e Emu a Presentation 03

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EEMUA

The EEMUA was established in 1982 as the combination of

two users associations.

- Oil Companies Materials Association (O.C.M.A.)

- the Engineering Equipment users Association (EEUA)


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API Standards

EMMUA Publication

have been written to complement


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List of Member Organisations of the European Committee

United Kingdom

Holland

France

Switzerland

Sweden

Germany


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List of Technical Committees:

Committee of User Inspectorators

Electrical Engineering

Instrumentation & Control

On Line Analysers

Inspection and NDT Technology

Machinery

Materials for Offshore Services

Pressure Relieving Safety SystemsPressure Vessels

Piping Systems

Standards and Services

StorageStorage TanksTanks

Valves

Full Members

Shell Exxon/Mobil

Foster Wheeler Energy BP/Amoco

Innogy (National Power) Caltex

Dow Corning Conoco / Phillips

ABB Assocated Octel

Power Gen Total Fina Elf

Transco / Advantica TXU Energy

Associate Members

AEA Technology BASF

ICI CAN

Chevron / Texaco AstraZeneca

D&C Engineering Flexsys

Phillips Petroleum UK Royal Vopak


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Guidelines established by the StorageTank Committee

- No. 147: Recommendations for the Design and Construction of Refrigirated

Liquified Gas Storage Tanks

-No. 154: Guidance to Owners of Demolition of Vertical Cylindrical Steel Storage

Tanks, Refrigerated Tanks and LPG Spheres

-No. 159: Usess Guide to the Maintenance and Inspection of Above-Ground

Vertical Cylindrical Steel Storage Tanks

- No. 180: Guide for Designers and Users of Frangible Roof Joints for Fixed RoofStorage tanks

- No. 183: Guide for the prevention of Leakage from Vertical, Cylindrical Steel

Storage tanks

- No. 190: Guide for the Design Construction and Use of Mounded, Horizontal,

Cylindrical Vessels for pressurized Liquified Gases at ambient

temperatures


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EEMUA Publication No. 159 :2003

EEMUA Best seller

Uses Guide to the Maintenance and Inspection of Above-Ground Vertical Steel Storage Tanks

API Standard 653

Tank Inspection, Repair, Alteration and Reconstruction

Has been written to complement

3rd Edition


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EEMUA Publication No. 159

It deals with Tank inspection and covers various areas in

more depth and because it is a recommendation rather than a

standard it has more scope for explanation.This publication will assist the owner and inspector to

understand the reasons for carrying out inspection in

particular areas.


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EEMUA Publication No. 159 :2003 3rd Edition

This publication is intended as a general inspection,

maintenance and repair guide applicable to above ground

storage tanks.

The detailed topics covered are the more significant knownto require attention, selected by the authors based on many

years experienced in storage tank operation.

However for such requirements to be properly interpreted

and understood, comprehensive guidance is given on many

key design features, on common problems experienced

during operation and on repair methods

1 Introduction and Scope. (Contd)


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The descriptions of key tank components that require

inspection and/or maintenance, of degradation mechanisms,and of common inspection techniques, are followed by

sections describing the probabilistic (risk-and reliability-

based) preventive maintenance (PPM) concept and for eachtank component, a detailed description of inspection and

repair methods.

Guidance is given on sources of additional information that

will assist both continued operation and inspection.



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The recommendations contained herein are written

particularly for the guidance of inspection and maintenanceengineers. Recent developments in maintenance philosophy

and practices have led to the formulation of new

maintenance programmes, and this revision of Publication

159 includes a large section on such programmes.

This document sets out the key features required for

planning and executing inspection, maintenance and repairworks on aboveground vertical steel storage tanks.



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2 Tanks and their Components:

Terminology and Materials of Construction

2.1 Tank Components

2.2 Glossary of Terms

2.3 Types of Storage Tanks

2.4 Materials


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3Degradation Mechanisms and Failure Modes

3.1 Corrosion

3.2 Tank Settlement and Consequential Problems

3.3 Structural Failure / Failure of Tank Components

3.4 Combination Of Degradation Mechanisms

3.5 Bacterial Corrosion


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4 Corrosion of Tanks4.1 General

4.2 Corrosion Rates

4.3 Bottom Plates4.3.1 Bottom Plates (Underside / External)

4.3.2 Bottom Plates (Topside / Internal)

4.3.3 Shell Plates (Internal and External)4.4 Roof Plates

4.4.2 Fixed Roofs Including Roof support

Structure

4.4.3 Floating Roof Including Support Legs

4.5 Corrosion under Insulation (CUI)

4.6 Corrosion of Stubs and Appendages


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5 General Inspection Techniques and Interpretation of

