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RAMP 3.5

User Manual

Process Plant Availability Modelling

Copyright 2004 by TA Group Limited

RAMP Version 3.5 Manual version 1.00

Manual Issue Date 9th March 2004


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Trademarks

Microsoft Windows is a registered trademark of Microsoft Corporation. All other product names,

corporate names or titles within this document may be trademarks or registered trademarks of other

companies. These are recognised as such, and are mentioned only in an explanatory manner to the

user's benefit and with no intention of infringement.

Farnham, March 2004


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RAMP 3.5 - A Quick Reference Guide

Creating a New Model:

ChooseNewfrom the Filemenu

The outermost block of the Model is drawn on the screen and the system is given the default name New System. The

system block can now be converted to a group as follows:

Double-click the undefined system block to activate the Element Details dialogue box. Click the Convert to Groupbutton (or press ). Enter a value for the number of elements to be included in the group and click OK. Click the arrow to the right of the Group Type selection window to open the drop-down list box and choose

the group type from the list.

Distributions:

RAMP allows the user to select from five in-built distribution types for specifying element failure and repair times and

CMF occurrence times. In addition, the user can specify up to 30 Empirical distributions of their own (e.g. from

actual failure time records).

Distribution Type Defining Parameters Uses

No Occurrence None Defining non-repairable elements or makingan element with constant q value.

Fixed Time of Occurrence Fixed Time to Failure or Repair Make events happen at predetermined times(e.g. repair always takes 3 hours).

Weibull Characteristic Life and Shape Modelling increasing or decreasing failure (orrepair) rates.

Negative Exponential Mean Time Between Failures For data taken from generic sources or formodelling at equipment level as opposed to

failure mode level.

Lognormal Median and Dispersion or 50 and 95

Percentile Points

Most repair times follow a lognormal. For

modular repair, Median = MART x 0.84 and

Dispersion = 0.6, while for component level

repair, Median = MART x 0.38 and Dispersion

= 1.4

Element States:

Elements are the basic building blocks of the RAMP PDD and each one has user specified failure, repair and

preventive maintenance characteristics. An element may be in one of five possible states and its q value is determined

by its state.

State Description q Value

State 1 Undergoing preventive maintenance. q = 0

State 2 Being Repaired following failure (including queuing for repair). q = 0

State 3 Failed but undetected (a dormant failure). q = 0

State 4 Up and Passive (available but currently not required). q = 0

State 5 Up and Active (being used). q = Q


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Groups:

Eleven different group types are definable in RAMP. A group consists of a combination of elements and/or groups in

either series or parallel configurations.

Group Type Series/

Parallel

q Value Combination Rule Example Uses

Minimum S qM= min[q1, q2, q3, ...qn] Performance is limited to the capabilityof the worst component.

Active Redundant P qA= min[R, (q1+q2+q3+...+qn)]

unless qA< C, then qA= 0

A number of components each

contributing to the total performance.

Standby Redundant P As for Active Redundant Items not required to contribute to thetotal performance.

Buffer S qB= q2if buffer not empty

qB= min[q1, q2] if empty

Buffer storage in order to maintain

operation levels regardless of fluctuations

in output or failures.

Product S qP= q1x q2x q3x ... x qn Cumulative effect of items restrictingperformance to a proportion of

theoretical maximum.

Quotient S qQ= q1/q2 Availability of a system (ie the capacitydivided by the demand).

Greater Than S If q1> q2then qG= q1else qG= 0

To balance loads or compensate for

failure by increasing output from another

sub-system.

Less Than S If q1< q2then qL= q1else qL= 0

As for Greater Than.

Difference S qD= max[q1- q2, 0] Monitoring lost production.

Equality S qE= q1 if q1is outside range

qE= q2if q1is in defined range

Non-linear relationship between the

number of parallel items and their total

output.

Time Delay P If q1= 0 then qT= 0

After time T q1> 0, qT= q1

After further time T q1is still > 0, qT

= q1+ q2

After further time T q1is still > 0, qT

= q1+ q2+q3, etc

Stepwise approximation to the gradual

build-up in capacity of a process plant

following repair, shutdown or switching

from the standby to the active state.

When using Standby groups, remember RAMPs rules for placing items in the Active or Passive states. These can be

summarised as follows:

Only sufficient elements are put in the Active state to meet the groups specified rating. Elements are takenin order of priority from the top of the group.

The same element may appear in more than one Standby group. If a conflict arises, the program will selectthe Active state.

An element in a Standby group may appear in another non-Standby group. Here, the state of the element isdictated solely by the requirements of the Standby group.

Where a Standby group contains other groups, the Standby group works in a similar way.


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RAMP for Windows

Contents

INTRODUCTION TO RAMP FOR WINDOWS....................................................................................................7What is the purpose of RAMP?............................................................................................................................7Why use Monte Carlo Simulation? ......................................................................................................................7Input to RAMP - The Model ................................................................................................................................8Results Produced by RAMP.................................................................................................................................8Program Limits.....................................................................................................................................................8Conventions and Notations used in the Manual ...................................................................................................8Consultancy Services............................................................................................................................................9

GETTING STARTED WITH RAMP ....................................................................................................................10Checking your RAMP Package..........................................................................................................................10Hardware and Software Requirements...............................................................................................................10Licence Protection Device (dongle) ...................................................................................................................10Installing RAMP.................................................................................................................................................10Starting RAMP...................................................................................................................................................11Online Help ........................................................................................................................................................11RAMP Customer Support Help Desk.................................................................................................................11

CHAPTER 1 BASIC SYSTEM DETAILS.........................................................................................................12Elements and Groups..........................................................................................................................................12Elements and Q Values in the Model .................................................................................................................13Element States and Events..................................................................................................................................13Element Data ......................................................................................................................................................13Group Data .........................................................................................................................................................15Mission Data.......................................................................................................................................................16Other Model Data...............................................................................................................................................17

CHAPTER 2 BUILDING A RAMP MODEL ....................................................................................................18Creating a Simple Model....................................................................................................................................18Detailed Element Parameters..............................................................................................................................23Detailed Group Parameters.................................................................................................................................27Further Editing Facilities....................................................................................................................................29

CHAPTER 3 RAMP MISSION DATA..............................................................................................................31The Mission Data Form General Information Tab ..........................................................................................31The Mission Data Form Rolling Averages Tab...............................................................................................33The Mission Data Form Histograms Tab ........................................................................................................34The Mission Data Form Criticality Tab...........................................................................................................35Running the Simulation ......................................................................................................................................35

CHAPTER 4 RESULTS OF THE SIMULATION.............................................................................................37Uses of RAMP Results.......................................................................................................................................37RAMP Files........................................................................................................................................................37RAMP Results Tables ........................................................................................................................................37Histograms..........................................................................................................................................................41Rolling Averages ................................................................................................................................................44Results Overlay View.........................................................................................................................................46Text Files and Logs ............................................................................................................................................48

CHAPTER 5 MENU OPTIONS .........................................................................................................................50The File Menu ....................................................................................................................................................50The Edit Menu....................................................................................................................................................52The View Menu..................................................................................................................................................55The Data Menu...................................................................................................................................................58The Simulation Menu .........................................................................................................................................62The Results Menu...............................................................................................................................................63The Validation Menu..........................................................................................................................................65The Options Menu..............................................................................................................................................67The Help Menu...................................................................................................................................................71Mouse and Keyboard Operations .......................................................................................................................72


