Terex Evoquip Bison 120, Operation Manual

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9 Maintenance
Operations Manual
Bison 120
20-07-2018
Page 9-14
Revision 2.0
(1) Hydraulic System Overview
The Hydraulic system which is used in your machine was chosen for its effectiveness and
resistance to climatic and operating conditions.
This must be kept topped up with the correct hydraulic fluid and regular checks must be made
to ensure this.
The system should be checked for leaks and the hydraulic oil analyzed after 500 hours and
replaced if necessary.
(a) Hydraulic Fluids
Hydraulic fluids play an important part in any hydraulic system. They have two main functions.
• To transmit power
• To lubricate moving parts
As a power transmitting medium the fluid must flow easily and be as incompressible as possible.
In most hydraulic components, the fluid provides internal lubrication only. For long component
life, fluids are available containing additives that have high anti wear properties. The fluids are
known as anti-wear type hydraulic oils, which are recommended for your machine.
In most cases the fluid is the only oil seal present. For example, there are no sealing rings between
the spool and the body of the directional valve. As the sealing characteristics of the fluid depend
on its retaining viscosity, it is important that the oil selected is capable of maintaining the minimum
viscosity change over a wide range of operating temperatures.
Some adverse effects of incorrect viscosity are:
• Increased power consumption
• High oil temperatures
• Entrapment of air in oil
• Increase pressure drop
• Excessive wear or even seizure under heavy loads
• Poor pump performance
In addition to the qualities outlined earlier the selected fluid should also:
• Prevent rot
• Depress foaming
• Prevent formation of sludge, gum and varnish
• Retain its own stability, thereby reducing fluid replacement
• Prevent corrosion and pitting
For best operating results it is strongly recommended that the hydraulic fluid used is selected
from the recommended range listed in section: Lubrication, Quantities, and Levels.
In the service it is recommended that the hydraulic system is analyzed every 500 hours and the
oil changed if necessary. The hydraulic fluid should be changed after the machine has stopped
work. The drain plug for the hydraulic system is mounted underneath the tank. In the event of
pump or motor failure, all filters must be changed.