Inspection Data

5.1 References

5.2 Inspection

5.2.1 General5.2.2 Operator Observation

5.2.3 In-Service Inspection

5.2.4 Out-of-Service Inspection

5.2.4 Safety Considerations During Inspection


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5.3 Ultrasonic Thickness Gauging

5.3.2 Area to be Examined

5.3.3 Remote Gauging5.3.4 Gauging from Access Ladder

5.3.5 Grid System

5.3.6 Gauging of Tank Shell and Bottom

5.3.7 Gauging of Nozzles and Manhole Neck Plates

5.3.8 Roof Gauging

5.4 Eddy Current Thickness Measurement Techniques5.5 Evaluation of Tank Shell Inspection Data


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6 Probabilistic Preventive Maintenance (PPM) for Tanks

6.1 Introduction

6.2 Risk Management

6.2.1 Introduction to Risk Management

6.2.2 Risk-Based Inspection (RBI)

6.2.2.1 Introduction6.2.2.2 Probability of a Specific Failure

6.2.2.3 Consequences of a Specific Failure

6.2.2.4 Risk Rating6.2.2.5 Determination of Next Inspection

6.2.2.6 Inspection Plan


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6.2 Risk Management (Contd)

6.2.3 ReliabilityCentred Maintenance (RCM)

6.2.3.1 Introduction

6.2.3.2 Preparatory Steps

6.2.3.3 Description of the RCM Analysis

6.2.3.4 Maintenance Task Selection

6.2.3.5 Execution6.2.3.6 Review


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6.3 The PPM Process

6.4 RBI Methodology : The EEMUA Approach

6.4.1 General

6.4.2 Introduction

6.4.3 The Risk Assessment

6.4.4 Follow-Up Actions

6.4.5 Calculation Before Next Inspection


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6.5 RCM Methodology : The EEMUA Approach

6.5.1 General

6.5.2 Introduction

6.5.3 Estimated Time Between Failures (ETBF)

6.5.4 Risk Analysis

6.5.5 Preventive Maintenance Plans and Tasks


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6.6 PPM Implementation

6.6.1 Introduction

6.6.2 Resources6.6.3 Minimum Requirements for PPM

6.6.4 Involvement of Regulatory Bodies and

Local Authorities


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7 Tank Foundations

7.1 General

7.1.1 Introduction7.1.2 Failure Modes of Tank Foundations

7.2 Soil Settlement

7.2.1 Settlement under Loads7.2.2 Consolidated Settlement


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7 Tank Foundations (Contd)

7.3 Effects of Soil Settlement

7.3.1 Even (Uniform) Settlement7.3.2 Tank Shell Settlement into the Foundation

7.3.3 Difference in Soil Settlement Between

Centre and Periphery of the Tank7.3.4 Uneven Settlement

7.3.5 Edge Settlement

7.3.6 Planar Tilt

7.3.7 Differential Shell Settlement around

Circumference


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7 Tank Foundations (contd)

7.4 Leakage

7.5 Maximum Tolerances and Limits for Settlement

and Out-Of-Verticality of Tank Shell

7.5.1 Differential Settlement

7.5.2 Edge Settlement7.5.3 Out-of-Verticality

7.5.4 Centre-to-Edge Bottom Settlement

7.5.5 Bottom Ripples


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7 Tank Foundations (contd)

7.6 Relevelling of Tank Foundations

7.7 Repair / Modification Methods Some TypicalExamples

8 Tank Bottoms (With or Without Annular Plates)

8.1 General8.2 Introduction

8.3 Determination of Floor Thickness and Condition

8.4 Rejection Limits8.4.1 Floor Area

8.4.2 Annular Area


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8 Tank Bottoms (With or Without Annular Plates) (Contd)

