Health and Safety at Work
1
Learning Outcomes
On completion of this module, student should be able to:
1. Explain the reasons for safety problems in maintenance
2. Explain the moral, social and economic (financial) reasons
for maintaining and promoting good standards health and
safety in the workplace
3. Explain the principle and practice of risk assessment
4. Explain the Principles and basic Hierarchy of control
5. Define PPE and list the most common PPE in workplace
Health and Safety at Work
2
Learning Outcomes
On completion of this module, student should be able to:
7. Define Permit-to-Work (PTW) and list the typical activities that
need PTW
8. Define Control Of Substances Hazardous to Health (COSHH)
and identify the control measures required under the COSHH
Regulations
Various reasons for safety problems in
maintenance
3
Various reasons for safety problems in
maintenance
4
Health and Safety Procedures
Some elements of a GOOD safety program

Management policy

Employee selection/placement

Employee orientation/training

Educational activities

Employee meetings

Inspections

Accident reporting

Safety responsibilities
Hazard and Risk definition
5
 Hazard:
Is anything that has the potential to cause harm, ill- health and
injury, damage to property, products or the environment; for
examples, electricity, chemicals, mechanical, non- mechanical.
 Risk:
The likelihood that a hazard will cause harm in combination
with the severity of injury, damage, or loss that might occur.
 Health:
The absence of disease or ill-health
 Safety:
The absence of risk of serious personal injury.
Reasons for managing health and safety
6
The three main reasons why an organisation has to
manage health and safety:
 The moral reason relates to the moral duty that one person has to
another. Many people are killed, injured or made sick by their work. This
is morally unacceptable and society expects good standards of health and
safety.
 The social (legal) reason relates to the framework of laws that govern
the conduct of businesses and organisations.
 The financial reason relates to the fact that accidents and ill-health cost
money. When an accident occurs there will be direct and indirect costs
associated with that event.
Risk assessment
7
Risk assessment definition:
is a formalised process of identifying hazards, evaluating risk and
then either eliminating or controlling that risk to an acceptable
level.
Activity
Workplace
Hazard
Maintenance
Risk
Control
5 Stages of risk assessment
8
Risk assessment can be described as a five stages:
1
2
3
4
5
 Identify the hazards
 Identify who can be harmed and how
 Evaluate the risks and decide on suitable precautions
 Record the significant findings and implement them
 Review assessment and update as necessary
Principles and basic Hierarchy of control
9
The control of risks is essential to secure and maintain a
healthy and safe workplace which complies with the relevant
legal requirements.
The general Hierarchy of control is:
1.
2.
3.
4.
5.
Elimination
Substitution / Reduce
CONTROL AT THE SOURCE
Engineering controls
Limits the hazard but doesn’t entirely remove it.
Administrative controls
Personal protective equipment
The Hierarchy of control is a concept used a great deal in health and safety
and can be defined as: a list of options in order of importance, effectiveness
or priority, written so that the most extreme and effective method of control
is at the top of the Hierarchy , with the least effective is at the bottom
Principles and basic Hierarchy of control
10
Hierarchy of Controls
Elimination/Substitution
Most Effective
Requires a physical
change to the
workplace
Requires worker
or employer to
do something
Requires
worker to
wear
something
Least Effective
Personal Protective Equipment (PPE)
11
PPE can be defined as an equipment or clothing that is worn by
workers that protect them from one or more risks to their safety
and health.
Engineering controls and safe systems of work must always be
considered first. Provide and ensure the use of PPE as a last
resort
There are many reasons for this, The most important limitations
are that PPE:
3/5




3Only
/ 5 protects the person wearing the equipment, not others nearby
Relies on people wearing the equipment at all times
Must be used properly
Must be replaced when it no longer offers the correct level of protection
This last point is particularly relevant when respiratory protection is used
Personal Protective Equipment (PPE)
12
The benefits of PPE are:
 It gives immediate protection to allow a job to continue while
engineering controls are put in place;
 In an emergency it can be the only practicable way of effecting
rescue or shutting down plant in hazardous atmospheres;
 it can be used to carry out work in confined spaces where
alternatives are impracticable. But it should never be used to
allow people to work in dangerous atmospheres, which are, for
example, enriched with oxygen or potentially explosive
 It is usually cheap
Personal Protective Equipment (PPE)
13
Control of LAST RESORT! PPE example

