KOC_MV_007.pdf

KUWAIT

OIL

COMPANY (K.S.C.)

STANDARDS PUBLICATION

KOC STANDARD

FOR

FIELD ERECTED STORAGE TANKS

DOC.

NO. KOC-MV-007

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KOC STANDARD

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FIELD ERECTED STORAGE TANKS

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KOC-MV-007

ISSUING AUTHORITY:

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1 TABLE OF CONTENTS

FOREWORD SCOPE

'EALTH, SAFETY AND ENVIRONMENT

SEFERENCE CODES, STANDARDS AND SPECIFICATIONS

4.1 National/lnternational Standards 4.2 KOC Standards

4.3 Other Relevant KOC Standards 4.4 Project Specifications 4.5 Units 4.6 Conflicts 4.7 Exceptions/Deviations ENVIRONMENTAL CONDITIONS QUALITY SYSTEMS

6.1 Documentation & Accreditation

6.2 Inspection & Test Plan

6.3 Sub-contractors and Vendors

MATERIALS 7.1 .Material Selection 7.2 Procurement 7.3 Inspection of Materials 7.4 Certification Requirements 7.5 Marking

7.6 Weld Consumables etc. 7.7 Notch Ductility

7.8 Weld Repairs to Materials

DESIGN GENERAL REQUIREMENTS 8.1 Safe Practice 8.2 Capacity 8.3 Seismic Loads 8.4 Wind Loads 8.5 Wind Girders

8.6 Uplift 1 Overturning

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Sliding Stability 8.7 Foundations

8.8 Design Metal Temperature 8.9 Corrosion Allowance 8.1 0 Tank Bottoms 8.1 1 Bottom Connections 8.1 2 Shell

8.13

Shell Connections

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General 8.14 Shell Access Connections

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8.15 Stairways, Ladders and Platforms

8.16 Cathodic Protection 8.1 7 Earthing Clips 8.18 Settlement References 8.1 9 Calculations 8.20 Drawings 8.21 Weld Details

8A.0 REQUIREMENTS SPEClFIC TO FIXED CONICAL ROOF TANKS

8A. 1 Vapour Pressure

8A.2 Vacuum

8A.3 Roof Loads

8A.4 UplifttOverturning Stability

8A.5 Shell Connections

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General

8A.6 Top Angle

8A.7 Roof

8A.8 Roof Support

8A.9 Roof Connections

8A. 10 Stairways, Ladders & Platforms

8A.1 1 Weld Details

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86.0 REQUIREMENTS SPECIFIC TO EXTERNAL FLOATING ROOF TANKS 27

Overall Configuration

Design and Operating Levels Roof Types

Pontoon Configuration

. Double-Deck Configuration Flotation Compartments Centre Deck of Pontoon Type Operating Flowrates

Stability

Main Tank Connections

Roof Connections and Openings Rolling Ladder

Anti-Rotation and Centering Devices Roof Sealing

Earthing

Roof Support Legs Gauging

9.0 LOSS PREVENTION

9.1 Fire Protection

9.2 Overpressure Protection

9.3 Venting Capacity

9.4 Setting of Protective Devices

9.5 Design of PressureNacuum Protective Devices

9.6 Sparing of PressureNacuum Protective Devices

9.7 Location & Installation of Protective Devices

9.8 Overfill Protection

9.9 Boilover Prevention 9.10 Evaporation Loss Control 9.1 1 Protection Against Ignition

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FABRICATION & ERECTION

10.1 Health, Safety & Environment 10.2 Fabrication and Erection Procedure 10.3 Plate Squareness

10.4 Cutting, Forming and Pre-fabrication 10.5 Marking and Traceability

10.6 Plate Preservation 10.7 lnterpass Cleaning 10.8 Weld Proximity 10.9 Preheating

10.10 Post Weld Heat Treatment 10.1 1 Temporary Attachments 10.1 2 Tank Isolation

10.13 Coating & Lining 10.14 Tank Calibration

SITE

INSPECTION & TESTING

11.1 General 1 1.2 Welded Joints 1 1.3 Dimensions 1 1.4 lnternals

1 1.5 Floating Roof Compartments 1 1.6 Testing Procedure

1 1.7 Shell Test

11.8 Floating Roof Test 1 1.9 Fixed Roof Test 11.10 Coils

1 1.1 1 Internal Examination '

.

.

NON-DESTRUCTIVE EXAMINATION

12.1 General

12.2 Volumetric Examination

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General Requirements 12.3 Image Quality Indicators

12.4 Film Density 12.5 FilmType

12.6 KOC Acceptance

12.7 Retention of Radiographs 12.8 Surface Examination

WELDING PROCEDURES & QUALIFICATIONS

13.1 General

13.2 Weld Procedures

13.3 Qualification Testing of Weld Procedures 13.4 Welder Qualification

MARKING & FINAL DOCUMENTATION

14.1 Certifying Letter 14.2 Marking

14.3 Safety Precautions 14.4 Certification Dossier

- . 14.5 Technical, Operating and Maintenance Manuals

PAGE NO. 39 39 39 39 39 40 40 40 40 4 1 4 1 42 42 42 43 44 44 45 46 47 47 47 48 49 49 50 50 5 1 5 1 5 1 5 1 52 52 52 52 52 5 3 53 53 53 54 55 55 55 55 55

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15.0 SPARE PARTS & MAINTENANCE 56

APPENDICES APPENDIX A : A. 1 A.2 A.3 A.4 A. 5 A.6 A.7 A.8 A.9 A. 1 0 APPENDIX B : APPENDIX C : C. 1 C.2 APPENDIX D : APPENDIX E :

FIELD INSPECTION CO:ORDINATION 57

Scope 57 57 Forms Design Documents Punchlisting Communications

lnspection & Test Equipment & Personnel Activity Notification

lnspection Notification lnspection & Test Records Repairs, Non-Conformities etc.

ESTABLISHMENT & MAINTENANCE OF

WELDER QUALIFICATIONS 60

Qualification Testing

Qualification on Production Welds Qualification Test Records

Identity Cards Records

Maintenance of Qualifications through Produl: tior; Welding DATA SHEETS

Standard Data Sheet for Fixed Roof or Unroofed Tank

Standard Data Sheet for External Floating Roof Storage Tank. SUMMARY OF DOCUMENTS

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ACTIONS FOR

KOC APPROVAL 7 1

TANK CAPACITY & LEVEL DEFINITIONS 7 2 TABLES :

Table 8.9 Summary : Internal Coatings, Lining & Corrosion Allowance Table 11.7.5 Hydrotest "Hold" Points

Table 12.3 Radiographic Sensitivity

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FOREWORD

This document has been generated by the Task Force (TF-Mech.102) and is approved by the Standard Technical Committee (STC) and Standards Division for use throughout the corporate engineering and operational functions of Kuwait Oil Company (KSC).

The document sets out t o achieve the following:-

To set standard requirements for tanks which are not project-specific but which have general applicability for all new construction and will ensure a consistent approach.

