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Comparison of Comparison of EEMUA 159 to EEMUA 159 to API StandardsAPI Standards
Mark A. Baker, P.E.Mark A. Baker, P.E.
National Petroleum Management Association’sPetro 2012
May 28 – 31, 2012Washington D.C.
EEMUA 159EEMUA 159
User’s Guide to the Inspection, Maintenance and Repair of Aboveground Vertical Cylindrical Steel Storage Tanks
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Edition: 3rd Engineering Equipment and Materials Users Association / Jan-2003 / Amendments Feb-2004
API Standard 653API Standard 653
Tank Inspection, Repair, Alteration, and Reconstruction
Fourth Edition April 2009Addendum 1, August 2010Addendum 2, January 2012
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API Standard 653API Standard 653
This document addresses:Tanks built to API 650 and its predecessor API
12C.Minimum requirements for maintaining the
integrityThis standard employs the principles of API
650 Owner/operators may apply this standard to
any tank constructed to a tank specification.
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EEMUA 159EEMUA 159
This Standard addresses: Establishment of essential inspection requirements for tanks. Minimize problems and extend useful life. Gives guidance on design features, common problems
experienced during operation and on repair methods. This addresses tanks built in accordance with British Standards Where appropriate it refers to and makes use of international
standards and codes such as those from API. This publication is intended as a general inspection, maintenance
and repair guide applicable tanks
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Inspector QualificationsInspector Qualifications
API 653◦ Authorized inspector
Must have experience and pass a written examination Recertification is required every 6 years
◦ Owner/Operator Inspectors Must have knowledge tanks and local operating
conditions EEMUA 159◦ No certification process for tank inspectors◦ Inspectors should be experienced
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Inspection RequirementsInspection Requirements
Routine External InspectionsAPI 653:
◦Required to be conducted on a Monthly Basis
EEMUA 159:◦Required to be conducted on every 3 Months
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Inspection RequirementsInspection Requirements
Formal External Inspections
API 653:◦Required to be conducted the lesser of 5
years or the quarter corrosion rate life of the shell.
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Inspection RequirementsInspection Requirements
Formal External InspectionsEEMUA 159:
◦Ranges from 1 year to 15 year intervals. Factors include climate and type of product..
◦5 years – crude oil, and refined products with no internal liner
◦8 years finished products with internal liner
◦10 years for Jet A with internal liner
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Table B.3-1Table B.3-1
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Inspection RequirementsInspection RequirementsFormal Internal Inspections API 653:
◦ Based on the bottom corrosion rate not to exceed 20 years◦ Risk based inspection can be used – See API 580, “Risk-Based
Inspection”. MRT is:
0.100 for with no RPB or thick film liner 0.050 when RPB or Thick film liner is present
MRT = (Minimum of RTbc or RTip) – Or (StPr + UPr)
where:
MRT = minimum remaining thickness at the end of interval Or.
Or = in-service interval of operation (years to next internal inspection)
RTbc = minimum remaining thickness from bottom side corrosion after repairs,
RTip = minimum remaining thickness from internal corrosion after repairs,
StPr = maximum rate of corrosion not repaired on the top side.
UPr = maximum rate of corrosion on the bottom side.
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Inspection RequirementsInspection Requirements
Formal Internal Inspections EEMUA 159:
◦ Based on Table B.3 Ranges from 3 years to 20 year intervals. Factors include climate and type of product.
◦ 8 years – crude oil◦ 16 years finished products with internal liner◦ 10 years finished products with no liner◦ Allows for use of probabilistic preventive maintenance –
detailed explanation and guidelines are given. ◦ MRT at next inspection 2.5 mm or 1.5 mm
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Inspection RequirementsInspection Requirements
Formal Internal Inspections
EEMUA 159:
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Bottom ExtensionBottom Extension
API 653 requires a minimum thickness of 0.100 inches at 3/8 inch from the shell-to-bottom weld.
EEMUA 159 requires a minimum of 2.5 mm (0.098 in) at 9.5 mm (0.374 in) from the shell-to-bottom weld
Approximately the same requirements for each document.
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Inspection RequirementsInspection Requirements
Inspections Checklists
Both API 653 and EEMUA 159 use the same checklists
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Foundation SettlementFoundation SettlementDifferential Settlement
◦API 653 requires a total of D/10 survey locations with a minimum of 8. Tolerances are given as
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)(2
)11( 2
ExH
xYxLS
Where:
S = maximum permissible deflection inft
L = arc length between measurements points in ft
YS = yield strength in lbf/in2
E = Young’s modulus in lbf/in2
H = tank height in ft
Foundation SettlementFoundation SettlementDifferential Settlement
◦EEMUA requires a total of D/10 survey locations with a minimum of 8 with the distance not exceeding 10 m.
