Test and Diagnostic Equipment for Hydraulic Systems

Frequently Asked Questions About Professional Inspection and Diagnosis of Hydraulic Systems

Faults in hydraulic systems can manifest as insufficient force, slow movements, unusual heating, or erratic operation. A systematic diagnosis therefore considers not only the system pressure but also—depending on the fault symptoms—the flow rate, temperature, and pressure conditions at multiple measurement points. Here, we answer common questions about the professional testing and diagnosis of hydraulic systems.

• Which parameters are important in hydraulic diagnostics?

  Depending on the system and the fault symptoms, three parameters are particularly relevant:

  • Hydraulic pressure
  • Volume flow or flow rate
  • Hydraulic oil temperature

  A single pressure measurement is not sufficient for every fault.

  For example, a system may reach the required pressure but at the same time deliver an insufficient volume flow.

  For more comprehensive testing, digital hydraulic diagnostic devices for pressure, flow, and temperature are therefore available.

• Why is hydraulic pressure measured?

  The pressure reading indicates the hydraulic load or force transmission at a specific measurement point.

  A pressure measurement can help, for example, with:

  • labor shortages
  • insufficient lifting capacity
  • abnormal pressure buildup
  • problems with valves or regulators
  • comparing different hydraulic circuits
  • testing after repairs

  Digital hydraulic pressure gauges or complete hydraulic test kits are suitable for pure pressure measurements.

• What is the flow rate in a hydraulic system?

  Flow rate describes the volume of fluid that flows through a specific section of the hydraulic system per unit of time.
  
  It is typically expressed in liters per minute.
  
  Among other things, flow rate affects the speed of hydraulic movements.
  
  A low flow rate can therefore cause a cylinder or hydraulic motor to operate too slowly, even when pressure is present.

• What is the difference between hydraulic pressure and flow rate?

  Pressure and flow rate describe different characteristics of the system.

  Pressure, in simple terms, represents the available hydraulic force or load.

  Flow rate affects the velocity of flow or the volume of fluid transported per unit of time.

  For a comprehensive diagnosis, both parameters should therefore be taken into account, depending on the fault symptoms.

• Why is the hydraulic oil temperature measured?

  Temperature affects the properties of the hydraulic oil and, consequently, the operational behavior of the entire system.

  An unusually high temperature may, for example, indicate:

  • high power loss
  • internal leakage
  • unfavorable throttling
  • overload
  • cooling problems.

  Temperature must always be evaluated in the context of the system, operating conditions, and manufacturer specifications.

• What symptoms might indicate a hydraulic problem?

  Possible indications include, for example:

  • insufficient lifting or operating force
  • slow movements
  • jerky movements
  • unusual noises
  • excessive heating
  • fluctuating system pressure
  • functions failing under load
  • unusual behavior of individual consumers

  These symptoms are not definitive. Therefore, the diagnosis should be based on appropriate measurement data.

• Can a hydraulic system build up pressure and still be faulty?

  Yes.

  Correct or seemingly adequate pressure does not automatically mean that the entire system is operating flawlessly.

  For example, there may be a simultaneous problem with:

  • flow rate
  • internal leakage
  • temperature
  • valve control
  • pump
  • consumer.

  Therefore, in cases of more complex fault patterns, a combined measurement of pressure, flow rate, and temperature may be useful.

• How is hydraulic pressure measured?

  The test device is connected to the designated measuring point via a suitable test connection and a pressure-resistant measuring hose.
  
  The system is then operated under the specified operating conditions, and the pressure is read.
  
  The pressure gauge’s measurement range must be suitable for the application.
  
  The Leitenberger DM-80 series currently covers measurement ranges from very low differential pressures up to high-pressure models rated at 2,500 bar.

• What measurement range should a hydraulic pressure gauge have?

  The measurement range should be appropriate for the expected system pressure.

  An unnecessarily large measurement range can reduce the useful resolution of the measurement, while a measurement range that is too small can overload the measuring instrument.