To reference established KOC Standards wherever possible but t o allow other specifications wherever KOC Standards are pending. ( A list of these t o be appended by the controlling department of a particular project or contract.)

The utilization of past operational experience t o avoid repetition of problems and t o consolidate worthwhile and beneficial features.

Recognition of the different criticalities of the duties of different categories of tanks.

To comprehensively and clearly cover all aspects of design, construction and testing so as t o minimize clarifications and t o avoid disputes.

To avoid conflicts with the basic requirements of API 6 5 0 or other KOC standards.

To avoid repetition of basic API 6 5 0 requirements.

To standardize wherever a benefit to KOC is envisaged, but t o allow some freedom of design where it is envisaged that this might result in a more economical design or more competitive tendering.

To maintain KOC requirements for safety and environmental protection as established by KOC regulations and procedures.

To introduce data sheets which:

i) incorporate all essential features of the API 6 5 0 Data Sheet. ii) maintain consistency with the text of the standard.

iii) act as a check sheet t o assist in ensuring that all relevant topics are considered.

iv) provide a mechanism for KOC engineers t o specify options permitted both by this standard and by API 650.

V ) will serve as a useful consolidation of data not only during design and construction but also for long term record purposes.

Feedback as well as any comments or suggestions derived from the application of this Standard at any stage of design, construction or operation are encouraged and should be directed t o :

The Superintendent Standard Division

( Chairman, KOC Stds Technical Committee) Engineering Group, K.O.C.

Compliance with this KOC Standard does not of itself confer immunity from legal or statutory obligations.

Acknowledsernent

The preparation of this document has been entrusted by the Standards Technical Committee (STC) t o the Task Force (TF-Mech102) comprising the following members:-

Mr. Mohammed Emam (Insp. & Corr. Div.) : Team Leader Mr. Phil Brooks (Insp. & Corr. Div.) : Author, Member Mr. Salah Heikal (Insp. & Corr. Div.) : Member

DOC. NO. KOC-MV-007

1.0 SCOPE

This Standard specifies the minimum requirements for materials, design, fabrication, erection, inspection and testing of vertical, aboveground, field erected, welded steel tanks.

This Standard is based on API Standard 650 : Welded Steel Tanks for Oil Storage, and modifies and/or amplifies the requirements of that standard to suit the specific requirements of Kuwait Oil Company (KOC) hereafter referred to as "KOC". It extends beyond the scope of API 650 to include tanks which have a process rather than a storage function and also to include tanks intended to contain water for fire fighting or process use. Tanks with open tops for firewater storage or similar applications are described as "unroofed" in this standard to avoid confusion with external floating roof tanks which are sometimes also described as "open".

This Standard is not intended to be applied to the following:

(a) Tanks with structurally supported Aluminum dome roofs (API-650 Appendix

G)

(b) Tanks with internal floating roofs (Appendix H) (c) Shop assembled tanks (Appendix J)

(d) Tanks operating at elevated temperatures (Appendix M)

(el Austenitic stainless steel tanks (Appendix S)

This Standard complements the data sheets (Appendix C] for the equipment, in which the operating conditions and other basic design requirements are listed in detail.

This Standard is based on the Ninth Edition of API Standard 650 including up to the 1995 Addendum. However, this does not necessarily preclude its use in conjunction with later editions.

Note : To facilitate cross-reference, corresponding API 650 clauses which have been amplified or modified are shown in brackets

{.

. . .

.].

These references are for information only. It should not be assumed that the API 650 references are comprehensive or complete.

1

2.0 TERMINOLOGY

Throughout this Standard, the following terms shall have the meaning indicated for each one:

"shall" is used where the provision is a requirement to be followed strictly in order to conform to the standard. (Deviations will only be permitted as outlined in

4.7 of this standard.)

"will" is used normally in connection with an action by KOC rather than by a contractor or supplier.

"should" is used where a provision is recommended. (A Contractor must, on request, be ready to justify any deviation from these provisions.)

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"must" is used where a requirement or action is statutory or considered to be essential.

"may" is used where an alternative course of action is acceptable within the limits of the standard.

"KOC" means Kuwait Oil Company (K.S.C.I.

3.0 HEALTH, SAFETY AND ENVIRONMENT

Design and construction practices (including those of any sub-contractorl shall be consistent with KOC's Health, Safety and Environment policies and guidelines. In particular, during construction, and as far as practical during subsequent operation and maintenance, the risks of all of the following shall be minimized:-

*

Safety and Health of Personnel

Damage t o or Degradation of KOC Assets

Damage t o or Degradation of the Environment (liquid discharges or gaseous emissions whether planned or unplanned)

4.0 REFERENCE CODES, STANDARDS AND SPECIFICATIONS 4.1 National 1 International Standards

Except as modified or amplified by this Standard, the requirements of API 650 latest edition shall be met together with all relevant requirements and recommendations of the standards referenced therein. Standards referenced herein are listed below:

API RP 2 0 0 3 API 2 5 5 5 API Manual o NFPA-11 NFPA- 1 5 NFPA-30

API RP 6 5 1 Cathodic Protection of Above Ground Petroleum Storage Tanks.

API STD 6 5 3 Tank Inspection, Repair, Alteration & Reconstruction API STD 2 0 0 0 : Venting Atmospheric and Low Pressure Storage

Tanks.

Protection Against Ignition Arising out of Static, Lightning and Stray Currents.

Method for Liquid Calibration of Tanks. f Petroleum Management Standards : Sections 2A & 2B.

Standard for Low-Expansion Foam.

Water Spray Fixed Systems for Fire Protection. Flammable and Combustible Liquids Code 1S0.9000 series : Quality Management and Quality Assurance

Standards.

EN. 1 0 2 0 4 Metallic Products

-

Types of Inspection Documents. ASTM & ASME : As referenced in the text.

BS 3 9 7 1 Image Quality Indicators for Industrial Radiography. lnstitute of Petroleum : Model Code of Safe Practice.

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4.2 KOC Standards

This Standard makes reference t o the following KOC Standards, Recommended Practices and Standard Drawings:-

4.2.1 Standards

KOC-C-026 : Storage Tank Foundations KOC-G-007 : Basic Design Data

KOC-G-009 : Spare Parts & Maintenance Data KOC-ME-026 : Tank Side Entry Impeller Mixers

KOC-P-001 : Painting and Coating of Metal Surfaces

-

New Construction

KOC-P-002 : Internal Lining of Tanks and Vessels

-

Part 2 : Rigid Reinforced Fibreglass Lining

4.2.2 Recommended Practices

KOC-E-024 : Earthing & Bonding

KOC-L-026 : External Cathodic Protection of New Steel Tank Bottoms

4.2.3 Standard Drawinas

0 1 5-CB-1013 : Earthing Clip

0 1 5-MB-1002 : Standard Handrail Details 4.3 Other Relevant KOC Standards

KOC-(2-033 Bund Wall for Storage Tanks 4.4 Proiect Specifications

This Standard also makes reference t o other specifications which should be designated by the Controlling Department on a project specific addendum sheet.

i) General Welding Requirements

ii) Structural Steel Design, Materials & Fabrication iii) Cathodic Protection Design Requirements iv) The Use of Brackish Water for Site Hydrotesting

V) Fire Protection & Safety Equipment

vi) Fire & Gas Detection Equipment

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4.5 Units

Units adopted by this Standard are generally SI metric but some US Customary units have been retained for consistency with API and ASTM standards or where these are more familiar within the industry.