8.5 Bulges and Depressions in Tank Bottom

8.6 Cathodic Protection8.6.1 Sacrificial Anodes

8.6.2 Impressed Current Systems

8.6.3 Monitoring and Maintenance of CP System

8.6.4 Electrical Isolation

8.7 Repair / Modification Methods Some Typical

Examples


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9 Tank Shells

9.1 General

9.2 Determination of Effective Shell Plate Thicknessand Condition

9.3 Rejection Limits for Shell Plates

9.4 Top Wind Girder and Intermediate Wind Stiffeners

9.4.1 Shell Top Wind Girders

9.4.2 Intermediate Wind Girders


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9 Tank Shells

9.5 Buckling Problems of Tank Shell and Top Wind Girders

9.5.1 Buckling Problems of Tanks9.5.1.1 Buckling Due to Wind Gusts

9.5.1.2 Buckling Due to Partial Vacuum Inside

the Tank

9.5.1.3 Buckling at the Bottom to Shell

Connection

9.6 Manholes, Nozzles and Connecting Piping

9.6.1 Shell Manholes and Nozzles9.6.2 Connecting Piping


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9 Tank Shells

9.7 Clean-Out Doors and Openings

9.7.1 Clean-out Doors9.7.2 Clean-out Openings

9.8 Earthing

9.9 Repair / Modification Methods Some Typical Examples

10 Tank Roofs

10.2 Determination of Roof Plate Thickness and

Condition10.3 Rejection Criteria


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11 Fixed Roofs (Cone Roofs and Done Roofs)

11.1 General

11.2 Roof Manholes and Nozzles11.3 Roof Vents and Emergency Relief Valves

11.3.1 The Functioning of Roof Vents

11.3.2 Venting Requirements for Fixed Roof Tanks

11.3.3 Inspection and Maintenance of Roof Vents

11.3.4 Possible Ventilation Problems

11.3.5 Flame Arresters

11.3.6 Pressure Test of the Fixed Roof


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11 Fixed Roofs (Cone Roofs and Done Roofs)

11.3 Roof Vents and Emergency Relief Valves (Contd)

11.3.7 Temporary Closure of Openings in OpenVents or Pressure-Vacuum Valves during

Operation

11.3.8 Protection Against Static Electricity and

Lightning

11.4 Internal Floating Covers

11.5 Repair / Modification Methods


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12 Floating Roofs

12.1 Types

12.1.2 Pontoon Type Floating Roof12.1.3 Double-Deck Floating Roof

12.1.4 Special Roofs Such as Buoy Type and

Radially Reinforced Roofs

12.2 Roof Drains

12.2.2 Steel Articulated Primary Roof Drains

12.2.3 Flexible Hose Primary Roof Drains12.2.4 Special Primary Roof Drains

12.2.5 Syphon Drains

12.2.6 Emergency Roof Drains


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12 Floating Roofs

12.3 Roof Seals

12.3.1 General12.3.2 Design

12.3.3 Rim Seal Material

12.3.4 Seal Replacement

12.4 Roof Supporting Legs

12.5 Floating Roof Venting

12.6 Rolling Ladders

12.7 Earthing of Floating Roofs


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12 Floating Roofs

12.8 Guidelines for the Operation of Floating Roofs

12.8.1 Introduction12.8.2 Before the Roof is Taken into Service

12.8.3 During the First Month of Operation

12.8.4 During Operation

12.8.5 Before Landing the Roof

12.8.6 Roof Standing on its Supports

12.8.7 Recommended Filling Rates for

Floating Roof Tanks12.8.8 Ballooning of Single-Deck Floating

Roof


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12 Floating Roofs

12.9 Possible Problems

12.9.1 Leaking Pontoon Compartments12.9.2 Cracking in Centre Deck due to Wind

Loading

12.9.3 Out-of-Roundness Tolerances

12.10 Aluminum Done Roofs

12.11 Repair / Modification Methods


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13 Tank Appendages

13.1 Ladders, Stairways, Platforms and Railing, Lighting

13.2 Side Entry Mixers13.3 Tank Instrumentation

13.3.1 General / Records

13.3.2 Instrument and Component Failure

13.3.3 Electronic Instruments

13.3.4 Tank Cooling and Fire Protection System


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14 Tank Coatings

14.1 Introduction

14.2 External Coating System

14.2.1 General14.2.2 Bottom

14.2.3 Shell and Roof

14.3 Internal Coating Systems14.3.1 General

14.3.2 Bottoms

14.3.2.1 Coatings14.3.2.2 Laminates

14.3.3 Shell and Roof

A i i 1 9 2003


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14 Tank Coatings (Contd)

14.4 Repair / Modification Methods Some Typical

Examples

15 Tank Insulation

16 Hydrotesting

16.1 General

16.2 Hydrotesting after Repair and Modification

16.2.1 Full Hydrostatic Test

16.2.2 Partial Hydrostatic Test16.2.3 No Hydrostatic Test

16.2.4 No Hydrostatic Test (API 653 Exemptions)

EEMUA P bli i N 159 2003


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16 Hydrotesting (Contd)16.3 Requirements for Hydrotesting

