MAINTENANCE
ENGINEERING
Engr. Muhammad Sajid
Lecturer
Department of Chemical Engineering

• MAINTENANCE
• SAFETY
Note: Some data/images in this presentation is takes from different books and internet and is
only used for educational purposes. Credit goes to original authors only.

MAINTENANCE ENGINEERING
MAINTENANCE
 The act of maintaining or the state of being maintained.
 The work of keeping something in proper condition; upkeep.
 care or upkeep, as of machinery or property: With proper mai
ntenance the carWILL last for many years.
 Any activity – such as tests, measurements, replacements,
adjustments and repairs — intended to retain or restore
a functional unit in or to a specified state in which the unit
can perform its required functions.
 For material — all action taken to retain material in a
serviceable condition or to restore it to serviceability. It
includes inspection, testing, servicing, classification as to
serviceability, repair, rebuilding, and reclamation.

MAINTENANCE ENGINEERING (Cont.)
 All actions necessary for retaining an item, or restoring
to it, a serviceable condition, include servicing, repair,
modification, overhaul, inspection and condition
verification
 Increase availability of a system
 Keep system’s equipment in working order
 Maintenance is a set of organised activities that are
carried out in order to keep an item in its best
operational condition with minimum cost acquired.

PURPOSE OF MAINTENANCE
 To keep equipment/system operative.
 Attempt to maximize performance of
production equipment efficiently and regularly
 Prevent breakdown or failures
 Minimize production loss from failures
 Increase reliability of the operating systems
 To keep operation safe
 To prevent leakages/losses

OBJECTIVES IN MAINTENANCE
 To achieve product quality and customer
satisfaction through adjusted and serviced
equipment
 Maximize useful life of equipment
 Keep equipment safe and prevent safety
hazards
 Minimize frequency and severity of
interruptions
 Maximize production capacity – through
high utilization of facility

PROBLEMS IN MAINTENANCE
 Lack of management attention to maintenance
 Little participation by accounting in analyzing
and reporting costs
 Difficulties in applying quantitative analysis
 Difficulties in obtaining time and cost estimates
for maintenance works
 Difficulties in measuring performance
 Production load
 Continuous operation
 Unskilled staff

CAUSES OF PROBLEMS IN
MAINTENANCE
 Failure to develop written objectives and policy
 Inadequate budgetary control
 Inadequate control procedures for work order,
service requests etc.
 Infrequent use of standards
 To control maintenance work
 Absence of cost reports to aid maintenance
planning and control system
 Unavailability of spares

MAINTENANCE OBJECTIVES
 Must be consistent with the goals of
production (cost, quality, delivery, safety)
 Must be comprehensive and include
specific responsibilities

Maintenance Objectives
PLANT
M
A
I
N
T
E
N
A
N
C
E
Reduce Breakdowns
Reduce Downtime
Improving Equipment
Efficiency
Improving Inventory
Control
Implementing Cost
Reduction
Maximising Production
Optimising Resources
Utilisation
Optimising Useful Life
of Equipment
Minimising Energy
Usage
Providing Budgetary
Control
Figure 2.3 Maintenance Objectives

MAINTENANCE COSTS
 Cost to replace or repair
 Labor/Labour cost
 Losses of output
 Delayed shipment
 Scrap and rework
 Safety measurements

Question?
 Why do we need maintenance?
 What are the costs of doing maintenance?
 What are the costs of not doing
maintenance?
 What are the benefits of maintenance?
 How can maintenance increase profitability
of company?

MRO
MAINTENANCE, REPAIR & OVERHAUL/OPERATIONS (MRO)
All actions which have the objective of retaining or restoring an item in or
to a state in which it can perform its REQUIRED FUNCTION. The
actions include the combination of all technical and corresponding
administrative, managerial, and supervision actions."

TYPES OF MAINTENANCE
 Generally maintenance is classified into four categories:
 Preventive maintenance
 Corrective or Breakdown maintenance
 Scheduled maintenance
 Predictive (Condition-based) maintenance
(some authors prefer three categories- scheduled and preventive
maintenances are merged)

TYPES OF MAINTENANCE (Cont.)
There are also some other types of
maintenance; i.e.
 Operational Maintenance
 Reliability Centered Maintenance
 Improvement Maintenance (IM)

Types of Maintenance (Cont.)
MAINTENANCE
UNPLANNED
MAINTENANC
E (REACTIVE)
BREAKDOWN
EMERGENCY
PLANNED
MAINTENANC
E (PROACTIVE)
CORRECTIVE
MAINTENANC
E
REMEDIAL
DEFERRED
PREDECTIVE
MAINTENANC
E
CONDITION -
BASED
STATISTICAL
- BASED
PREVENTIVE
MAINTENANC
E
ROUTINE
RUNNIN
G
DESIGN -
OUT
ENGINEERING
SERVICES
WINDO
W
IMPROVEMENT
MAINTENANCE
SHUTDOWN
CORRECTIVE
SHUTDOWN
PREVENTIVE
SHUTDOWN
IMPROVEMENT
Shutdown Maintenance
OPPORTU
-NITY

PREVENTIVE MAINTENANCE
 Principle – “Prevention is better than cure”
 Procedure - Stitch-in-time
 Preventive maintenance is maintenance performed in an attempt to
avoid failures, unnecessary production loss and safety violations. where
equipment is maintained before break down occurs. This type of
maintenance has many different variations and is subject of various
researches to determine best and most efficient way to maintain
equipment. Recent studies have shown that Preventive maintenance is
effective in preventing age related failures of the equipment. For
random failure patterns which amount to 80% of the failure patterns,
condition monitoring proves to be effective.
 It
◦ Locates weak spots of machinery and equipments
◦ Provides them periodic/scheduled inspections and minor
repairs to reduce the danger of unanticipated breakdowns