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4.6 Conflicts

Any conflict between this Standard and other drawings, standards, codes, specifications, contractual or purchase requirements, shall be notified in writing t o the Superintendent of the Contract for clarification.

Exceptions or deviations will only be considered when submitted in writing and supported b y evidence of merit or justification. (If documents are inadvertently approved or released for construction when these show exceptions or deviations from this Standard which have not received prior approval, then this will not be deemed t o constitute acceptance by KOC of these variations)

Where proposed exceptions and deviations are judged to have general

relevance, then the Superintendent of a Contract

may

bring these to the attention of KOC Standards Division for possible incorporation into the next revision of the standard.

5.0 ENVIRONMENTAL CONDITIONS

For environmental conditions in Kuwait, refer to KOC Standard for Basic Design Data (KOC-G-0071, which provides the detailed design information regarding the environmental, site and utility supply conditions prevailing throughout the KOC facilities.

6.0 QUALITY SYSTEMS

6.1 Documentation and Accreditation

The constructor shall operate a quality system t o ensure that the technical and quality requirements are achieved. The quality system should be based on I S 0 9 0 0 0 series of specifications or other internationally recognized standard. It shall be fully documented and should have been verified by a recognized accreditation scheme.

6.2 Inspection & Test Plans

Inspection and test plans covering procurement, pre-fabrication and field erection shall be submitted for KOC's approval prior to commencement. This shall include but not be restricted t o the relevant inspection notification points listed in para.

A.8 of Appendix A of this standard.

6.3 Sub-contractors & Vendors

6.3.1 A contractor shall ensure that QA requirements specified in the inquiry

and purchase documents are applied t o all materials, equipment and services provided by vendors and sub-contractors.

6.3.2 The selection of sub-contractors for fabrication, erection, non- destructive testing, coating and lining shall be subject t o KOC approval. Subcontractors who fabricate pipe supports and other non-containment items but with

the

exception of roof trusses may however be selected in accordance with the contractor's quality system.

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7.0 MATERIALS

7.1 Material Selection

7.1.1 Materials used for tank fabrication shall be as specified on the tank data sheet. The materials shall be new and shall not have suffered undue deterioration in storage or transit. Any substitutions shall be agreed in writing by KOC before any procurement or fabrication commences. 7.1.2 Except where materials have been specified on the data sheet by KOC,

a Contractor may select appropriate ASTM plate materials from those listed under para. 2.2.2 of API 650, except as below:-

a) ASTM A 6 7 8 shall not be used.

b) ASTM A 3 6 shall not be used for shell, roof, bottom or annular plates. (2.2.2a)

C) Components of frangible joints shall be Group lllA as a minimum.

d l The bottom shell course and annular plates of crude oil tanks in excess of 50,000 bbls nominal capacity shall be Group lllA as a minimum.

Where steels complying with specifications of other standards organizations are offered as equivalents, then these shall be subject to KOC's approval.

7.1.3 Selection of plate material for shells and annular rings shall be limited to steels w i t h a specified minimum tensile strength of 7 0 0 0 0 psi or less, but in exceptional circumstances, higher grades may be acceptable t o KOC in order t o limit shell thickness.

.

.

7.1.4 Shell and annular ring plates shall have a minimum manganese t o carbon ratio of 2.5:1. Rimming steel shall not be used. (2.2.6)

7.1.5 Annular plates shall be of the same material specification and grade as the bottom course of shell plates.

7.1 - 6 All shell nozzle flanges shall be in accordance with ASTM A 1 0 5 or A 3 5 0 Gr.LF2. (2.5.1.2)

7.1.7 Piping for internal or external connection shall be seamless t o ASTM A 1 0 6 Gr. 8, A333-6 or API 5L Gr.

B

or alternatively may be rolled and welded plate of the same specification as the shell. Electric resistance welded (ERW) pipe is not permitted for shell connections or loaded structural components but may be used for internal distributor or collector piping (2.5.1.1)

7.1.8 Bolts and nuts shall conform t o ASTM A1 93 Gr. 8 7 and ASTM A1 94

Gr.2H respectively. (2.7)

7.1.9 Selection of materials for internals shall take due account of the possibilities of galvanic corrosion and static discharge.

7.2 Procurement

Manufacturers of plates for the shell and bottom shall be subject t o KOC's approval. (2.2.6.1) Unpriced sub-orders for these materials and for welded pipe used for shell nozzle or manway necks shall also be subject t o KOC's approval together with technical purchase specifications. These should include any relevant requirements for steelmaking, heat treatment, toughness, forming, beveling or coating. Technical purchase specifications shall also be submitted for fittings such as seals, drains, venting devices, flame arrestors, heating coils, foam pourers, gauging devices and anodes,

7.3 lns~ection of Materials

7.3.1 KOC shall be afforded the right t o inspect any or all material at source. 7.3.2 In the event that KOC opts not t o inspect shell and bottom plates at

source, but when the tank data sheet indicates any special material requirements t o be applied, then mill certificates shall be submitted for approval prior t o loading for transportation t o Kuwait. Certification of any other materials will be subject t o checking on receipt of the materials.

7.3.3 When it is proposed t o make large diameter shell connections from plate rolled and welded at the Constructor's local shop, then the plate shall be subject t o inspection on receipt.

7.4 Certification Requirements

7.4.1 Certification shall be provided to the 3.1

.B,

level of EN 10204 (DIN 50049) for the following:- (4.2.1)

(a) Materials comprising the containment envelope. (b) Wind girders and compression rings.

( c ) Anchorage and other load bearing attachments.

(dl Primary supporting sections of roof trusses and girders.

7.4.2 For shell plate and annular ring materials, a check analysis shall be made b y the mill, stockist or contractor t o at least the same frequency as required b y the relevant material specification for tensile testing. The results shall be furnished to KOC. All elements included in the long formula for carbon equivalent as below shall be determined.

7.4.3 The Carbon Equivalent (C.E.) shall be determined and reported for materials listed above using the following formula:

C.E. = C

+

( M n / 6 ) + (Cr+Mo+V)

/ 5 +

( N i + C u ) I 1 5

The CE shall not exceed 0.42% for plates exceeding 25 m m thickness and 0.43% for other materials comprising or intended t o be welded t o the containment envelope.

