Maintenance Guides 1 min read

Hydraulic Pump Cavitation Diagnostics: Detection of Inlet Flow Restriction, Reservoir Level, Fluid Viscosity, and Air Lock in Hoses

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

Діагностика кавітації гідравлічного насоса: виявлення обмеження вхідного потоку, рівня резервуару, в'язкості рідини та повітряного затвору в шлангах - UNITEC-D Industrial MRO
Цей технічний гайд призначений для діагностики кавітації гідравлічного насоса, включаючи виявлення обмеження вхідного потоку, рівня резервуару, в’язкості рідини та повітряного затвору у шлангах. Гайд

1. Problem description and scope

This guide is designed to diagnose hydraulic pump cavitation caused by improper inlet flow. The problem can occur in hydraulic systems in any industry, including the automotive, aerospace, food, chemical and energy industries. Cavitation is a critical problem as it can lead to significant wear, explosions or even pump failure.

This guide addresses the following symptoms: pump noise, low pressure, vibration, reduced system efficiency, fluid level changes in the reservoir, and air pulsations in the system. All of these symptoms can be related to cavitation, which occurs due to inlet flow restriction, insufficient fluid level, high viscosity, or an air lock in the hoses.

2. Preliminary safety measures

Requirements for personal protective equipment: Use special gloves, glasses and noise protection equipment. When working with liquid containing toxic or flammable substances, use protective equipment against chemical substances.
Lockout and Tagout Requirements: Before work, lockout power sources and tag all exposed hoses and piping. Use locking and tagging facilities to ensure security.
Energy Storage Warning: Before operation, turn off all power sources and check that there is no stored energy left in the system. If using electrical components, check for a hint of current.

3. Necessary diagnostic tools

Name of the tool Model/specification Measuring range The goal
Multimeter Fluke 87V 0–2000 Ω, 0–600 V, 0–10 A Checking electrical connections, measuring resistance and voltage
Thermal camera FLIR T1020 –20°C to +550°C Fluid and component temperature measurement
Vibration analyzer BBE VIBROTECH VAS 500 0–10,000 Hz Pump vibration measurement and fault finding
Manometer Keller M100 0–100 bar Pressure measurement in the system

4. Preliminary review: checklist

A sign Description
Working conditions Check the temperature, pressure and speed of the system
Recent changes Check if components that affect fluid flow have been changed
A history of anxiety Record all alarms that have been triggered in the system
Fluid level Check that the fluid level in the tank meets the requirements
Air lock Check for signs of air pulsations in the system

5. Systematic diagnostic scheme

  1. Noise in the pump:
    1. Measure the temperature of the pump using a thermal camera.
    2. Measure tank and inlet line pressure.
    3. Check if there is an airlock in the system.
  2. Low pressure:
    1. Measure the pressure in the inlet line.
    2. Check if there is a limit in the line.
    3. Check the fluid level in the tank.
  3. Vibration:
    1. Use the vibration analyzer to measure vibration.
    2. Check if there is a fault in the pump or in the inlet line.
  4. Air pulses:
    1. Check if there is an airlock in the system.
    2. Use a manometer to measure the pressure.
    3. Check the fluid level in the tank.

6. Matrix of causes of defects

Symptom Probable causes (by degree of probability) Diagnostic test Expected result
Noise in the pump
  1. Airlock (40%)
  2. Limitation of incoming flow (30%)
  3. Low fluid level (20%)
  4. High viscosity (10%)
  1. Measure the inlet pressure.
  2. Measure the temperature of the liquid.
  3. Check for air pulses.
  1. Inlet pressure is lower than 0.5 bar.
  2. The liquid temperature is higher than 60°C.
  3. Air pulses detected.
Low pressure
  1. Incoming flow limitation (50%)
  2. Low fluid level (30%)
  3. High viscosity (20%)
  1. Measure the inlet pressure.
  2. Check the fluid level.
  3. Measure the viscosity of the liquid.
  1. Inlet pressure is lower than 0.5 bar.
  2. The fluid level is lower than 50% of the maximum.
  3. The viscosity of the liquid is higher than 500 cSt.
Vibration
  1. Airlock (40%)
  2. Limitation of incoming flow (30%)
  3. Low fluid level (20%)
  1. Measure the inlet pressure.
  2. Check for air pulses.
  3. Measure the viscosity of the liquid.
  1. Inlet pressure is lower than 0.5 bar.
  2. Air pulses detected.
  3. The viscosity of the liquid is higher than 500 cSt.

