reliability centred maintenance -...
TRANSCRIPT
DNV GL ©
DRAFT
2015-08-20 SAFER, SMARTER, GREENER DNV GL ©
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2016-04-06
Simon Mockler/John Lee
MARITIME
Reliability Centred Maintenance (RCM)
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Origins, Developments and Maritime Applications
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Session Topics
Reliability Engineering and Maintenance Terminology
Reliability Centred Maintenance (RCM) – What is it?
Safety/Reliability/Quality
Maintenance Evolution > 1930s
Origins of MSG1, MSG2 and MSG3 in Civil Aviation and Basic Differences
RCM – Seven Basic Questions
RCM Process, Groups and Outcomes
Changing Maintenance Principles and Practises
RCM and Associated Challenges in the Commercial Maritime Environment.
Examples of RCM in Maritime Context
Conclusions
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What is Reliability Engineering?
The emerging world economy is escalating the demand to improve the
performance of products and systems while at the same time, reducing
their cost.
The requirement to minimize the probability of failures, whether those failures
increase costs or threaten public safety, is also placing emphasis on reliability.
The body of knowledge that has been developed for analysing such failures and
minimizing their occurrence cuts across virtually all engineering disciplines and
spheres.
In the broadest sense, reliability is associated with dependability, with successful
operation and with the absence of breakdowns or failures.
Source: Introduction to Reliability Engineering, Lewis E.E.
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Key Definitions
Reliability (Engineering Definition)
The probability that a system will perform its intended
function for a specified period of time under a given set of
conditions
Maintenance
Ensuring that physical assets continue to do what their
users want them to do.
Safety
The degree of freedom from danger and harm
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Maintenance Terminology
Reactive maintenance?
Proactive maintenance?
Condition Monitoring (CM)?
On Condition?
Preventive Maintenance (PM)?
Planned Maintenance (PM)?
Reliability Centred Maintenance (RCM)?
What is the difference?
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Effective Maintenance Management
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1. Management strategy
2. Processes and procedures
3. Organisation and competence
4. Technical account structure
5. Risk assessment
6. Maintenance plan
7. Spare parts management
8. Measure and follow up
Effective
maintenance
management
Management
Strategy
Processes
&
Procedures
Technical
account
structure
Risk
Assessment
Organisation
&
Competence
Maintenance
Plan
Measure &
follow up
Report
maintenance
Analyse
maintenance
performance
Initiate
improvement
initiatives
Report
maintenance
Report
maintenance
Analyse
maintenance
performance
Analyse
maintenance
performance
Initiate
improvement
initiatives
Initiate
improvement
initiatives
Identify &
adjust Goal &
Requirements
Adjust or
develop maint.
plan
Plan
maintenance
Carry out
maintenance
Identify &
adjust Goal &
Requirements
Adjust or
develop maint.
plan
Adjust or
develop maint.
plan
Plan
maintenance
Plan
maintenance
Carry out
maintenance
Carry out
maintenance
Consequence of event
Pro
pa
bility
to
ha
pp
en
High
(3)
Medium
(2)
Low
(1)
321Low
(1)
642Medium
(2)
963High
(3)
Consequence of event
Pro
pa
bility
to
ha
pp
en
High
(3)
Medium
(2)
Low
(1)
321Low
(1)
642Medium
(2)
963High
(3)Spare
parts
management
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What is RCM???
Reliability Centred Maintenance is a zero-based structured PROCESS used
to identify the failure management strategies required to ensure an asset
meets its mission requirements in its OPERATIONAL ENVIRONMENT in
the most SAFE and COST EFFECTIVE manner.
Zero-Based means that each RCM analysis is carried out assuming that no proactive maintenance is being
performed. Failure modes and effects are written assuming that nothing is being done to predict or prevent
the failure mode.
Source: The RCM Solution, Nancy Regan, 2012.
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Recommended Resources for RCM
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Quality and Reliability
Quality
The totality of features and characteristics of a product or services that
bear on its ability to satisfy given needs.