Limits apply t o both ladle and t o product or check analyses. It will not be acceptable t o assume zero content for a non-determined element for plates. However, for materials other than plates for which the relevant standard does not require analysis of all the above elements, it will be in order for acceptance t o be on the basis of a maximum carbon equivalent of 0 . 3 5 % by the short formula (C

+

MnI6)

Shell and annular plates shall be marked in accordance with the relevant material specification by the mill by die stamping. Other plates may be marked by stenciling when permitted by the material specification.

Weld Consumables, etc.

The constructor shall maintain sufficient records t o provide assurance of the identity and quality of weld consumables and other materials of construction. Notch Ductility (2.2.9.1, 2.2.7.4)

For tanks which are designed t o contain hydrocarbons, all plates in excess of 19 m m thickness for shell, annular ring, nozzle and manway necks, anchors and reinforcement shall be subject t o impact testing. Testing shall be in accordance with section 2.2.10 of API-650, but the test temperature shall be O°C in all cases.

Weld Repairs t o Materials

7.8.1 When unacceptable defects are found in materials forming part of the

. . tank containment (other than after removal of temporary attachments which is covered by paragraph 10.1 1 of this Standard), and when a constructor proposes t o undertake a weld repair, he shall submit his proposals t o KOC's site representative for approval, including weld procedures, qualification records, heat treatment procedures and NDE

proposals.

7.8.2 The constructor is required t o keep records of weld repairs t o materials, t o make these available for review, and t o include them in certification dossiers. These should record the nature, location and depth of defects, the weld procedure(s) used and NDE techniques employed and include NDE and heat treatment records.

7.8.3 When defects have been excavated with a view t o repair, ncrification shall be given t o KOC's field inspection representative for w.! -..qC of NDE and inspection.

8. DESIGN

GENERAL REQUIREMENTS 8.1 Safe

Practice

For topics and features not addressed in detail'in this Standard, the design shall incorporate the relevant recommendations contained in the various parts of the Institute of Petroleum : Model Code of Safe Practice.

8.2 Caoacity

8.2.1 The basis of capacities shall be as indicated on the Appendix E sketch. 8.2.2 Fixed roof and unroofed tanks shall be ordered on the basis of "nominal

(rated) capacity".

8.2.3 Floating roof tanks may be ordered on the basis of either "safe operating capacity" or "net working capacity". Whichever basis is used, the tank designer shall determine and set the other defined capacities.

8.3 Seismic Loads

When the Tank Data Sheet specifies that seismic design applies:- a) b c d

1

e 8.4 Wind Loads

Importance factor shall be taken as 1.0 except where otherwise specified on the Data Sheet.

Site coefficients shall be as specified on the Data Sheet or as agreed by KOC based on a site survey.

Where seismic design requires shell thickness t o be added, the minimum amount t o be added shall be the greater of the seismic element or the corrosion allowance.

Appropriate consideration shall be given t o possible combinations of loadings from sources such as earthquake, wind and internal pressure.

Configurations of floating roof crude oil storage tanks which require anchorage against seismic effects shall be subject t o

KOC

approval.

Tanks shall be designed for wind loads arising from a design wind speed V, of 45 m/s or 1 0 0 mph.

Prevailing wind directions are given in KOC-G-007.

8.5 Wind Girders

8.5.1 The spacing of intermediate wind girders shall be based on the net thickness (i.e: corroded thickness) of shell plate.

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8.5.2. A sufficient number af holes shall be provided for drainage of rain or deluge water when the section is not inherently self-draining.

8.5.3 The top of an open tank (unroofed or external floating roof) shall be stiffened by a top curb angle (3.9.3.2) and by a wind girder located one metre below the top of the curb angle which shall also be designed t o serve as a aalkway. (3.9.4) The effective width of the walkway shall be 1 0 0 0 m m minimum, and an outer handrail and kickplate shall be provided around the entire periphery. The walkway shall be reached from the access stairway of an open top tank or by access stairway from the gauger's platform of a floating roof tank.

8.6 U ~ l i f t I Overturnina I Slidina Stabilitv

Stability and /or anchor loads shall be calculated for all tanks. A safety factor of 1.5 shall be applied to sliding.

8.7 Foundations

The tank foundations shall be in accordance with KOC-C-026. 8.8 Desian Metal Tem~erature

Minimum metal design temperature shall be nominally plus 1OVdegrees Celsius. This is a conservative figure equal t o the minimum allowable test water temperature and is somewhat lower than the figure derived from published lowest one day mean temperature data for Kuwait. (2.2.9.3) In any case, impact testing of plate materials shall be in accordance with paragraph 7.7 of this Standard and weld procedure qualification impact testing shall be in accordance with paragraph 13.3.2 of this Standard.

8.9 Corrosion Allowance

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8.10

Tank Bottoms

The tank bottom shall have a slope of 1 in 120 from the centre down to the periphery (Apex up).

All tanks shall be provided with annular plates on which the shell plates shall rest.

(3.5.1)

Minimum width for annular plates shall be 750 mm.

{3.5.2){E.4.2)

Minimum un-corroded thickness of annular plates shall be 0.35 x the thickness of the bottom shell course or 0.375" whichever is the greater.

(3.5.3)

Water draw-off sumps shall be provided as shown on the tank data sheet. These shall be located so as to clear any 3-plate lap joints in the tank bottom and the bottom to annular joint by a minimum of 12 inches. Plating shall be 0.375" thick minimum. Draw-off piping from sumps shall be provided with a single pair of flanges inside the shell to facilitate removal and shall be securely supported from the tank bottom.

The minimum thickness of rectangular and sketch bottom plates shall be 0.375" including corrosion allowance.

(3.4.1)

Flat wear plates shall be provided below dip pipes and under pipes discharging against the tank bottom.

Wear plates shall also be provided in the vicinity of mixers. These shall be minimum 0.1875" plates continuously welded to the bottom and around the shell connections prior to applying the bottom lining.

8.1

1

Bottom Connections

when. connections are required to be made to a tank bottom, the recommendations of A3pendix 0 of API 650 shall in general be followed. Unless otherwise agreed by KOC, the arrangement shown in fig.O-2 shall be provided. The connections shall be located so as to clear any lap joints in the tank bottom.

The shell thickness shall be calculated using the one foot method for tanks up to and including 30 metres diameter.

(3.6.3.1)

Finite element analysis techniques shall be applied to tanks with diameters 61 metres and larger.

(3.6.5)

Any proposal to utilize "banding" to confine the shell stress of large tanks within the limits allowed by API 650 shall be subject to KOC approval.

A specific gravity of 1.02 shall be used for computing both the design shell thickness

(3.6.1.3)

and the hydrostatic test shell thickness

(3.6.1.4)

except that when a higher value is indicated on the data sheet this higher value shall be used.

8.13 Shell Connections

-

General

8.1 3.1 In general, all nozzles / manholes shall be of the flanged type. However foam chambers may be mounted on studded pads welded t o the shell. 8.1 3.2 Where anti-vortex arrangements are required for pumpout, these shall be

as indicated on the tank data sheet. In the case of the oil outlets of floating roof tanks, vortex breakers are mandatory t o allow for the possibility of the installation of pumps in the future.