Gloves

Eye Protection

Hearing Protection

Respiratory Protection

Hard Helmet

Safety shoes

Safety Goggles
Permits-to-work (PTW)
14
Permits-to-work (PTW) system is a formal legal documents
introduced to control specific work activities on employer’s
premises which require formal approval from an authorized
manager.
Typical work-to- permits systems activities include:
1. Hot work: example welding or grinding operations
2. Cold work: example rolling, bending or drawing
3. Work on live electrical system: high voltage system
4. Confined spaces
5. Excavation work
A Hot Work permit is
usually essential except
in designated
areas.
Permits-to-Work (PTW)
15
There are five main sections to Permit-to-Work:
1. Issue: define the work and location, identifies the hazards and determine
the necessary safety precautions such as isolation of power and supplies,
PPE, atmospheric monitoring
2. Receipt: the signature of the authorized person issuing the permit and
the signature of competent worker who will do the work in hazardous area
3. Clearance / return to service: signature of the competent worker
stating that the area has been made safe (e.g. work completed)
4. Cancellation: signature of the authorized person stating that the
isolation have been removed and the area has been accepted back and
that the equipment can be started (known as Sign Off)
5. Extension: this section is included in some PTW in case there is any
overrun of the work, it allows the authorizing manager to grant an extension
to the timescale of the permit
PTW for Confined space entry
16
Control Of Substances Hazardous to
Health (COSHH)
17
What is COSHH?
Control Of Substances Hazardous to Health (COSHH) is the
law that requires employers to control substances that are
hazardous to health. You can prevent or reduce workers
exposure to hazardous substances by:








Finding out what the health hazards are
Deciding how to prevent harm to health (Risk Assessment)
Providing control measures to reduce harm to health
Making sure they are used
Keeping all control measures in good working order
Providing information, instruction and training for employees and others
Providing monitoring and health surveillance in appropriate cases
Planning for emergencies
Control Of Substances Hazardous to
Health (COSHH)
18
COSHH covers:
COSHH covers substances that are hazardous to health.
Substances can take many forms and include:









Chemicals
Products containing chemicals
Fumes
Dusts
Vapours
Mists
Nanotechnology
Gases and asphyxiating gases and
Biological agents (germs). If the packaging has any of the hazard
symbols then it is classed as a hazardous substance.
Control Of Substances Hazardous to
Health (COSHH)
19
A COSHH assessment is very similar to a risk assessment
but is applied specifically to hazardous substances.
Step 1. Gather information about the substances, the work and working
practices by identifying the hazardous substances present or likely to be
present in the workplace
Step 2. Evaluate the risks to health either individually or collectively
Step 3. Decide what needs to be done to control the exposure to hazardous
substances
Step 4. Record the assessment
Step 5. Review the assessment
Control Of Substances Hazardous to
Health (COSHH)
20
The control measures required under the COSHH
Regulations:
Measures for preventing or controlling exposure to hazardous substances
include one or a combination of the following:






Elimination of the substance
Substitution of the substance (or the reduction in the quantity used)
Total or partial enclosure of the process
Local exhaust ventilation
Dilution or general ventilation
Reduction of the number of employees exposed to a strict minimum
Reliability Engineering and Maintenance
21
Reliability Engineering and Maintenance
22
Learning Outcomes
On completion of this module, student should be able to:
1. Define reliability and explain the factors associated with it.
2. Explain the various techniques to obtain reliability
3. Explain the Reliability Properties for Systems
4. Determine mean time between failure (MTBF), Mean Time To
Failure (MTTF and Mean Time To Repair (MTTR)
5. Define availability and maintainability
Reliability Engineering and Maintenance
23
 Reliability
 Improving individual components
 Providing redundancy
 Maintenance
 Implementing or improving preventive
maintenance
 Increasing repair capability or speed
Reliability Management
24
Why is it needed?
 Reliable
operation of critical equipment
 Planning
 Improved
of maintenance activities
‘quality’ of an item
Reliability Management
25
Employee Involvement
Partnering with
maintenance personnel
Skill training
Reward system
Employee empowerment
Maintenance and
Reliability Procedures
Clean and lubricate
Monitor and adjust
Make minor repair
Keep computerized records
Results
Reduced inventory
Improved quality
Improved capacity
Reputation for quality
Continuous improvement
Reduced variability
Definition of Reliability
26

Reliability management is concerned with
performance and conformance over the expected
life of the equipment
Reliability definition:
“the probability that a product or a piece of equipment
performs its intended function for a stated period of
time under specified operation conditions’”