High Quality (two criteria must be satisfied)
Performance standards must be highly optimised to the user’s requirements
The performance standards must be robust.
Performance Variability
Three main causes of performance variability:
Variability or defects in the manufacturing process
Variability in the operating environment
Deterioration resulting from wear or ageing
Note: Quality implies performance optimization and cost minimization
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Performance Standards (UKSCR Verification Process)
Safety Assessment
s
1 Hydrocarbon Containment
2 Primary Structure
3 SMS
4 ESD
5 F & G Systems etc etc......
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7
8
9
10
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Major Accident Hazard Register
Record of Safety Critical
Element Performance Standards
Verification Scope Examination
ICP Review & Comment
ICP Review & Comment
ICP
Examination
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Asset Integrity Management
Identification of Safety Critical Elements (SCEs) and
maintaining associated pre-defined performance
standard's (PSs) is the foundation of asset integrity
management
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Failure Distributions
Longstanding assumption that failures are related to age of asset and the length
of time in service. True for high load bearing ship structures operating in a range
of extreme environmental conditions and salt water environment.
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Intervention before failure
Failure
rate
λ
Time t
Calendar-based maintenance
schemes
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Complex Engineering Systems
Complex engineering products such as aircraft and marine/offshore units,
comprise a number of different sub systems including:
– Structural systems
– Electrical, electronic, instrumentation and control systems
– Mechanical systems including static and rotating machines
– Piping and fluid systems
– Hydraulic systems
– Software systems
What are the failure distributions???
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Deep Groove Ball Bearing Failure Distribution (NASA)
The figure shows the failure distribution of a group of thirty identical 6309 deep groove ball bearings installed
on bearing life test machines and run to failure, using standard test procedures.
The X-axis identifies the individual bearing being tested while the Y-axis is the number of revolutions
achieved prior to fatigue failure of the individual bearing.
The wide variation in bearing life precludes the use of any effective time-based maintenance strategy
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Six Failure Patterns Identified (mid 1970’s aircraft maintenance)
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Fatigue
Time t
Failure
rate
λ
Wear out
Failure
rate
λ
Time t
Bathtub
Failure
rate
λ
Time t
Infant mortality
Failure
rate
λ
Time t
Random
Failure
rate
λ
Time t
Break in period
Failure
rate
λ
Time t
Age related failures ~10% in aerospace
Random failures ~ 90% in aerospace
A B C
D E F
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Nowlan and Heap, December 1978
“Despite the time-honoured belief that reliability was directly related to
the intervals between scheduled overhauls, searching studies based on
actuarial analysis of failure data suggested that the traditional hard-time
policies were, apart from their expenses, ineffective in controlling failure
rates”
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Infant mortality
Failure
rate
λ
Time t
68%
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CM - Proactive Tasks
Means overhauls or component replacement at fixed intervals based on the
assumptions that most items operate reliably and then wear out.
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Preventive Maintenance/On Condition Tasks
Preventive Maintenance (PM)
Scheduled restoration and scheduled discard entails remanufacturing a
component or overhauling at or before a specified age, regardless of its condition
at the time.
On Condition Tasks
Most failures give warnings (potential failures) which are defined as identifiable
physical conditions which indicate that a functional fault is about to occur or is in
the process of occurring.
Predictive Maintenance
Condition Based Maintenance
Condition Monitoring (CM)
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Preventive and On-Condition Maintenance
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Proactive
Maintenance
Preventive
Maintenance
On-Condition
Maintenance
Condition-Based
Maintenance
Scheduled
Restoration
Scheduled
Replacement
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Potential Failure
A potential failure is an identifiable condition which indicates that a
functional failure is either about to occur or in the process of occurring
(e.g. hot spots in electrical insulation, vibrations, cracks, particles in lubricating
oil, excessive wear patterns etc.
