1)
Understanding the system
2)
Safety procedures
3)
Planning Maintenance
4)
Prepare the site for maintenance
5)
Inspect and assess the system
6)
Fix the faults
7)
Check that system operates correctly
8)
Record information on work completed
Understanding the
system.
The principles of lubrication systems (How does it work?)
A lubrication system applies oil or grease to parts
of a machine to reduce friction between the parts and to keep them moving
smoothly. It keeps the machine in good working condition and reduces wear and
tear on the moving parts. Parts that needs lubrication are bushing slides,
bearings and gears.
Lubrication systems can be:
Manual – Works with a spot lubrication
gun and needs a person to operate it or
Automatic – This system is built into a
machine and work as part of the machine based on the requirements of the
machine. Although the work without an operator they still need to be
maintained.
A lubrication system consists of the following main
parts.
a.
A reservoir
or container to store the lubricant.
b.
A pump,
to force the lubricant through pipes to the parts that need to lubricated.
c.
A filter to
ensure that the lubricant is kept clean.
In addition to reducing friction, lubrication has the
following functions.
v
They prevent corrosion
v
They cover dirt and/or dust particles to prevent
the moving parts from seizing
v
They reduce the operating temperature by
reducing friction
v
They provide insulation in electrical systems
such as oil cooled transformers
v
They transmit power in hydraulic systems.
(hydraulic fluid, brake and clutch fluid)
The characteristics of a lubricant:
v
It will stay viscous (fluid) and will not become solid
v
It is not acidic
v
It is not abrasive
v
It keeps it film thickness
v
It is very slippery.
There are four main types of lubrication systems:
·
The gravity feed oil lubrication system
·
The grease lubrication system
·
The oil splash lubrication system
·
The forced oil and grease lubrication system.
The gravity feed oil lubrication system:
This system uses the force of gravity to feed the oil into
the system. This method is usually used in parts requiring a small amount of
oil. Two types of lubricators using this system are:
The siphon-wick
lubricator: This lubricator consist of a container filled with oil.
A pipe is positioned in the middle of the container ending above the level of
the oil. A wick is placed in the oil and fed down the pipe. The wick soaks up
the oil in the container and gravity makes it flow down the wick in the pipe
delivering it as drops at the end of the wick. The amount of oil delivered
depends on the thickness of the wick.
Sight-feed
lubricator: This lubricator is a container mounted on a metal base with a
hole in the center. The container has a metal cap fitted with a tapered needle
valve that extends to the hole at the bottom. A lever connected to the needle
lifts the needle when oil flow is needed and lowers the needle when no oil is
required.
The grease lubrication system:
This system is only used for plain bearings that carries
small loads at low speeds. There are three types of lubricators that use this
lubrication system:
The Stauffer grease
cup: This lubricator consist of a closed container filled with grease and
screwed down onto a base with a tapered hole in it. The grease is forced
through this hole onto the surface of the bearing.
The telltale grease
cup: This lubricator has a fluted upper container filled with grease. The
bottom part of the container narrows to a very thin pipe. The top part has a
spring-loaded piston that is smaller than the cup. This prevents the piston
from forcing all the grease from the cup. The piston forces the grease through
the narrow opening at the bottom of the cup onto the surface of the bearing.
The hand grease gun: The hand grease gun has a cylinder filled
with grease. A spring loaded piston connected to a handle provide mechanical
advantage to assist in forcing the grease through a bendable pipe into a grease
nipple. The grease nipple is positioned on the bearing surface where the grease
is then delivered. Modern grease pumps works with rechargeable batteries.
The splash lubrication system:
this system is designed into the machine when it is
manufactured. It consist of a reservoir or sump, filled with oil or lubricant
through which one or more of the moving parts will operate. As these parts move
through the lubricant, pick up the lubricant and splashes it onto the rest of
the parts. There are two types of splash systems in operation:
The scoop system
used in machines that run at high revolutions. The scoop picks up the oil and
splashes it onto the parts.
The ring oiler system
used in machines that run at low revolutions has an oil ring that dips into the
oil and scoops it up to lubricate the applicable parts.
The forced lubrication system:
This system uses a pump to deliver the lubricant (mostly
oil) under pressure onto the part(s) that need it. The oil is drawn from the sump through a filter and discharged through
pipes and channels to be delivered onto the parts that need lubrication. This
system forms part of the machine and is fully automatic. It starts when the
machine starts and stop when the machine stops.
The correct sequence of activities to follow:
Step 1.
Study and understand the instructions and
information on the job card, previous reports and engineering drawings to
determine the service history of the lubrication system.
Step 2.
