Maintenance Lectures

1. Preventive Maintenance Elements

2. Preventive Maintenance Elements
1 Inspection:
Periodically inspecting materials/items to determine their
serviceability by comparing their physical, electrical,
mechanical, etc., characteristics (as applicable) to expected
standards
2. Servicing:
Cleaning, lubricating, charging, preservation, etc., of items/
materials periodically to prevent the occurrence of incipient
failures

3. Preventive Maintenance Elements
3. Calibration:
Periodically determining the value of characteristics of an
item by comparison to a standard; it consists of the
comparison of two instruments, one of which is certified
standard with known accuracy, to detect and adjust any
discrepancy in the accuracy of the material/parameter being
compared to the established standard value
4.Testing:
Periodically testing or checking out to determine serviceability
and detect electrical/mechanical-related degradation

4. Preventive Maintenance Elements
3. Calibration:
Periodically determining the value of characteristics of an
item by comparison to a standard; it consists of the
comparison of two instruments, one of which is certified
standard with known accuracy, to detect and adjust any
discrepancy in the accuracy of the material/parameter being
compared to the established standard value
4.Testing:
Periodically testing or checking out to determine serviceability
and detect electrical/mechanical-related degradation

5. Preventive Maintenance Elements
5.Alignment:
Making changes to an item’s specified variable elements for
the purpose of achieving optimum performance
6.Adjustment:
Periodically adjusting specified variable elements of
material for the purpose of achieving the optimum
system performance
7.Installation:
Periodic replacement of limited-life items or the items
experiencing time cycle or wear degradation, to maintain
the specified system tolerance

6. Corrective Maintenance Elements

7. Corrective Maintenance Elements
1. Fail-repair:
The failed item is restored to its operational state.
2. Salvage:
This element of corrective maintenance is concerned with disposal
of non-repairable material and use of salvaged material from non-repairable
equipment/item in the repair, overhaul, or rebuild programs.
3. Rebuild:
This is concerned with restoring an item to a standard as close as possible to
original state in performance, life expectancy, and appearance.
This is achieved through complete disassembly, examination of all
components, repair and replacement of worn/unserviceable parts as per
original specifications and manufacturing tolerances, and reassembly and
testing to original production guidelines.

8. Corrective Maintenance Elements
4.Overhaul:
Restoring an item to its total serviceable state as per maintenance
serviceability standards, using the “inspect and repair only as
appropriate approach”.
5. Servicing:
Servicing may be needed because of the corrective maintenance
action, for example, engine repair can lead to crankcase refill,
welding on, etc. Another example could be that the replacement
of an air bottle may require system recharging.

9. Maintenance Tasks
Explanations of the terms used in the possible tasks are as follows:
• Lubrication/servicing (all categories)—this involve any act of
lubricating or servicing for maintaining inherent design
capabilities.
• Operational/visual/automated check (hidden functional
failure categories only)— an operational check is a task to
determine that an item is fulfilling its intended purpose. It does not require
quantitative checks and is a failure-finding task. A visual check is an
observation to determine that an
item is fulfilling its intended purpose and does not require
quantitative tolerances. This, again, is a failure-finding task. The
visual check could also involve interrogating electronic units that
store failure data.
•

10. Maintenance Tasks
• Inspection/functional check/condition monitoring (all
categories)—an inspection is an examination of an item against a
specific standard. A functional check is a quantitative check to determine
if one or more functions of an item perform within
specified limits. Condition monitoring is a task,
which may be continuous or periodic to monitor the condition
of an item in operation against preset parameters.

11. Maintenance Tasks
• Restoration (all categories)—restoration is the work necessary
to return the item to a specific standard. Since restoration may
vary from cleaning or replacement of single parts up to a
complete overhaul, the scope of each assigned restoration task
has to be specified.
• Discard (all categories)—discard is the removal from service of
an item at a specified life limit.
Discard tasks are normally applied to so-called single-cell parts
such as cartridges, containers, cylinders, turbine disks, safe-life
structural members, and the like.

12. Maintenance Procedure
 All frequent repairs and maintenance tasks should have a
standard procedure that will specifically define the correct
method required for competition.
 These procedures should include all of the information,
such as: tools, safety concerns, and repair parts, required for
the task and a step-by-step sequence of tasks required to
complete the repair.

13. Maintenance Procedure
 Each procedure should be complete and contain
all information required to complete the repair
or recurring preventive maintenance task.
 The craftsperson should not be required to find
or have supplemental information in order to
complete the repair.

14. Maintenance Procedure
A complete evaluation of the Standard Maintenance
Procedures (SMPs) and actual practices should be conducted.
The procedures should be compared with maintenance
requirements defined by both the design review and the
vendor’s O&M manuals.
Actual maintenance practices can be by visual
observation of similar repairs.