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CHAPTER 6 ANALYSIS AND SIMULATION................................................................................................73The Simulation Process ......................................................................................................................................73The Modelling Process .......................................................................................................................................75Model Development ...........................................................................................................................................76Model Validation................................................................................................................................................78

CHAPTER 7 - RAMP MODELLING CONCEPTS ..............................................................................................79The Model Diagram............................................................................................................................................79

Q Value...............................................................................................................................................................79Flow and Flow Potential.....................................................................................................................................80Time Units..........................................................................................................................................................80The Mission........................................................................................................................................................80Element States ....................................................................................................................................................81Element Data ......................................................................................................................................................82Groups ................................................................................................................................................................86Common Mode Failures .....................................................................................................................................88

CHAPTER 8 CASE STUDIES ...........................................................................................................................89RAMP Case Study 1 - User Exercise.............................................................................................................90RAMP Case Study 2 - Compare Production with Demand - Quotient ..........................................................92RAMP Case Study 3 - Compare Production with Demand - Difference.......................................................93RAMP Case Study 4 - Representing Profiles of Q Value Changing Over Time ...........................................94RAMP Case Study 5 - Non-Linear Relationship of Number of Items and Output........................................97

RAMP Case Study 6 - Stacking Buffers in Series .........................................................................................99RAMP Case Study 7 - Delayed Impact of Failure on Flow.........................................................................101RAMP Case Study 8 - Availability of Waste Acceptance Function............................................................104RAMP Case Study 9 - Intermittent Flow Increase.......................................................................................105RAMP Case Study 10 - Seasonal Changes.....................................................................................................106RAMP Case Study 11 - Complex Flow Distributions....................................................................................107

APPENDIX A GROUP TYPES........................................................................................................................109APPENDIX B DISTRIBUTIONS ....................................................................................................................115APPENDIX C SOURCES OF FAILURE DATA.............................................................................................119APPENDIX D MODELLING LIMITS ............................................................................................................121APPENDIX E TROUBLE SHOOTING...........................................................................................................122APPENDIX F RESULTS AND OUTPUT FILES............................................................................................123


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INTRODUCTION TO RAMP FOR WINDOWS

What is the purpose of RAMP?

RAMP is a Monte Carlo simulation computer program for the assessment of the Reliability, Availability and

Maintainability characteristics of Process systems hence the name. It is a very flexible tool, capable of

modelling a wide range of process plant and generative systems. It allows the user to examine the operational

capability of systems in situations beyond the scope of manual or analytical calculation.

Modelling using RAMP may be conducted to optimise the design and support (e.g. maintenance and spares) of a

plant, to examine the likely Availability or Productivity when sizing the plant or setting contract terms for the

output or to conduct 'what if' studies. RAMP will allow the user to quantify the plant Availability or Productivity

using whatever measure is most appropriate to the particular case.

Why use Monte Carlo Simulation?

Simulation using Monte Carlo methods allows the operational capability of complex plants to be examined,

including the interaction of many complicating factors such as queuing for repairs and spares, common mode

failures, the effects of preventive maintenance, changes in plant configuration, changes in plant loading (e.g.

demand) etc.

Results from simulations using RAMP allow the user to study the likely range of plant operational capability as

well as average values. It may be important in risk studies to know that for one year in fifty the Availability could

be as low as 82%, even though on average it is over 95%.

Simulation with RAMP has many advantages over other forms of assessment, and these include:

The visual representation of the system on screen gives better 'physical visibility' of a situation than complexsets of equations, aiding validation and interpretation of output.

The RAMP model offers scope for easy development to examine the system in greater detail or differentwhat if' studies. The 'Top-Down' approach for model development is particularly suited to refining the model

as more design detail becomes available.

The size of models which can be handled by RAMP means that it can be used for studies beyond the scope ofmanual and analytical methods.

Introduction


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Input to RAMP - The Model

In order to simulate a process, the program needs three types of data:

A representation of the system, which takes the visual form of a model diagram, in which the contribution ofelements and groups of elements to the performance of the entire system is defined. The diagram is a failure

logic model of the system, the basic building blocks of which are the system elements. The diagram describes

how failure and repair characteristics of these elements and groups of elements relate to each other and to the

system as a whole. The reliability and repair parameters of the individual elements of the system and the capacity (Q) value of

each element. Each element possesses specific failure and repair characteristics and can be in an 'up' condition

- active and functioning - or in a 'down' condition - either failed, being maintained or dormant, depending on

the type of group.

Information on the conditions under which the simulation is to be run, i.e., the duration of a mission and thenumber of missions to be simulated.

Results Produced by RAMP

RAMP provides results for each element (corresponding to individual equipment items), as well as groups of

elements (which represent subsystems or the overall system). From the capacity of the elements at any time, the

performance values are calculated for each group using a set of defined rules. The results are given as averagevalues over all simulated missions and include:

The average q value - the processing or generative capacity - of each group. The number of times per mission that each element was in a particular state (active, failed under repair, failed

undetected etc).

Rolling average performance figures, if required. Criticality figures - the amount that each element has contributed to the overall loss of capacity.

The results enable the user to identify major factors influencing the overall system performance and reliability.

Program Limits

Certain program limits apply to RAMP for Windows, for instance the maximum numbers of elements, groups,

element types, spares types, etc. that can be defined. These program limits are detailed in Appendix D.

Conventions and Notations used in the Manual

Hierarchy for Section TitlesThe head of this page shows the style for main section titles within chapters, and such titles appear in the contents

listing. Beneath them, the sequence for titles is light blue, (as for this section), then dark blue, then black, as

shown below.

Third Level is Dark Blue

Fourth Level is Black

ListsLists or step-by-step instructions are identified by round bullets, thus:

Click on the Deletebutton. Click on OK to delete or Cancel to abandon.

Bold Indicates either buttons on forms as above, or menu options, for example:

Choose Open from the File Menu.


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Keyboard InputWhere certain keyboard actions are necessary to execute a command, the manual will use the following

conventions:

The designated key should be pressed.

< Key 2> Key l is pressed and held down and then Key 2 is pressed. For example,

means you press and hold down the Alt key, then press the C key and then release

both keys.

Consultancy Services

Advantage Business Group offers a service to enable you to obtain the maximum benefit from RAMP in the

shortest possible time. This includes both on-site and in-house user training as well as the complete design and

production of individual RAMP models.

In addition, ABG provides support on a wide range of reliability, availability, maintainability, logistic support and

safety services, covering both hardware and software systems. Further details on these services can be provided

on request ring +44 1252 741700 and ask for Chris Barber, or email [email protected]


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GETTING STARTED WITH RAMP

This section covers the installation and first use of RAMP. It is assumed that the user is already familiar with

standard Windows operations such as use of the mouse, selecting items from a menu etc.

Checking your RAMP Package

The installation package should contain a CD, a RAMP manual, a licence agreement, and a dongle (a small

rectangular plastic object) which plugs into the parallel port of your PC. If any of these items are missing please

contact Advantage Business Group in the UK or your local distributor.

Hardware and Software Requirements

To use RAMP you will need the following hardware and software:

Component Recommended Minimum

Computer Pentium 133 or above 80486-based

RAM 32 MB or above 8 MB

Monitor SVGA 800 x 600 or above VGA 640 x 480

Operating System Windows 95 or above Windows 95 or above

For installation of the software you will need at least 25 MB of free space on your hard drive. Operation of the

software requires the use of a Microsoft Windows-compatible mouse or similar pointing device.

