Errors during commissioning and repair
Employees filling a unit
Errors often occur before the system is switched on for the first time, leading to disruptions and failures. When it comes to proportional and servo-hydraulic valve technology, the following rules of thumb help to avoid common pitfalls.
Hydraulic systems with proportional or servo-hydraulic valve technology (continuous valves) are used when consumers need to be controlled precisely and highly dynamically. To ensure that these systems work trouble-free over a long period of time, a few points must be taken into account when setting up and commissioning.
The documentation of a hydraulic system also includes detailed operating instructions with important information for commissioning. Unfortunately, these are not always taken into account in practice. This begins with filling in the hydraulic fluid.
Fresh oil often does not meet the required fluid purity and must always be filtered and filled into the hydraulic system due to possible solid contamination. Filling filtered does not mean pouring the oil directly from the oil container into the tank via the filler screen of the ventilation filter. The filling must be carried out using a suitable filter that has the same filter fineness as the filters in the hydraulic system. Special filter units are available commercially for this purpose. Users should also be sure to
Pay attention to the minimum and maximum fluid levels in the hydraulic tank. The filling volume of lines and consumers must also be taken into account.
If a different fluid is to be used than permitted on the nameplate, the seal compatibility must be agreed with the supplier. If there are incompatibilities, the seals can dissolve, resulting in leaks, jammed valves and clogged nozzles!
The required one Fluid purity class depends on the most sensitive component, i.e. the continuous valves. When using servo and proportional valves, absolute filtering must already take place in the inlet (pressure filter). The filter fineness should be 3 µm for servo valves and 5 – 6 µm for proportional valves.
The hydraulic units must never be commissioned with proportional or servo valves installed. Despite the greatest care when manufacturing a hydraulic system, residues such as weld beads, lint, chips or paint particles usually remain in the system. These are larger than the clearance of the valves and can lead to jamming of the sensitive valve technology.
Before commissioning, users should therefore replace proportional valves with flushing plates or “black-and-white valves” and flush the system sufficiently until the required cleanliness class is achieved.
Only then can the continuous valves be installed. The purity classes can be displayed and checked directly using a particle counting device. If this measurement technology is not available, the rule of thumb for the flushing process is: the oil volume of the hydraulic system
should have passed through the filter at least 150 times to achieve the correct purity class. The contamination indicators on the filters must be observed.
For this reason, an initial filter change may be necessary during the rinsing process. The filter cartridge should be replaced after the rinsing process at the latest. Another filter change is often recommended after 50 hours of operation. First
The regular filter change intervals then follow, in accordance with the recommendations of the system manufacturer and the operating conditions.
The system is now almost ready for the first test run.
Caution is advised with automatic program sequences. For example, if the sensors are not positioned correctly, this can lead to a crash.
It is therefore advisable to run systems with such program sequences with low pressures and small setpoints in so-called setup mode. If this is not provided for in the electrical control, it may be necessary to separate the valve technology from the control and operate the hydraulic system manually using an external power supply. The focus should be on the direction of rotation of the electric motor: an incorrect direction of rotation can destroy the hydraulic pump within a short time. Ideally, users switch on the electric motor in inching mode to check and compare the direction of rotation with the directional arrow on the fan cover of the electric motor. If all settings have been made correctly, another important step follows.
Bleeding the entire hydraulic system
Air in the system changes the control behavior of the continuous valves extremely, causing start-up jumps in the cylinders or vibrations in the system. Vent points should be provided for ventilation. Some pumps require the casing to be filled
Data sheets must be observed. After bleeding, users should drive the consumers a few times and slowly increase the pressure. The fluid level in the hydraulic tank must be checked and corrected if necessary. If necessary, have to
The electromagnets on the proportional valves must also be vented.
During operation, the connection points should be checked for leaks. If leaks occur, they must be eliminated immediately. It is also urgently necessary to precisely check the oil temperature in the tank (temperature display in the sight glass). The temperature must be within the permissible temperature range.
Important: Only trained and instructed personnel with special hydraulics expertise may carry out commissioning and repair work.
With kind approval: International Hydraulics Academy GmbH
Source: https://www.hydraulik-akademie.de/medien-presse
If you have any questions about hydraulics, we are happy to help!
lars.benk@schuhmacher-tech.de +49 7424 9495-663
Contact details:
LARS BENK
+49 7424/9495-663
Lars Benk: Profile of a field-tested expert
Basic training: Tool mechanic, specializing in stamping and forming technology.
Further training: State-certified technician with a focus on mechanical engineering.
Additional qualification: Degree in technical business administration, combining technical know-how with business expertise.
Professional experience: More than a decade of active work in the field of hydraulics.
Specialization: Certified specialist in oil analysis (MLA II – Machine Lubrication Specialist), with a specific focus on the maintenance and optimization of machines through professional lubricant analysis. Certified specialist for hydraulic fluids – specialist knowledge for optimal hydraulic systems.
