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

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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