Licence Protection Device (dongle)

The program will not run unless the licence protection device is correctly installed on your computer. This device

is a simple plug which is inserted into the LPT1 printer port of your computer. If a printer is already connected to

this port,insert the printer plug into the rear of the device. This will have no effect on output to the printer.

Installing RAMP

Save any current work and close any open applications (including mail or Internet applications). Install the dongle in your LPT1 parallel port. Insert the RAMP CD in your CD drive.

The installation will start automatically, if not: Run SETUP.EXE on drive D: (or the appropriate drive for your CD).

If necessary, specify the directory where RAMP should be installed.

During the installation, the RAMP installation process checks for the presence of the correct system files before

proceeding. If you receive an error message stating that certain system files are out of date, allow the RAMP

installation program to update these files and then restart the installation process from the beginning.

On installation of RAMP, the following window will be seen without fail:

Getting

Started


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The error window should cause no concern, simply click OK and continue with the installation.

Starting RAMP

Once installation is complete, you should have a new program group available click on the RAMP Builder icon

to start the program. You will be prompted to enter your name and company details to register the software.

After the introductory screen has been displayed (the logo remains visible for about 5 seconds, or can be clearedby clicking on it), the Builder is loaded ready for you to construct a model. If RAMP fails to start, displays a

dongle error message or refuses to save or load correctly, please contact Technical Support.

Online Help

Use the commands on the RAMP Help menu to find online information about RAMP. For detailed information

on the Help menu options, choose Search for Help On... from the Help menu. For basic information on the

Windows Help system itself, choose How to Use Help... from the Help menu.

The RAMP Help system is context-sensitive. When you press F1, the Help sections relevant to the current form

or menu item will be displayed.

RAMP Customer Support Help Desk

The Help Desk offers phone or email support, through which all registered users of RAMP can request technical

information, obtain help with using the product, report faults and submit requests for enhancements and

modifications. In the UK, call 01252 741700 during normal working hours and ask for the RAMP Help Desk.

We may also be contacted by fax (01252 711314) or email ([email protected]) at any time.


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1CHAPTER 1 BASIC SYSTEM DETAILS

Elements and Groups

This chapter provides an introduction to some RAMP concepts and should be read before constructing

any models.

RAMP models are made up of elements and groups. The elements carry failure, repair and capacity

data and the groups provide the model structure. If an element is 'up' then it has a capacity Q which is

set by the user. If it is 'down' for any reason it has a capacity of zero.

The amount of time that an element spends either up or down is governed by a number of factors

including the failure distribution specified, the repair distribution, whether maintenance resources areavailable to fix it when it goes wrong, and so forth. The contribution that an element makes to the

system as a whole is more complex and can be affected by the following factors:

Whether or not the element or group is up and running. The output of the element or group in its normal 'up' condition. The frequency with which the element goes into a 'down' condition, i.e., is in need of maintenance or

repair.

The length of time the element or group is in a 'down' condition which depends on: the availability of repair trades,

the availability of spare parts,

storage levels (if defined),

the state of other elements (if required),

the state of other groups (if required), the duration of prescribed maintenance schedules,

the repair time of the element,

the logistic delay in carrying out the repair.

An element's dependency for function on the correct function of one or more other elements.

Most models, however, don not need all this to be specified and a simple model can be constructed and

checked very quickly. To do this, two main types of information are required:

Element Information - Failure and repair details e.g. how often a pump fails and how soon it isrepaired.

Configuration Information - What equipment there is, how process works, what happens if an itemfails.

The 'Configuration information' must be translated into a group structure which RAMP understands.RAMP provides a wide variety of group types, which can contain elements, other groups or a mixture of

both. Groups can contain elements in series or in parallel. In a series group, failure of any single

element will bring the whole group down, whereas a parallel group will often have some redundancy

and single failures won't lead to failure of the group as a whole.

Chapter


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Elements and Q Values in the Model

Elements are the basic blocks of the model and each element has failure and repair characteristics, plus a

capacity, Q. If an element is 'up', its performance is equal to Q. When the element is 'down', it has a

performance value of zero.

Although only one 'up' state exists where performance = Q, RAMP has four possible states for eachelement where performance (also known as q ) = 0. Three of these are 'down' states (repair,

maintenance, dormant failure) and one is a passive 'up' state.

Every time an event occurs in the model, the q values are calculated for each sub-group upwards until q

values have been calculated for all groups and, ultimately, for the system as a whole, represented by the

outermost group.

Element States and Events

The simulation of a system is done by generating, and calculating the effects of, simulated 'events'

which occur according to the element data in the model. An 'event' is anything which can change the

state of a model or a group.

The possible states for an element are as follows:

State 1 Undergoing preventive maintenance. State 2 Being repaired following a failure (including being in the repair queue). State 3 Failed but not detected (a dormant failure). State 4 'Up' and passive (available, but not being currently used). State 5 'Up' and active (being used).

The q value of the element for states 1 to 4 is equal to zero, and for state 5, q = Q.

Element Data

There are three main types of data used by elements in a RAMP model, organised according to the

following headings:

Reliability Parameters Repair Policy Planned Maintenance


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Reliability ParametersAre the basic data required to populate a model - these include failure and repair details, capacity, a

name and any comments. See Figure 1.1 below.

Figure 1.1 : Element Details form, Reliability Parameters tab

Repair PolicyDetails are required for any element which has repair conditions - for example, a switchboard would

need an electrical technician to be available and a pump might need a new seal set. Other conditions

which can be set include logistic repair delay (the amount of time that will elapse before a repair starts),

startup delay for passive items, and repair priority. See Figure 1.2 below.

Figure 1.2 : Element Details form, Repair Policy tab


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Planned MaintenanceDetails can be entered for any element which will be unavailable at known times due to the performance

of preventive maintenance. Three PM cycles are available per element and more elements can be used

if more PM cycles are desired. See Figure 1.3 below.

Figure 1.3 : Element Details form, Planned Maintenance tab

Group Data

RAMP supports eleven different group types, which allows a lot of flexibility when simulating varied

process conditions. The group types can be roughly divided into Process type groups (designed to

simulate process conditions) and Logic type groups (designed to provide decisions or logical

conditions) although all types of group can be mixed together in the same model without restriction.

Process GroupsThe Process groups consist of the following types:

Active Redundant Standby Redundant Minimum Buffer Time

The Minimumgroup is the basic series group - all elements are configured in a single line and failure

of any element will take the group Q value to zero. When no element has failed, the group Q value is

the minimum of all the elements in the group, hence the name of the group.

The Buffergroup provides storage - this can be used to model tanks or similar process items and canalso be used to provide a delayed effect on failure.

The Timegroup provides one means of steadily increasing or decreasing a capacity over time - starting

with a minimum value the Time group will increase by specified steps up to a maximum.

The Active Redundantgroup allows simulation of a system where two or more items are in parallel.

This may give protection against failures (e.g. a 3 x 50% system) or partial degradation instead of

complete loss (e.g. 3 x 33%). All items in an Active Redundant group are active all the time, hence the

name of the group.


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The Standby Redundant group allows simulation of a duty/standby redundant system where not all

items are required to run at the same time to deliver the required performance. If an item in a Standby

Redundant group is not required at any time then it is put into a Passive state.