ADVANTAGES OF PM
 Reduces break down and thereby down time
 Less odd-time repair and reduces over time of crews
 Greater safety of workers
 Lower maintenance and repair costs
 Less stand-by equipments and spare parts
 Better product quality and fewer reworks and scraps
 Increases plant life
 Increases chances to get production incentive bonus

CORRECTIVE or BREAKDOWN
MAINTENANCE
 Corrective or Breakdown maintenance implies that
repairs are made after the equipment is failed and can
not perform its normal function anymore
 Corrective maintenance can be defined as the
maintenance which is required when an item has
failed or worn out, to bring it back to working order.
Corrective maintenance is carried out on all items
where the consequences of failure or wearing out are
not significant and the cost of this maintenance is
much greater than PREVENTIVE MAINTENANCE.

CORRECTIVE or BREAKDOWN
MAINTENANCE (Cont.)
 Quite justified in small factories where:
◦ Down times are non-critical and repair costs are
less than other type of maintenance
◦ Financial justification for scheduling are not felt

DISADVANTAGES OF CORRECTIVE MAINTENANCE
 Breakdown generally occurs inappropriate times
leading to poor and hurried maintenance
 Excessive delay in production & reduces output
 Faster plant deterioration
 Increases chances of accidents and less safety for
both workers and machines
 More spoilt materials
 Direct loss of profit
 Can not be employed for equipments regulated
by statutory provisions e.g. cranes, lift and hoists
etc

SCHEDULED MAINTENANCE
 Scheduled maintenance is a stitch-in-time
procedure and incorporates
◦ inspection
◦ lubrication
◦ repair and overhaul of equipments
 If neglected can result in breakdown
 Generally followed for:
◦ overhauling of machines
◦ changing of heavy equipment oils
◦ cleaning of water and other tanks etc.

PREDICTIVE (CONDITION-BASED)
MAINTENANCE
 In predictive maintenance, machinery conditions
are periodically monitored and this enables the
maintenance crews to take timely actions,
such as machine adjustment, repair or overhaul
 It makes use of human sense and other sensitive
instruments, such as
◦ audio gauge, vibration analyzer, amplitude meter,
pressure, temperature and resistance strain gauges
etc.

PREDICTIVE MAINTENANCE (CONTD.)
 Unusual sounds coming out of a rotating
equipment predicts a trouble
 An excessively hot electric cable predicts
a trouble
 Simple hand touch can point out many
unusual equipment conditions and thus
predicts a trouble

MAINTENANCE COSTS
Maintenance
Commitment
Cost
Breakdown Cost

MAINTENANCE COSTS
Maintenance
Commitment
Cost
PM Cost
Breakdown Cost

MAINTENANCE COSTS
Maintenance
Commitment
Cost
PM Cost
Breakdown Cost
Total Maintenance Cost

MAINTENANCE COSTS
Maintenance
Commitment
Cost
PM Cost
Total Maintenance Cost
Breakdown Cost
Optimal

OPERATIONAL MAINTENANCE
 Where equipment is maintained in OPERATING CONDITION.
 Operational maintenance is the program focused on the regular
task that will maintain all the critical machinery and the system in
optimum operating conditions. The major objectives of the
program are to
1.Eliminating breakdown
2.Eliminating deviation
3.Eliminating unnecessary repairs
4.Optimize all the critical planned system

RELIABILITY CENTERED MAINTENANCE
 It is a process to ensure that assets continue to do what their users
require in their present operating context.
 It is generally used to achieve improvements in fields such as the
establishment of safe minimum levels of maintenance, changes to
operating procedures and strategies and the establishment of capital
maintenance regimes and plans. Successful implementation of RCM
will lead to increase in cost effectiveness, machine uptime, and a
greater understanding of the level of risk that the organization is
managing.

RELIABILITY CENTERED
MAINTENANCE (Cont.)
 It regards maintenance as the means to maintain the
functions a user may require of machinery in a defined
operating context.As a discipline it enables machinery
stakeholders to monitor, assess, predict and generally
understand the working of their physical assets.This is
embodied in the initial part of the RCM process which
is to identify the operating context of the machinery,
and write a Failure Mode Effects and Criticality Analysis
(FMECA).The second part of the analysis is to apply the
"RCM logic", which helps determine the appropriate
maintenance tasks for the identified failure modes in the
FMECA.

DETERMININGTHE SIZE OF
REPAIR CREWS
 Problem:
 A factory has 200 machines and the
maintenance engineer supervises the repair
crews who repair malfunctioning machines.
The maintenance policy is to repair the
broken down machine and bring back in
production within 2 hours on the average. If
average breakdown rate is 3.5
machines/hour and each repair crew can
repair 0.25 machine per hour on the
average. How many repair crews are
required ?

SOLUTION
The formula for average repair rate () is
1
ts = ---------- or  =  + 1/ ts
 - 
Where  = repair rate
 = arrival rate of malfunctioning machines
ts = average time arrivals in the system
Required average repair rate
 = 3.5 + 1 / 2 = 4 machines / hour
No. of Crews =   machines/hour a crew can repair
= 4  0.25 = 16 repair crews required