15. Maintenance Procedure
This task should determine if all maintenance personnel
assigned to or involved with the area that is being
investigated consistently follow the SMPs.
Special attention should be given to the routine tasks, such
as lubrication, adjustments, and other preventive tasks.
Determine if these procedures are being performed in a
timely manner and if proper techniques are being used.

16. Maintenance Procedures
Following are the Basic Maintenance procedures.
 Inspection
 Lubrication
 Measuring Operating Temperatures
 Maintenance tools

17. Inspection
Inspection: The qualitative observation of an item’s
performance or condition.
Regular visual inspection of the machinery and systems in
a plant is a necessary part of any predictive maintenance
program.
In many cases, visual inspection will detect potential
problems that will be missed using the other predictive
maintenance techniques.
Routine visual inspection of all critical plant systems will
add to the other techniques and ensure that potential
problems are detected before serious damage can occur.

19. Inspection
 Most of the vibration-based predictive maintenance systems
include the capability of recording visual observations as part
of the routine data-acquisition process.
 Since the incremental costs of these visual observations are
small, this technique should be incorporated in all predictive
maintenance programs.
 All equipment and systems in the plant should be visually
inspected on a regular basis. The additional information
provided by visual inspection will augment the predictive

20. Inspection
Continuous inspection by plant personnel is necessary to
detect and correct mechanical defects or conditions
which prevent efficient operation.
The following must be checked on a continuing basis.
(1) Each machine has a characteristic operating sound or
appearance. A change from this normal sound or
appearance requires the supervisor's immediate
attention.

21. Inspection
(2) Vibration is evidence of basic faults which should be
corrected. Loose bearings may be either the cause or
the result of vibration. Report all unusual vibration to
the supervisor.
(3) Cleanliness is essential for trouble-free performance of
mechanical and electrical equipment. moisture, dirt, and
oil cause deterioration of equipment systems.

22. Inspection
(4) Conditions which cause excess heat must be eliminated.
(5) Couplings should be checked for misalignment. In cases
of mechanical troubles, always check alignment.
Misalignment may result in overheated and worn
bearings or cause stresses which result in failure of the
motor shaft.

23. Inspection
(6) Electrical overload shortens the life of a motor and
contributes to unreliable performance. Motors are designed
for greater mechanical overloads than electrical overloads.
The motor shaft, frame, and bearings can stand several
times the rated load for long periods of time, but wiring
will overheat when overloads as low as 15 to 25 percent are
imposed continuously. Electrical overloads increase the
temperature of the windings. The allowable temperature
rise is usually stamped on the nameplate.

24. Lubrication
 Lubrication is an important part of preventive
maintenance. Proper lubrication prevents damage to
wearing surfaces, reduces the maintenance required, and
cuts power costs and equipment outages.
 Contaminants in lubricants produce wear and assist in
the ultimate failure of the
 lubricated equipment.
(1) Use of the proper type of lubricant for the application
is critical to successful maintenance results.
(2) Equipment manufacturer's detailed instructions should
be consulted in all cases to ensure that the proper
lubricant is being used.

25. Lubrication
(2) In order to avoid plant failures due to improper
lubrication, the following lubricating
precautions should be observed.
(a) Do not over lubricate. Over lubrication causes
antifriction bearings to heat and may damage
grease seals; it may also cause damage to the
windings in electrical motors.
(b) Do not lubricate totally enclosed or
insufficiently guarded equipment.

26. Lubrication
(c) Keep lubricant containers tightly closed, except
when in use, to prevent contamination of he
lubricant by the entrance of dust, grit, abrasives, and
moisture.
Lubricants should be stored in dust free areas. Before
using lubricant containers, the spouts and lips should
be wiped; before using grease guns, the gun and
fitting should be wiped to ensure the absence of
foreign matter.
(3) The principal deteriorating elements in oil are dirt,
water, oxidation, and excessive heat. If these are
controlled, oil deterioration between lubrication
periods is unlikely.

27. Measuring operating temperatures.
 Equipment cannot be maintained properly, unless limits of safe
operating temperatures are known.
 Safe upper limits of operating temperatures are given by manufacturers
and can be obtained on request.
 Use of touch to determine whether operating temperatures are under
these maximum limits is unreliable, especially when operating
temperatures are above 125°F.

28. Measuring operating temperatures.
One of the following temperature measuring devices should be used
instead.
(1) A hand type portable pyrometer, if available in the range required,
provides a satisfactory method for measuring external surface
temperatures of mechanical equipment.
(2) An ordinary mercury thermometer without a guard is satisfactory for
measuring external surface or bearing temperatures. It should be
calibrated for the range of use.

29. Measuring operating temperatures.
Details of the use of a thermometer in each of these applications are
as follows.
(a) To measure surface temperature, fasten the thermometer to the
surface with adhesive tape with the bulb touching the surface.
Read only after indicated temperature has reached a constant
value.
(b) To measure bearing temperatures, insert the bare thermometer
bulb inside the inspection hole at the top of the bearing. Fit
cardboard around the thermometer to cover the inspection hole.
Read after a constant value has been reached.