• To set in place, and implement, the systems and processes to assure ongoing availability of storage tanks, without compromising Technical Integrity and HSE.

Integrity Management Objectives

Storage tank RBI• EEMUA 159• API 581 Appendix O• Inspection plans

Storage tank RBI: goals

• Meet requirements from legislation• Cover risks that can be foreseen• Evaluate and improve operational maintenance plans• Reduce direct and indirect costs (consequences) of ineffective

maintenance• Provide evidence for “good ownership”

Tank Maintenance Plan

Tank MaintenancePlan

Maintenancehistory

Inventure bestpractice

Norms andguidelines

Inspectiontechniques

Input client

Inspectionhistory

Repairs and modifications

Condition assesment and failures

AvailabilityCleaning procedures

NDTOn stream methods

ClusteringMethodologies

API 581, EEMUA 159, API 653

Closing the loopMaintenanceRBI-based

Maintenanceplanning

Repair procedures

RBI-basedmaintenance plan

RBI re-evaluation

Tank fixed inspection intervals

years

Cleaning

Inspection

Maintenance

Production loss

cost

s

Tank flexible inspection intervals

years

Cleaning

Inspection

Maintenance

Production loss

cost

s

API 581 appendix O

• Specifically developed for storage tanks• Statistical background• Very comprehensive• Worldwide accepted• Follows the API 653

Statistical background API 581Leak

Rupture

Api 581: Leak and rupture scenarios

Api 581: Acceptable damage factor

Api 581: Status of tank

Damage factor now

Damage factor can grow to 630. The ar/t can grow to 0,88

Api 581: most important parameters• Risk category• FFP acceptable wallthickness• Degradation mechanisms• Inspection rating• Product leakage scenario• Repair plan tankfloor• Coating tankfloor• Acceptable damage factor

Api 581: Risk matrix tank

X

A DC E

1

2

3

10005

4

B

100

20

2

Likelihood (Damage Factor)

Likelihood (category)

Consequence (category)

Consequence ($)

$10K $100K $1M $10M

Low Risk Medium-High Risk

High RiskMedium Risk

Api 581: Damage factors

EEMUA 159: example tankfloor• Tank 44• built in 1986• 56 meter diameter• Product is crude • Floor new 7 mm, annular 12 mm• One inspection from 1996, dataset with UT wallthickness

measurements• Last inspection in 2006, new dataset with UT wallthickness

measurements• An RBI analysis is carried out

EEMUA 159: example tankfloorCharacteristics:• Risk analysis is carried out• In statistical analysis UT datasets extreme value fit is used.

Corrosion rate is calculated• Fitness for service criteria are being established• Based on remaining lifetime calculation and criticality factor

an inspection interval is determined• Based on the analysis a maintenance plan is made to maintain

the integrity such that the inspection interval is 15 years

1) Guidelines for use of statistics for analysis of sample inspection of corrosion, HSE 20022) Kowaka M: ‘Introduction to life prediction of industrial plant materials – application of extreme value statistical method for corrosion analysis’. Allerton Press Inc, New York, 1994,

EEMUA 159: UT datasets tankfloorWallthicknesses tank 44

0

2

4

6

8

10

12

14

16

18

4,5 5 5,5 6 6,5 7 7,5 8 8,5Wall thickness

Freq

uenc

y Wanddiktes 1996

Wanddiktes 2006

EEMUA 159: RBI results tankfloor

• Corrosion rate 0,125 mm/year• Remaining life: 17 years• Rejection limit (fitness for purpose): 2,5 mm• Probability rating: Negligible• Consequence rating: High• Overall risk rating: Medium• Next inspection in years: 10; yr. 2016

EEMUA 159: Handling the results

Client wants to close the tank for 15 years, however the inspection term from the EEMUA RBI study is 10 years.

Solution: weld patch plates on all areas with a wallthickness lower than 4,9 mm.

Added Value

• Regular ‘health checks’ undertaken and documented

• Strategies aligned to Client business drivers• Safe operation• Optimised inspection costs• Higher up time• Avoidance of losses to the environment

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