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P-F Interval
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Time t
Perfo
rm
an
ce P
Functional failure
Detection threshold
P-F Interval
Inspection
interval
P
F
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Maintenance Evolution Since 1930s
First Generation (up to WW2)
Fix when broken
Second Generation (after WW2 up to mid 1970’s)
Concept of Preventative Maintenance (PM) Introduced in 1960s
Growth of Maintenance Planning and Control Systems
Scheduled overhauls
Big slow computers
Third Generation (since mid 1970s).
Condition Monitoring
Design for reliability and maintainability, hazard studies and FMEA
Small fast computers and expert systems
Multi-skilling, teamwork and expert systems
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Origins of RCM in Civil Aviation
MSG-1: 1968 - Maintenance Evaluation and Programme Development
Prepared by the 747 Maintenance Steering Group and published in 1968.
MSG-2: 1970 - Airline/Manufacturer’s Maintenance Programme Planning
Document
Improvements to MSG-1 led to the development of MSG-2.
MSG-3: 1978 - Operator/Manufacturer’s Scheduled Maintenance
Development
In the mid-70’s, the DOD was interested in learning how maintenance plans were
being developed within the commercial airline industry.
In 1976, DOD commissioned United Airlines (UAL) to write a report which detailed
their process.
Stanley Nowlan and Howard Heap wrote Reliability Centred Maintenance
which was published in 1978.
MSG-3 continues to be used within the airline industry today but is still intended
to develop a maintenance program for prior to service aircraft.
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Basic Differences between MSG-1, MSG-2 and MSG-3
MSG-1 applicable to 747-100
MSG-2 applicable to all aeroplanes (process orientated)
MSG-3 (task orientated)
MSG-2
HT (Hard Time – component lifetime)
OC (On Condition – leave on aircraft until failure, but perform T&I to ensure
component not compromised)
CM (pay attention, but no inspections or tests, wait until failure)
MSG-3
HT
OC
ZIP (CM replaced by Zone Inspection Programs)
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Fatalities/Year Passenger Aircraft (Data from World Bank)
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RCM – The 7 Basic Questions
1. What are the functions and associated performance standards of the
asset in its present operating context?
2. In what ways does it fail to fulfil its functions?
3. What causes each functional failure?
4. What happens when each failure occurs?
5. In what way does each failure matter?
6. What can be done to predict or prevent each failure?
7. What should be done if a suitable proactive task cannot be found?
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Failure Modes/Effects/Consequences
Functional Failures
Failed state: when an asset is unable to fulfil a function to a standard of
performance which is acceptable to the user.
Failure Modes
Events which are reasonably likely to cause each failed state (includes wear and
tear, design flaws and human error).
Failure Effects
What happens when each failure mode occurs
Failure Consequences
The only reason for doing proactive maintenance is to reduce the consequences of
failures.
Hidden failure consequences
Safety and environmental consequences
Operational and non-operational consequences
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FMEA (Central to RCM)
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RCM Process
Planning
Which assets will benefit from RCM and how?
Assess resources required to apply process
Decide who is perform and audit each analysis and arrange training
Ensure that operating context is clearly understood
RCM Group
Facilitator
Engineering supervisor
Mechanical/electrical engineer
External specialist
Operator
Operations supervisor
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Outcomes/Results of RCM
Outcomes of RCM Process
Maintenance schedules
Revised operating procedures
A list of areas where one-off (design) changes are required
What RCM Achieves
Greater safety and environmental integrity
Improved operating performance (output, product quality and customer service)
Greater maintenance cost-effectiveness
Longer useful life of expensive items
A comprehensive database
Greater motivation of individuals
Better teamwork
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Standards for RCM
SAE JA1011 Evaluation Criteria for RCM Processes (RCM2) – 1999
(updated 2009).
MIL-HDBK-2173 US DOD Handbook, RCM Requirements for Naval Aircraft
Weapons Systems and Support Equipment
MIL-STD-3034 US DOD Practise RCM Process
NASA RCM Guide for Facilities and Collateral Equipment
TM 5-698-2 Technical Manual RCM for Command, Control, Communications,
Computer, Intelligence, Surveillance and Reconnaissance Facilities, US Army.
Etc.