8.1 3.3 Anchoring brackets, if required, shall be provided at centres specified in API 650. Caution shall be exercised in locating brackets so as not to land or interfere with stress relieved assemblies, shell vertical seams or other appurtenances or reinforcement plates.

8.13.4 Shell nozzles shall be designed not only for the static liquid load (3.7.2) but also for the loads imposed by connecting pipework, and in the case of manways utilized for mounting of side entry mixers, for the loads transmitted by the mixers. For connections situated in the bottom shell course, it shall be verified that allowable loads derived from Appendix P of API-650 are not exceeded. (3.7.1.5)

8.13.6 L o w type shell reinforcement plates

(3.7.3.3)

shall only be used where it is impractical t o raise the nozzle opening by an amount sufficient t o avoid this condition.

8.1 3.5 All shell nozzle reinforcement plates shall be of the same material as the shell. These plates shall be provided with 114" diameter threaded vent I

telltale holes t o facilitate pneumatic testing and after testing shall be left unplugged but weather sealed with grease. (3.7.6.1)

8.13.7 For piping routed t o nozzles at high shell elevations or on the tank roof, suitable support pads and reinforcing steelwork shall be provided to enable such piping t o be completed after tank hydrotest.

.

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8.14 Shell Access Connections

8.14.1 Requirements for the number and orientation of 3 6 " x 48" flush type cleanout doors shall be as indicated on the tank data sheet.

8.14.2 One of the shell manways shall be located near the foot of the main access stairway or ladder. The others shall be spaced approximately equally.

8.1 4.3 Shell manways shall be at least 24" nominal and shall be provided with suitable hinged cover davits. Manways shall be provided with external handgrips positioned approximately 400 m m above the top of the manhole. Internal handgrips shall also be provided except that when they would be located in a fibreglassed area they shall be omitted.

8.14.4 When rnanways are also used for mounting side-entry mixers, they shall have ANSI type forged flanges.

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8.15 Stairways, Ladders & Platforms

8.1 5.1 Main access t o the top of a fixed or floating roof tank shall be provided

by an outside double stringer radial stairway 1000 m m wide or, for fixed roof tanks only, b y a spiral stairway where so indicated on the tank data sheet. A radial stairway shall extend t o the tank bund wall with additional provision for access from inside the tank bund area.

8.15.2 Main access t o the top windgirder walkway of an unroofed tank'shall be

by spiral stairway.

8.15.3 Stairways shall have a minimum width of 1000 m m and be arranged

with the angle of slope t o the horizontal plane from 35 degrees t o 40

degrees. Angles greater than 40 degrees shall be subject t o approval by

KOC.

8.1 5.4 Intermediate landings shall be provided at approximately 6 metre

intervals for all types of fixed stairways and ladders.

8.1 5.5 All treads and platform floors shall be galvanized safety tread or equal as

approved by

KOC.

Hand and knee rails and 200 mm high toe kick plates shall be provided for platforms, and hand and knee rails shall also be provided for stairways. Handrails shall conform t o Standard Drawing

01 5-MB-1002.

8.16 Cathodic Protection

8.16.1 Cathodic Protection shall be generally in accordance with the designated

Project Specification and with API RP 651. Reference should also be

. made t o the Scope of Work for delineation of responsibilities.

8.1 6.2 In addition t o protective coating, the underside of all tank bottoms shall be cathodically protected by an impressed current system in accordance w i t h KOC-L-026.

8.1 6.3 An impressed current system shall be applied t o the internal surfaces of

tanks containing predominantly aggressive water such as fire, brackish or untreated seawater. Cable support studs shall be provided for unroofed tanks, and arrangements shall be made for connecting and suspending the C.P. Anodes.

8.1 6.4 Fixed sacrificial anodes shall be installed in tanks containing fuel gas blanketed or treated water.

. 8.16.5 No additional internal cathodic protection is required for oil tanks with

bottoms lined with fiberglass (or equivalent thick) linings.

8.17 Earthina C l i ~ s

Earthing facilities shall be in accordance with clause 8.5 of KOC-E-024 and Standard Drawing 01 5-CB-1013.

8.18 Settlement References

TO facilitate settlement checks, reference markers shall be provided on the shell at an elevation of 1 m and at an early stage of erection. They shall be made from angle bar, 5 0 x 5 0

x

5

mm and 100 m m long. The number and distribution of markers shall be accordance with 10.5.1.2 of API Standard 653 except that N shall be rounded up t o the next multiple of four. When large connections are made t o the tank bottom, additional reference markers shall be provided inside the shell t o enable their settlement t o be checked. When a tank is t o be constructed b y a "jack-up" method, the erection procedure shall address other means of monitoring foundation settlement during erection.

8.1 9 Calculations

8.19.1 Detailed design calculations are required. Computer printouts which have insufficient steps or which do not declare input data and assumptions will not be acceptable.

8.19.2 Calculations t o be submitted for approval or information shall include any of the following aspects which are applicable.

Nozzle sizing, process and hydraulic. Derivation of allowable stresses. (3.6.2)

Design pressure P (F.4.1) and maximum design pressure P,,, (F.4.2) for tanks subject t o small internal pressures.

Foundation and annular ring loading.

Required compression area at the roof t o shell. Shell thicknesses. (3.6.1.3, 3.6.1.4)

Venting (including open vents, rim vents and automatic bleeder vents) and emergency pressure relief.

Overflow capacity. Anchorage.

Cathodic protection (current density, anode life etc.) Uplift.

Sliding.

Required top wind girder sections for open top tanks. {3.9.1){3.9.6.1}

Wind induced buckling / intermediate wind girder height & section. (3.9.7)

Roof support.

Shell opening reinforcements (3.7.2) (including significant piping loads at nozzles (3.7.1.5))

Support of bottom connections (0.2.3) Rainwater drainage from floating roofs.

Buoyancy, stability and strength of floating roofs.(C.3.4) Water and foam requirements for firefighting.

DOC.

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8.20 Drawinqs

Drawings shall be issued to provide as a minimum the information listed below.

8.21 Weld Details 8.21.1 The

Design pressure (for fixed roof tanks) and design temperatures (minimum design metal temperature and other limitations such as for coatings or linings).

Allowable stresses.

Material specifications and grades. Required and/or nominal thicknesses. Dimensions.

Weights

Dimensional tolerances. Slopes.

References to any Standard Drawings.

NDE requirements (including any NDE of butt welds in roof support trusses or rafters.)

Proximity limits for openings

(3.7.3)

and for both permanent and temporary attachment welds.

Location of major load bearing temporary attachments (eg for roof raising)

Weld details and dimensions. Special attention shall be given to the profiles and tolerances of fillet welds connecting the shell plate to the bottom annular plate and to frangible joints.

shell to bottom joint shall be made with a minimum of two weld passes on each side of the shell. Each leg of the finished weld shall be of equal length.