These groups may be distinguished from each other in the Model Diagram by the prefix letter in the title

and by the group colour. More detailed descriptions of the properties of these groups can be found in

Appendix A.

Logic GroupsThe Logic groups consist of the following types:

Greater Than Less Than Difference Equality Product Quotient

The Greater Thangroup allows the user to detect if a group or element capacity is Greater Than a set

condition, hence the name.

The Less Thangroup is similar to the Greater Than group - it allows the user to detect if a group or

element capacity is Less Than a set condition.

The Difference Groupreturns the difference between the capacities of two items.

The Equality Groupallows the user to detect if a group or element capacity is equal to a set condition.

The Product Groupreturns the product of the capacities of two items, i.e. it multiplies one by the other.

The Quotient Groupreturns the quotient of the capacities of two items, i.e. it divides one by the other.

These groups may be distinguished from each other in the Model Diagram by the prefix letter in the title

and by the group colour. More detailed descriptions of the properties of these groups can be found in

Appendix A.

Mission Data

Several items of information required for the running of a RAMP model are input through the Mission

Data form, which can be found under Simulation \ Mission Data. The most important of these items of

information are the Model Title, the Mission Lengthand the Number of Missions.

Model Title

RAMP requires a Model Title before any simulation can be run. This title will appear on printouts ofresults from the model.


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Mission LengthRAMP does not make any assumptions about which particular time units are used in a model, but it

does assume that all time units used in the model are the same. For example, if you have defined all

your failure and repair data in terms of hours, and want to run the simulation for a period of 1 year, then

you should enter 8760 for the Mission Length.

Number of MissionsRAMP produces events from a set of distributions which are sampled by a pseudo-random number

generator. This process produces variation in the results, which may be reduced by running multiple

simulations of the model. The number of simulations to be run must be left to the judgement of the user

but it is recommended that at least 10 should be run for most models, but preferably 100 if time is

available.

Figure 1.4 : Mission Data form, General tab

Other Model Data

Rolling AveragesRolling Averages provide a graph of the performance of any specified group over the simulation life

span. For a detailed view of group performance, try running for one simulation only - the results from

multiple simulations will be averaged.

Histograms

Histograms are used to graph performance or down time from specified groups. They must be usedwith multiple missions as the figures used for the graph refer to the average figure achieved at the end of

each mission.

CriticalityCriticality is a measure of how much loss of performance can be attributed to a particular element or

group. RAMP allows groups to be specified for Criticality calculation - all sub groups and elements for

the specified group will be assigned a criticality result for that group based on their performance.


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2CHAPTER 2 BUILDING A RAMP MODEL

This chapter describes how to build a simple RAMP model. It is divided into two sections: the first section is a

step-by-step description of a worked example. The second section provides more detail on the various screens

through which the elements and their repair and failure characteristics are defined. If you have any problems with

the worked example, go through the detailed descriptions in the second section.

Creating a Simple Model

Getting StartedIn this section you will create a small model from scratch and, in doing so, familiarise yourself with some of the

essential features and functions of RAMP. The example we will use is a simplified representation of a fuel mill,consisting of a fuel feeder and a mill house. The mill grinds solid fuel fed from the feeder which enters the mill

house through the mill doors. Grinding takes place on a grinding table with the help of a mill motor and a mill

gearbox. Before the ground fuel leaves the mill house, it passes through a separator.

The system has an overall design capacity of 25 tonnes per hour. There are three mill doors working in active

redundancy, each with a capacity of 9 tonnes per hour.

Thus the system as a whole is made up of the following components:

The fuel feeder feeding raw material into the mill house. A group of three mill doors, all of which are operating (i.e. no standby items). The mill motor. The mill gearbox. The grinding table.

The separator.

Figure 2.1 : Fuel Mill Block Diagram

Chapter


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The mill also has a stock of spare parts to be used for repairs in the case of a breakdown, and a team of repair

workers to carry out maintenance and repairs. A block diagram of the fuel mill showing each of the components

is shown in Figure 2.1 above.

Group StructureRAMP enforces a 'top-down' approach to building - the model structure is started at the topmost level and

expanded downwards. The first thing to do is to start a new model - use File \ Newor . The block that

appears on your screen is a single element and must be expanded if it is to do anything useful:

Double-click the block to open the Element Details form. Click the Convert to Groupbutton or press - this turns the element into a group. Specify that you want 2 elements in the group and click OK.

You now have an undefined group with two elements. Since any element can be converted into a group, the

model can be expanded downwards almost indefinitely.

The default group is a Minimum, which is required for the top level group:

Change the group name from UNDEFINED to FUEL MILL PART A. Click OK or press - you now have a group with two elements in it. Double-click on the right hand element and convert it into a group with five elements in it. Name this group 'MILL HOUSE' and click on OK to close the form.

You should now start to see some similarity between the model you have on screen and the model in Figure 2.1

above. The major differences are that one of the groups has not been defined yet, and no element data has been

entered.

To construct the redundant group representing the Mill House doors:

Double-click the left-hand element in the MILL HOUSE group to open the Element Details form. Convert the element into a group of three elements called DOORS. Click on the Group Typedrop-down list and select Active Redundant - name this group DOORS. Enter 25 for the Ratingand 0 for the Cut Off. Click OKto close the form - you have now completed the group structure for the model.

Element Details

To enter element details, double-click on the element and the Element Details form will open, as shown in Figure2.2 below.

Starting with the left-most element in the model, enter the following details:

Name : Fuel Feeder

Q Value : 25

Failure Distribution : Negative Exponential (click on drop-down list)

Failure Mean : 50000

Repair Distribution : Lognormal (click on drop-down list)

Repair Dist 50thPercentile : 7.6

Repair Dist 95th

Percentile : 14

If the repair distribution does not show 50thand 95

thpercentiles, click on Options \ Repair Distributionand

select 50/95th

Percentile. When you have finished, close the form. The element block should now have changed

colour from orange to yellow, signifying that it has been named and is no longer Undefined.


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Figure 2.2 : Reliability Parameters tab, Element Details form

For the remaining elements, working from the left, enter the following data:

Name Q

value

Failure

Dist

Failure

Mean

Repair

Dist

Repair

50th

pctile

Repair

95th

pctileMill Door 1 9 Neg Exp 1,500,000 Lognormal 3.8 14

Mill Door 2 9 Neg Exp 1,500,000 Lognormal 3.8 14

Mill Door 3 9 Neg Exp 1,500,000 Lognormal 3.8 14

Mill Motor 25 Neg Exp 10,000 Lognormal 1.9 4.5

Mill Gearbox 25 Neg Exp 200,000 Lognormal 1.5 6

Grinding Table 25 Neg Exp 175,200 Lognormal 3.8 9

Separator 25 Neg Exp 1,000,000 Lognormal 5.7 16

Once these are all complete, the model should look like Figure 2.1 above. Note that all time data given in this

chapter is assumed to be in hours.

Mission Data

Mission Data is required to define the overall conditions of the simulation. Essential Mission Data includes aModel Title, a Mission Lengthand the Number of Missionsrequired.



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To reach the Mission Data form, click on Simulation \ Mission Data and enter the data as shown. You now have

a model with enough data to run - save it by clicking File \ Saveor pressing .

Defining Repair ResourcesYou now have a workable model, but it is not a complete model according to the original description of the

system, which says, 'The mill also has a stock of spare parts to be used for repairs in the case of a breakdown,

and a team of repair workers to carry out maintenance and repairs'.