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Changing Principles of Maintenance Management
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“Maintenance is about preserving
physical assets”
“Routine maintenance is about
preventing failures”
“The primary objective of the
maintenance function is to optimise
plant availability at minimum cost”
“Most equipment becomes more
likely to fail as it gets older”
Maintenance is about preserving the
functions of assets
Maintenance affects all aspects of business effectiveness and risk – safety, environment and energy efficiency, quality– as well as availability and cost.
Most failures are not more likely to occur as equipment gets older
Routine maintenance is about avoiding, reducing or eliminating the consequences of failures
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Changing Practices of Maintenance Management
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“Comprehensive data about failure
rates must be available before it is
possible to develop a really successful
maintenance program”
“Equipment manufacturers are in the
best position to develop maintenance
programs for new assets”
“The quickest and surest way to
improve the performance of an existing
unreliable asset is to upgrade the
design”
“Generic maintenance policies can be
developed for most types of physical
asset”
Decisions about the management of equipment failures will nearly always have to be made with inadequate data about failure rates
It is nearly always more cost-effective to try to improve the performance of an unreliable asset by improving the way it is operated and maintained.
Generic policies should only apply to identical assets with identical operation, functions and desired performance
Equipment manufacturers can only play a limited (but still important) role in developing maintenance programs
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Reliability Centred Maintenance (RCM)
The principles
Select only maintenance tasks which are applicable and effective
Prioritise need for functions
Identify failure modes that lead to loss of function
Preserve functions
The process
What are the functions and desired performance of the asset?
What are the functional failures?
What are the failure modes?
What are the failure effects?
What are the failure consequences?
What should be done to predict or prevent the failure?
What should be done if proactive measures are not practical?
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Maintenance Strategies
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Failure rate distribution P-F Intervals Condition monitoring
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Maintenance Strategy Selection
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RCM Flowchart (NASA)
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Critical Equipment – a Matter of (International) Law
10 MAINTENANCE OF THE SHIP AND EQUIPMENT (ISM Code)
10.1 The Company should establish procedures to ensure that the ship is maintained in
conformity with the provisions of the relevant rules and regulations and with any
additional requirements which may be established by the Company.
10.2 In meeting these requirements the Company should ensure that:
1. inspections are held at appropriate intervals;
2. any non-conformity is reported with its possible cause, if known;
3. appropriate corrective action is taken; and
4. records of these activities are maintained.
10.3 The Company should identify equipment and technical systems the sudden
operational failure of which may result in hazardous situations. The SMS should
provide for specific measures aimed at promoting the reliability of such equipment
or systems. These measures should include the regular testing of stand-by arrangements
and equipment or technical systems that are not in continuous use.
10.4 The inspections mentioned in 10.2 as well as the measures referred to in 10.3
should be integrated in the ship's operational maintenance routine.
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Machinery Damages – Most Prevalent Claim Type
Lloyds List, Thursday 20 May 2004, 00:00
Despite the improved casualty picture, underwriters remain very concerned about
attritional losses, particularly resulting from machinery damage.
Machinery-related claims are still the single most frequent claim type, with some
markets such as Norway recording about 40% of the total number.
For instance, the loss of main propulsion, steering or electrical power at a critical
time in a narrow fairway may result in a collision.
In the Salvage Association’s annual report earlier this year the Piraeus office
reported: “Machinery damages continue to increase and as the majority of these
are on medium- or high-speed engines there is usually the necessity to fit a new
crankshaft, which is not only expensive for the underwriter but also keeps the
ship out of service for an extended period.”
Elsewhere in casualty experience structural failures, though reduced in number,
are still a big problem, often resulting in a total loss or very expensive repairs.
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“Shocking Failures of New Engines”
Lloyds List, Friday 11 July 2008, 00:00, by Michael Grey
A “SHOCKING” number of damages to engines, often aboard new ships, indicate
that machinery systems are not becoming more reliable, the president of the
Society of Consulting Marine Engineers and Ship Surveyors has complained.
