenance Tips

Do not mix different brands of hydraulic oil

Replace filters and hydraulic oil periodically

Avoid working with low oil level

Check suction pipe seals regularly

Reduce long-time idle pressure holding