Maintenance and repair 59/68
RE 15302-WA/05.2019, Hägglunds CB, Installation and maintenance manual ,
Bosch Rexroth Mellansel AB
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
15.1.1
and Data sheet
RE 15414 Hydraulic fluid quick reference.
Note!
All hydraulic fluids are affected differently. Obtain the advice of your oil supplier or
by nearest Bosch Rexroth representative
Analysis
It is recommended that the oil should be analysed every 6 months. The analysis
should at a minimum cover viscosity, oxidation, water content and 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
RE 15302
.
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
neutralization number (TAN). Typical oxidation is slow initially and
increases rapidly later. A sharp increase (by a factor of 2 and 3) in the TAN 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
of 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.