Speaking in London, John Lillie suggested that breakdowns are a serious problem
even with ships of less than five years old. Even if the machinery performs well
when new, it will be unlikely to survive the ship changing hands, and the eventual
“ownership spiral” as the vessel is sold on.
Casualty statistics indicate that at over 40%, machinery damage is the largest
category of incidents, although only represents only 19% of the cost of claims.
He had asked 50 surveyors around the world to send him details of damages they
had attended during a two-month period.
The “horrendous” returns revealed 127 cases, involving products of all major
manufacturers. Average costs of main engine repairs was $500,000, while for
auxiliaries it was $300,000. Turbochargers and crankshafts were causing concern,
and high claims.
.
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Aircraft Maintenance - Nowlan and Heap, December 1978
“In the case of commercial aircraft, continuous evolution of the design
requirements promulgated by airworthiness authorities and the feed
back of hardware information to equipment designers by operating
organizations have led to increasing capability of the equipment for safe
and reliable operation. Thus most modern aircraft enter service with
design features for certain items that allow easy identification of
potential failures…in nearly all cases, essential functions are protected
by some form of redundancy or by backup devices that reduce the
consequences of failure to a less serious level”
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Challenges for Marine Maintenance
Traditional “fix when broken” approach.
Maintenance in the operational phase is characterised by calendar based
prescriptive rules
Maintenance planning not considered at the design stage
Lack of standardised designs
Lack of redundancy of safety critical equipment (e.g. single main propulsion
system).
One year warranty period for large assets and no further obligation from the
designer or manufacturer.
Running hour basis typically used by equipment suppliers
Lack of industry-wide reliability data so far.
Maintenance budgets are often the first operational costs to be cut when freight
rates decrease.
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Research - Commercial Maritime Applications of RCM
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Example - “Optimizing Maintenance in a Maritime Environment”
MAINTWORLD, 2013: A study about optimizing maintenance in a
maritime environment investigated the total operating costs of a fleet of
vessels. This fleet of the Rijksrederij, the Netherlands state owned
company consists of about 125 vessels.
Propulsion gearbox found critical in relation to the main function of the vessel.
Breakdown occurred prior to OEM recommended 20,000 hour overhaul.
Condition-based monitoring introduced with vibration monitoring of bearings, oil
analysis for wear particles and visual inspection of gears and seals. 30%
reduction in maintenance costs and increased vessel availability.
Authors
Tim Zaal, Emeritus Professor of Integrated Maintenance and Asset Management,
HU University of Applied Sciences, Netherlands.
Dirk Kuijt, Senior Consultant, Rijksrederij
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Hurdles to Full Implementation of RCM in the Marine Industry
Lack and portability of failure data
Basic equipment condition cannot be taken for granted
Shipboard personnel are rarely trained in maintenance management or statistical
risk assessment techniques
Shipboard personnel are operators as well as maintainers
Ships operate in isolation from repair and spares facilities
Lack of “adequate” redundancy
Prescriptive requirements from Flag and Class
Original Equipment Manufacturer’s guarantee period (and insurance)
Limited application of FMEA
Every ship is different (operating profile, operating conditions)
Frequent crew changes
Source: A Study of Reliability-Centred Maintenance in Maritime Operations (Mokashi.A, Wang.J, Vermar A.K)
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Changes Required to Embrace RCM
Strong knowledge base about ship functions, systems and components (i.e. top
down approach) needed.
Structured and collaborative design phase where the maintainability of the asset
is taken into account is needed.
Better training requirements for operators are needed.
Current competences will not be sufficient to deal with the complexity of systems.
Introduction of more complex systems necessitates increased attention to the
effects arising from interacting and interdependent components.
Developments in maritime data transfer offer the potential for increased onshore
support for maintenance activities.
The correct adoption of new technologies generally requires big changes to
maritime management culture.
