Supplementary Specification For Offshore Topside Structures [PDF]

Zitiervorschau

S-631-04

Supplementary Specification for Offshore Topside Structures

JUNE

2020

Supplementary Specification for Offshore Topside Structures

Acknowledgements This IOGP Specification was prepared by a Joint Industry Project 35, Standardization of Offshore Structures Specifications organized by IOGP with support by the World Economic Forum (WEF).

Disclaimer Whilst every effort has been made to ensure the accuracy of the information contained in this publication, neither IOGP nor any of its Members past present or future warrants its accuracy or will, regardless of its or their negligence, assume liability for any foreseeable or unforeseeable use made thereof, which liability is hereby excluded. Consequently, such use is at the recipient’s own risk on the basis that any use by the recipient constitutes agreement to the terms of this disclaimer. The recipient is obliged to inform any subsequent recipient of such terms. This publication is made available for information purposes and solely for the private use of the user. IOGP will not directly or indirectly endorse, approve or accredit the content of any course, event or otherwise where this publication will be reproduced.

Copyright notice The contents of these pages are © International Association of Oil & Gas Producers. Permission is given to reproduce this report in whole or in part provided (i) that the copyright of IOGP and (ii) the sources are acknowledged. All other rights are reserved. Any other use requires the prior written permission of IOGP. These Terms and Conditions shall be governed by and construed in accordance with the laws of England and Wales. Disputes arising here from shall be exclusively subject to the jurisdiction of the courts of England and Wales.

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Supplementary Specification for Offshore Topside Structures

Revision history VERSION 1

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DATE

AMENDMENTS

23 June 2020

Issued for Publication

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Supplementary Specification for Offshore Topside Structures

Contents Foreword ............................................................................................................................................................ 5 1.

Scope ....................................................................................................................................................... 6

2.

Normative References ............................................................................................................................. 6

3.

Supplementary Requirements for Topside Structures ............................................................................ 6

Bibliography ..................................................................................................................................................... 14

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Foreword A series of Specifications (all parts of S-631) was prepared under a Joint Industry Project 35 (JIP35) by the ‘Offshore Structures Specifications Task Force’ organised by the International Oil & Gas Producers Association (IOGP) with support from the World Economic Forum (WEF). Recent trends in oil and gas projects have demonstrated substantial budget and schedule overruns. The Oil & Gas Community within the World Economic Forum (WEF) have implemented a Capital Project Complexity (CPC) initiative which seeks to drive a reduction in upstream project costs with a focus on industry-wide, non-competitive collaboration and standardisation. Further to the publication of the IOGP Operators’ Position and Key Messages on Standards (April 2017) and successful pilot study for IOGP JIP 33 Standardisation of Equipment Specifications for Procurement, the IOGP Offshore Structures Subcommittee discussed improving efficiency in this discipline by reducing or eliminating variation in requirements between operating companies and developing common operator requirements for offshore structures. The Offshore Structures Subcommittee established a Task Force (with administrative support funded by JIP35) to agree on the industry and/or international standard for each discipline and then develop minimum common requirements to improve efficiency and quality while reducing variation and cost. Ten key Oil & Gas Companies from the IOGP membership participated in developing these Specifications, with the objective to leverage and improve industry level standardisation for projects globally in the oil and gas sector. The work has developed a minimised set of supplementary requirements for the design and operation of offshore structures based on a critical review of the ten participating members’ company specifications, building on recognised industry and/or international standards. The task covers 11 subdisciplines, each associated with one industry and/or international standard, for application in the Petroleum and Natural Gas Industries: 1. 2. 3. 4. 5. 6.

S-631-01 General requirements for offshore structures S-631-02 Arctic offshore structures S-631-03 Concrete offshore structures S-631-04 Topsides structures S-631-05 Foundations S-631-06 Weight management

7. 8. 9. 10. 11.

S-631-07 Station keeping S-631-08 Seismic S-631-09 Metocean S-631-10 Marine soil investigations S-631-11 Fixed steel offshore structures

A twelfth subdiscipline, floating offshore structures, was specified as part of the task but has been deferred due to the complexity of having a range of classification society rules and the volume of additional company requirements for this subdiscipline. The expectation is that the participating and other operating and engineering companies will adopt and reference all parts of the specification series IOGP S-631 for offshore structures, with the participating companies eliminating the supplemental requirements from their in-house specifications. Tracking the adoption of the parts of this specification and of the reduction in company requirements will be managed by the IOGP Offshore Structures Subcommittee. This series of Specifications has been developed to promote the opportunity to realise benefits from standardisation and achieve significant cost reductions for upstream project costs. The Offshore Structures Specification Task Force performed their activities in accordance with IOGP’s Competition Law Guidelines. Terminology used within this Specification is in accordance with ISO/IEC Directives, Part 2 and as defined in the parent standard. This series of Specifications aims to significantly reduce waste, decrease project costs and improve schedule through precompetitive collaboration on standardisation. These specifications define the supplementary requirements to recognised industry and/or international standards which are indispensable for the application of this specification. Following approval by the IOGP Offshore Structures Subcommittee, IOGP has authorised the publication of this Specification. Where adopted by the individual operating companies, this Specification aims to supersede existing company documentation for the purpose of industry-harmonised standardisation. In the event of a conflict between these Specifications and a relevant local law or regulation, the relevant law or regulation shall be followed. If these Specifications create a higher obligation, it shall be followed as long as this also achieves full compliance with the law or regulation.