Reliability It is an important factor in equipment maintenance
because lower equipment reliability means higher
need for maintenance
Definition of Reliability
27

From the definition, There are five factors
associated with Reliability:

Probability (Numerical Value)

Time (Equipment’s life)

Performance

Intended function

Operating conditions / Environmental Conditions
Reliability Factors
28
1. Probability (Numerical Value)
A
value between 0 and 1
 Precise meaning
e.g. probability of 0.97 means that 97 of 100
items will still be working at stated time
under stated conditions
Reliability Factors
29
2. Time (equipment’s life)
How long the equipment is expected to last?
 Means Reliability is quality over time.
 A machine that “works” for a long period of time is
a reliable one.
 Since all equipment / machines / parts will fail at
different times, reliability is a probability.
Reliability Factors
30
3. Performance

Some criterion to define when equipment has failed
e.g. bearing clearances in an engine or amount
of emissions from a car
Reliability Factors
31
4. Intended Function
Equipment are designed for particular applications and
are expected to be able to perform those applications.
Reliability Factors
32
5. Operating conditions / Environmental Conditions
These describe the operating conditions that correspond to
the stated equipment life.
e.g. for a car engine this might mean
 Speed
 Loading
 Effects of an expected amount of
misuse such as over-revving and stalling.

Indoors, outdoors and storage.
System Reliability
33

As equipment become more complex (have more
components), the chance that they will not function increases.

The method of arranging the components affects the reliability
of the entire system.

Examples of tools and techniques used for analyzing failures
are:
Reliability Block Diagram (RBD)
 Fault Tree Analysis (FTA)

System Reliability
34

Reliability Block Diagram

Components can be arranged in a system as:
1. Series (system will work if all components work)
2. Parallel (system will work if one component work) or
3. Combination (series-parallel system)
Series System
35
 For a series systems, the reliability is the product of the
individual components.
1
2
n
The block diagram of an n-unit series system.
Series System
36
RS = R1 x R2 ... Rn,
Where:
RS = series system reliability,
n = number of units,
Ri = reliability of unit or block i shown in the figure, for i = 1, 2,
3,…, n.
 As components are added to the series, the system
reliability decreases.
Example:
battery
Parallel System
37
1
2
n
The block diagram of an n-unit parallel system.
Rs = 1 - (1 - R1) (1 - R2)... (1 - Rn)
Where:
Rs = parallel system reliability,
n = total number of units,
Ri = reliability of unit i, for i = 1, 2, 3,…,n.
Parallel System
38
 When a component does not function, the product
continues to function, using another component,
until all parallel components do not function.
Rs = 1 - (1 - R1) (1 - R2)... (1 - Rn)
We can simplify the equation:
Rs = R1 + R2(1 - R1)
Example:
For a Parallel System
(usually for a system with
redundancy),we consider
reliability + unreliability= 1
Series-Parallel System
39
C
RA
RB
A
B
RD
RC
D
C
RC
The block diagram of an n-unit series-parallel system.