8.21.2 The bottom rectangular and sketch plates shall be lap welded with double-pass fillet welds to provide continuous drainage to the periphery. 8.21.3 The shell vertical and horizontal joints shall be double butt-welded with

full penetration and fusion. For floating roof tanks only, abutting shell plates at horizontal joints may at the designer's option have their internal surfaces aligned. However there shall be no measurable "overhang". (3.1.5.2, 3.1.5.3)

4 All piping supports and other welded attachments to the shell, bottom and roof shall be welded to pads and not directly except for nameplate brackets, earthing clips and settling markers. Pads welded to the shell shall have any corners radiused to 50 mm minimum.

8.21.5 Internal fillet welded attachments shall as far as practicable be seal welded. The use of non-seal welded internal fillets direct to the shell or bottom shall be subject to KOC's approval. Seal welding is mandatory on tanks susceptible to pyrophoric scaling.

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8A.0 REQUIREMENTS SPECIFIC TO FIXED CONICAL ROOF TANKS 8A. 1 V a ~ o u r Pressure

8A.2 Vacuum

8A.Z. 1

Tanks with fixed roofs shall always be designed for a vapour pressure. Tanks with open vents shall have a design vapour pressure assigned such as t o avoid lifting of the roof plates (1.1.1)

Tanks which normally operate with a vapour pressure whether this arises from gas blanketing or from vapour evolution from the contained liquid shall have a design vapour pressure assigned t o provide a suitable operating margin t o minimize discharge t o the environment from pressure relief valves.

Tanks with open vents shall be assigned the basic 1 inch water gauge vacuum design. (3.2.4)

The basic 1 inch water gauge vacuum design shall also be applied t o other tanks as far as practicable. However a higher design vacuum may be deemed necessary for operational reasons, or t o limit the number of vacuum breakers required for tanks from which vapour recovery compressors draw. In such cases, the higher design vacuum shall be supported by finite element analysis or other appropriate calculation method, and shall take into consideration the combined effects of wind loading and external pressure (vacuum) on the empty tank.

8A.3 Roof Loads

The uniform live load t o be applied in the design of a fixed roof and its supporting structure shall be in accordance with API 6 5 0

-

3.10.2.1.

8A.4 Uulift 1 Overturnins Stability

Shell dead weight (W) shall be corrected for uplift due t o design pressure rather than due t o operating pressure. (3.1 1)

8A.5 Shell Connections

-

General

8A.5.1 Inclined inlet distributor pipe with slots/perforations (except on upper 3

meters section) shall be provided inside crude test tanks and dry crude tanks. Horizontal spreader

1

collector pipes shall be provided inside w e t crude tanks. Oil inlets shall be sized such that flow velocity does not exceed 1.25 m/s.

Internal pipes shall be provided with flanges t o ensure easy removal /

installation through manholes and shall be protected internally and externally with epoxy coatings. When agreed by KOC, they may be designed for removal through cleanout doors.

A top angle shall be provided with the horizontal leg turned outwards (3.1.5.9)

except where a strong roof to shell joint is specified by KOC, in which case detail "h" of API 650 Fig

F-1

shall be used.

Roofs shall be of conical form whether they are supported or of the self su,pporting type.

8A.8 Roof

S u ~ ~ o r t

8A.8.1 Roof supporting columns and trusses shall be designed in accordance with the designated Project Specification covering structural steelwork, and taking into account the appropriate loadings applied to them from all possible sources. Roof suppox columns of hollow section shall be designed to be internally dry and shall be seal welded top and bottom. It shall be verified that the loading of any support column will ensure that it cannot become buoyant.

8A.8.2 Support columns shall be provided with means of height adjustment to compensate for settlement.

8A.8.3 The base of support columns shall be restrained against lateral movement irrespective of whether or not the tank is designed to withstand seismic loads. (E.8.2)

8 A . 9 Roof Connections

8A.9.1 One or more 24" diameter roof manways shall be provided complete with suitable davit arms / hinges. These will be primarily for venting purposes during maintenance work rather than for access.

8A.9.2 Unless otherwise specified, oil tank roofs shall be equipped with a centre cylindrical gas dome to which the tank vapour line and vent shall be connected. Both the diameter and cylindrical height of the dome shall be at least twice the diameter of the vapour outlet connection, but with a minimum of 900 mm.

8A.9.3 Main vapour connections to the tank roof shall be adequately reinforced to take care of vibration

I

stress transmitted by piping. 8A.9.4 2 diametrically opposed dip hatches with covers and dip-tubes shall be

provided near the stair and ladder heads of crude oil tanks. The hatches shall be readily accessible and suitable for manual dipping. The dip-tubes shall be protected internally and externally with epoxy coatings, and shall be provided with two rows of slots (50 mm x 300 mm) facing the shell and continued above the maximum level of the liquid.

Flat plates, not be less than 600 mm square, shall be provided below the dip pipes. They shall be mounted level not less than

75

mm from the tank bottom and supported from the tank shell.

8A.9.5 'Nozzles for purging the tank shall be provided at the highest point of oil tanks (gas dome) and at an elevation of 900 m m above the tank bottom.

8A.10 Stairways, Ladders & Platforms {Tables 3-19 to 3-21)

8A. 10.1 A walkway shall be provided giving access to the roof from the head of the stairway.

8A. 10.2 When the roof slope exceeds 1 : 12, access to all accessories located away from the rim shall be bar treaded. Handrails shall surround the accessories area, and hand and knee rails and 200 m m high toe kick plates shall be provided for platforms and the complete circumference of the roof.

8A.10.2 A vertical caged ladder shall be provided as a second means of escape from the roof and shall be located at the opposite side of the tank roof t o the main stairway. This ladder may also be utilized in conjunction with platforms t o access instruments, valves, foam chambers etc.

8A. 1 1 Weld Details

8A. 1 1.1 The top angle-to-shell joint of fixed roof tanks shall be butt-welded w i t h complete penetration and complete fusion except where KOC approves a design with continuous double fillet welding. (3.1 -5.3) 8A.1 1.2 Frangible roof t o shell joints shall not be offset by more than half the

dimension of the angle leg from the vertical line of the shell.

8A. 1 1.3 Roof plates shall be lapped so that the lower edge of the uppermost plate is beneath the upper edge of the lower plate (ie. optimized for internal drainage of condensation rather than for external drainage). Plates shall be continuous fillet welded on the outside with a minimum 25 m m overlap. (3.1.3.5) Double pass welding is mandatory on roofs requiring leak tightness. Double lap or butt welding is mandatory on tanks susceptible to pyrophoric scaling.

88.0 REQUIREMENTS SPECIFIC TO EXTERNAL FLOATING ROOF TANKS 88.1 Overall Confiauration

Prior t o proceeding with detailed design, the following features shall be established:-

Overall height and diameter.

Minimum and maximum operating levels and measures proposed t o optimize these.

Roof type.

Shell material specification(s1 and gradeb).

