HYDRAULIC SYSTEM
SUB-SECTION 4A
8. When removing any hydraulic component, be sure to cap
arise as to what the correct operating pressure is. If it is not
and tag all hydraulic lines involved. Also plug the ports of
specified, the following rule should be applied:
the removed components.
The correct operating pressure is the lowest pressure which
will allow adequate performance of the system function
9. All hydraulic components must be disassembled and
and still remain below the maximum rating of the corn
assembled in spotlessly clean surroundings. During dis-
ponents.
assembly, pay particular attention to the identification of
parts to assure proper reassembly. Clean all metal parts in a
Once the correct pressures have been determined, note
clean mineral oil solvent. Be sure to thoroughly clean all
them for future reference.
internal passages. After the parts have been dried thor-
oughly, lay them on a clean, lint-free surface for inspection.
DEVELOPING SYSTEMATIC PROCEDURES. Analyze
the system and develop a logical sequence for setting relief
10. Replace all O-rings, back-up rings, and seals when over-
valves and mechanical stops. Develop a cause and effect
hauling any component. Lubricate all parts with clean
troubleshooting guide similar to the charts shown. The
hydraulic oil before reassembly. Use small amounts of
initial time spent on such a project could save hours of
petroleum jelly to hold O-rings in place during reassembly.
downtime.
11. Be sure to replace any lost hydraulic oil when com-
RECOGNIZING TROUBLE INDICATIONS. The ability to
pleting the installation of the repaired component, and
recognize trouble indications in a specific system is usually
bleed any air from the system when required.
acquired with experience. However, a few general trouble
indications can be discussed.
12. All hydraulic connections must be kept tight. A loose
connection in a pressure line will permit the oil to leek out
1. Excessive heat means trouble. A misaligned pump or
or air to be drawn into the system. Air in the system can
motor places an excessive load on bearings and cm be
readily identified by the heat generated. A warmer than
cause damage to the components and noisy or erratic sys-
normal return line indicates that the system is operating at
tem operation.
relief valve setting. Hydraulic oils which have a low viscosity
will increase the internal Ieakage of components resulting in
TROUBLESHOOTING GUIDE
a heat rise. Cavitation and slippage in a pump will also
generate heat.
GENERAL. The troubleshooting charts and maintenance
hints that follow are of a general nature, but should provide
2. Excessive noise means wear, misalignment, cavitation or
an intuitive feeling for a specific system.
air in the oil. Contaminated oil can cause a relief valve to
stick and chatter. These noises may be the result of dirty
KNOWING THE SYSTEM. Probably the greatest aid to
filters, or fluid, high fluid viscosity, excessive drive speed,
troubleshooting is knowing the system. Every component
low reservoir level, or loose intake lines.
has a purpose in the system. The construction and oper-
ating characteristics of each one should be understood.
Some additional practices which will increase your ability
MAINTENANCE. Three simple maintenance procedures
to troubleshoot the system, and also the useful life of the
have the greatest effect on hydraulic system performance,
system are listed below:
efficiency, and life. Yet, the very simplicity of them may be
the reasons they are so often overlooked. What are they?
Simply these:
1. Know the capabilities of the system. Each component in
the system has a maximum rated speed, torque, or pressure.
1. Change filters.
Loading the system beyond the specifications simply in-
creases the possibility of failure.
2. Maintaining a sufficient quantity of clean hydraulic fluid
of the proper type and viscosity in the reservoir.
2. Know the correct operating pressures. Always set and
check pressures with a gauge that is known to be accurate.
How else can you know if the operating pressure is above
3. Keeping all connections tight, but not to the point of
the maximum rating of the components? The question may
distortion, so that air is excluded from the system.
4A-3