Convert to equivalent series system
RA
RB
A
B
RD
C’
RC’ = 1 – (1-RC)(1-RC)
D
Reliability calculation
40
Example 1:
How to calculate Reliability using block diagram
Calculate the system Reliability?
.95
.95
.95
.95
Solution:
The system consists of two components in series, so the system reliability Rs
Rs = R1 x R2
Rs = 0.95 x 0.95 = 0.9025
Reliability calculation
41
Example 2:
How to calculate Reliability using block diagram
Calculate the system Reliability?
.9
.95
.95
.95
Reliability calculation
42
Example 2: Solution:
.9
.95
R1
.95
.95
R2
We simplify the system by calculating reliability R1
and R2 in series
R1 = 0.9 * 0.95 = 0.855
R2 = 0.95 * 0.95 = 0.9025
Then we calculating reliability R1
and R2 in parallel
Rp = 1-(1-R1)(1-R2), we can simplify the equation as Rp = R1 + R2(1 - R1)
= 0.855 + 0.145 * 0.9025
Rp = 0.855 + 0.130863 = 0.985863
Reliability calculation
43
Example 3:
How to calculate Reliability using block diagram
Calculate the system Reliability?
.95
.90
.75
.80
.9
.95
.9
Reliability calculation
44
Example 3: solution
1. First, we simplify the system and find reliability in series system
.75
.80
.9
R1 = 0.9 * 0.95 = 0.855
.95
.90
.95
.9
R2 = 0.8 * 0.75 = 0.6
R3 = 0.9 * 0.95 * 0.9
= 0.7695
R1
R2
R3
44
Reliability calculation
45
Example 3: solution
2. Second, we calculate reliability for components R2 and R3 in parallel
R1
Rp1 = 1 – (1-R2)(1-R3)
= 1 – (1-0.6)(1-0.7695)
= 1 – 0.4 x 0.2305
R2
= 0.9078
R1
R3
R1 = 0.855
R2 = 0.6
R3 = 0.7695
Rp1
3. we calculate reliability for R1 and Rp1 in parallel
Rp = 1 – (1-R1)(1-Rp1)
= 1 – (1-0.855)(1-0.9078)
= 1 – 0.145 x 0.0922
Rp = 0.9866310
Reliability calculation
46
Fault tree analysis (FTA)
Fault tree analysis (FTA) is one of the most widely used
methods in the industrial sector to perform reliability analysis of
complex engineering systems.
A fault tree is a logical representation of the relationship of
primary/basic events that lead to a given undesirable event (i.e.,
top event). It is depicted using a tree structure with logic gates
such as OR and AND.
Reliability calculation
47
Fault tree analysis (FTA)
FTA begins with identification of an undesirable event called the
top event of a given system. Fault events which could make the
top event occur are generated and connected by logic gates
such as OR and AND.
Reliability calculation
48
Fault tree analysis (FTA)
The OR gate provides a TRUE (failure) output if one or more of
its input faults are present. In contrast, the AND gate provides a
TRUE (failure) output if all of its input faults are present.
Circle and rectangle symbols denote a basic fault event and the
resultant fault event which occur from the combination of fault
events through the input of a gate, respectively
Reliability calculation
49
Fault tree analysis (FTA)
The development or construction of a fault tree is a top-down
process (i.e. starting from the top event moving downward). It
consists of successively asking the question, “How could this
event occur?”
Reliability calculation
50
Fault tree analysis (FTA)
The following basic steps are involved in performing FTA:
 Define factors such as system assumptions, and what
constitutes a failure.
 Develop system a block diagram showing items such as
interfaces, inputs, and outputs.
 Identify undesirable or top fault event.
 Using fault tree symbols, highlight all causes that can make the
top event occur.
 Construct the fault tree to the lowest level required.
 Analyze the fault tree as per the requirements.
 Identify necessary corrective measures.
 Document and follow up on highlighted corrective measures
51
Reliability calculation
52
The following example demonstrate the development of a fault
tree.
Example:
A room has two light bulbs and one switch. Develop a fault tree
for the top event — room not lit. Assume the following:
• The room is windowless.
• The switch can only fail to close.
• The room will only become dark if there is no electricity, both
light bulbs burn out, or the switch fails to close
Reliability calculation
53
Solution:
A fault tree for the example is shown in the below figure.
Each event in the figure is labeled E1, E2, E3, E4, E5, E6, E7,
E8.
Probability Evaluation
The probability of OR and AND gate output fault event
occurrence can be calculated using the following two equations:
𝑘
𝑘
𝑃 𝐸0 = 1 −
{1 − 𝑃(𝐸𝑖) }
𝑖=1
and
𝑃 𝐸𝑎 =
𝑃(𝐸𝑖 )
𝑖=1
Reliability calculation
54
Solution:
𝑘
𝑃 𝐸0 = 1 −
𝑘
{1 − 𝑃(𝐸𝑖 )}
𝑖=1
and
𝑃 𝐸𝑎 =
𝑃(𝐸𝑖 )
𝑖=1
Where:
𝑃 𝐸0 = probability of occurrence of OR gate output fault event,
𝑃(𝐸𝑎 ) = probability of occurrence of AND gate output fault
event,
k = total number of input fault events,
𝑃(𝐸𝑖 ) = probability of occurrence of input fault event 𝐸𝑖 , for 𝑖 = 1,
2, 3,…, k.
Reliability calculation
55
Solution:
A fault tree analysis of the example
Reliability Prediction
56
Reliability predictions are one of the most common forms of
reliability analysis.
Reliability predictions predict the failure rate of components and
overall system reliability.
These predictions are used to evaluate design feasibility, compare
design alternatives, identify potential failure areas, trade-off
system design factors, and track reliability improvement.
Reliability Prediction
57
Reliability predictions are based on failure rates.
Failure Rate,  (t), can be defined as the anticipated number of
times an item will fail in a specified time period, given that it was
as good as new at time zero and is functioning at time t.
Items Failed
Failure rate 
Total Operating Time
Some products are scrapped when they fail e.g. hairdryer
Others are repaired e.g. pumps / air compressor
Reliability Prediction uph
58
The failure rate is expected to vary over the life of a product –
‘Bathtub Curve’
Failure Rate
A
D
B
infant
mortality
C
useful life period
Time
wearout
period
Reliability Prediction
59






