Maintenance Guides 4 min read

Guide to the Diagnosis and Resolution of Cavitation in Industrial Hydraulic Pumps

Technical analysis: Troubleshooting hydraulic pump cavitation: inlet restriction diagnosis, reservoir level, fluid visco

1. Problem Description and Scope

Hydraulic cavitation is a destructive physical phenomenon that occurs when the static pressure of the fluid at a point in the system drops below its vapor pressure. This causes the formation of vapor bubbles (or cavities) which, when transported to areas of higher pressure (for example, inside the pump), violently implode. These implosions generate micro-jets and shock waves that progressively erode metal surfaces, leading to irreversible damage, excessive noise, vibrations and reduction in system performance.

This guide focuses on diagnosing and resolving cavitation in positive displacement (gear, vane, piston) and centrifugal hydraulic pumps, typically used in machine tools and industrial systems. The goal is to provide a systematic approach to identify root causes related to:

  • Suction line restrictions.
  • Insufficient fluid level in reservoir.
  • Abnormal viscosity of the fluid.
  • Air infiltration in the suction line.

Severity Rating:

  • Critical: Cavitation accompanied by loud noise, extreme vibrations, uncontrolled overheating, loss of pressure or flow. Requires immediate intervention to avoid catastrophic failure.
  • Major: Audible but not extreme noise and vibration, slight decrease in performance, presence of foam in the oil. Requires short-term corrective maintenance planning.
  • Minor: Slight hiss or intermittent hum, minimal local heating. Requires preventive maintenance monitoring and planning.

2. Safety Precautions

WARNING: Carrying out diagnoses and interventions on hydraulic systems involves high risks. Failure to follow safety procedures can cause serious injury or death, as well as significant damage to equipment.

  • BLOCK/TAGOUT (LOTO): Before any intervention, ensure that the system is completely de-energised and blocked according to the company procedure UNI EN ISO 14118 (Machinery safety - Prevention of unexpected start-up).
  • STORED ENERGY: Completely relieve pressure from all accumulators and hydraulic lines before disconnecting piping or components. Use pressure gauges to confirm the absence of pressure.
  • HYDRAULIC FLUID UNDER PRESSURE/HOT: Hydraulic fluid can cause severe subcutaneous injections even at low pressures. Always wear appropriate PPE: oil-resistant gloves (EN 388, EN 374), safety glasses or visor (EN 166). The fluid can reach high temperatures (>60°C), causing burns.
  • MOVING PARTS: Keep hands and clothing away from couplings, shafts and other rotating parts.
  • ELECTRICAL EQUIPMENT: Disconnect the electrical power supply to the pump motor before carrying out inspections or electrical interventions, in compliance with CEI regulations EN 60204-1 (Machinery safety - Electrical equipment).

3. Necessary Diagnostic Tools

An accurate diagnosis of cavitation requires the use of specific instrumentation.

Tool Specifications / Recommended model Typical measurement range Purpose
Pressure gauge (for suction) Class 1.0, full scale -1 to +5 bar -1 to +5 bar Measures the absolute or gauge pressure on the pump suction line. Critical for detecting excessive depressions.
Pressure gauge (for delivery) Class 1.0, full scale adapted to the system pressure (e.g. 0-250 bar) 0-250 bar (or higher) Check the pump outlet pressure and the correct functioning of the system.
IR or Contact Thermometer Accuracy ±1°C, range -30°C to +250°C 0-100°C Measures the temperature of the fluid in the tank and lines, and the surface temperature of the pump.
Sound level meter Class 2, IEC 61672-1 compliant, with A filter 30-130 dB(A) It quantifies the intensity of the noise generated by the pump, useful for comparison over time.
Vibration Analyzer With piezoelectric accelerometer, range 10 Hz - 10 kHz 0-50 mm/s RMS (speed) Detects anomalous frequencies (cavitation harmonics) and quantifies the vibrational energy according to UNI ISO 10816.
Portable Viscometer Range suitable for hydraulic fluid (e.g. 10-1000 cSt) Varies depending on the fluid Verifies the kinematic viscosity of the fluid in service for comparison with the manufacturer's specifications.
Particle/Moisture Analyzer For offline or online analysis Standard ISO 4406, % humidity Detects solid contamination and water in the oil, which can affect viscosity and vapor pressure.
Clamp Meter (only for electric motors) True RMS, range 0-1000A AC/DC 0-1000A Monitors pump motor current consumption, overload indicator or mechanical anomalies.

4. Initial Assessment Checklist

Before proceeding with any instrumental diagnosis, carry out a visual assessment and document the operating conditions. This helps to contextualize the problem and guide the investigation.

Control Element What to Observe / Record Rating / Notes
Tank oil level Check the hydraulic fluid level against the visual indicator (min/max) with the machine off and running. Acceptable: Between the minimum and maximum levels. Alarm: Below minimum (probable cavitation).
Operational Noise Listen carefully to the pump and suction/delivery lines. Note any abnormal noises (crackles, gurgling, rattling, hissing). Normal: Regular hum. Alarm: Intermittent or continuous noises similar to

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