16.3.1 Pipe Connections

16.3.2 Water Quality16.3.3 Test Temperature

16.3.4 Filling Rates

16.3.4.1 General

16.3.4.2 Procedure

16.3.5 Maximum Filling Height

16.3.6 Holding Time

16.3.7 Emptying after Hydrotest

16.4 Settlement Monitoring

EEMUA P bli ti N 159 2003 d i i


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17 Re-Siting of Vertical Tanks

17.1 General

17.2 Moving Using a Crane with Spreader Beam17.3 Moving on Railway Tracks

17.4 Moving by Air-Cushion Method

17.5 Moving by Floating17.6 Moving by Self-Propelled trailers

17.7 Testing Requirements

EEMUA P bli ti N 159 2003 3 d Editi


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Appendix A: Tank Assessment, Records and Reports

Appendix B: Inspection Checklists and Frequencies

Appendix C: Typical Repair Solutions

Appendix D: Sample Calculations

Appendix E: Probabilistic Preventive Maintenance (PPM)

Appendix F: Refrigerated Storage Tanks for Liquefied Gases

References

EEMUA P bli ti N 159


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2.2 Tank Foundations

Tanks are seldom built on piled foundations. At locations

where weak, compressible layers are present in thesubsoil (clay, peat and silt), soil settlement may occur due

to the weight of the tank and its liquid contents.

Tanks will generally follow the settlement of the subsoil

Soil settlements may be even or uneven, depending on the

possible variation in thickness of the soil layers and theirlocation

EEMUA Publication No 159


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2.2.2 Problems Caused by Soil Settlement

Even soil settlements are generally not dangerous because

they occur gradually and increase uniformly. When the

become excessive however, some remedial action may be

necessary. The extent of settlement should therefore be

checked, to avoid problems during operation of the tank.

Pipe connection. Excessive settlement may cause problems

for the pipe connections at the tank shell. Alternatively the

pipe support may settle faster than the tank on its

foundation. Any difference in the level may seriously

overstress the pipe connection.

Tank Settlement into the Foundation EEMUA 159


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Tank Shell

Tank Bottom

Location of Possible Corrosion

Water and Debris Collected

Shape after Repair

Tank Settlement into the Foundation EEMUA 159

Difference in Settlement between Center and Periphery


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Tank Shell

Tank Bottom

Difference in Settlement between Center and Periphery

Settlement at center 30% greater than at Shell

EEMUA 159

Shell settlement



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2.2.3 Additional Problems caused by Uneven Soil Settlements

Uneven soil settlement under the shell of the tank places the

bottom periphery at greater risk than even soil settlement. Theweak flat bottom plates will follow the uneven pattern of the

soil settlement. The tank will try to form a bridge over the area

where local increased settlement occurs. The bottom plates at

that location may not be properly supported by the tank

foundations, but may be suspended from the shell.

This is an unfavourable condition for the shell to bottom

connection and ultimately a rupture at the inner fillet weld

may occur.

Local uneven Settlement under the Tank Shell


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Tank Shell

Tank Bottom

Local uneven Settlement under the Tank Shell

Possible Fracture

EEMUA 159

Local uneven settlement under the tank should always be treated

seriously



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2.2.5 Leakage

If external inspection reveals leakage from the tank

bottom, it is an indication that product is penetrating intothe foundation. This may cause a serious condition for the

safety of the tank and at the same time cause soil pollution.

Leakage close to the periphery of the shell should be

considered as a major problem requiring urgent attention.

It should therefore be remedied immediately as the leak

may cause a local wash out of the tank foundation under

the shell



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2.2.5 Leakage

Wash out will cause loss of support for the bottom plates and

may result in a rupture at the inner fillet weld of the bottom-to-shell connection or the bottom lapwelds. This would cause

a sudden complete discharge of the tank contents.

As it is impossible to predict the probability of a washoutoccurring, corrective action should always be taken as soon as

possible

The possibility of a rupture increases when the tank is filledto a high level



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2.2.7 Relevelling of Tanks and Foundations

When settlements have reached their maximum limits,

relevelling of the foundations and the tank will be necessary.

The tank is jacked up to a level 8 feet (2.4 meters) above the

foundation to provide sufficient space under the tank for the

repair of the tank foundations

Jacking of tanks has been successfully carried out for tanks

up to 300 foot (90 meters) diameter. The jacking of largetanks requires a contractor with specialised experience


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2.3 Corrosion of Tanks

General underside corrosion should be slight where there is

a well prepared and maintained foundation.