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1. Scope This specification provides supplementary requirements and recommendations to ISO 19901-3: 2014.

2. Normative References The following normative references shall apply: API Spec. 2SC

Manufacture of Structural Steel Castings for Primary Offshore Applications

ASTM A307

Standard Specification for Carbon Steel Bolts, Studs and Threaded Rod 60000 PSI Tensile Strength

ASTM F1136/F1136M

Standard Specification for Zinc/Aluminum Corrosion Protective Coatings for Fasteners

ASTM F2329/F2329M

Standard Specification for Zinc Coating, Hot-Dip, Requirements for Application to Carbon and Alloy Steel Bolts, Screws, Washers, Nuts, and Special Threaded Fasteners

ASTM F2833

Standard Specification for Corrosion Protective Fastener Coatings with Zinc Rich Base Coat and Aluminum Organic/Inorganic Type

ASTM F3125/F3125M

Standard Specification for High Strength Structural Bolts and Assemblies, Steel and Alloy Steel, Heat Treated, Inch Dimensions 120 ksi and 150 ksi Minimum Tensile Strength, and Metric Dimensions 830 Mpa and 1040 Mpa Minimum Tensile Strength

CAP 437

Standards for offshore helicopter landing areas

EEMUA PUB NO 176

Specification for structural castings for use offshore

ISO 19901-3: 2014

Petroleum and natural gas industries -- Specific requirements for offshore structures -- Part 3: Topsides structure

ISO 19901-5

Petroleum and natural gas industries — Specific requirements for offshore structures — Part 5: Weight control during engineering and construction

ISO 23693

Determination of the resistance to gas explosions of passive fire protection materials

ISO 898-1

Mechanical properties of fasteners made of carbon steel and alloy steel – Part 1: Bolts, screws and studs with specified property classes – Coarse thread and fine pitch thread

3. Supplementary Requirements for Topside Structures Requirements for topsides offshore structures shall be in accordance with ISO 19901-3: 2014 and the following amendments to the referenced clauses in ISO 19901-3: 2014. NOTE: ANSI/API RP 2TOP:2019 is a modified adopt-back of ISO 19901-3:2010.

Amend the following referenced Clauses in ISO 19901-3: 2014: 4

Symbols and Abbreviated Terms

4.2

Abbreviated terms

Add the following terms: CoG

Centre of Gravity

FRP

Fibre Reinforced Polymer

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6

Design requirements

6.7

Design for fatigue limit states (FLS)

Add at the end of the last sentence of the first paragraph: … or other suitable standards shall apply (see Clause A.6.7). A.6.7

Design for fatigue limit states (FLS)

Substitute the existing text with: A suitable code for design for fatigue limit states in cases where the support structure standard does not provide adequate fatigue guidance for a topsides structure is DNVGL-RP-C203. 6.9

Robustness

Substitute the first paragraph with: Robustness is defined and discussed in ISO 19900. 7

Actions

7.1

General

Delete from the penultimate bullet point: •

, and

Add before the last bullet point: •

Damage and survival conditions, and

Add at the end of the second-last paragraph: Specific variable loads requirements are reported in each relevant Clause. General guidance on variable loads on deck areas are reported in ISO 19904-1 (A.7.3 Variable actions (Q)). Add before the last paragraph: Design of topsides structure shall make use of Not-to-exceed weights (see 19901-5) and CoG envelopes. 7.4

Vortex-induced vibrations

Substitute the last paragraph with: Wind induced fatigue analysis and vortex shedding analysis shall be performed on lattice structures (e.g. flare booms and drilling derricks) and exposed pipework. 7.10

Accidental situations

7.10.1 General Add the following to the list of the second paragraph: g) Clashes between jack-up and topsides during seismic and metocean events. However, jack-up clashes with topsides primary steelwork and potentially manned areas (e.g. LQ, muster areas, emergency escape routes) shall not be permitted.