Study the records and manufacturers manual to
determine the correct lubricants to be used.
Step 3.
Find out which filtration parts you need to use.
Step 4.
Identify the tools and equipment you will need
to complete the maintenance.
Step 5.
Check the worksite and make sure it is safe to
work in.
Step 6.
Isolate the equipment and make sure that the
system is safe to work on.
Step 7.
Inspect the lubrication system while in
operation.
Step 8.
Diagnose the system faults.
Step 9.
Identify the parts to be serviced and the parts
to be replaced.
Step 10.
Remove the parts and service or replace them.
Step 11.
Fit the serviced and replaced parts.
Step 12.
Select the testing tools and equipment.
Step 13.
Run a full operational test to check that the
system is working properly and without leaks.
Step 14.
Write a report on your work.
The implications of not following this sequence of
activities:
Ø
You will contaminate the workshop floor with oil
if you do not drain the oil from the system first.
Ø
You will damage the lubrication system and the
machine if you use the wrong lubricant.
Ø
You will waste time if you realise halfway
through the job that you don’t have the right tools, equipment or spares to
continue.
Ø
You will damage parts, have breakdowns or cause
leaks if you fit the parts in the wrong order.
Ø
You will get an electrical shock if you haven’t
isolated the equipment before you start working on it.
Safety procedures.
Safety in the workshop is very important. Failing to comply
to safety measures can lead to injury or even death to yourself or someone
else.
Safety rules to follow while working on lubrication
systems:
o
Check that the machine you are working on is
disconnected from the power supply or you will get an electrical shock.
o
Use a lock-out device to make sure the machine
can’t be switched on while you are working on it.
o
If you get oil or grease into an open wound, get
medical treatment immediately or the wound may become infected.
o
Drums containing oil and grease are very heavy.
Get someone to help you move it in the workshop. If you drop a drum it can crack
or burst, spilling oil or grease all over the floor. People may slip on the oil
or grease and hurt themselves.
o
Never add lubricants in a machine that is still
running.
o
Never reach over, under, through or around
moving parts of machinery.
o
Don’t remove any protective guards from moving
parts of the machine, like open gears or couplings, until the machine is
isolated and disconnected. Make sure you replace the guards as soon as you have
finished the job.
o
Wear rubber gloves while working with grease and
solvents to prevent yor skin from becoming irritated.
o
Never smoke around any petroleum products, and
handle them with care as they can catch fire.
o
Dispose of any leftover solvents and waste rags
soaked with this liquid in the special hazardous waste material containers
provided in the workshop.
o
Dispose of the lubricants that you removed from
during maintenance in the special hazardous waste material containers in the
worksite, as they are harmful to people, animals and the environment.
Planning Maintenance.
Obtain the following documents to investigate the service
history and obtain details about lubricants.
o
The job card
o
The maintenance schedule
o
The manufacturer’s manuals for the machine
o
The reports on all work done to the machine
o
The engineering drawings
The job card: You will get the job card from your
supervisor. The job card will tell you if it’s a scheduled maintenance job or
if there is a problem on the machine that needs repairing. It will also include
information like the name and number of the machine.
The maintenance schedule: this is a schedule that
describes all the inspections, tests, service details and repair or replacement
work that needs to be done on the specific machine or specific parts of the
machine. This will help you to plan the work. You need to complete all the
tasks on the schedule and your supervisor will sign the schedule after the work
is complete.
The manufacturer’s
manual: This will give you specific information on the type of lubrication
to use, as well as any important maintenance you need to know about the
lubrication system. It will also contain technical specifications about
settings, tolerances and performance requirements you need to know.
The reports on all work done to the machine: This is
a complete history of all work done on the machine. This will tell you how
often the system has been serviced and when the filters have been replaced.
Other problems related to the lubrication system like;
§
Bearings overheating
§
Leaking seals
§
Couplings changing color
can all indicate problems with the lubrication system. It
will also tell you about all the lubricants used in the past and problems
experienced with specific lubricants.
The engineering drawings: These detailed drawings
show all the parts, their sizes, as well as how they fit together. It will also
indicate all the lubrication points on the machine. Find the position of the
lubrication system and you will see which parts you must remove to get to the
lubrication system.
Additional information on the nameplate (also called a
data plate) of a machine: The following information are required for
nameplates and will help you choose the correct lubricant. Lubricants are
designed to work under specific conditions like pressure, load and temperatures
and you need to confirm the details on the nameplate with the information of
the manufacturer’s manual, as the manufacturer will specify the lubricant to
use on the machine.