The major causes of underside corrosion are:

- Poor drainage around tank

- Mill scale, which when present on the underside of the

tank bottom, causes preferential attack

- Water collecting around the tank and migrating under the

tank



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2.3 Corrosion of Tanks- Significant tank settlement that lowers the tank below a

good drainage level. This may lead to corrosion of

the annular plate around the tank perimeter.

- High natural water or underground springs

- Coral or beach sand with high chlorides used for the

foundation.

- Acidic coal based cinders or slags being included in the

foundation.

- Sharp or large stones being included in the foundation. Thismay give rise to deep pitting by oxygen concentration

cell corrosion.



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2.3 Corrosion of Tanks- Poor quality of bitumen sand mix. B.S. 2654

- Cathode protection may have been installed after the tankhas been commissioned. In this case it makes it

difficult to ensure that sufficient protective current

reaches all areas of the bottom.- In tanks storing heated products, there are large differences

in the tank to soil potential across the bottom. This

can cause deep random pitting. Potentials becomemore anodic from the center of the tank outwards.



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2.3 Corrosion of Tanks- Hot tanks increase water permeation under bottoms and

corrosion rates increase at higher temperatures.

- Stray D.C. currents may cause extremely high local corrosion.

This occurs when an external source of direct current

such as an electric railway causes current to flow

through the ground to the tank bottom.

- Other isolated cases have included rapid galvanic corrosion

resulting from installation of a new bottom on top of

an old bottom and higher than average corrosion ratescaused by elevated temperature.



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2.4 Tank Bottoms

2.4.3 Bottom Settlement

2.4.1 Shape of Tank Bottoms due to settlement

2.4.2 Ripples in the tank bottom

a) Edge settlement

- Rain water collected in the depression around the shell

will decrease the quality of the foundation under

the shell and increase the possibility of edgesettlement.



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a) Edge settlement

- Edge settlement may be caused by a tank pad shoulder

with insufficient width or poor quality construction.

- Edge settlement may be caused when the tank pad

shoulder is damaged or eroded by rain and wind

- Edge settlement may occur when the shell

penetrates into the foundation due to poorcompaction of the tank pad under the tank shell

Typical Tank Settlement Curve


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Settlements cause ovality of tank shells


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Effect of Shoulder Width EEMUA 183


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S1.5 m



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b) Bulges or Depressions in Bottom Plates

- Sometimes it is proposed that these voids are filled with liquid

concrete to give support to the bottom plates at thatlocation. How ever this is incorrect. Slurry will not fill

these voids but will flow to those locations where the

bottom can move easily, so that ultimately the tankbottom will rest on a number concrete points instead of

being supported evenly over its entire surface.

- When bulges are formed and not filled with foundation material

(void) there is a risk of rippling when the tank is filled andthe product contained will press the plate downward.


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2. -Tank Foundations: Design

3. -Tank Bottoms: Design

4. -Main Causes of Tank Bottom Leakage

5. -Inspection Records and Techniques

1. -Introduction and Scope



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8. -Condition Monitoring and Maintenance

9. -Main Conclusions and Recommendations

7. -Available Systems for Detecting leakage and MinimizingSoil Pollution.

6. -Other measures for preserving the Integrity of Tank

Bottoms.

2. Foundations of Storage Tanks EEMUA 183


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5 types

- type A: Traditional Sand Pad- type B: Sand Pad with Crushed Rock Annular Section

- type C: Concrete Ring Beam Foundation

- type D: Concrete raft

- type E: Underpiled Concrete raft

Type A: Traditional Sand Pad EEMUA 183


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Top View Sand Pad Foundation EEMUA 183


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Type C: Concrete Ring Beam Foundation

EEMUA 183


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Type D and E: Concrete Raft Foundation EEMUA 183


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Foundations of Storage tanks


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g

Required Data for Design

Soil Investigations:

- Cone Penetration Tests

- Soil Borings


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A soil investigation report shall contain:


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Apply soil improvements?

or

Pad is to be constructed directly on existing grade?

Squeezing possible?

Advice foundation type with predicted settlement >> height of pad

Maximum Tank Height

Maximum Filling height

Settlements: - Short/Long Term- Even/Uneven

Required No. of Cone Pentration Tests


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Soil Improvement Method


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Dry Excavation (ground water level min. 0,5 m belowdeepest point of excavation)

Building from layers with height of max. 0,4 m

Every layer is to be tested

Or by hand test min. 5 MPa

Or 98% Proctor value

TOTAL SOIL IMPROVEMENTS ARE TO BE

CHECKED WITH CONE PENETRATION TESTS(quick, efficient, cheap and must be done when adhering to EEMUA 159)

Schematic Geometry


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Execution of Soil Improvements


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To what depth: same depth every where?