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Add before the sixth paragraph ("In addition, the protection of the asset and the costs of failure should be considered with respect to importance to the owner and to the relevant national authorities."): The risk shall be estimated for adjacent structures collapsing onto and significantly damaging the Temporary Refuge (TR) or its systems, or obstructing escape and evacuation routes. Adjacent structures can include derricks, flare towers, cranes, jack-up etc. Add the following reference at the end of the last paragraph, after “ISO 19902”: … and ISO 19904-1. 7.10.2.3 Risk assessment 7.10.2.3.1 General Substitute the last paragraph with: Accidental events for platforms with risk levels 2 and 3 shall be considered as load cases for structural design. 7.10.3 Hydrocarbon incidents Add as the last bullet point: - prevention of escalation of a hazardous event. 7.10.4 Explosion Delete the last sentence of the second paragraph: The explosion overpressure at the limit of significant probability, often taken as a probability of 10−4 per year, should be the minimum value used for design explosion overpressure. Add after the second paragraph: Structural components subject to blast load and required for business risk and/or life-safety risk shall have sufficient blast capacity to achieve the business risk performance objective and the life-safety performance objectives. The business risk performance objective typically requires little or no repair costs when the structural component is exposed to loading with annual probability of exceedance of 10-2. This can be achieved by requiring the structural component to remain elastic (or only localised regions with limited peak stress above material yield) under SLB (strength level blast) loading, where SLB loading is the blast load with an annual probability of exceedance of 10-2. A less frequent event for SLB loading may be adopted based on the business consequences of the facilities (e.g. annual probability of exceedance of 10-3). The life-safety risk performance objective typically requires no escalation of the blast or fire event when the structural component is exposed to loading with annual probability of exceedance of 10-4. This can be achieved by requiring the structural component not to fracture or collapse under DLB (ductility level blast) loading, where DLB loading is the blast load with an annual probability of exceedance of 10-4. A less frequent event for DLB loading may be adopted based on the life-safety consequences (e.g. annual probability of exceedance of 10-5) for catastrophic events where life-safety by evacuation cannot be demonstrated). Plastic design may be used for the DLB loading with fracture prevented by limiting the magnitude of plastic strain (typical limit plastic strain is 5% for welds).

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A.7.10.4

Explosion

A.7.10.4.3

Method of analysis

A.7.10.4.3.1

General

Delete the second paragraph, i.e.: Structures can be designed to respond elastically (i.e. in the elastic deflection range) or plastically, in response to explosion pressures. In the latter case, structures will be found to have resistance to higher levels of explosion. In design this can be accounted for by specifying two different explosion levels:  elastic design: a strength level explosion (SLB), being an explosion with a probability of exceedance of around 10−2 per year;  plastic design (no fracture or collapse): a ductility level explosion (DLB), being an explosion with a probability of exceedance of around 10−4 per year. 7.10.6 Explosion and fire interaction Add: The structural design or assessment shall include the consequences of blast and fire scenarios with either event occurring first. Refer to API RP 2FB and ANSI/API RP 2TOP for more guidance. a)

The endurance period to allow a controlled evacuation from the TR (or LQ) shall be demonstrated for a blast event followed by a fire event. Performance of the structure in a fire event followed by a blast event shall be demonstrated for credible scenarios. The return periods may be taken from the Fire Hazard Analysis and Explosion Hazard Analysis or using the UK’s HSE Guidance on TR Integrity.

b)

Following a blast event, PFP applied to a blast wall or primary structure shall remain functional in order to achieve the required fire endurance period in a subsequent fire event. ISO 23693 provides requirements for barriers and structural elements.

c)

Where plastic strains are incurred under the design blast, fire, or sequence blast/fire event, the post-accident integrity of the damaged structure shall be demonstrated under permanent and environmental loads (for a 1year return period).

A.7.10.6

Explosion and fire interaction

A.7.10.6.1

General

Delete the last sentence of the second paragraph: Fire and explosion assessments should demonstrate that the escape routes and safe areas survive the fire and explosion scenarios. A.7.10.6.3

Explosion and fire walls

Delete the point: a) 7.11

fire protection should be able to maintain integrity at the required strain, Other actions

7.11.2 Conductors Add before the second-last sentence: Where drilling is performed from a derrick cantilevered from a jack-up through a platform conductor, the ULS check shall include forced displacements and any consequent actions on the conductor and its supports due to the relative movement between the structure and the drilling jack-up. Page 9 of 15

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7.11.6 Bridge supports Add at the end of potential action b): When active or passive motion compensated gangways are used for transfer of personnel or goods from floating support vessels to a topsides structure the designer shall use data from the gangway vendor to determine the design actions on the topsides during installation and operation of the gangway. 8

Strength and resistance of structural components

8.4.3

Bolted connections

Add before the bulleted list: Bolts in conformance with ISO 898 Gr 4.6 or ASTM A307 shall not be used. Higher strength bolt designations than ISO 898 Gr. 10.9 or ASTM F3125 A490 Type 1 shall not be used. Note: Higher strength bolt designations can cause hydrogen embrittlement in sea environment.