RAMP assumes that all repair resources are available in the quantities required, unless you specify limits. To

specify resource details for this model, we will need to define Repair Tradesand Spares.

Specifying repair resources is a two-part procedure - firstly the resources must be defined for the model as a

whole, then the repair resource requirements must be defined for each element.

Repair TradesRepair Trades correspond to maintenance workers. To define one, open the Repair Tradesform under the Data

menu. Click on the Createbutton, enter a name (Repair Team) and a number (1), click on the Addbutton and

close the form.

Spares

The mill keeps one each of the following parts in stock: Fuel feeder Mill gearbox Grinding table Mill door Separator Mill motor

Choose Sparesfrom the Datamenu and click on Create. This will open up the Spares form with an

UNDEFINED spare for editing.

Figure 2.4 : Spares form

For Nameenter 'Spare Fuel Feeder'. Set Policyto Re-order. Enter a value of 0 for Re-order Leveland 336 for Time Delay. Click Addto save your entry and close the form.

Repeat this procedure for the remaining spare parts and close the Sparesform.


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Using Repair ResourcesRepair resources are allocated to each element separately. To enter repair resource details, double-click on an

element block to open up the Element Details form, and click on the Repair Policy tab at the top of the form. This

will bring you to the Repair Policy form as shown in Figure 2.5 below.

The Repair Policytab on the Element form shows a number of items of information which can be used to control

some aspects of unscheduled failure and repair. To add a Repair Resource, click on the Addbutton and select

either Repair Tradeor Spareas appropriate. Select the Repair Team trade for each element and also the

appropriate spare. The model is now complete.


Printing and Saving the Model DiagramWhen you have finished constructing the model, you can print out the model diagram or save it as a graphics file

for documentation and reporting purposes. Note that this is not the same as saving the model itself.

To print the model diagram, choose Print from the File menu. Make any required adjustments in the Print form

and click the Printbutton to print the diagram.

To save the model diagram, choose SaveModel Graphic from the File menu. The Save As form will then open

for you to save the graphics file, as either a bitmap (BMP) file or a Windows Meta Format (WMF) file.


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Detailed Element Parameters

Element Details Form - Reliability Parameters TabOnce the general structure of the model in terms of elements and groups has been put together using the RAMP

Builder, the reliability characteristics of the individual elements must be defined. This can be done either by using

the Element Details form for each individual element, or for several elements at one time using the Element Table

View.

To edit element details using the Element Details form, simply double-click within the bounds of the required

element. To create an Element Type from the element, click the Create Element Type button.

More information about Element Types is given in Chapter 5.

Figure 2.6 : Element Details form, Reliability Parameters tab

The layout of the Element Details form is shown above. The data items that can be entered into the form are listed

below. The form consists of three parts, each accessed using the appropriate 'tab'. In addition, buttons are

provided in the form with the following functions:

General Data on the Reliability Parameters tab:Parameter Name Data Type Description

Name String Up to 32 characters. This should be a meaningful description of the block being

modelled. The name is merely a label for you to identify elements in the model and in

the tabular results. It is not used to define the model structure (this is done with an

internal numbering system invisible to the user).

Q Value Real > 0 The Q value of the element when it is in an Up and Active state.

Element Type Menu This may be a Unique type (default) or a defined Element Type. The parameter should

be set to Unique Type if the element is the only one of its type in the system, or is the

first of its type to be entered. Optionally it may be set to equal to a defined Element

Type from the drop-down list. When set, it is assumed to be of the same type as that

element, that is it has the same failure and repair characteristics and shares a common

pool of spares (see Chapter 5, Sparesin the Datamenu). If set to a defined elementtype, then all parameters for that element are set to the values for that type and cannot

be changed.

Comments String This is a notepad area which can be used to store information about each Element.


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Failure and Repair Distributions on the Reliability Parameters tab:

Parameter Name Data Type Description

Distribution Type Menu Weibull

Negative Exponential

Lognormal

Fixed

Failure Free - available only on the Failure menu.

Un-Repairable - available only on the Repair menu.

Failure Parameters Real Parameters are presented on the form according to the Distribution Type

specified:

Negative exponential

Weibull

Lognormal

Fixed

Failure Free

Param 1 - Mean

Param 1 - Characteristic Life

Param 2 - Shape

Param 1 - Median

Param 2 - Dispersion

Failure Time

None

Repair Parameters Real Parameters are presented on the form according to the Distribution Type

specified:

Negative Exponential

Weibull

Lognormal

Fixed

Un-Repairable

Param 1 - Mean

Param 1 - Characteristic LifeParam 2 - Shape

Param 1 - Median

Param 2 - Dispersion

Repair Time

None

For Repair distributions only, there is an option of specifying Weibull and

Lognormal distributions as percentiles:

Param 1 - 50thPercentile

Param 2 - 95thPercentile

Choose Repair Distribution from the Optionsmenu to select the method

of display and entry.

Element Details Form - Repair Policy TabThis set of parameters relates specifically to the repair conditions of the element. The various options areexplained in the tables given below.



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General Data on the Repair Policy tab:

Parameter

Name

Data Type Description

Logistic Repair

Delay

Real or

integer > 0

The logistic delay is a period that must elapse before a repair can start. Time units must

be the same as for the mission time.

Repair to Good-

as-New

Boolean This field should be checked to indicate whether or not the element is restored to 'Good-

as-New' following repair of a random failure. (The alternative is 'Bad-as-Old'.) By default

this field is checked, i.e. repair to Good-as-New. This parameter is only appropriate for

use with items whose probability of failure increases with time.

Repair Priority Integer > 0 This field is used only if Resource/Repair Conditions are specified for the element (see

below). Elements are repaired according to their repair priority, where 1 is highest

priority. Elements with the same priority number are repaired on a 'first come first served'

basis.

Standby Elements Data on the Repair Policy tab:

Parameter

Name

Data Type Description

Passive failure

rate factor

Real, > 0 This field specifies the factor by which the element 'failure rate' is multiplied when

operating in the 'Passive' as opposed to the 'Active' state. Usually this factor will be

between zero and one, indicating a lower passive failure rate than active failure rate. This

field is used only if the element is contained in one or more Standby Redundant groups.

Switching Failure

Probability

Real, 0% to

100%

This field shows the probability (between 0% and 100%) that the element fails when

switched from a standby state into the active state. If a switching failure occurs, the

element must be repaired in the normal way before it can be used again.. This field

applies only if the element is contained in one or more Standby Redundant groups.

Startup Delay Real or

integer > 0

The startup delay is a period that must elapse before an element currently on standby can

go to an active state. Time units must be the same as for the mission time. This field is

only useful if the element is in one or more Standby Redundant groups.

Resource/Repair Conditions on the Repair Policy tab:This section of the form allows you to define up to eight Resource/Repair conditions, all of which must be

satisfied before the element can be withdrawn from the repair queue to be sent for repair.

Type Description

Repair Trade Any number of units, up to the defined limit, of any previously defined repair trade.

Spare Any number of units, up to the defined limit, of any previously defined spare.

Group Q value Any model group can be compared, using one of six logical operators, to any desired

fixed Q value.

Buffer Level Any model buffer group level can be compared, using one of six logical operators, to any

desired fixed buffer level value.

Element State Any element state (from 5) can be compared, using one of six logical operators, to any

desired element state.