Extend of excavation: D + 2S + 2T + 4d (+Dd)

At un-equal soil excavation depths the excavation does not

have a circular shape

Excavation shall not exceed ground water level (No soil

improvements possible)

High quality of used materials is required


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Soil Improvement on un-equal level


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Foundation Conclusions: EEMUA 183


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Width (S) of Tank Pad Shoulder:

- 1.0 m (3FT) for tanks < 15 m (45ft) diameter

- 1.5 m (5FT) for tanks > 15 m (45ft) diameter

High Pad down-grades the Stability

- Preferable Height above Grade: 600 mm (24 inches)

- Crushed Rock Annular Section increases Stability

Location of Leak Detection Membrane is Crucial

EEMUA 1832: Tank Foundations


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2.6 Sand Pad Foundation with Crushed Stone Piles

Stone piles will increase the risk of ground water

pollution from leaking tanks by providing good leakage

paths deep into the soil. Such designs are not therefore

recommended for oil/chemical storage tanks

2.7 Provision of Oiled Sand or Permeable Bitumen Sand layer

The provision of an oiled sand or permeable bitumen-sand

layer is considered a very important requirement for

inhibiting underside corrosion. (see Appendix 1, Fig. 2)

3 Tank Bottoms, Designs EEMUA 183


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3.2 Tank Bottoms with Annular Plates

3.4 Double Bottoms

3.3 Tank Bottoms without Annular Plates

3.4 Double Bottoms Fig.10 EEMUA 183


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3.4 Double Bottoms EEMUA 183


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Fig. 10 The Letter Box Method

When the new primary bottom is installed, support for the

bottom has to be re-established both outside and inside

the tank shell such that the old bottom and intermediateshell are effectively redundant.

The letter box method of installing a new bottom in a single

bottom tank has been in use for more than 35 years.



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Although there is no requirement to provide support for the

new bottom outside the shell, (API 650) paragraph 1.4.1

requires proper support of the primary bottom and

evaluation of the design to verify that the primarybottom and shell are not over-stressed under the

specified loading conditions including tank settlement.

Such evaluation is not required where the primary bottom is

uniformly supported on both sides of the shell and not

structurally attached to the secondary bottom orprimary bottom support.



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-The installation of double bottoms should be carefully

evaluated, taking into account the relatively high cost of

the design and of the rectification work required whentanks undergo progressive settlement.

-Also the lower or secondary bottom cannot be inspected even

when the tank is out of service and consequently its

integrity is always questionable.

3.4 Double Tank Bottoms EEMUA 183


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Complicated to Install

Relocation of Nozzles & Manholes Sensitive to tank Settlements

Releveling virtually impossible

Removal of contaminated material from double bottom

(following leakage) potentially hazardous

New Tank Foundation Construction with Liner


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9. Main Conclusions and Recommendations

EEMUA 183


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-Codes and standards covering the design and construction of

storage tanks are based on over 100 years of experience.

There is no need to question the integrity of the tankstructure as a as a primary container, provided it is

properly designed and built to recognised standards.

-Effective prevention of ground and ground water pollution from

storage tanks depends on the design and construction of a

good foundation, a properly construction tank bottom andregular, effective inspection.


EEMUA 183


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-Tank foundations should have a minimum height above grade as

recommended in 4.2 (24 inches 600mm)

-Tank bottom annular plates should be 3/8 in (8 mm) minimum

thickness and butt welded with backing strips (see 3.2)

-A course crushed rock tank pad shoulder (annular ring) under

the tank shell is preferred to a sand pad. Fig. 3 (see 2.3)


EEMUA 183


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-A concrete raft structure with or without piling, though

more costly to build than other foundation types, may

be justified on the basis of long-term maintenancecosts (see 2.5)

-For storage of hot products, tank bottoms should have cone

up configuration. However for small tanks a conedown floor on a concrete raft might be acceptable

(see 4.2)

EEMUA Publications


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3rd Floor, 20 Long Lane

London EC1A9HL

Telephone from outside UK: 44 20 7796 1293

Fax from out side UK: 44 20 7796 1294

E-Mail: [email protected]

Website: www.eemua.co.uk


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e Emu a Presentation 03