64/72
Maintenance and repair
Bosch Rexroth AB
, RE 15300-WA, Version 06.2021
10.4 Maintenance
10.4.1 Filter maintenance
Filters in the hydraulic system must be changed after the first 100 working hours
and the second change is to be carried out after 3 months or 500 working hours
whichever is earlier. They must then be changed at regular intervals of 6 months or
4000 working hours.
10.4.2 Oil maintenance
See chapter
and Data sheet
Analysis
It is recommended that the oil should be analysed every 6 months. The analysis
should cover viscosity, oxidation, water content, particle counting possibly including
element analysis of particles.
Most oil suppliers are equipped to analyse the state of the oil and to recommend
appropriate action. The oil must be replaced immediately if the analysis shows that
it is outside the specifications.
Viscosity
Many hydraulic oils display viscosity loss with increasing use, and this means
poorer lubrication. The viscosity of the oil in service must never fall below the
minimum allowed viscosity for the actual fluid or the recommended viscosity for
the motor, see chapter Hydraulic fluids in data sheet
.
Oxidation
Hydraulic oil oxidizes with time of use and temperature. This is indicated by
changes in colour and smell, increased acidity or the formation of sludge in the
tank. The rate of oxidation increases rapidly at surface temperatures above 60 °C
(140 °F), and the oil should then be checked more often.
The oxidation process increases the acidity of the fluid; the acidity is stated
in terms of the "neutralisation number". Typical oxidation is slow initially and
increases rapidly later.
A sharp increase (by a factor of 2 and 3) in the neutralisation number between
inspections is a signal that the oil has oxidized too much and should be replaced
immediately.
Water content
Contamination of the oil by water can be detected by sampling from the bottom
of the tank. Most hydraulic oils repel the water, which then collects at the bottom
of the tank. This water must be drained off at regular intervals. Certain types
transmission oils and engine oils emulsify the water; this can be detected by
coatings on filter cartridges or a change in the colour of the oil. Obtain the advice
of your oil supplier in such cases.
Degree of contamination
Heavy contamination of the oil causes increased wear of the components in
hydraulic system. The cause of the contamination must be immediatly investigated
and remedied.
All hydraulic fluids are
affected differently.
Obtain the advice of
your oil supplier or by
nearest Bosch Rexroth
representative.