A-B Early Failure (infant mortality)
‘Teething’ problems. Caused by design or installation
B-C Constant Failure Rate (useful life period)
Lower than initial failure rate and more or less
constant until end of life
C-D End of life failure (wearout period)
Failure rate rises again due to components reaching
end of life or aging
Reliability Prediction
60
Simplifying Assumption
Exponential distribution of failure rate is assumed. This
means that the failure rate remains constant over life of
product
 Bathtub curve becomes a straight line

Failure Rate
constant failure rate
Time
Reliability Prediction
61
Items Failed
Failure rate  
Total Operating Time
usually expressed by the Greek letter lambda ()
Failure Rate ( ), which is defined as: number of failures / total time in service.
The probability of a product surviving until time (t) is given by
the following function:
Reliability at time (t) =
e
e is the exponential function
 t
Reliability Prediction
62

To establish reliability of an item or component:

Conduct a series of tests until a number of them fail.

Calculate failure rate (Lambda).

Calculate reliability for a given time using exponential
distribution,
R(t) =
e
 t
R(t): Reliability at time t
Reliability Prediction
63
Example:
Trial data shows that 105 items failed during a test with a total
operating time of 1 million hours. (For all items i.e. both failed
and passed). Find the reliability of the product after 1000 hours
i.e. (t) =1000
Solution: first we find the failure rate
105
4
The failure rate  
 1.05 x10
1000000
Reliability Prediction
64
Solution: then we find the reliability
 Find the reliability of the product after 1000 hours
i.e. (t) =1000
Reliability at 1000 hours:
R(1000)
e
e
 t
 (1.05 x104 x1000 )
= 0.9
Therefore the item or component has a 90% chance of
surviving for 1000 hours
Reliability Prediction
65
Reliability V.S Availability V.S Maintainability
For long-lasting machines and services such as
pumps, electric power lines, and front-line services,
the time-related factors of availability, reliability, and
maintainability are interrelated.
Reliability Prediction
66
The Availability of a component or system is defined
as:

It is a time-related factor that measures the ability of a
component or system to perform its designated function

The component or system is available when it is in the
operational state, which includes active and standby use
Reliability Prediction
67

Maintainability The probability that a failed component or
system will be restored to adequately working condition.

Maintainability is the totality of design factors that allows
maintenance to be accomplished easily.

Preventive maintenance reduces the risk of failure.

