engineering reliability report

7/28/2019 Engineering Reliability report

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UNIVERSITY OF THE HIGHLANDS AND ISLANDS

PERTH COLLEGE

ENGINEERING RELIABILITY


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Contents

1.0 INTRODUCTION ........................................................................................................................... 5

1.1 ENGINEERING RELIABILITY ................................................................................................. 5

GRAPHICAL NOTIFICATION .................................................................................................... 5

Relationship between failure rate and time .............................................................................. 6

RCM ( RELIABILITY CENTERED MAINTENANCE )................................................................. 6

ADVANTAGES OF RCM ............................................................................................................ 7

1.2 AIM AND OBJECTIVE .............................................................................................................. 7

1.3 system description of A340 hydraulic system ....................................................................... 7

OPERATION OF GREEN SYSTEM.......................................................................................... 7

BLUE SYSTEM................................................................................................................................. 8

YELLOW SYSTEM .......................................................................................................................... 8

COMPONENTS FUNCTION .......................................................................................................... 8

PRIORITY VALVES ..................................................................................................................... 8

FIRE SHUTOFF VALVES ........................................................................................................... 8

FILTERS ........................................................................................................................................ 8

HYDRAULIC SYSTEM MONITORING UNIT ( HSMU ) ............................................................. 9

RAT ( RAM AIR TURBINE )


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2.3 ANALYSIS .................................................................................Error! Bookmark not defined.

3.0 Reliability analysis and evaluation............................................................................................ 18

3.1 RELIABILITY DATA SELECTION......................................................................................... 18

3.2 COMPONENT WRD PARAMETER CLACULATIONS USING COMPUTATIONAL

TECHNIQUE................................................................................................................................... 18


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1.0 INTRODUCTION

1.1 ENGINEERING RELIABILITY

Reliability of a system / item is the probability that the specific system / item performs

specific function under specific operational and environmental conditions at and

through a specific time period. (The University of Tennesse Knoxville, 2012)

The opposite of reliability is unreliability and the relationship between the two

parameters is :-

R ( t ) = 1 Q ( t )

Where,

R ( t ) = reliability,

Q ( t ) = unreliability

R ( t ) and Q ( t ) are both functions of time ( t ).

Engineering Reliability is basically a group of planned or organised activities which

are formed through formal or informal management systems and working all together

efficiently to prevent any malfunction or loss of the system. (The University of

Tennesse Kno ille 2012)


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Whereas,

T is the time elapsed before the failure event and it is also known as MEAN time as itis constant.

The relationship between failure rate, reliability density and reliability function is ;

( ) ( )

( )

RELATIONSHIP BETWEEN FAILURE RATE AND TIME


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ADVANTAGES OF RCM

Creates a cost effective maintenance program to tackle equipment or system

failure.

Total knowledge of causes of equipment and system failure along with

preventative measures to be taken. Emphasises mostly on Predictive maintenance ( PdM ) over preventive

measures.

Provides reliability and availability at a very lower cost.

1.2 AIM AND OBJECTIVE

AIM :- Reliability Analysis and evaluation of HYDRAULICALLY ACTUATED

RUDDER CONTROL SYSTEM OF A340

OBJECTIVES :-

A l i d l ti f i t f A340 h d li t


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A pump driven by a Ram Air turbine ( RAT ) pressurize the green system in an

emergency. When the RAT pressurize the green system, the aileron, elevator and

spoiler servo control operating speeds are reduced. (Airbus, 2012)

BLUE SYSTEM

Blue system is pressurize by engine 2 and a manually controlled electric pump can

also pressurize the system.

YELLOW SYSTEM

Yellow system is pressurize by engine 3. An electric pump can also pressurize theyellow system which can be operated manually or automatically controlled which

enables ground operations when the engines are stopped.

The electric pump runs in flight in the event of engines 3 failure, if flaps lever is not at

0 and aircraft speed is above 100 knots.

COMPONENTS FUNCTION

PRIORITY VALVES

It cuts off hydraulic power to heavy load users if green system hydraulic pressure

gets low.

FIRE SHUTOFF VALVES


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HYDRAULIC SYSTEM MONITORING UNIT ( HSMU )

The HSMU monitors the hydraulic system. It processes :

Control and monitors the hydraulic system.

RAT extension.

ENG 1 and ENG 4 FSV closure in case of green reservoir low level.

Hydraulic quantity indication correction for fluid temperature.

Reservoir overheat warning

FAULT light illumination logic. Leak measurement valve control

RAT ( RAM AIR TURBINE )

A drop out RAT coupled to a hydraulic pump allows the green system to function.

The RAT may be extended at any time by the pilot. The RAT deploys

automatically in the event of four engine failure or electrical power loss when

i 1 d 4 t d l l l i th d bl i


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ACCUMULATORSEach of the hydraulic system has an accumulator which helps to maintain a

constant pressure by covering transient demands during normal operation.

HYDRAULIC GENERATION


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PRESSURIZATION OF THE RESERVOIR

Bleed air from ENG 2 pressurize the hydraulic reservoirs automatically. When the

bleed air pressure becomes too low, the system takes bleed air pressure from the

crossbleed duct. Thus all the three systems maintain a high pressure to prevent

their pumps from cavitating.


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LEAK MEASUREMENT VALVES

They are used only when the aircraft is on the ground and are positioned upstream

of the primary controls. They are used for the leak measurement of each system and

may only be closed on ground by using the LEAK MEASUREMENT VALVES

pushbutton the maintenance panel.

