Introduction
Heavy equipment is a mechanical
device to assist humans in carrying out heavy material moving work (Peurifoy,
Schexnayder, & Shapira, 2005). Initially developed for the construction
sector, heavy equipment is then widely used in the mining industry (Haycraft,
2011). It is widely used to support the mining process, from opening mines,
building roads, excavations, and even transporting mining materials to the next
process (Mononen & Matilla, 2022).
One type of heavy equipment that is
often used in the mining industry is a bulldozer. It is a chain tractor that is
useful for digging, digging, pushing soil or material and pulling logs or
portable camps that can be operated in various fields (UT School, 2008).
Bulldozer is equipped with a blade on the front side. The movement of this blade
is controlled with a hydraulic system. Bulldozers, equipped with a standard
blade for pushing materials, can be enhanced with additional tools on the rear
side. According to UT School (2008), one such attachment is the ripper, a
spur-shaped device designed to break rock and hard earth into manageable chunks
that can be subsequently pushed. Another useful addition is the winch, employed
for pulling materials and commonly utilized in the forestry industry,
particularly for the movement of timber logs. These supplementary attachments
significantly expand the versatility and functionality of bulldozers in various
applications.
For the bulldozer to work optimally
it is necessary for the entire system to function properly. One system that
supports bulldozer performance is the blade lift hydraulic system that raises
and lowers the blade. The operator controls the blade position by lengthening
or shortening the rod of the blade lift hydraulic cylinders through control
levers in the bulldozer cabin (Ito, 1991) (Thariq,
2022). Blade position determines the amount of material pushed by the
bulldozer, also an important features when working on an uneven terrain or when
spreading material over an area. Because the blade is the main component for
the bulldozer in carrying out work, interference with the blade control system
can cause the bulldozer to become unusable (Uzny & Kutrowski,2019)(Zhou,
Lingyu & Xiaoming, 2022).
One of the Komatsu D70 LE bulldozer
units operated by PT Primanuka Nunukan experienced problems with the blade lift
cylinder operations. The operator has difficulty maintaining the blade in a
floating position, so the operator has to adjust the blade position repeatedly
during work. This problem affects the work quality of the bulldozer because it
is hard for the operator to maintain a smooth and steady blade position.
The purpose of troubleshooting in
machinery maintenance is to localize various possible causes of machine
trouble, as well as carry out repairs and prevent the same machine troubles
from happening again (Prabowo, 2008) (Doddannavar & Barnard, 2005). Therefore, to restore the optimal
performance of the bulldozer and prevent the same trouble from happening again,
it is necessary to troubleshoot the blade lift hydraulic system (Yang, Xiao,
& Ze, 2014).
Research Method
This
research was carried out at PT Primanuka site Nunukan. The
method of data collection carried out is as follows:
1. Literature Study
The
literature study stage aims to collect additional information relevant to the
problem. Literature study helps the researcher to achieve a better
understanding of the unit and the problem itself. The source of information
comes from the shop manual and part book of the studied bulldozer unit,
previous research articles, and the internet.
2. Field study
In the
field study stage, direct observation o the troubleshooting process for
problems with the Komatsu D70 LE hydraulic system blade lift is conducted. The
activities carried out in the field study were observation, interviews and
documentation.
3. Observation
The observation
stage aims to directly observe the bulldozer unit that is suspected of having a
problem, while having the unit operating in the field. Through this stage, the
information and data about the symptoms of the disorder that occurs can be
obtained. At this stage a visual inspection was also carried out on the parts
suspected to be related to the problem that occurred in the bulldozer unit.
Furthermore, during this stage, observation of the preliminary testing,
disassembly, inspection, part repair and/or replacement, assembly, and testing
are conducted (Arifin, 2018).
4. Interview
Interviews
were conducted with the operator in charge of the bulldozer unit that was
suspected of having a problem. The aim of the interview is to obtain facts about
the problem experienced by the bulldozer.
5. Documentation
The data
and information obtained from field study are documented to make it easier in
the data processing and analysis stages as well as writing reports later.
When working in the field, all workers
and researchers are required to wear personal protective equipment such as a
safety helmet, safety shoes, gloves, protective goggles, and a high-visibility
vest.
Tools were also needed to carry out
the removal, disassembly, and inspection of components suspected of being the
source of the trouble. The tools that are prepared includes spanners, socket
wrenches, pipe wrenches, hammer, chisel, set of slotted screwdriver and special
tools. The research flow chart is shown in Figure 1.
Figure 1.
Flowchart
Results and Discussion
Observation
When
carrying out field observations, the first thing to do is a visual inspection
of the bulldozer unit and its hydraulic system components. Visual inspection is carried out on
the following components:
1.
Oil
tank; this inspection aim to check the quality and quantity of hydraulic oil.
During the inspection it is found that the unit has sufficient amount of
hydraulic oil and good quality.
2.
Hydraulic
pump; the visual inspection on the hydraulic pump shows the pump working properly
and there are no oil leakage occurred.
3.
Control
valve; here are no leaks found on the control valve body and the control lever
are functioning properly.
4.
Hydraulic
hoses and fitting; the inspection on the hydraulic hoses along the path for the
blade lift cylinder shows no leakage, wheter from the hoses or the fittings.
5.
Hydraulic
cylinder; the inspection shows no leaks found around the cylinder. The cylinder
rod is straight and smooth on the surface. The fittings and hoses for the
hydraulic cylinders are also in good condition.
Interviews
Interviews were conducted with the
operator who was working with the bulldozer when trouble occurred. The operator is also the one who
reported the problem with the unit when it happened the first time. The
results of interview is shown in Table 1.