Proposed arrangement of mixers (if required) and mixing timetable. Rim seal type and materials.

Roof drain type and minimum maintenance / replacement intervals. Sealing facilities for deck fittings.

Note : A Contractor should be required to submit the above data prior to

a ward.

8B.2 Oesian and Operatina Levels

86.2.1

Levels and associated capacities shall be as defined in Appendix E of

this standard.

8B.2.2

For the purposes of calculating shell thicknesses of floating roof

tanks, the level t o the top of the top angle shall be used in conjunction with the hydrostatic test stress S, (3.6.1.4) and the design liquid level shall be used in conjunction with the product design stress S,. (3.6.1.3).

88.3 Roof Tvpes

Floating roofs shall be either of the pontoon or double deck type. Pan type roofs are not permissible. (C.1)

88.4 Pontoon Confiquration

The top pontoon deck shall slope downwards towards the centre of the tank and the bottom pontoon shall slope upwards towards the centre. (ie "low type" roofs are not permissible) The height of attachment of the centre deck t o the inner pontoon rim shall be at a height such that no significant bendin? moment is applied t o this joint when the roof is floating normally (without s.iditiona1 loading from rainwater accumulation or pontoon flooding).

88.5 Double Deck Confiauration

The bottom deck shall slope upwards towards the centre of the tank. The top deck may either slope t o drain towards the centre ("converging double deck" type) or it may slope down from both the rim and the'centre.

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8B.6

Flotation Corn~artrnents

88.6.1 Compartments shall be designed and constructed so as to provide reasonable access for inspection and maintenance. Where stiffening is necessary, preference shall be given to underside external stiffening. Any internal stiffening shall be essentially non-obstructive to personnel.

88.6.2 All compartments and bulkheads shall be internally seal welded along top, bottom and vertical edges.

88.6.3 Topside surfaces, including the outer rim, shall be painted.

88.6.4 The minimum thickness of the bottom deck shall be 6 mm. The minimum thickness of outer rim plating shall also be 6 mm except where a greater thickness is specified on the Data Sheet. (C.3.3.2)

88.7

Centre

Deck of Pontoon Tvoe

85.7.1 The minimum thickness of the bottom deck shall be 6 mm.

(C.3.3.2)

8B.7.2 The joint between the centre deck and inner pontoon rim shall be sufficiently reinforced where necessary to minimize the possibility of failure at this location due to flexing of the deck.

88.7.3 Fabrication of the centre deck shall ensure that it is essentially flat in form. If fabricated on the tank bottom, steps shell be taken to ensure that the deck does not take the conical form of the bottom.

8B.8

O~eratina

Flowrates

For oil storage tanks the overall design and the operating manual shall specify a suitably low filling rate at commissioning and at start-up after maintenance shutdown to avoid the tendency of "ballooning" of the centre deck of pontoon type roofs due to higher than normal amounts of gas being introduced into the tank. In any case the inflow rate shall be such that a flow velocity of 3 ft/s is not exceeded up to the point at which the roof leaves its supports, in accordance with the recommendation in clause 4.2.b of API RP.2003.

88.9 Stability

. 88.9.1 In addition to the buoyancy criteria of C.3.4.1 of API-650, a pontoon type roof shall also have sufficient buoyancy to remain afloat on product of the lowest specified specific gravity with the centre deck flooded with firewater and t w o adjacent pontoons concurrently flooded with product.

88.9.2 The designer shall declare the allowable stress and stability criteria

that he proposes to use to verify strength and stability. The tilt

which needs to be taken into account in setting the upward height

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88.10 Main Tank Connections

8B.10.1 The oil inlet shall be arranged t o project well into the tank so as t o

avoid the local accumulation of entrained gas under the roof deck or overpressuring of the seal. I t shall also be arranged t o minimize turbulence which may affect the roof seal, roof drains, mixers, etc.

88.10.2 The oil outlet shall connect t o the tank bottom plates unless

otherwise agreed by KOC. A weir shall be provided around this connection which shall also be provided with a vortex breaker. The weir height shall be as indicated on the Data Sheet.

The bore of the oil outlet, up to thefirst flange outside the tank, shall be lined with the same system as applied to the tank bottom.

88.1 1 Roof Connections 81 O~enincrs

8B.11.1 Manwavs

A second manway shall be provided for each double-deck buoyancy compartment if, in KOC's judgment, the size and/or configuration is such that a single manway would be insufficient t o provide safe and rapid escape. (C.3.5)

8B. 1 1.2 Deck Hatches (C.3.11)

T w o

-

30" deck hatches shall be provided for all tanks, located diametrically opposite t o provide access from the underside t o topside of the roof during maintenance. In the case of double deck roofs, the top and bottom deck openings shall be connected by a tube w i t h ladder rungs. The bottom deck opening shall not be covered.

88.1 1.3 Primarv Roof Drains (C.3.8)

88.1 1.3.1 The rainfall t o be considered in sizing roof drains is

defined in KOC-G-007.

88.1 1.3.2 Primary roof drains shall be of either the articulated joint

or flexible hose type as specified on the Data Sheet. The drain pipes shall be located so that they are not unduly affected by the forces imposed by the operation of the mixers or by the tank inlet flow.

88.1 1.3.3 The maximum nominal size of articulated drain lines shall

be 4". A n additional drain shall be provided if one

-

4"

drain would have insufficient capacity. It is not permissible t o branch t w o drain lines from a single deck opening.

8B.11.3.4 For pontoon type roofs the check valve shall be made

accessible from the top of the deck by mounting it in a recess. This shalt

afiow

the valve t o

be

replaced without entry into the tank.

88.1 1.3.5 The drain shall be valved at the tank shell so that it can be isolated in the event of failure of the pipe inside the tank. If more than one drain is provided then each one shall be individually valved at the shell.

Emerqencv Drains

Double deck roofs shall be provided with at least one emergency drain (draining into the product). It shall be located close t o the centre. Its upward projection shall be such as t o be midway between the high and low points of the upper deck. Inside the tank, the drain shall be fitted with a deflector to minimize vapour losses.

Maintenance Drains

Pontoon type roofs shall be provided with t w o

-

3" brass drain plugs, one located close t o the centre and the other close t o the inner rim and fitted from the top for use when the roof is landed on its supports.

The drainage of double deck roofs may be achieved by removing (unscrewing) the emergency drain.

Roof Vents (C.3.9)

88.1 1.6.1 The arrangement and configuration of all roof vents shall be such as t o minimize the possibility of oil contamination of working snd sealing components.

88.1 1.6.2 A minimum of one rim vent shall be installed for each tank.

88.1

1.6.3

The design, size and location of automatic bleeder vents shall be adequate t o breathe air / vapours at a volumetric rate at least equal to the maximum tank outflow and t o twice the specified commissioning liquid inflow. A t least one bleeder vent shall be located near the centre of the deck.