7. Analysis of the root causes of each defect

7.1. Air lock

Cause: An airlock is caused by an improperly secured or missing shutoff valve, which causes air to enter the system. Air can appear during connection, disassembly, or through stomachs that are open.

How to determine: Use a pressure gauge to measure system pressure. If the pressure is uneven or higher than 0.5 bar, it may be an air lock.

Impact: An airlock leads to cavitation, which can cause pump wear, explosions, or reduced system efficiency.

7.2. Limiting the incoming flow

Reason: Inlet flow restriction may be caused by a device preventing fluid from entering the pump. This may be the occurrence of clogging, corrosion, the absence of a filter, or incorrect execution of fittings.

How to determine: Measure the inlet pressure. If the pressure is lower than 0.5 bar, it may be an inlet flow restriction.

Impact: Inlet flow restriction leads to cavitation, which can cause pump wear, explosions, or reduced system efficiency.

7.3. Low fluid level

Reason: A low fluid level can be caused by a leak, improper system performance, or a missing filter. This leads to cavitation because there is not enough liquid to meet the pump's needs.

How to determine: Check the fluid level in the tank. If the level is less than 50% of the maximum, it may be a low fluid level.

Impact: Low fluid levels lead to cavitation, which can cause pump wear, explosions, or reduced system efficiency.

7.4. High viscosity

Reason: High fluid viscosity can be caused by using the wrong fluid, clogging, or temperature change. This results in reduced fluid flow, which can cause cavitation.

How to determine: Measure the viscosity of the liquid. If the viscosity is higher than 500 cSt, it may be high viscosity.

Effect: High viscosity leads to cavitation, which can cause pump wear, explosions or reduced system efficiency.

8. Step-by-step solution procedures

8.1. Air lock detection

  1. Use a manometer to measure system pressure.
  2. Check for uneven pressure.
  3. Measure the temperature of the liquid.
  4. Check for air pulses.
  5. If an air lock is detected, drain the fluid.
  6. Check all hoses for leaks.
  7. Install a shutoff valve in the inlet line.

8.2. Incoming flow limitation detection

  1. Measure the inlet pressure.
  2. Check if there is a limit in the line.
  3. Check for clogging or corrosion.
  4. Measure the viscosity of the liquid.
  5. Check the fluid level in the tank.
  6. If a restriction is found, clean or replace the component.
  7. Install a filter in the input line.

8.3. Low fluid detection

  1. Check the fluid level in the tank.
  2. Measure the temperature of the liquid.
  3. Check for leaks.
  4. Measure the viscosity of the liquid.
  5. If the fluid level is low, add fluid to the reservoir.
  6. Install a filter in the input line.
  7. Check all hoses for leaks.

8.4. Detection of high viscosity

  1. Measure the viscosity of the liquid.
  2. Check that the correct fluid is used.
  3. Measure the temperature of the liquid.
  4. Check for clogging.
  5. If high viscosity is detected, replace the fluid.
  6. Install a filter in the input line.
  7. Check all hoses for leaks.

9. Preventive measures

The root cause Prevention strategy Control method Recommended interval
Air lock Installation of a shut-off valve in the inlet line Checking for air pulses Annual inspection
Limiting the incoming flow Installation of a filter in the input line Checking the inlet pressure Annual inspection
Low fluid level Installation of a level sensor in the tank Checking the fluid level Annual inspection
High viscosity Using the right type of fluid Checking the viscosity of the liquid Annual inspection

10. Spare parts and components

Description of the component Specification When to replace Category UNITEC
Input stream filter Filter type 100 microns, durability 1000 hours After a blockage or flow restriction occurs Filters
Shut-off valve Shut-off valve with a pressure of 100 bar After the occurrence of an air lock Valves
Reservoir Tank with level sensor, volume 100 l After a low fluid level occurs Reservoirs
liquid Liquid type ISO 4406:18/16/13 After the occurrence of high viscosity liquids

To learn more about the parts used in your system, visit our e-catalog: https://www.unitecd.com/e-catalog/

11. Authentic standards and documents

  • ISO 4406:2017 – Standard for measuring the purity of liquids
  • ISO 10426:2007 - Standard for measuring the viscosity of liquids
  • EN 12141:2006 – Standard for pressure measurement in hydraulic systems
  • DSTU 4931:2009 – Standard for temperature measurement in industrial systems
  • UNITEC Maintenance Guide 2023 – Additional recommendations for performing diagnostics

This guide is intended to effectively solve the problem of cavitation in hydraulic systems. Use it to quickly and accurately determine the causes and solve problems in the system.

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