  Therefore, the following should be known before taking a measurement:

  • expected operating pressure
  • maximum allowable pressure
  • desired measurement accuracy
  • intended measurement location
• Can hydraulic measurement values be saved?

  Yes, on devices equipped with the appropriate features.
  
  The DM-80-UMS pressure gauges, for example, have an internal data memory. Measurement data can be saved in CSV format and transferred to a PC via USB.
  
  The HD-01 digital diagnostic system also supports data logging via USB.

• What is the advantage of digital hydraulic diagnostics?

  Depending on the model, digital systems offer, for example:

  • electronic pressure display
  • flow measurement
  • temperature measurement
  • multiple measurement channels
  • data logging
  • storage of measured values
  • easy data analysis

  The HD 01, for example, can measure pressure, temperature, and flow and features automatic sensor detection.

• When is an analog hydraulic tester a good choice?

  Analog devices do not require an electronic display and can be useful for rugged, direct measurements in workshop or field applications.
  
  The current Leitenberger HD_RFIK200-B-6_LR analog system, for example, is designed for pressure, flow rate, and temperature measurements and does not require batteries.

• What is the difference between a hydraulic pressure gauge and a hydraulic diagnostic tool?

  A hydraulic pressure gauge primarily measures pressure.

  A comprehensive diagnostic device can also measure additional parameters such as:

  • flow rate
  • temperature.

  If the goal is simply to verify whether a specific system pressure has been reached, a digital hydraulic pressure gauge may be sufficient.

  For more complex functional analyses, a hydraulic diagnostic device for pressure, flow, and temperature is recommended.

• What is a hydraulic test kit?

  A hydraulic test kit combines one or more pressure gauges with:

  • measuring hoses
  • test connections
  • adapters
  • connectors

  in a portable case.

  This makes it particularly suitable for workshops and mobile service technicians.

  Leitenberger offers digital hydraulic test kits and analog hydraulic test kits with various pressure gauge combinations.

• When is it a good idea to use a test kit with multiple pressure gauges?

  Multiple pressure gauges make it possible to test different measurement ranges or multiple pressure points.
  
  For example, the digital HPKD 20_LR includes pressure gauges for 0–400 and 0–600 bar. The analog HPK 20_LR combines 0–100 and 0–400 bar.
  
  This allows for a wider range of hydraulic applications to be covered.

• What is a hydraulic test bench?

  A hydraulic test panel combines multiple pressure gauges and connections on a single mounting bracket or manifold block.
  
  This allows for the quick and organized setup of multiple pressure measurements.
  
  The digital Leitenberger HPLD 20_LR uses two digital pressure gauges; the analog HPL30_LR uses three analog pressure gauges.

• For which vehicles and machines are hydraulic testers suitable?

  Typical applications include, among others:

  • Agricultural machinery
  • Construction machinery
  • Forestry machinery
  • Commercial vehicles
  • Municipal machinery
  • Material handling equipment
  • Stationary hydraulic systems

  The digital HD 01 is specifically designed for mobile and stationary systems.

• Can electronic vehicle diagnostics replace hydraulic measurement?

  Not entirely.

  For example, an electronic diagnostic system can:

  • display error codes
  • sensor signals
  • ECU information
  • setpoints
  • actuator commands.

  Mechanical or hydraulic measurement, on the other hand, shows the actual pressure, flow rate, or temperature present in the system.

  For agricultural, construction, and commercial vehicles, hydraulic measurement can therefore be usefully combined, for example, with the Jaltest multi-brand diagnostics for commercial vehicles and machinery.

• What kind of hydraulic testing equipment is suitable for a workshop?

  That depends on the fleet of vehicles and machinery.

  Typical equipment may include:

  • Digital hydraulic pressure gauges
  • Appropriate test fittings and measuring hoses
  • Digital or analog hydraulic test kits
  • For more complex diagnostics, a hydraulic diagnostic device for pressure, flow, and temperature
  • For multiple measurement points, a hydraulic test strip

  This allows for both simple pressure tests and more comprehensive system analyses.