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Element Details Form - Preventive Maintenance (PM) TabFour fields are employed to define each of up to three Maintenance (PM) cycles adopted for the element. These

are the Up time, the Down Time, the point in the cycle at which the Down Time starts, and whether PM returns

the Element to Good-as-New.

Figure 2.8 : Element Details form, Planned Maintenance tab

Parameter Name Data Type Description

Up Time, Down Time,

Down Time Starts At

Positive integer If Up Time is set to a value greater than zero, this is interpreted as the time

period during which the element is not undergoing preventive maintenance

(although it may suffer random failure and repair during this period). The

Down Time field specifies the period required for preventive maintenance to

be carried out. The Down Time Starts At field identifies the position in the

preventive maintenance cycle at which the down time starts.

PM to Good-As-New Boolean This field should be checked to indicate that this PM cycle restores the

element to Good-as-New, or left unchecked for Bad-as-Old. Note that

Preventive Maintenance takes precedence over all other possible eventswhich can occur for that element; whatever state the element is in, it is

always sent for preventive maintenance at the appointed time in the cycle.

PM carried out

intelligently

Boolean This field indicates whether 'intelligent' PM is to be modelled; if this is so,

the box should be checked. Note that the setting of this flag for the

individual Element can be 'overridden' globally as described in Chapter 3.


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Detailed Group Parameters

Displaying the Group Details FormGroups are defined using the Edit Group Details form. To display the Group form, simply double-click within the

bounds of the required group but not on any element. The form displayed contains data fields appropriate to the

group type. If the model is complex and the required group is not easily visible, then use the Go To and Zoom

facilities, as described in Chapter 5.

Figure 2.9 : Group Details form

Defining Group ParametersIdentifying the GroupGroups in RAMP are identified by a Group Name. As with elements, the Group Name is user-defined and

therefore does not affect the structure or the operation of the model. It can be helpful, especially when revisiting

an old model, if the Comments field contains a brief description of what the group is supposed to do.

Assigning the Group Name Double-click the Group to display the Edit Group Details form. Click on the Name field (which initially shows the name UNDEFINED) and enter a valid name. Click on OK.

Once the Group name has been changed from UNDEFINED, the specified group is displayed in the defined

colour for that group type. The forms for the different Group types are described in the following sections.

Defining the Group TypeThe data items that should be entered into the form are listed in the following table. Groups that do not appear inthis table have no parameters to set. More details as to what these parameters actually mean are provided later on

in this chapter. Note that the Rating parameter in the Active Redundant group can be disabled by checking the

Rating Not Limited box. In this case the output of the group is the sum of the q values of the group components.


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Group Name Parameters

Active Redundant Rating - this refers to the expected output of the group.

Cut Off- this is the point below which the output of the group will be zero.

Standby Redundant Rating - this refers to the expected output of the group.

Cut Off- this is the point below which the output of the group will be zero.

Time Time Delay- the time period between successive activations of the contained elements.

Buffer Capacity- the size of the storage contained in this buffer, which should be consistent with

the unit chosen for q elsewhere in the model.

Initial Level- the initial level of the substance contained in the buffer, which should beconsistent with the units chosen for q elsewhere in the model.

Input Constraint- a new feature in RAMP 3.5 which allows the user to cap the input

capacity of the buffer to the q level of another specified group or element.

Output Constraint- a new feature in RAMP 3.5 which allows the user to cap the output

capacity of the buffer to the q level of another specified group or element.

Equality Lower Limit- the lower limit of the range that equality will be tested against.

Upper Limit- the upper limit of the range that equality will be tested against.

Model Editing Facilities in the Group Details FormChanging the Group TypeTo change the group type of an existing group:

Double-click on the required group to display the Edit Group Details form. Click on the Group Typefield to display the drop-down menu.

Choose the new group type from the Group Type list.

The Edit Group Details form changes to show the parameters appropriate to the new group type, and the builder

screen shows the new group in the selected colour for that group type.

Series, Active and Standby Redundant groups are freely interchangeable. For instance, an N-element Series group

becomes an N-element Standby group.

Increasing the Number of Elements in a GroupTo increase the size of any existing group:

Double-click the required group to display the Group Details form. Click on and edit the Number of Itemsparameter. Click on OK.

The model will be re-displayed showing the extra elements, if allowable given the group type. If not, a warning is

displayed.

The extra items are always added to the right-most position of Series groups and to the bottom-most position of all

other group types. The order of items within a group can be changed by use of the Copy/Cut and Paste facilities,

or by using the right-click and drag feature.

Reducing the Number of Items in a GroupThe Edit Group Details form includes a Deletebutton with which items within the group can be deleted. To

delete an element or group:

Locate the element or group by name in the Group Structure list and click on the item to highlight it Click on the Deletebutton - a confirm dialog is displayed showing the name of the item to be deleted.

Click on Yes to delete or No to abandon. Alternatively, highlight the item in the Model Diagram and press to remove it.

The selected item will be deleted from the Group Structure list. Click on OK and the model is redrawn without

the deleted item.

If all items in a group are deleted, then the group reverts to a single element having the name and identifier

number of the original group.


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Further Editing FacilitiesRAMP provides standard Windows editing facilities, (e.g. Cut, Copy, Paste and Delete) either from the keyboard,

e.g. , from the Edit menu, or from the pop up menu on the mouse right click.

In order to address the problems of finding and editing data in large models, additional facilities (Select and

Element Table View) have been provided in version 3.5. A more detailed description of these facilities is given in

Chapter 5.

Select FunctionThe Select function can be found on the Edit menu, and provides a search facility for finding elements, based on

parameters such as the element name or failure distribution.

The selected elements will be displayed as a table if Table View is selected. Otherwise, the model diagram will be

displayed with all element and group colours set to white except for the selected items, which are set to green.

Any element or group which is edited while in Select View will return to its standard colours. This is designed to

help the user keep track of what has been edited whilst in Select View. Choose Deselect from the Edit menu to

return to the normal model diagram.

The Select Children function is used with the Model Diagram only and does not provide a search facility.

Highlight a group in the Model Diagram and click on Edit \ Select Children. All elements immediately below

the level of the selected group will be selected.

Element Table ViewThe Element Table View provides a spreadsheet view of the element data in the model. The data is organised in

three tabs which correspond to the tabs on the Element Details form. This function is provided to allow rapid

editing and checking of model data and will also accept data pasted from other applications. Note that it is not

possible to paste data into any field that uses a drop-down box.

The Element Table View is available from View \ Element Table View, or from the Selection Criteria form. If

less than two elements on the model diagram are highlighted, then all elements are shown in the table. If two or

more elements are highlighted then only those elements are shown in the table. More than two elements can be

selected directly from the model by clicking on the elements with the Ctrl key depressed, as well as the Select

Children described above.

The Element Table View is used with the Select facility to show selected elements. When using the Select facility(Edit \ Select), click on Table View to display the selected items in a table.

Element Parameter FactorsThe Element Parameter Factors facility allows you to change parameters on multiple elements. It is used with the

Element Table View. With the Element Table View selected, click on Edit \ Element Parameter Factorsto

bring up the Factors form. Note that changes made through the Factors form will apply to all elements displayed

in the Element Table View and that some changes are irreversible.

Data fields available for change through the Element Parameter Factors form are:

Element Q Value. Logistic Repair Delay. Failure Distribution. Repair Distribution. Preventive Maintenance.

Note that fields contain default values which are applied to elements, containing the value 1 when the factors are

used for multiplication or division of element parameters and zero when used for addition purposes.