Ø
The manufacturers name, model and serial number
Ø
The rated voltage and full load amperage
Ø
The rated electrical frequency
Ø
The phase
Ø
The rated full load speed
Ø
The rated temperature rise or insulation class
and ambient temperature
Ø
The duty rating
Ø
The rated horsepower
Ø
The design code letter.
Different types of lubricants:
We will look at oil, grease and a material called
self-lubricating thermoplastics.
Oil – The four
categories of oil are
Animal oil: - examples- lard, sperm oil and tallow. Animal oils are
much better than mineral oils with regard to the pressure they can stand but
unfortunately they are expensive and turn to sludge easily.
Vegetable oil: - examples- castor oil, palm oil, olive oil and
linseed oil.
Mineral oil: - found under the earth’s service in the form of crude
petroleum. It keeps its properties well in air and if it is pure, it do not get
sticky or dry up. This properties makes mineral oil an ideal, all-purpose
lubricant to use in all systems.
Synthetic oil: - made using a chemical process to change carbon
dioxide, carbon monoxide and methane into oil. Synthetic oil is always a better
option than conventional oil in the following situations:
·
In high temperatures, conventional oil becomes
thin and tents to leak, while synthetic oil remains at the right grade of
viscosity.
·
In low temperatures, conventional oil becomes
thick while synthetic oil remains at the right grade of viscosity.
·
For engines and machines that run at high
revolutions, synthetic oil causes them to run more quietly at all speeds than
conventional oil does.
·
In outdoor conditions, synthetic oil is the
better choice because of its stability over a wide temperature range.
A thin, light lubricant like oil is chiefly used in in
machines that operate at high speeds and with light loads.
Grease – A common
lubricant used on slow-moving machinery parts such as bearings, bushes and hinges. It consist of a
combination of a lubricating agent, and additives like graphite and a thickener
(made of substance like copper or non-metallic substance like graphite, lithium
or Teflon.)
Conventional greases use a petroleum-based product like
mineral oil as base.
Synthetic greases
use a synthetic lubricant made of plant oils. This ingredients mean that
synthetic greases can cope with much wider temperature extremes than
conventional greases. Synthetic greases is a better choice than conventional
greases in the following applications:
·
In high temperatures, conventional grease soften
and leaks, while synthetic grease remains more stable.
·
In low temperatures, conventional grease becomes
thick while synthetic grease remains more pliable.
·
For high speeds, synthetic grease is quieter at
high speeds than conventional grease.
·
In outdoor conditions, synthetic grease is the
better choice because of its stability over a wide temperature range.
Self-lubricating
thermoplastics – This is a type of plastic material that has a lubricant
already build into it. This has been developed to overcome the problem of oil
and grease building up dirt and grit over time which is what a lubricant
actually try to prevent. Parts made from thermoplastic are not affected by this
problem because they don’t need oil or grease lubricant, they are able to
resist friction and, therefore, wear extremely well.
Self-lubricating thermoplastics components are starting to
replace metal and ceramics parts because they have the following advantages:
·
The parts can be assembled easily
·
The parts are easy to manufacture
·
The parts are flexible with regard to design
·
The parts are very reliable because they do not
deteriorate quickly
·
The parts can operate at very high performance
levels at high or low speeds, and with high and low fixed loads.
However, thermoplastic material has the following
disadvantages:
·
They are expensive
·
Thermoplastics bushes or bearings cannot carry
heavy axial loads.
Identify the filtration components to be used:
The lubrication system will have a filter to prevent dirt
from getting into the pumped oil. This filter will be accessible from the
outside of the machine for easy replacement and will come with a seal to prevent
leakage of lubricant, and damp from entering the system. You will need to
identify the component so you can order a replacement part before you remove
the used filter. The manufacturers manual will provide you with the information
to order the correct part.
Identify the correct tools and equipment for the job:
Once you identified the machine you can draw up a list of
tool and equipment that you are going to use. Don’t forget to include the
safety equipment you may need. Some of the common tools and equipment you may
need for maintenance on a lubrication system may include:
·
A complete set of ring and flat spanners
·
An oil filter wrench
·
A complete set of screwdrivers
·
A complete set of Allan keys
·
Cleaning materials like waste rags
·
A container into which you can drain the used
oil.
Prepare the site for
maintenance.
Make sure the worksite is safe to work in, taking into
account the type of machine you are going to work on. (Heavy, electrical,
hydraulic, etc.)
Identify the type of lubricating system.
If the machine has a filter and a sump, then it uses an oil
lubrication system. (high speed machine)
If the machine has a grease nipple, then it uses a grease
lubrication system. (slow speed machine)
Prepare the work site so that it is safe:
Make sure the work site is clean and there is no water or oil
on the floor. Check that all the necessary safety signs are visible and the
personal protective gear needed for the job is checked and ready for use.