88.1 1.6.4 Pontoon type roofs shall also be provided with t w o weighted pressure relief valves t o discharge excess tank vapour and incondensibles whilst the roof is afloat. One of these devices shall be located within one t o t w o metres of the centre and the other shall be located adjacent t o the inner rim and oriented 180" from the pivot of the rolling ladder. The set pressure of each valve shall be 25% above the pressure exerted by the weight of the centre deck and its fittings so that there will be no discharge under normal operation, but only in the event of a pronounced "ballooning" of the centre deck.

I

88.1 1.7' Sam~lina Hatch

A sampling hatch shall be provided where required by the Data Sheet. The hinged cover shall be brass to preclude the risk of sparking. A bare steel datum plate shall be provided below the sampling hatch to enable this fitting to be used as an alternative gauging device. This shall be mounted level on the lined bottom and held in place by resin as for the manual still well.

I

88.1 2 Rollina Ladder (C.3.7)

88.12.1 A rolling ladder with rails shall be provided for all floating roof tanks. The rails shall be welded to pads and not direct onto the roof deck. The ladder shall connect to the gauger's platform. The pivot and wheel bearings shall be of a type which does not require any lubrication after commissioning. The wheels shall be non-sparking. The slope of the ladder shall not exceed

50"

to the horizontal at the extreme low position. Treads shall be self-leveling. The minimum inside width of the ladder shall be 750 mm. If it is necessary for the rails to be significantly elevated, then suitable steps shall be provided down to the deck.

8B.12.2 The design shall ensure that the ladder will not be damaged or derailed when exposed to the design wind velocity with the roof at its highest operational level. The anti-derailment device shall be such that there is no locking or permanent distortion.

88.1 2.3 The tilting effect of the loading from the rolling ladder and runway shall be assessed and avoidance of the accumulation of rainwater at local depressions shall be addressed for centredecks of pontoon type roofs.

88.13 Anti-Rotation and Centerina Devices (C.3.12)

The type and configuration of anti-rotation and centering devices shall limit lateral and rotational movement to the extent necessary to ensure that free vertical movement and rim sealing are not compromised and that drain piping is not unduly stressed. Roller type devices shall be provided with grease nipples. 88.14 Roof Sealing

The roof perimeter shall incorporate a flexible double sealing mechanism except where KOC approves an alternative type. Irrespective of the type of seal, details of the proposed sealing mechanism shall be provided to

KOC

for approval. Details shall include data on the following:-

-

the suitability of non-metallic materials for the stored product and for temperatures up to 80°C;

-

_{the fire-retardant properties of non-metallic materials;}

-

foam application considerations;

-

the shell and roof (or rim gap) tolerances necessary to maintain the seal;

-

operational constraints for inspection, maintenan,ce and component replacement;

-

_{whether maintenance can be performed on secondary sealing without}

affecting the primary sealing;

-

_{self cleaning characteristics (eg. wax scraping);}

-

means of electrical insulation of mechanical shoe hangers to ensure that no lightning induced arcing can occur;

-

drainage of the seal system for maintenance;

-

_{Corrosion resistance of metallic sealing materials.}

Irrespective of the type of primary / secondary rim sealing, a weather shield shall also be provided. This shall be selected primarily on its ability t o protect the main seals from dust, sand and painting operations rather than its rainwater shedding capability

Bonding of the roof and rolling ladder t o the shell shall be in accordance with KOC-E-024.

8 8 . 1 6 Roof S U D P O ~ ~ Leqs

Roof supports shall be designed to support the weight of the roof with 2 adjacent flooded compartments and with 25 pounds per square foot uniform loading of the centre deck of pontoon type roofs. Pads of minimum 600 m m diameter shall be provided t o distribute the support loads at the landing of the legs t o the tank bottom. The pads shall be continuously welded t o the tank bottom. After lining of this pad along with the tank bottom, an additional pad shall be provided t o avoid damage t o the bottom lining by the legs. This second pad shall be slightly smaller than the first and shall be located and lightly secured by an epoxy fillet round its edges. (C.3.10.2) Drain holes at the bottom of support legs shall be ample t o ensure that blockage by sludge does not prevent the legs from draining completely with the tank emptied. (C.3.10.1)

The upward projection of support leg sleeves through the centre deck shall be sufficient t o ensure that product cannot flow onto the deck under either of the conditions described in

C.3.4.1

of API

650.

Sleeves shall be adequately reinforced by means of topside pads and gussets but shall also be welded t o the underside of the deck.

Supporting legs shall be adjustable so that, whatever is the grounding height for operation, the height can be set t o give 2 metres clearance up t o the lowest deck for maintenance. (C.3.10.1)

T w o slotted still wells of minimum 8" diameter shall be provided for manual dipping and for level gauging. These shall be located close to the shell so that they are operable from the gauger's platform or the wind girder accessway.

88.17.2 The still wells for manual dipping shall be provided with a hinged brass cover to preclude the risk of sparking. A semicircular top reference plate, notched 25 mm wide x 40 mm deep, shall be welded inside the manual still well.

88.17.3 The lower end of the still well pipes shall be restrained from lateral movement by sleeves supported from the shell.

88.17.4 A datum plate shall be provided below the manual still.wel1. This shall be bare steel, mounted level on the lined bottom and held in place by resin.

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9.0 LOSS PREVENTION

This section deals with potential losses associated with tanks used t o store or process liquids. Where issues are not strictly within the scope of this standard and may also not be within the tank constructor's scope, then the relevant provisions are written as recommendations.

9.1 Fire Protection

9.1 .1 Water SoravlDeluqe

A fixed water spray deluge system shall be provided t o cover the exposed side(s) of roofs of fixed roof tanks as per the designated project specification for Fire Protection & Safety Equipment and NFPA-15 in the following circumstances.

a) When the tank is designed t o contain crude or other low flash flammable liquid.

b) Other tanks where KOC has determined that the location or content necessitates protection from adjacent tanks or other facilities.

9.1.2 Fixed Foam installations

9.1.2.1 Fixed roof oil tanks require fixed installations t o apply a foam blanket t o the liquid surface. KOC may also require these facilities t o be provided for other tanks which are primarily designed t o contain water but which normally have a layer of flammable liquid having a volume of 1 0 m3 or more floating on the surface. The foam pourers shall be of the flanged type as specified on the data sheet and shall be readily accessible for maintenance.

9.1.2.2 Floating roof tanks require facilities for applying foam t o the rim space and these shall also be fixed installations when specified on the data sheet. They shall be arranged t o be compatible w i t h the selected roof seals.

9.1.2.3 In either of the above cases, fixed installations shall be according t o NFPA-1 1 except that a minimum of 4 pourers shall be required for tanks from 120 f-t to 140 f-t in diameter.

9.1.3 Heat Detectors

Fixed roof tanks shall have fusible link heat detectors i r ~ s r ~ ~ t -, ,.. indicated on the Data Sheet. Floating roof tanks shall have I~i?a=r heat detectors installed as indicated on the Data Sheet. Heat detectors shall comply w i t h the designated project specification for Fire & Gas Detection Equipment.