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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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