Results of interviews conducted with
operators
|
No |
Question |
Answer |
|
1 |
How many hours does this unit operate in one day? |
8 hours per day |
|
2 |
How is the condition of the unit when it is operated? |
When the blade lift cylinder lever is pulled, the blade
will automatically go up but slowly the blade will go down by itself even
when the lever is in floating position |
|
3 |
What steps do you take when the unit has trouble? |
Stop the unit in a safe place and immediately report to the
mechanic |
Preliminary Testing
The preliminary testing was
carried out to more precisely determine where the troubles in the Komatsu
D70-LE bulldozer occured. Based on the report from the operator on duty, where there was a problem
for him maintaining the bulldozer blade in floating position during the
operation. The mechanic then checks and tests by operating the blade drive
hydraulic system. The hydraulic control system functions properly, the actuator
follows the input from the control levers. The problem appears when the control
lever is left in the floating position, the blade will drop due to its own
weight. This symptom shows that the lift cylinder cannot hold the blade
position according to the command of the control lever. From the test
result, it
turned out that the problem was in the blade lift cylinder
component. where the lift cylinder cannot maintain it�s pressure, which resulted
in the blade going down by itself (hydraulic drift). From the preliminary testing and the
results of visual inspection it is concluded that the source of the trouble is
in the blade lift cylinder. To correct this problem it is necessary to
dismantle the blade lift hydraulic cylinder (Anhar & Faisal, 2021)
(Simanjuntak & Novan, 2019)(Yang, Xiao, & Ze, 2014).
Figure 2. Blade
lift hydraulic cylinder
Tools Preparation
Tools
that are prepared for the disassembly work are spanners, socket wrenches, pipe wrenches, hammer,
chisel, set of slotted screwdriver and special tools.
Disassembly
Disassembly aims
to separate the components into smaller parts so as to facilitate the
inspection stage.
Disassembly must be done carefully so as not to cause new damage. Some
components of the hydraulic cylinder are reusable and some are not which have
to be replaced disregarding the condition of the hydraulic cylinder. Before
removing the hydraulic cylinder, the system pressure must be relieved. The
blade is rested on a solid base, the hydraulic fittings are released and the
cylinder pins are removed. The hydraulic cylinder then removed from the blade
and disassembled to reach the inner components of the hydraulic cylinder.
Figure 3. Dust
seal removal
Inspection and Part Recomendation
The disassembled hydraulic cylinder
parts were then inspected, and it was found that the cylinder seal kit
components were damaged. The problem started with the delay in performing
hydraulic oil changes. The service life of hydraulic oil that exceeds the
standard service life will result in a decrease in the quality of quality,
especially with regard to lubrication capabilities (Anhar & Faisal, 2021)
(Simanjuntak & Novan, 2019). Hydraulic oil also serves to reduce friction
and wear and tear, dissipate heat, and drain debris (cleaner) on the parts that
mutual motion sliding (ASM International, 1992). This matter corresponds to the
results of visual observations internal elevator cylinder that is experiencing
wear. Friction between internal components of the lift cylinder becomes
excessive due to not maximizing lubrication. Periodic Service (PS) plays an
important role in maintaining the performance of the unit, especially the
hydraulic system and oil. More than 50% of hydraulic system problems hydraulic
system are related to hydraulic oil (Doddannavar & Barnard, 2005) (Wen
& Chuan, 2014).
�The seal kit consists of a wear ring seal,
piston ring seal, o-ring, dust seal, and rod seal. The damage to these
components causes internal leakage in the lift cylinder, thus causing the lift
cylinder to be unable to maintain the hydraulic pressure required to maintain
the piston position. The mechanic made a part recommendation list to replace
the damaged components. The recommended part should fulfill the manufacturer
standard. The part number reference is shown in Figure 4 (D70 LE Lift Cylinder
Part Number, n.d.).
Figure 4. Part
number reference
Assembly
Assembly is the
process of assembling components into a ready-to-use form, returning to its
initial form. After the
hydraulic cylinder is assembled, it is then reinstalled on the bulldozer body
and blade. The hydraulic hoses and fittings also reconnected. This process is
done by following the manufacturer shop manual (Prabowo, 2008).
Figure 5. New wear
seal on cylinder piston
Performance Test
After
the installation is complete, a performance test is carried out on the repaired
components. The bulldozer engine is started and allowed to reach its working
temperature. Then, with
the bulldozer stationary, the operator raises the blade until it hangs above
the ground. This blade position is observed for approximately five minutes to
see if the blade still descends on its own, this test indicates whether the
internal leakage in the blade lift hydraulic cylinder is still occurring or
not. After the results of this first test are considered satisfactory, the
second test is conducted. The bulldozer is run forward and backward while
maintaining the blade in a floating position. During the bulldozer's travel
movement, the position of the blades is observed. If the blade remains in its
designated position, then it is known that the internal leakage has been
repaired. The result of the second test are also considered satisfactory, so
the troubleshooting process is considered complete.
Conclusion
The research findings indicate that
the low power in the lift cylinder is attributed to worn and damaged components
within the lift cylinder seal kit, leading to an internal leak and hydraulic
drift. The failing components include the wear ring seal, piston ring seal,
o-ring, dust seal, and rod seal, primarily affected by wear, tear, and age. To
address the low power issue, the recommended solution is the replacement of the
lift cylinder seal kit with a new set. The author expresses gratitude to the
Director of Politeknik Negeri Nunukan for their support in the paper's
development and acknowledges family and colleagues for their assistance in
completing the research.
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