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Element TypesRAMP provides the Element Type facility to speed up the entry of data into a model. Element Types are

predefined sets of element data which can be loaded quickly into any element. To create an Element Type, click

on the Create Element Typebutton on any named Element Details form (i.e. any element which is not

UNDEFINED). Alternatively, click on Data \ Element Typesto open the Element Types list, as shown in Figure

2.10 below. Clicking the Create button will open up a new Element Details form which you can populate with

information.

Once the Element Type has been created, it can be used by any element - click on the Element Type drop-down

list on the Element Details form to select from among the defined Element Types. Note that this will overwrite

any existing information (except the name) in the chosen element and that the imported element data cannot be

changed until the Element Type is changed back to Unique, or the data for the Element Type is edited itself.

Figure 2.10 : Element Type list

Element Types are saved in the model file and will be loaded whenever a model is loaded. They can also be

imported from other model files and can therefore be passed between models. It is recommended that a model file

with useful Element Types in it should be maintained by anyone using RAMP frequently.


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3CHAPTER 3 RAMP MISSION DATA

This chapter gives you more information about the Mission Data used in a RAMP model. In Chapter 2, we

covered the Element and Group data required for a model in some detail. Although this is necessary, it is not

sufficient to define everything about the model that we wish to run.

RAMP is a Monte Carlo package and simulates events based on distributions set by the user. Because the element

failure and repair times are sampled randomly from the distributions, the modelled time period represents only one

history of possible events. It is necessary to repeat the mission (perform many simulations) in order to produce a

picture of the spread of possible results and to give statistical confidence in the results.

The data required to control the simulation, in contrast to the data required to define the model, is entered via the

Mission Data form, available from the Simulationmenu. Some information about results from the simulation is

given in Chapter 4.

The Mission Data Form General Information Tab

The Mission Data form consists of four main parts, each part of which is accessed by clicking on the appropriate

tab.


The first field on this form is the Model Title - this appears on any printed results and must be filled in before the

model can be run. The title can be any length up to 60 characters and it is useful to give a short description of the

model here.

Chapter


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Simulation Start and Termination ConditionsMission LengthThe mission length is a measure of how long the simulated system is to run for. For example, if the system is to

be simulated over a period of 1 year and the unit of time in use in the model is hours, then the mission length will

be set to 8760.

Number of MissionsThis determines how many times RAMP repeats the simulation before finishing the run.

Random Number SeedThe random number seed determines the base from which calculation starts in the model. If the random number

seed is set to a specific number, then the simulation can be repeated exactly. If the random number seed is set to

zero, then RAMP will choose a seed based on the number of seconds after midnight and there will be variation

between one run and another.

Q Value TerminationRAMP normally completes a run when all the specified missions have been completed. The results from the run

are then calculated. However, if Q value termination is chosen, then RAMP will stop the simulation after a named

group has changed its Q value a specified number of times.

Intelligent Preventive MaintenanceIntelligent Preventive Maintenance (IPM) may be used for any element which has both unscheduled failures (i.e. a

failure distribution) and preventive maintenance specified. IPM will take advantage of an unscheduled failure to

perform the next scheduled PM cycle, if the two events are close enough together.

No IPM for any element (default). IPM determined for every element (all elements with PM will use IPM). IPM depends on element IPM flag (only items which specify IPM on the Element form use it).

The typical result of setting IPM would be a slight increase in availability as the total downtime is reduced.

Logging OptionsEventsThe Event Log is a listing of all events which have taken place during the simulation, for as many runs as

specified. The information contained in the Event Log consists of the Mission Number, the event time, the

element name and ID and the specific state change for the element.

Warning -log files can get very large! It is recommended that you should try using the log file for 1 simulation

only (specify 1 in the Missions to Logbox) and check the resulting log file size before logging lengthy multiple

simulations. The log file is called FILENAME.LOG and is written in the same directory as the other model files.

BuffersThe Buffer Log is a listing of buffer performance during the simulation. The information contained in the Buffer

Log consists of the Mission Number, the time, the buffer name and ID, the buffer level, the nominal buffer input

Q value, the nominal buffer output Q value and the actual buffer output Q value. Note that the value of the output

from any buffer group is a function of the nominal output Q value, the nominal input Q value and the buffer level

- this is why the nominal and actual buffer output Q values may differ.

Missions to LogSet the number of missions for which a log is required - this applies to both the event and buffer logs.


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The Mission Data Form Rolling Averages Tab

The Rolling Average function provides a graph of group performance over time. You can select up to eight

groups to monitor (including the topmost System group if required). The graphs produced can be displayed on

screen or printed out and the data file produced may be imported into a spreadsheet for further processing if

required.

Time Span and IncrementThese two parameters control the 'granularity' of the graph - ie how much detail it will show. The Rolling

Average is produced by averaging the performance of the selected group over an initial period equal to the Time

Span. Once this is complete the time span is incremented and the rolling average is calculated again. The end

result is a graph of up to six thousand points which gives a good representation of the Q value output of your

chosen groups, although care should be taken not to exceed the points limit when specifying the time span and

increment.

It should be noted that most monitors do not have a resolution of more than about 1,000 pixels widthways, so

more than this will not be visible on screen. For multiple missions, the results are accumulated with the set of

rolling average figures generated from all previous missions in order to construct a single, averaged set of data.

Selecting Groups

To add a group to the list, click on Addand choose from the drop-down list presented. Up to eight groups forrolling averages can be defined. Use the Find facility if your model is large and the group is not easily found. To

delete a group from the list, highlight the chosen group and click on Delete.

Figure 3.2 : Mission Data form, Rolling Average tab


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The Mission Data Form Histograms Tab

The Histogram function provides a graph of a frequency count based on the results from multiple simulations.

The range of results derived from the simulations is split into a number of bands, and the number of results falling

into each band is displayed as a histogram. Up to ten histograms can be defined.

Figure 3.3 : Mission Data form, Histograms tab

Histogram TypeTwo types of histogram are supported. The Down Time histogram records the total downtime for each selected

group over a number of missions and graphs these over a range selected by the user. The Q value histogram

performs the same function for the average Q value of a particular group. It should be noted that the range for the

graph display is specified by the user - the Q value range is normally easier to specify as it will only vary between

zero and the maximum Q value of the group. The same group may be specified for both the Down Time and

Average Q histograms if required.

Specifying HistogramsTo add a histogram, click on Addon the Histogram form and select from the drop-down list. Use the Find

function to locate your specified group if the model is large. Having selected the group, you will also need to

specify whether the group will have a Down Time or Average Q histogram generated for it, and a range of values.

If the range of values is set too narrow, then some or all of the graph may not be displayed. To remove a

histogram, select a group from the Defined Histograms list and click on the Deletebutton. To modify histogram

details, select a group and click on the Editbutton, or edit the data directly within the table.


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The Mission Data Form Criticality Tab

RAMP calculates the effect of every element failure or event on the overall Q value of the surrounding groups.

The Criticality function provides a ranked list of elements based on their failure effects. Those elements that

cause the most downtime or production loss for the selected groups will appear at the head of the criticality list.

This function allows 'hot spots' and bottlenecks to be identified easily and can be used for plant optimisation or

design improvement.

Specifying Criticality GroupsTo use the criticality function, select up to twenty groups using the Addbutton on the criticality tab. For those

groups, the criticality effects of the elements within them will be calculated. The criticality results are available on

the Resultsmenu.

