UNIVERSITY OF SOUTH AFRICA
College of Science, Engineering and Technology
⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄⋄
INE2602: Reliability Engineering
Assignment 1 — Year Module, 2026
⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄⋄
INE2602
Module Code:
Reliability Engineering
Module Name:
Assignment 1
Assignment Number:
109
Total Marks:
Refer to myUnisa
Due Date:
Submitted in partial fulfilment of the require-
ments for Reliability Engineering — UNISA 2026
,UNISA | INE2602 Reliability Engineering — Assignment 1
Question 1: Reliability Fundamentals and Metrics
1.1 Define Reliability Engineering and Reliability Metrics
Question: Define the terms reliability engineering and reliability metrics, identifying their
purposes in industry.
Reliability engineering is the discipline concerned with ensuring that a system, product, or
component performs its required function without failure, for a specified period, under stated
operating conditions. Its purpose in industry is to design and produce systems that meet
performance targets while minimising unplanned failures, reducing maintenance costs, and
improving safety outcomes across the product life cycle (Modarres, Kaminskiy and Krivtsov,
2016).
Reliability metrics are quantitative measures used to assess and monitor the dependabil-
ity of systems or components over time. Their purpose in industry is to provide engineers
and managers with objective data that supports maintenance scheduling, warranty decisions,
design improvements, and risk management (Ebeling, 2010).
Key Distinction
Reliability engineering is the practice of designing for dependability; reliability metrics
are the measurement tools that tell you whether that dependability has been achieved.
1.2 Key Reliability Metrics
Question: Name and define the key indicators or metrics for reliability.
1.2.1 Failure Rate (λ)
The failure rate is the number of failures occurring per unit time over a given observation
period. It is expressed as:
Number of failures
λ=
Total operating time
Page 2 of 25
, UNISA | INE2602 Reliability Engineering — Assignment 1
1.2.2 Mean Time Between Failures (MTBF)
MTBF is the average time elapsed between successive failures of a repairable system. It is the
reciprocal of the failure rate:
1
MTBF =
λ
1.2.3 Mean Time To Repair (MTTR)
MTTR is the average time required to restore a failed system to full operational status. It
measures the effectiveness of the maintenance process.
1.2.4 System Reliability
System reliability is the probability that a system will perform its required function without
failure for a specified time interval under given conditions. For a constant failure rate:
R(t) = e−λt
1.2.5 Maintainability
Maintainability is the probability that a failed system will be restored to operational status
within a specified time, given that maintenance is performed under stated conditions. It re-
flects how easily a system can be repaired.
1.2.6 Availability
Availability is the proportion of total time during which a system is in an operable and com-
mittable state. It combines reliability and maintainability:
MTBF
A=
MTBF + MTTR
1.2.7 Uptime
Uptime is the total time during which a system is operational and available for use. It repre-
sents the periods when the system is functioning correctly.
Page 3 of 25
College of Science, Engineering and Technology
⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄⋄
INE2602: Reliability Engineering
Assignment 1 — Year Module, 2026
⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄⋄
INE2602
Module Code:
Reliability Engineering
Module Name:
Assignment 1
Assignment Number:
109
Total Marks:
Refer to myUnisa
Due Date:
Submitted in partial fulfilment of the require-
ments for Reliability Engineering — UNISA 2026
,UNISA | INE2602 Reliability Engineering — Assignment 1
Question 1: Reliability Fundamentals and Metrics
1.1 Define Reliability Engineering and Reliability Metrics
Question: Define the terms reliability engineering and reliability metrics, identifying their
purposes in industry.
Reliability engineering is the discipline concerned with ensuring that a system, product, or
component performs its required function without failure, for a specified period, under stated
operating conditions. Its purpose in industry is to design and produce systems that meet
performance targets while minimising unplanned failures, reducing maintenance costs, and
improving safety outcomes across the product life cycle (Modarres, Kaminskiy and Krivtsov,
2016).
Reliability metrics are quantitative measures used to assess and monitor the dependabil-
ity of systems or components over time. Their purpose in industry is to provide engineers
and managers with objective data that supports maintenance scheduling, warranty decisions,
design improvements, and risk management (Ebeling, 2010).
Key Distinction
Reliability engineering is the practice of designing for dependability; reliability metrics
are the measurement tools that tell you whether that dependability has been achieved.
1.2 Key Reliability Metrics
Question: Name and define the key indicators or metrics for reliability.
1.2.1 Failure Rate (λ)
The failure rate is the number of failures occurring per unit time over a given observation
period. It is expressed as:
Number of failures
λ=
Total operating time
Page 2 of 25
, UNISA | INE2602 Reliability Engineering — Assignment 1
1.2.2 Mean Time Between Failures (MTBF)
MTBF is the average time elapsed between successive failures of a repairable system. It is the
reciprocal of the failure rate:
1
MTBF =
λ
1.2.3 Mean Time To Repair (MTTR)
MTTR is the average time required to restore a failed system to full operational status. It
measures the effectiveness of the maintenance process.
1.2.4 System Reliability
System reliability is the probability that a system will perform its required function without
failure for a specified time interval under given conditions. For a constant failure rate:
R(t) = e−λt
1.2.5 Maintainability
Maintainability is the probability that a failed system will be restored to operational status
within a specified time, given that maintenance is performed under stated conditions. It re-
flects how easily a system can be repaired.
1.2.6 Availability
Availability is the proportion of total time during which a system is in an operable and com-
mittable state. It combines reliability and maintainability:
MTBF
A=
MTBF + MTTR
1.2.7 Uptime
Uptime is the total time during which a system is operational and available for use. It repre-
sents the periods when the system is functioning correctly.
Page 3 of 25