◦Tolerances are given as: 100 mm (3.94 inches) between any two
points at 10 m intervals
◦Alternatively
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Foundation SettlementFoundation Settlement
Differential Settlement◦Fixed roof tanks without an internal floating
cover
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Foundation SettlementFoundation Settlement Differential Settlement
◦ Floating roof tanks and large fixed roof tanks equipped with internal floating covers of diameters exceeding 40 m
)(2
)11000( 2
ExH
xYSxLS
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Where:
S = maximum permissible deflection in mm
L = arc length between measurements points in meters
YS = yield strength in MPa
E = Young’s modulus in MPa
H = tank height in meters
Foundation SettlementFoundation SettlementPlanar Settlement
◦API 653 does not address planar tilt tolerance
◦EEMUA 159 permits a maximum out-of-verticality should not exceed h/100
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SettlementSettlementAPI 653 Edge Settlement
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SettlementSettlementEEMUA 159 Edge Settlement
◦Maximum permissible edge settlement to 125 mm (4.92 in)over 750 mm (29.5 in)
◦If it is exceeded then the tank should be re-leveled
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SettlementSettlement
API 653 Bottom Depressions
◦Maximum permissible bottom settlement or Bulges is given by:
BB = 0.37R
Where:BB = maximum height of bulge or depth of local depression, in
R = radius of inscribed circle in bulged area or local depression, in ft
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SettlementSettlement
EEMUA 159 Bottom Depressions◦Depressions are acceptable provided
The aspect ratio of height to width of the ripple is not greater than 75:500 (mm:mm) i.e. 0.15 – (3”:20”)
They do not form a severe crease over any of their length
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SettlementSettlement
Center-to-Edge Settlement (Sagging)API 653 – Does not directly address the overall
center-to-edge settlementEEMUA 159 – The maximum settlement is
given as
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Shell ThicknessShell ThicknessAPI 653
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SE
DGHt
)1(6.2min
Shell ThicknessShell Thickness
EEMUA 159The procedure for evaluation of tmin is
essentially the same as API 653.
EEMUA adds a term for internal pressure which is not considered in API 653.
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))3.0(98(20min PHWSE
Dt
Shell ThicknessShell Thickness◦API 653 allows for the authorized inspector to
determine the number and location of UT measurements during an inspection
◦EEMUA 159 requires a grid system for obtaining UT measurements
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Roof ThicknessRoof Thickness
API 653 ◦Min of 0.090 in. in any 100 in2 area◦Structure corrosion is to be evaluated
EEMUA 159◦Min of 2 mm in a 500 mm by 500 mm area
(0.079 in. in 387.5 in2 area)◦Structure corrosion is limited to 25% before
replacement is required.
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Brittle FractureBrittle FractureAPI 653 Assessment per
Section 5 of API 653
EEMUA 159No specific guidance
for brittle fracture considerations
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RepairsRepairsAPI 653
Comprehensive repair section for the tank shell and bottom including nondestructive examination
Section 8 – Design Considerations for Reconstructed TanksSection 9 – Tank Repair and AlterationSection 10 – Dismantling and ReconstructionSection 12 – Examination and Testing
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RepairsRepairs
EEMUA 159◦The document provides minimal guidance to
the user.
◦The document refers the user to international standards
◦Appendix C has some examples for welding sequence and tank jacking
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Hydrostatic TestingHydrostatic Testing
API 653
◦Comprehensive section detailing when a hydrostatic test is required
◦Provides calculation for maximum fill level
◦Provides rules for foundation settlement surveys when settlement is anticipated.
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Hydrostatic TestingHydrostatic Testing
EEMUA 159
◦Provides a detailed filling sequence
◦Water quality requirements
◦Provides a reprint from API 653 as well as discusses the BS 2654 requirements
◦Discusses survey requirements
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Filling SequenceFilling Sequence
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EEMUA 159
Hydrostatic Test Flow Chart
Additional Requirements Additional Requirements EEMUA 159 EEMUA 159
Details not in API 653: Tank painting
Cathodic protection
Corrosion mechanisms
Product characteristics
Risk based inspection
Tank jacking
Detailed foundation design
Tank relocation
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Other informationOther information
◦Much of the information presented in EEMUA 159 is present in other API standards: Tank painting - API 652 Cathodic protection - API 651 Corrosion mechanisms - API 570 Product characteristics - API 570 Risk based inspection - API 580 Tank jacking - API SCAST
studying this issue for inclusion in API 653
Foundation design - API 650 (Appendix B)
Tank relocation - API 653 (reconstruction)
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CollaborationCollaboration
No official collaboration between the two standards is underway
The Chairman of the EEMUA 159 committee has attended API SCAST meetings
Some members of the SCAST committee have attended EEMUA 159 meetings
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ConclusionsConclusions◦API 653 and EEMUA 159 are both good
documents
◦API 653 provides a procedure to demonstrate that the tank inspector posses a minimum body of knowledge and experience
◦In general, API 653 is more conservative than EEMUA 159
◦EEMUA 159 contains information which fills in topics not covered in API 653
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