Figure 3.4 : Mission Data form, Criticality tab

Significance of Criticality ResultsIt should be noted that the criticality of an element may vary according to which group is selected for the

criticality calculation. An element may be highly critical to a group which is several levels down in the hierarchy,

but have little or no effect on the performance of the system as a whole, owing to redundancy or other overriding

effects. Therefore, it is always recommended that you should know what results are required from the criticality

calculation before specifying groups.

Running the Simulation

To start the simulation, choose Run from the Simulation menu. If the model has been changed since being

loaded or last saved, RAMP will ask you to save the file before it is run.

Click the Savebutton to save the file using its present name, the Save Asbutton to save the file under anothername or the Cancelbutton to cancel the run. When you save the file, RAMP goes through a validation procedure

to make sure that the structure of the model is correct and that there are no problems with the model data. If

problems are found then the validation will halt with an appropriate error message.

The simulation may take seconds, minutes or hours, depending on the complexity of the system, the number of

events (failures, repairs, etc.) which occur during a mission and the duration and number of missions to be

simulated.


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The Progress MonitorDuring the simulation run, the Progress Monitor is displayed to show how far the simulation has advanced. The

Progress Monitor normally displays two bars - the top bar displays the progress of the individual simulation and

the bottom bar displays the progress of the run as a whole. If you have specified 'Q Value Termination' in the

Mission Data form (see above) then a third bar will be displayed which shows the simulation progress against the

number of Q value changes required.

Figure 3.5 : Progress Monitor

Control of the SimulationWhile it is running, you may interrupt the simulation run at any time in one of the following ways:

By clicking the Abortbutton in the Progress Monitor form. In this case, no data will be produced. By clicking the Halt and Calculatebutton in the Progress Monitor form. In this case, the simulation

will halt at the end of the current mission. RAMP will calculate all data accumulated up until termination

of the run and write these to the appropriate files.

On completion of the simulation run, RAMP will display a message box stating that "Simulation completed

successfully.

A Worked Example of a RAMP Simulation

After constructing the worked example of a model in Chapter 2, you may now like to complete the task byrunning a simulation of the mill. If so, proceed as follows.

First, you need to inform RAMP of the conditions under which the simulation is to be run. This includes

information on the duration of each mission, the number of missions and the way in which rolling averages are to

be calculated:

Select Mission Data from the Simulation menu to open the Mission Data Form. Choose a meaningful Mission Lengthand Number of Missions. Add any groups required to the Rolling Averages, Histogram or Criticality tabs, as described above. Click OK to save the data close the form. Choose Run from the Simulation menu.

The progress bar will be displayed indicating the degree of completion of the simulation and the number of

missions completed. Assuming no errors are encountered, you will then see the message "Simulation completed

successfully".


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4CHAPTER 4 RESULTS OF THE SIMULATION

Uses of RAMP Results

This Chapter gives details of the various results provided by RAMP. It should be noted that, although the results

provided are detailed and extensive, they have no particular meaning until they have been interpreted and

understood with relation to the system being modelled. With the correct understanding of the model and

reasonable interpretation of the results, these are some of the uses which can be made of RAMP simulation

models:

Identification of bottlenecks. Calculation of optimal reserve holdings. Assessment of demand profiles.

Checking performance against requirements. Checking the real benefits of redundancy. Assessment of changes to operational and maintenance procedures. Checking adequacy of maintenance resources. Calculation of failure times for complex systems.

RAMP Files

The results of the simulation are recorded in data files which RAMP writes to your computer's current working

disk drive. If a simulation run has completed successfully, RAMP may produce up to eight separate files

containing data relevant to the actual run as follows:

FILENAME.REC The Record file is created by the simulation engine when a simulation isperformed and contains all of the input data in tabular form.

FILENAME.OUT The Output file contains the results of a successfully executed simulation.The Output file is used to generate the various results tables.

FILENAME.RAV The Rolling Average file containing data points from rolling averagecalculations.

FILENAME.D20 The Histogram file containing data points from histogram calculations. FILENAME.CRT The Criticality file containing details of the selected group criticality lists. FILENAME.TMP A file generated by RAMP which is passed to the simulation engine. FILENAME.LOG The Event Log file, containing details of all the events in the simulation. FILENAME.BUF The Buffer Log file, containing details of buffer performance.

If execution of the simulation was unsuccessful owing to the presence of faulty data in the model, only the REC

files and OUT files will be created, which will contain appropriate error messages. Another file which is created

is FILENAME.VAL, which contain the results of the validation operation performed when the model was saved.

Note that if you have made changes to the model since the last simulation was run, some results may not be

available as RAMP will detect that the results files are older than the model. In order to avoid this problem, and

as good general practice, always save the model under another name before making changes.

RAMP Results Tables

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The main results from the RAMP simulation are presented as a set of tables, some of which will be available for

all models and some of which depend on the model configuration. The table names are shown under the Results

menu. Details of each Results table are given below.

The tabulated numerical results may be the best way of identifying the cause of low Availability or Productivity.

Examination of these results may indicate a particular problem such as the following:

A group which has a very low average q value.

An element which has a very low average q value. A Buffer group which spends a very large proportion of the time empty. An element which spends a long time in State 2 (repair) - this may indicate queuing for repair,

e.g. because of insufficient resources.

Insufficient Repair Trade resources. Insufficient Spares of a particular type.

Modelling details should always be checked if any unexpectedly low values are noticed this often indicates a

mistake in data entry or model design.

The interpretation of the results from a simulation will depend on the design of the model (i.e. the user's intentions

and the chosen measure of interest). It is the user who decides during the system analysis stage what measure of

capability is to be examined, and therefore what the q value of elements and groups should mean.

Results Tables - Group and Element ResultsPart 1 - Group ResultsThese results are available for all models:

Name Description

Group Name of group plus group number.

Type Type of group - eg Minimum , Buffer, etc.

Average Q Average Q of group as calculated over entire run.

% SD for Average Q Standard Deviation of average Q calculated at the end of each simulation.

Average Time, Q = 0 Average time during the run for which the Q of this group is zero.

Average Frequency, Q = 0 Average frequency during the run of events which brought the Q of this group to

zero.

Part 2 - Buffer Group ResultsThese results are available only where Buffer groups are specified:

Name Description

Group Name of buffer group plus group number.

Average Freq Empty Average frequency per simulation that buffer group is empty.

Average Freq Full Average frequency per simulation that buffer group is full.

Average Time Empty Average time per simulation that buffer group is empty.

Average Time Full Average time per simulation that buffer group is full.

Minimum Level Minimum buffer level achieved during run.

Maximum Level Maximum buffer level achieved during run.


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Part 3 - Element Q value ResultsThese results are available for all models:

Name Description

Element Element name plus element number.

Specified Q Q specified for element as nominal capacity.

Actual Q Achieved average Q over run.

Actual / Specified Q Percentage of specified Q achieved.

Percentage SD for Average Q Average frequency during the run of events which brought the Q of this elementto zero.

Average q divided by specified q for the mission is a particularly useful result as it gives a direct indication of how

well individual elements perform. However, it should be noted that elements in the passive branch of a standby

group will always have a low q/Q value and this should not be taken to mean that the element is particularly

unreliable.

Part 4 - Element Time in Each StateThese results are available for all models:

Name Description

Element Element name and element number.

PM Average amount of time per simulation spent in Planned Maintenance.

Repair

combined manual

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