Corrective maintenance is the response to failures.
Reliability Prediction
68
Understanding the Difference Between Reliability
and Availability
People often confuse reliability and availability. Simply put
availability is a measure of the % of time the equipment is in
an operable state while reliability is a measure of how long the
item performs its intended function.
Availability is an Operations parameter as, presumably, if the
equipment is available 85% of the time, we are producing at
85% of the equipment’s technical limit.
Reliability Prediction
69
Understanding the Difference Between Reliability
and Availability
A piece of equipment can be available but not reliable.
For example the machine is down 6 minutes every hour. This
translates into an availability of 90% but a reliability of less than
1 hour.
That may be okay in some circumstances but what if this is a
paper machine? It will take at least 30 minutes of run time to
get to the point that we are producing good paper.
Generally speaking a reliable machine has high availability but
an available machine may or may not be very reliable.
Reliability Prediction
70
Failure rate calculations are based on complex models which
include factors using specific component data such as
temperature, environment, and stress.
Reliability is a measure of the probability that a component will
perform its intended function for a specified interval under
stated conditions. There are several commonly used measures
of reliability.
For the Evaluation of Maintenance Effectiveness.
There are three common basic categories of failure rates:
 Mean Time Between Failures (MTBF)
 Mean Time To Failure (MTTF)
 Mean Time To Repair (MTTR)
Reliability Prediction
71
Mean time between failures (MTBF) is a basic measure of
reliability for repairable components.
MTBF can be described as the time passed before a
component, assembly, or system fails, under the condition of a
constant failure rate.
Another way of stating MTBF is the expected value of time
between two consecutive failures, for repairable systems.
It is a commonly used variable in reliability and maintainability
analyses.
Reliability Prediction
72
Mean time between failures (MTBF) can be calculated as the
inverse of the failure rate, λ, for constant failure rate systems. For
example, for a component with a failure rate of 2 failures per
million hours, the MTBF would be the inverse of that failure rate,
λ, or:
MTBF = total time in service / number of failures
Mean Time Between Failure (MTBF) is a reliability term used to provide the
amount of failures per million hours for a product.
NOTE: Although MTBF was designed for use with repairable items, it is
commonly used for both repairable and non-repairable items.
For non-repairable items, MTBF is the time until the first (an only) failure after
t0.
Reliability Prediction
73
Failure Rate is usually expressed in Failures per 106 or
109 hours
MTBF is usually expressed in terms of hours
Example: for a system with a predicted MTBF of
1000 hours, on average the system experiences one
failure in 1000 hours of operation or a Failure Rate
of 1000 per 106 hours
Reliability Prediction
74
Mean Time To Failure (MTTF)
Mean time to failure (MTTF) is a basic measure of reliability for
non-repairable systems. It is the mean time expected until the first
failure of a piece of equipment.
MTTF is a statistical value and is intended to be the mean over a
long period of time and with a large number of units. For constant
failure rate systems, MTTF is the inverse of the failure rate, .
If failure rate, , is in failures/million hours, MTTF = 1,000,000 /
Failure Rate,  , for components with exponential distributions. Or
For repairable systems, MTTF is the expected span of time from repair to the
first or next failure.
Reliability Prediction
75
Mean Time To Failure (MTTF) :
Then,
Reliability Prediction
76
Mean Time To Failure (MTTF) :
Reliability Prediction
77
Mean Time To Failure (MTTF) example:
Assume that the constant failure rates of tires 1, 2, 3, and 4 of a car are =
0.00001 failures per hour,
= 0.00002 failures per hour, = 0.00003
failures per hour, and
= 0.00004 failures per hour, respectively.
For practical purposes, the car cannot be driven when any one of the tires
punctures. Calculate the total tire system failure rate and Mean Time To
Failure (MTTF) of the car with respect to tires.( the tire will not be repaired)
Solution:
failure rate,
The total tire system failure rate and mean time to failure of the car
with respect to tires are 0.0001 failure per hour and 10,000 h, respectively.
Reliability Prediction
78
Mean Time to Repair (MTTR)
Mean time to repair (MTTR) is defined as the total amount of time
spent performing all corrective or preventative maintenance
repairs divided by the total number of those repairs.
It is the expected span of time from a failure (or shut down) to the
repair or maintenance completion. This term is typically only used
with repairable systems.
Reliability Prediction
79
Repairable and Non-repairable items
It is important to distinguish between repairable and nonrepairable items when predicting or measuring reliability.
Non-repairable items:
Non-repairable items are components or systems such as a light
bulb, transistor…etc.
Repairable Items:
Repairable Items are components or systems which can be
restored to satisfactory operation by any action, including parts
replacements or changes to adjustable settings such as pumps,
valves, heat exchangers…etc.
Reliability Prediction UPH
80
There is also the concern for availability, A(t), of repairable items
since repair takes time.
Availability, A(t), is affected by the rate of occurrence of failures
(failure rate, ) or MTBF plus maintenance time; where
maintenance can be corrective (repair) or preventative (to
reduce the likelihood of failure).
Availability, A(t), is the probability that an item is in an operable
state at any time.
Some systems are considered both repairable and nonrepairable, such as a missile. It is repairable while under test on
the ground; but becomes a non-repairable system when fired.
Dependability and maintenance
81
Availability
performance
Reliability
performance
Maintainability
performance
Dependability relationships
Maintenance
support performance
Dependability and maintenance
82
Performance can be defined as the capability of the system to
deliver the required functions.
Availability performance can be defined as the capability of
the system to deliver the required functions under given
conditions at a certain moment or time interval, if the required
external resources are provided.
Reliability performance is the ability of an item to perform a
required function under given conditions for a given time
interval.
Dependability and maintenance
83
Maintainability performance is the capacity of an item to be
retained in, or restored to a state in which it can perform a
required function, in an expected operational environment, when
maintenance is performed under stated conditions and using
stated methodologies, procedures and resources.
Maintenance support performance is the ability of a
maintenance organization, in an expected operational
environment, to provide when needed the resources required to
maintain an item in a state it can deliver its function.
Dependability and maintenance
84
Why we monitor availability performance?
 Because it provides information for the maintenance
(company) effectiveness
 Because it can be used as a motive for further improvement
 Because it can be used to detect problems
Maintenance Planning and Scheduling
85
Learning Outcomes
On completion of this module, student should be able to:
1. Define Maintenance Planning and Scheduling
2. State the Maintenance Planning procedure
3. State the objective of Maintenance Planning and Scheduling
4. Explain the basic levels of planning process
5. State the role of Maintenance Planner / Scheduler
Maintenance Planning and Scheduling
86
Maintenance Planning
Maintenance Planning is the process by
which the elements required to perform a task
are determined in advance of the job start.
Maintenance Planning and Scheduling
87
Maintenance Planning

