Stephen Rowbotham, Quest Integrity: Critical spares: Who needs them and why?
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Transcript of Stephen Rowbotham, Quest Integrity: Critical spares: Who needs them and why?
Critical Spares Who Needs Them and When?
Australian Gas Turbines Conference
30th October 2013
Agenda
• Definition
• Strategy
• Types of spares
• Factors to consider
• Equipment / spares management
• Determination of criticality
• Spare levels
• Spares Identification
2
Critical Spares Who Needs Them and When?
• To answer the first part is easy
Everyone who operates a system that has to perform when
required will have critical spares
• The second half, now that’s the difficult part!
3
But First - Definition
• All parts of a system can be
critical unless redundancy is built
into the design
• One definition is :
“A part that if not available when
required results in the loss of
production, power generation or
endangers peoples lives or
seriously damages the
environment”
4
Two Extreme Maintenance Strategies
Conservative
Run till it drops
Most
companies fall
somewhere in
between
5
Strategy Affected by
• Contracts in place
• Type of equipment
• Fuels used
• Maintenance Strategy
• Skills availability
• Spares availability
• Geographic location
• Age of plant
Not static – review ever 2 years
6
Types of Maintenance and Repair
• Breakdown
• Routine
• Planned
• Preventative
• Predictive
• Corrective
• Design Out/Elimination Maintenance
• Total Production Maintenance
• Contracted Out Maintenance
• Cannibalisation7
Types of Spare Parts
Commissioning
Spare parts
Initial Spare
parts (1st year)
Operating Spare parts (2 year rolling)
Me
an
Fa
ilure
Ra
te h
(t)
Operating Time
Capital Insurance and Critical
Outage
8
Where do you Start – Original Procurement and
Build
• Due Diligence
• Fleet data
• Operating history
• Number of similar units in fleet
• Availability required
• Storage facilities
9
Other Factors to Consider
• Assessment of the whole system
• Identify redundancy
• Cost of holding spares – 20 to 40 %
of purchase price per year
• Maintenance of the spare part
• Change of operation
10
Equipment /Spares Management
• Implement full Reliability-Centered Maintenance (RCM) to high risk components– Covered in standard SAE JA1011, Evaluation Criteria for RCM
Processes
• Identify all failure modes for each component
• Develop detailed monitoring & inspection test plans specific to each component
• Identifying equipment risk through reliability based inspection is the first step toward this
11
Determination Criticality
• Review history of failed components for the individual
plant and across the fleet
• Review OEM Manuals
• Talk to the Plant Engineers
• Check PID
• Review supply chain
• Component availability
• Risk assessment for mechanical and electrical systems
12
Likelihood Questions
• Age of component?
• Are there damage processes and what is the likelihood?
• Rapid unpredictable failure likely?
• How good is the inspection?
• How good is the maintenance?
• How well is it operated?
13
Consequence Questions
• Extent of damage to other equipment?
• Part availability?
• Length of repair time?
• Safety hazard to personnel?
• Potential loss of production ?
• Cost to repair or replace?
• Potential damage to environment?
14
Total Risk
• Total Risk is defined as the likelihood versus
consequence
• The risk profile can then be generated as a plot of the
risk for each piece of equipment or area
15
Distribution of Risk for a Frame Unit
16
Distribution of Risk for an Aero-derivative Unit
17
Likelihood versus Consequences
• Frame Unit - GE Frame 9
• Aero-derivative Unit - GE
LMS100
18
Maintenance / Critical Spares – Reliability – Failure
Rates
• Assume a constant failure rate
• With a constant failure rate the reliability is based on the exponential
distribution –
� � � exp��
• Failure rate (λ) reciprocal is the mean time between failure (MTBF)
� �� �1
�
• The survival probability time is given by using
tr � 1/� x ln(1/R(tr))
19
Maintenance Spares – Levels
• To determine maximum stock level required is given by
= λ +K√λ
λ = average consumption/failure rate per year
K = a factor depending on service level required
• Minimum stock is given by
= K√λ
• Should be reviewed - approximately every 2 years
20
Example Effect of Various MTBF on Spares
Service Level/
Reliability
75% 90% 95% 99%
K Factor 0.7 1.3 1.7 2.3
MTBF λ +K√� λ +K√� λ +K√� λ +K√�
0.75 month 19 22 23 26
1.5 months 12 13 15 16
2 months 8 10 11 12
3 months 6 7 8 9
1 year 2 3 3 4
10 years 1 1 1 1
100 years 1 1 1 1
21
Spare Parts Identification
• Depending on the model, year of manufacture and any
service bulletins applicable the correct part number may
have changed. The OEM spare parts manual details how
the system is structured
• The OEM manual structure is normally based on flange
to flange
TURB9EA2##/BA05A/0512 – 112E1407G016
Gas Turbine
Type/Model
Unit Number
Section Number Subsection Number
Article Number
22
Outside the Gas Turbine/ Balance of Plant
• The identification system relays on tag numbers which
are referred to on the process line diagrams
• Reference then has to be made to the manufacturers
operating manual for each component
23
Outage Spares –
• Planned Maintenance - regular inspection of the
combustion and hot gas path parts of the gas
turbine
24
Frame Hours Starts
CI 12000 450
HGP 24000 900-1200
Major
Inspection
48000 2400
Aero Derivative Hours
Inspection and Blade
wash
2000 -4000
Annual Inspection 8000
Hot Section Overhaul 25000
Full Overhaul 50000
Typical A/B Inspection Consumable Packages
Qty Description Part # Delivery (weeks)
24 Hexagon Socket Head
bolt
HTMA200312P0013 16
1 Packet Welding
Electrode
HZN 403494P0250 6
1 Welding Wire HTCZ401077P0003 9
2 Packet of shims GMD5246056R001 12
2 Gasket GMD0924574P0001 16
• 28 line items
• 131 components
25
C Inspection Consumable Package
• Broken down into six parts :
– C inspection package
– C inspection bolting package
– C inspection compressor spares
– C inspection consumables
– C inspection MTS consumables
– Noble parts assembly material
• Total number of line items 708
• Longest lead time 34 weeks
26
Critical Spares and Integrity Management
Equipment Integrity
Management
ActivitiesProcurement
Operation
Engineering
Inspection
Maintenance
ProcessesPolicies
Standards
Record practices
Procedures
Control
Disciplines Involved Everybody
OrganisationTraining
Competencies
Structure
People
Succession
27
Main Benefit of Critical Spares Review
Cost of
unplanned
outage or
failure
Cost of
undertaking
review and
holding
necessary
parts
28
Any Questions?
Remember look after your spares!
29