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[January 2007] This document is intended as general guidance on how to plan for achievement of the Reliability and Maintainability - R&M - requirements of a System or Equipment.
Good reliability is an all-pervading and essential requirement for any equipment as it impacts directly on the performance and hence, operational issues of usage and support – technical, physical and personnel - as well as overall costs. In short, reliability means sustained performance but it must be designed in from the beginning, including maintainability – it cannot be added on someway through the programme, anymore than quality can be inspected in at the end. Early consideration – when possible – of various options, including integration aspects, can allow their effect on use and whole life costs to be envisaged and evaluated allowing possible alternatives and trade-offs to be evaluated. Thus, potential risks can be identified and a plan developed to deal with them. The R&M Case (see Defence Standard 00-42 Part 3) provides a framework for achieving R&M requirements and its discipline is recommended.
There are then, a number of pre-requisites, which must be addressed prior to formulating a procedure for achievement of R&M, including, but not limited to: - Full discussion with all concerned during early studies so that the overall requirements are understood and agreed - what it is required to do, where, when, by whom, for how long, frequency of operation, etc., from which likely system/equipment solutions can be proposed.
- Identify major sub-systems and their functions, including any existing or associated equipment interface requirements, and consider trade-offs;
- Define transportation, support plans and storage, based on the above;
- Potential procurement strategies, e.g. New, Commercial off the shelf (CoTS), Finance Plans (PFI, PPP) and maybe Contractor Logistic Support (CLS).
A number of procedures and processes are available, which can help both in the definition stage and overall management of reliability during the equipments life, e.g. any relevant historical data, modelling, progressive assurance - the R&M Case, Reliability Centred Maintenance (RCM), integration, etc.
The major activities are summarized in three main objectives: - Objective 1 – Understand the Requirements,
- Objective 2 – Plan to achieve the Requirements, and
- Objective 3 – Demonstrate that the Requirements have been/will be, met.
These are further expounded in the R&M Case, which also explains the principles of Progressive Assurance as a means of showing achievement. Once the equipment is in development/production/use, achievement and performance should be recorded. A performance sustainment feedback system such as DRACAS plus monitoring of functionality can then be used to maintain capability.
The above is a broad overview of the processes involved to ‘set the scene.’
However, a frequent concern is how to approach what may well be a large and complex system, e.g. a ship, aircraft or even a vehicle. While the overall system must not be forgotten, it can be broken down into smaller sub-systems, which are more easily managed or may even exist. These might be – chassis, body, engine, braking system, accommodation, special equipment, etc. The following Table shows how these might be handled through various tasks:
| ITEM |
|
TASK |
|
HOW |
|
OWNER |
|
|
|
|
|
|
|
| 1 Top System |
|
Define o/a operational
requirement, success
and availability
Identify any requirements
to interface with other or associated equipment |
|
Clarify Top Level Key User
Requirements
Scenario modelling,
update of existing equipment,
Operational Profiles, etc. |
|
Customer |
2 |
|
Develop Operational Profiles, define
failure / success criteria.
Write user requirement
URD / Outline specification |
|
Scenario modelling, etc
(Initiate R&M case) |
|
Customer via Project Manager (PM) |
| 3 |
|
Analyse relevant data from similar equipment where applicable |
|
Research trials data as applicable; run trial |
|
Customer via PM |
| 4 |
|
Break down into a family of sub-systems
Confirm interface requirements / capability |
|
Engineering and programme judgement, feasability study |
|
PM via appointed sub-system managers |
5
sub-system |
|
Repeat 1-3 (&4?) to develop individual system R&M requirement; FMECA etc |
|
Scenario modelling, reference to existing equipment, etc. Specialist advisors |
|
PM via appointed R&M focus (training?) |
| 6 |
|
Integrate individual sub-systems to produce top system configuration
Write SRD / final specification |
|
Scenario modelling etc
Specialist advisors
Develop R&M case(s) |
|
PM and appointed R&M focus |
| 7 |
|
Develop upkeep cycle |
|
Modelling?
Established procedures |
|
Customer via PM |
Proposals to meet these requirements can then be formulated for consideration. Sub-system Managers develop similar procedures for the sub-systems and further define Failure/Acceptance/Success criteria with Specialist advice.
PM and Customer develop a System Requirement Document for Overall System and sub-systems; write System AR&M Statement, including R&M Case and Plans, demonstrations, etc. technically and contractually for the Request for Proposal (RFP). A formal RFP can then be prepared and issued to likely suppliers.
On receipt of tenders the Project Team – Customer and PM with Specialists – should meet to Assess both Tenders and Contractor capability, compare and discuss relevant merits and consider trade-offs. The Team can then finalise requirements, select contractor, let contract and subsequently monitor progress, assess demonstrations, review in-service support. All of this should be recorded in and controlled via the R&M Case.
It is considered essential that all interested participants, or their representatives, meet regularly from the earliest stage to review the progress - on all requirements not only R&M – and to agree and record decisions taken, with regard to ‘knock-on’ effects. Outcomes, with regard to R&M, form part of the R&M Case. While the concept is to Design for Success, this also means designing for manufacture, ease of use, maintainability and support.
From the above it can be seen that development of a procedure to satisfy R&M requirements requires identification and management of numerous key elements, such as:
- Understand the specific requirements and operational environment,
- including any interface/integration with other new or existing equipment
- Analysis of requirements to define appropriate R&M targets
- Identification of risk areas and methods for mitigation
- Design for R&M, including manufacture, maintenance, use and storage
- Regular assessment of R&M achievement during development
- Measurement and feedback of R&M achieved in service
Finally this must be underpinned by a sound contract containing sufficient and adequate, but not excessive, fully defined requirements. Suitable milestones or checkpoints, reporting procedures and acceptance criteria, etc., for effective control should also be defined and agreed.
Achievement of Reliability should not increase overall costs but rather minimise them; the more reliable the equipment - at all stages - the less repetitive development testing, numbers of systems and eventual support will be required. Thus, Availability will be higher while support costs and inventory will be lower. Back to top
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