INTRODUCCION A LA INGENIERIA DE

DISPONIBILIDAD

MANTENIBILIDAD CONFIABILIDAD

AQAP-NATOMIL-STD

Reliability analysis has

important function analysis:

Requirements

specification

Systems design

Hardware design

Software design

Manufacturing

Testing & Maintenance

Transport & Storage

Spare parts

Operations research

Human factors

Technical documentation

training

And more

Reliability Definitions (3)1) The ability of an apparatus, machine, or system to

consistently perform its intended or required function or

mission, on demand and without degradation or failure.

2)Manufacturing: The probability of failure-free

performance over an item`s useful life, or a specified

timeframe, under specified environmental and duty-cycle

conditions. Often expressed as Mean Time Between Failures

(MTBF) or Reliability Coefficient. Also called Quality over

time.

3)Consistency and validity of Test Results determined through

Statistical Methods after repeated trials.

Reliability Definition (4)As the probability that a system or product will

perform in a satisfactory manner for a given

period of time when used under specified operating

conditions

This definition stresses the elements of:

1) Probability

2) Satisfactory performance

3) Time

4) Specified operation conditions

RELIABILITY

May be defined in several ways:

The capacity of a device/system to perform as designed.

The resistance to failure of a device/system.

The ability of a device/system to perform a required

function under stated conditions for a specified period of

time

The probability that a functional unit will perform its

required function for a specified interval under stated

conditions.

RELIABILITY ENGINEERING

RELIABILITY

In the Business Plans:

Reliability engineering assessment is based on the results of testing from in-house (or contracted) labs and data pertaining to the performance results of the product in the field. It is often the temptation to save initial costs by using cheaper parts or cutting testing programs. Unfortunately, cheaper parts are usually less reliable and inadequate testing programs can allow products with undiscovered flaws to get out into the field.

RELIABILITY ENGINEERING

Disciplines Covered by Reliability Engineering:

Reliability Engineering covers all aspects of a product's life, from its

conception, design and production processes, its practical use lifetime,

with maintenance support and availability.

Reliability.

Maintainability. Dependability

Maintenance

Availability.

All three of these areas can be numerically quantified with the use of

reliability engineering principles and life data analysis. (The combination of

RAM areas introduces a new term, ISO-9000-4, Dependability.)

A Few Common Sense Application:

A Few Common Sense Application

A Few Common Sense Applications:

Advantages of a Reliability Engineering Program:

1) Optimum preventive replacement time for components. 2)Spare parts requirements and production rate, through

correct prediction requirements.3)Better information about the types of failures experienced,

research and development efforts to minimize these failures.

4)Establishment of which failures occur at what time in the life of a product and better preparation to cope with them.

5)Studies of the effects of age, mission duration and application and operation stress levels on reliability.

6)A basis for comparing two or more designs and choosing the best design from the reliability point of view, which will eliminate overdesign as well as under design.

7)Evaluation and estimation of the amount of redundancy require to achieve the specified reliability.

8)Guidance regarding corrective action decisions to minimize failures and reduce maintenance and repair times.

Reliability and Quality Control:

Failure Rate ():

Failure Rate () =

Mathematically, this may be expressed as:

The failure rate can be expressed in terms of: Failures / hour Percent Failures Per 1.000 hours Per million hours

Number of failures

Total Operating Hours

Failure Rate ():Example: Suppose that 10 components were tested under specified operating conditions. The components (which are not repairable) failed as follows at average periods of:

Component 1 failed ea. 120 hoursComponent 2 failed ea. 250 hours Component 3 failed ea. 330 hours Component 4 failed ea. 440 hours Component 5 failed ea. 650 hours

The total operating hours was six months.

1. Draw the Functional Diagraman 2. Draw the System Operational Cycle 6 months3. Calculate the failure rate per hour 4. Calculate the stock of Spare Parts you need 5. Which are more reliable?

Reliability (R):

The probability that a device will perform its intended

function during a specified period of time under stated

conditions.

Mathematically, this may be expressed as:

Where: f(x) is the failure Probability density function T is the length of period of time , which is assumed to

start from time zero.

Reliability (R):

Matematicamente, la confiabilidad se expresa como:

Donde: = MTBF n = nmero de fallos t = perodos de tiempo T = Tiempo operacional

Haciendo, = 1/ = n/T

Remplazando en R(t), tenemos que:

O

Reliability (R) and Failure Rate ():

Reliability Curve

SYSTEM RELIABILITY COMPONENTS

1.In Series Networks 2.In Parallel Networks 3.Combined Series-Parallel Networks

IN SERIES NETWORKS

= ()i = R(t)1.R(t)2. .R(t)n

= . .

IN PARALLEL NETWORKS

INFLUENCE OF COMPONENT RELIABILITY

DESCRIPTION 1 2 3 4 5

IN SERIES

Components Reliability, Ri

Number of Components, n 10 50 100 200 400

Systems Reliability, R 80 80 80 80 80

IN PARALLEL

Components Reliability, Ri

Number of Components, n 10 50 100 200 400

Systems Reliability, R 80 80 80 80 80

COMBINED SERIES-PARALLEL NETWORKS

EJERCICIOS