It comprises all the functions related to the preparation of:
1.
2.
3.
4.
5.
6.

The work order
Bill of material
Purchase requisition
Necessary drawings
Labor planning sheet including standard times
All data needed prior to scheduling and releasing the work
order
Good planning is a prerequisite for sound scheduling
Maintenance Planning and Scheduling
88
Maintenance Planning Procedures






Determine the job content.
Develop work plan. This entails the sequence of the
activities in the job and establishing the best methods and
procedures to accomplish the job.
Establish crew size for the job.
Plan and order parts and material.
Check if special tools and equipment are needed and
obtain them.
Assign workers with appropriate skills.
Maintenance Planning and Scheduling
89
Maintenance Planning Procedures






Review safety procedures.
Set priorities for all maintenance work.
Assign cost accounts.
Complete the work order.
Review the backlog and develop plans for controlling it.
Predict the maintenance load using effective forecasting
technique.
Maintenance Planning and Scheduling
90
Maintenance Scheduling
Is the process by which jobs are matched with
resources and sequenced to be executed at a
certain points in time.
Maintenance Scheduling techniques





Gantt charts
Critical Path method (CPM)
Project Evaluation and Review (PERT)
Math Programming
Stochastic Programming
Maintenance Planning and Scheduling
91
Planning and Scheduling Objectives

Minimizing the idle time of maintenance workers.

Maximizing the efficient use of work time, material, and
equipment.

Maintaining the operating equipment at a responsive level to
the need of production in terms of delivery schedule and
quality.
Maintenance Planning and Scheduling
92
Maintenance Planning is a System to Deliver Right Actions
Maintenance Planning and Scheduling
93
Maintenance Planners convert strategy into actions that the staff uses to
deliver the objective. Three levels of Maintenance planning process
3/5
3/5
Maintenance Planning and Scheduling
94
Maintenance Job Priority System




Priorities are established to ensure that the most critical and
needed work is scheduled first.
The development of a priority system should be well
coordinated with operations staff
The priority system should be dynamic and must be updated
periodically to reflect changes in operation or maintenance
strategies.
Priority systems typically include three to ten levels of priority.
Most organizations adopt four or three level priorities.
Maintenance Planning and Scheduling
95
Maintenance Job Priority System
Priority
Code
Name
Time frame work
should start
Type of work
1
Emergency
Work should start
immediately
Work that has an immediate effect on
safety, environment, quality, or will
shut down the operation.
2
Urgent
Work should start within 24
hours
Work that is likely to have an impact on
safety, environment, quality, or shut
down the operation.
3
Normal
Work should start within 48
hours
Work that is likely to impact the
production within a week.
4
Scheduled
As scheduled
Preventive maintenance and routine. All
programmed work.
5
Postponable
Work should start when
resources are available
or at shutdown period
Work that does not have an immediate
impact on safety, health,
environment, or the production
operations.
Control Of Substances Hazardous to
Health (COSHH)
96
The control measures required under the COSHH
Regulations:
Measures for preventing or controlling exposure to hazardous substances
(Continue…)
 Reduced time exposure by job rotation and the provision of adequate
breaks
 Good housekeeping
 Training and information on the risks involved
 Effective supervision to ensure that the control measures are being followed
 Personal protective equipment (such as clothing, gloves and masks)
 Welfare (including first aid)
 Medical records
 Health surveillance