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Business Value Case
Increased Output
– Aligned goals between maintenance and operation
Risk Reduction
– Compliance with Health & Safety Regulations
– Management of risk
– Improved audit trails
– Managed corporate standards
Cost Reduction
– Reduced working capital and inventory
– Better supplier procurement and warranty management
Strategic Positioning
– Better business information
– Improved supply chain integration
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RCM Example - Reference Vessel
Technical Particulars
Length over all ~80 m
Length between
perpendiculars ~75 m
Breadth (moulded) ~13 m
Depth to main deck
(moulded) ~8 m
Draught design (moulded) (approx.) 4.80 m
Gross Tonnage (approx.) 2 500 GT
Installed Power: 5100 kW
Maximum speed: (approx.) 15.5 knots
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Design:
Diesel electric, twin screw
Class Notations:
Special Service, Independent
Propulsion System
Vessel is designed for near-shore operations of extended duration. Operations take
place in congested waters and requires assurance of technical availability.
Specific operations include helicopter winching, vessel-to-vessel transfers and
replenishment at sea.
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RCM Example - Redundancy Design Intention
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Redundancy Design Intention Maximise the availability of propulsion and manoeuvring machinery following an electrical system failure. Segregation of equipment including propulsion auxiliaries and control systems.
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RCM Example - Critical equipment listing
Electrical system
– 400V/230V transformer*
– Emergency generator*
– 24V engine room switchboard
– 24V main switchboard
– Static converter DPMS PLC
Propulsion system
– Propulsion frequency converter*
– Propulsion frequency converter HEX
pump*
– Propulsion cooling fan frequency
converter*
– Stern tube (seal)*
– Main propulsion motor*
– Propulsion gearbox*
– Gearbox oil cooler
– Propulsion motor air cooler
– Propulsion wheelhouse master
controls
Cooling water system
– Cooling water pump*
– Box cooler
ALVAS system
– A&M PLC
– Control PLC
– Alarm server
– A&M switch
Lubricating/dirty oil system
– LO tank
Navigation system
– Radar interswitch*
– Radar scanner
– Radar processor
– Radar UPS
– DGPS
– DGPS power supply unit
Bilge, ballast and fire system
– General service pump
– Quick heeling pump*
Safety systems
– Anti-roll tank control solenoid valves*
– Firefighting foam pump*
– Firefighting foam mixing tank*
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Steering system
– Steering gear pump*
– Rudder*
– Steering control box*
– Steering gear*
– Motor controller*
– Autopilot
Davit system
– HPU
– Davit PLC
– Davit frequency converter
– Control panel
– Winch motor
Fuel system
– Fuel transfer pump*
– GO Separator
– GO day tank
– GO bunker tank
– Critical transfer valve
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RCM Example - Gas Oil Separator
Function Remove impurities from G.O. Containment
Functional failure Does not remove impurities Loss of seal
Failure mode Speed too slow Leakage
Effect(s) Damage to pumps, injectors, pistons, liners and valves and possibility of bad combustion
Localised G.O. leak/drop in service tank level
Consequence 4 (Environmental) 1 (Small effect on system)
Cause Friction clutch worn Seal or casing failure
Frequency 4 (1<5 years) 4 (1<5 years)
Current controls Filter on engine inlet Separator auto-shutdown, redundancy.
Probability 5 (Inadequate barrier/redundancy) 1 (Extremely remote)
Detection 5 (Not detectable) 2 (Continuous monitoring)
RCM index 400 8
Recommendation Scheduled inspection of friction pads N/A
Consequence 4 (Environmental) -
Frequency 4 (1<5 years) -
Probability 5 (Inadequate barrier/redundancy) -
Detection 3 (Manual monitoring) -
New RCM Index 240 8
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RCM Index = frequency x consequence x probability x detection
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Risk Centred Maintenance
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Conclusions
Benefits of RCM:
– Choose the right maintenance strategy for the right equipment
– Concentrate effort for the greatest return
– Safer, smarter and greener operations
Choosing a methodology carefully (and applying consistently) is critical:
– What it is implicit in failure data / service history?
– What equipment/component level of detail?
– Redundancy design intention?
– Functional failures vs. failure modes vs. failure effects?
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