DISTRIBUTION


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1.0 ENGINEERING RELIABILITY THEORY AND TOOLS

1.1 WEIBULLS RELIABILITY DISTRIBUTION

WRD is one of the best statistical tool for predicting reliability which is a probability

measure.

WRD function can be stated as :-

WRD 1- Parameter,

In this case = 0, = 1


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1.2 RELIABILITY BLOCK DIAGRAM

A Reliability Block Diagram (RBD) performs the system reliability and availability

analyses on large and complex systems using block diagrams to show networkrelationships. The structure of the reliability block diagram defines the logicalinteraction of failures within a system that are required to sustain system operation.

The rational course of a RBD stems from an input node located at the left side of thediagram. The input node flows to arrangements of series or parallel blocks thatconclude to the output node at the right side of the diagram. A diagram should only

contain one input and one output node.

The RBD system is connected by a parallel or series configuration.A parallel connection is used to show redundancy and is joined by multiple links orpaths from the Start Node to the End Node. (ITEM Software, Inc, 2007)

There are two RBD models

Series reliability model

Parallel or Redundancy Model

SERIES MODEL


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PARALLEL OR FULL REDUNDANCY SYSTEM

The reliability of the system can be expressed as :-

Rs = 1 ( 1 R1 ) ( 1 R2 )

In general

R 1 ( 1 R1 ) ( 1 R2 ) ( 1 R )


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2.3FAULT TREE ANALYSISFault tree diagrams (or negative analytical trees) are logic block diagrams that

display the state of a system (top event) in terms of the states of its components(basic events). Like reliability block diagrams (RBDs), fault tree diagrams are also a

graphical design technique, and as such provide an alternative to methodology to

RBDs.

An FTD is built top-down and in term of events rather than blocks. It uses a graphic

"model" of the pathways within a system that can lead to a foreseeable, undesirableloss event (or a failure). The pathways interconnect contributory events and

conditions, using standard logic symbols (AND, OR etc). The basic constructs in a

fault tree diagram are gates and events, where the events have an identical meaning

as a block in an RBD and the gates are the conditions. (reliasoft, 2012)

There are three main gates used in FTA :-

AND GATE

In an AND gate, the output event occurs if all input events occur.


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The figure below is an illustration of a FTA diagram

Source :- (Olufisan, 2012)


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3.0 RELIABILITY ANALYSIS AND EVALUATION

3.1 RELIABILITY DATA SELECTION

The various data selection for failure rates of components has been taken from

appendix 4 and the data which are not available has been taken from the table.

COMPONENT Failure Rate in Failures per Million HoursFilter 0.5 1 10

Non Return valve 1 20

Pressure Relieve valve 2 8

Electric Pump 200 500

Accumulator 20 200

Electric driven pump 10 50 100

Fire shut valve 8 20Turbine 30 40

Source :- (Smith, 2011)

3.2 COMPONENT WRD PARAMETER CLACULATIONS USING

COMPUTATIONAL TECHNIQUE


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= m,

The extracted table from MS Excel shows the following parameters of accumulator

using the above WRD 2-parameter :-

R ( t ) = 99.93 %

= 1.170626

= 18871

= 0.65535


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EDP ( Engine Driven Pump )

Using WRD 2- parameter the extracted table from MS Excel shows the following

parameters of EDP :-

= 1.4269

= 6869.405

R ( t ) = 99.97 %

= 0.948452866


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RAT ( Ram Air Turbine )

Using WRD 2- parameter the extracted table from MS Excel shows the followingparameters of RAT : -

R ( t ) = 100 %

= 0.988232

= 9.677184

= 30526.86


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ELECTRIC PUMP

Using WRD 2- parameter the extracted table from MS Excel shows the followingparameters of electric pump:-

= 0.822819

= 240494.7

= 0.863629

R ( t) = 99.99%


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ACTUATOR

Using WRD 2- parameter the extracted table from MS Excel shows the following

parameters of actuator :-

= 1.170626

= 18871.71

= 0.929252

R ( t ) = 99.97 %


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FIRE SHUTOFF VALVE


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RESERVOIR

Using WRD 2- parameter the extracted table from MS Excel shows the followingparameters of reservoir :-

= 1.08

= 340.1564

= 0.90090

R ( t ) = 99.399 %


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VERIFICATION OF COMPONENT WRD PARAMETERS ( GRAPHICALTECHNIQUE )

3.5 RELIABILITY DISTRIBUTION FOR EACH COMPONENT OVER

THE RANGE 0 < R < 100 %

ACCUMULATOR


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RAT

Source :- ReliaSoft Weibull ++

ELECTRIC PUMP


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ACTUATOR


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RESERVOIR


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3.6 SYSTEM RELIABILITY MODELLING

RELIABILITY BLOCK DIAGRAM


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The overall reliability of the system is 99.38 % which is found using MS Excel as

below :- ( taking average flight time of A340 as 18.25 )


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By using Reliasoft BlockSim software the reliability of the overall system is 95.833%

which is quiet closer to the results of MS Excel. ( taking average flight time of A340

as 18.25 )


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b) A group of non-scheduled tasks which result from:

(1) The scheduled tasks accomplished at specified intervals.(2) Reports of malfunctions (usually originated by the operatingcrew).(3) Data analysis.


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FAULT TREE ANALYSIS


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CONCLUSIONThe overall reliability of the hydraulic system of A340 of the actuation of rudder

control system is considerable which is 99.38 % which is very good whereas in

software its around 95% so there is some error. The various components in the

system has a very high percentage of reliability.


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engineering reliability report

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