DGUV Information 209-071e - Safe maintenance of hydraulic systems (DGUV Informat...

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Abschnitt 3, 3 Troubleshooting
Abschnitt 3
Safe maintenance of hydraulic systems (DGUV Information 209-071)
Titel: Safe maintenance of hydraulic systems (DGUV Information 209-071)
Normgeber: Bund
Amtliche Abkürzung: DGUV Information 209-071
Gliederungs-Nr.: [keine Angabe]
Normtyp: Satzung

Abschnitt 3 – 3 Troubleshooting

Naturally, preventive maintenance and repair measures, especially checking the oil cleanliness on a regular basis, are the best method to minimize errors and failures in the run-up already. Nevertheless, errors and failures can occur when operating a hydraulic system or machine, which impair the general operational sequence but also the safety of the hydraulic system or machines.

Apart from the impairment of the product quality, this can lead to hazards (see section 1.3) which no longer ensure safe working with the machine.

Thus, it is important that the machine operator reports all failures and errors to the supervisor or the maintenance department immediately. These persons decide whether it is possible to continue work with the machine or whether the machine has to be repaired immediately.

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Errors in hydraulic systems or machines have to be reported to the supervisor immediately.

Before starting troubleshooting, the procedure has to be determined. Along with planning the proper troubleshooting, this also comprises the measures for securing the work area (i. e. the danger and effective range), as well as the required protective measures.

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Troubleshooting and repair works must only be conducted by trained personnel.

At the beginning of troubleshooting, the required technical documents and information should be available, e. g. operating instructions, circuit and electrical diagrams, including measuring points and a list of items. If no hydraulic circuit diagram can be found for older systems, a circuit sketch should be established on the basis of design, signposting, and labeling of the parts.

The machine operators should be questioned regarding error behavior, failures, and reactions of the machine and system. If a maintenance book or log exists, it should be used to investigate if this or similar failures have already occurred. Furthermore, the error lists in the operating instructions of the manufacturer have to be taken into consideration.

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For troubleshooting, the technical documents of the system/machine have to be available.

If troubleshooting requires working methods which deviate from those applied for normal operation, e. g. test runs, setting, start-up, or is it necessary to run one cycle or several cycles with the defective machine in order to localize the errors, it has to be ensured that safeguarding equipment (movable safeguarding equipment, two-hand control devices, light barriers) on the machine is active in this phase as well. On the basis of the error that occurred, further machine-specific measures (and organizational measures) may have to be taken in order to avoid employees being endangered during troubleshooting (wide area safety fence using chains, instruction plates, reduced speed, and reduced pressure).

During troubleshooting, operating modes should be applied in which individual functions are operated outside the automatic operation at reduced speed, in tip operation (hold-to run control device), with enabling switch, or in the operating mode "Set-up/Hand".

Attention must be paid to the fact that dangerous follow-up movements are triggered when passing position switches, e. g. also for automatic program-controlled tool or work piece change, start-up of accessory devices.

Troubleshooting must only be conducted with activated safeguarding equipment.
If required, further organizational measures are necessary.

If troubleshooting also can be done with the machine turned off or if the machine is turned off for error correction upon localizing the error, the five-finger rule mentioned in section 1.5 has to be observed.

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Observe the five-finger rule of fluid power technology.

If the control system is not a purely hydraulic system, but the hydraulic system is operated as part of an electro-hydraulic control system, it may be necessary to have the troubleshooting procedure conducted by a specialist electrician. In case of complex systems operated with electronic control systems, it may also be necessary to call a specialist for electronic hardware or software. In this case, if several persons work on the machine for troubleshooting purposes, it is imperative to provide for sufficient coordination of the activities on the machine. This especially holds true if the machine operator has to be incorporated into the activities.

Furthermore, hazards caused by adjacent systems or hazards to persons working on adjacent systems have to be prevented.

For electro-hydraulic systems, a specialist for electrical engineering or electronics has to be called.
Activities of several persons have to be coordinated.

Even when pressed for time, following a systematic and targeted procedure is imperative, as a random and rash disassembly or adjustment activities could result in the fact that the initial error cannot be identified anymore.

It is recommended to document the implemented work steps, adjustment values, as well as their modifications. All modifications to the system have to be documented in a traceable manner, e. g. in the machine documentation and, if required, in a maintenance book or log.

A list of eliminated failures and error causes supports troubleshooting procedures in the future.

Many hydraulic system manufacturers have developed comprehensive service information in which they describe systematically possible malfunctions and their causes or possible sources and measures for eliminating them as the technical reasons for errors and the measures for their elimination can vary considerably.

Annex 1 letter A shows a general troubleshooting tree for hydraulic components.

Typical errors include for example:

  • clogged hydraulic filters,

  • stuck valves due to contaminations,

  • unexpected start-up of the machine due to tipping/triggering position/stop switches

  • failure of valves due to spring rupture.

The reason for part failure should be determined.


If the hydraulic energy has to be maintained for troubleshooting or due to other reasons, the provisions of the manufacturer have to be observed.

Regarding the re-commissioning procedure, further safeguarding measures have to be observed, see sections 5.1.2 and 6.1.9.