Select the correct tools and equipment and make sure you
know how to operate them safely.
Use the right lubricants and fluids or solvents for each
part making sure you wear protective gloves.
Isolate the system:
·
Switch off the machine and install a lock-out
device
·
Put up a safety sign to show that you are
working on the machine.
·
Isolate the machine you work on mechanically
according to the machine type.
Inspect and assess
the system.
·
Hold a screwdriver against the machine near the
bearings and listen for any strange noises or vibrations
·
Hold a thermometer against the machine to see if
the temperature runs to high
·
Check to see if the coupling have changed colour
or if the seals are leaking
·
Check through the sight glass if the lubricant
changed colour and if so take some oil samples
·
Test the
oil to see if it contains any water. Do so by pouring some in a glass container
and wait for a while. The water will sink to the bottom.
·
Put a couple of drops of oil on blotting paper.
If a star pattern or rings appear, the oil is contaminated or dirty
·
Check for thickness changes and service deposits
on the oil
·
Check the filters to see if they are blocked
System faults and possible causes:
Symptom
|
Possible
causes
|
The machine produces strange noises or vibrations.
|
Damage parts, for example the bearings or couplings, or loose parts
|
The temperature of the machine is to high.
|
Incorrect lubricants
|
Lubricants that have broken down chemically
|
Dirty lubricants
|
Abnormal friction or wear
|
The coupling change colour to blue or the seals leak.
|
Problems with the lubrication, causing a coupling to overheat
|
The colour of the oil has become darker
|
Oil has overheated
|
Dirt and impurities in the oil
|
Wrong lubricant has been used
|
Ongoing foam forms at the top of the oil.
|
Oil is dirty or contaminated
|
The oil separates.
|
The oil is contaminated with water
|
The oil shows the star burst or rigs during the blotting paper test.
|
Oil is dirty or contaminated. (clean oil forms a uniform oil colour
on the paper)
|
The viscosity or thickness changes in the oil, and service deposits.
|
May indicate an oil pressure problem
|
Filters are blocked.
|
May indicate the presence of soft contaminants like sludge and
organic material
|
Fix the faults.
Identify parts to be serviced or replaced:
Based on the results of your research you are now ready to
draw up a list of parts that need to be replaced and serviced. For instance:
you need to replace the seals, the filter and the oil. If the couplings changed
colour you need to replace them as well and depending on the condition of the bearings
you need to either replace or service them.
Remove, service and replace serviceable and new parts:
You should drain the oil at operating temperature because it
will flow more quickly. Replace any seals that are worn or damaged. Look for
loose clamps, worn or cracked pipes and leaking seals and replace any damaged
parts. Remove the old oil filter. Make sure that you do not burn your hands
with too hot oil. Replace the old filter with a new one. Put some oil on the
filter seal before you replace it to make sure of a good fit. Fit the drain
plug with a new washer and replace the plug. Once the plug is in place you can
fill up the reservoir with the right grade and quantity oil through the filler
hole.
If the lubrication system has an oil pressure sensor, check
the oil pressure when you restart the engine. If the oil pressure is too low,
make sure that you used the correct grade and amount of oil. If the type and
amount of oil is correct, check the lubrication system or the oil pump system
for possible leaks.
Check that system
operates correctly.
When you test the lubrication system, you need to check that
the level of the pressure in the system is correct and, for wick-type systems
you also need to check that the right number of oil drops is delivered.
Check the pressure level in a lubrication system:
Step 1.
Check the manufacturer’s manual to find out the
correct pressure at which the lubricating system must operate.
Step 2.
Connect the pressure gauge to the pipes in the
lubrication system that you are about to test.
Step 3.
Start the engine and let it run until it reach
the right operating temperature, as stated in the manufacturer’s manual.
Step 4.
Take a reading on the pressure gauge that you
have connected.
Step 5.
Check the fluctuations in pressure because any
fluctuations greater than specified in the manufacturer’s manual mean that the
lubrication system is faulty.
Record information on
work completed.
After the maintenance work on the lubrication system is
finished you must write a report on the work you have carried out. You need to include
the following information in your report:
·
The date you serviced the lubrication system
·
The procedure that you followed
·
The type of lubrication system you worked on
·
The different parts that you replaced
·
Your opinion about why these parts failed, for
example operator’s negligence
·
The type and amount of fluids and lubricants
that you used
·
Any defects relating to the specific machine
·
The results of all the tests you carried out.
Store the information in a safe place.
