LNG Carriers Ship Life Extension Ed Waryas

LNG Carriers
Ship Life Extension
Ed Waryas
Lloyd’s Register North America, Inc.
Longevity Study - Outline
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Owners Records
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Classification Records
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Ship inspection
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RAM Study
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Structural Integrity Analysis
Owner’s Records
„ Owners records
„ Classification Records
„ Shipboard Records
Ship Inspection
„ Single Ship or Fleet
„ Voyage
„ During Refit
Hull Structure
„ External Hull
„ Water Ballast Tanks
„ Thickness Measurements
„ Paint coatings
Machinery
„ Redundancy
„ Main Engine
„ Boilers
„ Auxiliaries
„ Pumps & Piping
Electrical
„ Alternators
„ Switchboards
„ Cabling
„ Motors
„ Control & Alarm Systems
Cargo Systems
„ Containment
„ Cargo Pumps
„ Piping
„ Auxiliaries
RAM Study
(Reliability, Availability, Maintainability)
„
The RAM study - provides information
on future fleet performance and
availability
„
Trade Feasibility
„
Utilization
RAM Study
„ The Task
„ The Method
„ Data
„ Simulation Input - Validation
„ Simulation Output
„ Conclusions
THE TASK
„
Assess the capacity of an LNG
carrier/fleet to maintain existing
availability over the 20 year life
extension period.
„
Identify performance critical
systems.
„
Availability?
THE METHOD
SYSTEM DATA AND
FUNCTION
INFORMATION
COLLECTION.
FLEET DATA INPUT
RUN FLEET ENOUGH
TIMES OVER PERIOD
REQUIRED TO GIVE
CONFIDENCE.
SYSTEM ANALYSIS
WITH MARINE TRADE
EXPERT INPUT.
IDENTIFICATION OF
SHIP, FLEET AND
TRADE CRITICAL
SYSTEMS.
AGREE DATA AND
PROCESSES FOR
SYSTEM MODEL
WITH CLIENT.
ANALYSIS OF RAM
DATA FOR CRITICAL
SYSTEMS AND
FUNCTIONS.
VALIDATION OK
DERIVE PROBABILITY
OF LOSS OF CRITICAL
SYSTEMS, FUNCTION
& TRADE TARGETS.
REVIEW RESULTS WITH CLIENT. DISCUSS
VARIATIONS IN CONFIGURATION AND
OPERATING POLICY.
... UNTIL
IF OPERATING POLICY IS INADEQUATE,
REVIEW MAINTENANCE POLICY
THROUGH APPLICATION OF RELIABILITY
CENTERED MAINTENANCE TECHNIQUES.
CLIENT
ASSESSMENT OF
RISK AND COST
ACCEPTABLE.
DATA - RECORDS
„
Company records
„
Supported by LR’s own database
„
For a five year period typical data
indicates:
Availability
97.11%
Dry-dock
2.25%
Delays
0.64%
DATA - TRADE
„ LNG cargo lifts from load ports
„ Regas delivery points
(Analysis of vessel trading routes)
SIMULATION INPUT VALIDATION
„
Trade detail
„
Seasonal weather detail
„
Ship critical system RAM data
„
Ship capacity
„
Operating rules
„
Ship and fleet speed control
SIMULATION OUTPUT
„
The following typical results can be
derived:
Data Analysis
Delay based Net
Availability
97.1%
FLEET modeling
96.1%
Typical Conclusions
„
Trade expansion may be limited.
„
Enhanced maintenance actions and data
recording will improve performance.
„
Fleet utilisation is low - RAM
performance does not affect the
current trades.
Structural Integrity Analysis
„ The main purpose of the Structural
Integrity Analysis is to compliment the
inspections, which establish the current
condition and past record, by calculating
the likely future structural performance
of key components.
„ From this, key structural components
which may require repair or modification
over the extension period can be
identified.
Structural Integrity Analysis
„ The three principal components are:
Š wave loading
Š evaluation of hull structure
Š evaluation of cargo containment
system
Wave Loading
„ Determination of long term wave loading,
ship motions and accelerations
Š for specified trading routes
Š in full load and ballast conditions
Š at typical operational speeds
Hull Structure
„ Investigation consists of two levels:
Š strength and fatigue of hull girder
Š finite element modelling to establish
detail stresses at critical connection
points
Fatigue of hull longitudinals
at typical transverse bulkhead
Hull Structure finite element analysis
„ To determine stresses and stress
concentrations at typical hull details, e.g.
Š hopper connections
Š trunk deck endings
Š double bottom girder / transverse
bulkhead connection
Finite Element Model
Ballast Hogging Condition
Inner Hull and Deck Stresses
Stresses at Detail : Hopper Knuckle
Fatigue analysis of cargo tank
membranes
„ Analysis examined, for N. Atlantic Š primary membrane strake end connections
Š secondary membrane chair washer
Š pipe tower base support to primary
membrane
Š trihedron connections to primary
membrane
Typical Conclusions
„ Steel hull structure Š Providing maintenance continues, and
structural repairs performed, then hull
integrity can be assured over proposed
total ship life of 40 years.
„ Cargo tank membrane system Š The membrane system could be expected
to perform satisfactorily for the
proposed 40 year life.