Substitute the existing bulleted list with: — For preloaded bolts, the effective length of the bolt (between the underside of the head and the nut) shall be sufficiently long to minimize the consequence of creep in reducing the tension in the bolt. Preloaded bolts should have a minimum effective length of L/D > 5 or collars should be added. — A 2nd re-tightening of the bolts shall be performed at a minimum of 40mins after the initial tightening. — A reduction in pretension over the life of the bolted connection (20 to 50 years) due to creep of 20% shall be assumed for bolts with any protective coating applied to the bolt surface. — Bolt hole edges shall be rounded and the connection shall be sealed with a durable sealant, or a durable paint system, or both. — Washers shall be used beneath both bolt heads and nuts to minimise coating damage. Loose washers (plain or spring) should not be used. — The nut should be prevented from loosening under vibration by chemical bonding (e.g. loctite) of the nut to the bolt thread. The nut may be prevented from loosening under vibration by wedge-locking using corrosion resistant alloy washers surface hardened via a low temperature carbon diffusion process. — Corrosion protection of bolted connections shall be assured by the adoption of corrosion resistant alloy or high durability coating or metallizing. All surfaces that are in contact or inaccessible after assembly should be coated in aluminium spray. ISO 898 Gr 8.8 and ASTM F3125 A325 type 1 bolts shall be hot dip spun galvanised (HDSG) in conformance to ASTM F2329. ISO 898 Gr 10.9 and ASTM F3125 A490 type 1 bolts shall be coated with a liquid applied Zn/Al based coating system in conformance with ASTM F1136 Gr3 or ASTM F2833 Gr1. After final assembly, accessible parts of the bolts shall be overcoated with an organic coating system to match the surrounding structure. Cadmium-plated bolts shall not be used as they can emit a lethal toxic fume when heated. — Regular inspection of bolted connections should be specified. — Structural bolts should be tensioned using one of the following:  Proprietary bolt tensioning devices (e.g. Hydratight)  Turn of nut procedures  Direct tension indicating devices or bolts (e.g. rotabolts)  Bench calibrated wrench — Bolt holes shall not be drilled in any members that are classified as DC 1 or 2, with reference to Table 7. — For repair clamps using grout or an elastomer liner, additional losses due to long-term effects shall be accounted for in deriving the residual bolt tension. 8.5

Castings

Add to the end of the Clause: The manufacture and testing of castings, including qualification of welding shall be in accordance with EEMUA 176 or API Spec. 2SC, unless company requirements indicate otherwise.

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9

Structural systems

Add as a new sub Clause: 9.1.4

Equipment and equipment supports

Equipment supports that are subject to uplift shall be mounted directly on the supporting steelwork and not on deck plate or grating. Deck plate or deck grating shall incorporate cut-outs to permit attachment to the supporting steelwork. 9.2.1

Topsides structure design models

9.2.1

General

Substitute the first paragraph with: Internal forces in structural components shall be derived using an indeterminate, three-dimensional structural analysis methodology. 9.2.2

Support structure model for topsides design

Add at the end of the Clause: During Front End Engineering Design (FEED) and detail design, primary steel joint eccentricities shall be modelled with additional nodes to reflect the true eccentricities in order to account for shear transfer through the chord. 9.2.4

Modelling for design of equipment and piping supports

Add at the end of the Clause: Equipment skids or packages shall be modelled such that the mass is lumped at the local vertical CoG for conditions subject to lateral accelerations. Dummy members shall not add stiffness to the model. 9.4

Flare towers, booms, vents and similar structures

Add before the last paragraph: The designed support of the access platform at the top of the flare tower/boom shall take into account the potential expansion of the platform in relation to the primary steelwork due to thermal radiation. Flare design shall account for the effects of the flare header filling with liquid. 9.5.3

Design actions and resistances

9.5.3.3 Helicopter emergency landing situation a) Helicopter dynamic actions (undercarriage local actions) Substitute point a) with the following: The dynamic helicopter landing action shall be calculated based on CAP 437.

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9.6

Crane support structure

9.6.1

General

Add at the end of the Clause: For the design condition, deflections and accelerations at the top of the crane pedestal/crane cab shall be evaluated and reviewed by operations personnel and the crane manufacturer. If the crane pedestal is used for storage, design actions and internal corrosion protection shall be based on the nature of the liquid to be stored and the maximum levels and pressures under normal operating, test or failure of level control conditions. Note: Under certain circumstances, it could be advantageous to use crane pedestals for diesel or water storage.

9.8

Bridges

Add after the first paragraph: Bridge primary steelwork and supports should be evaluated for fatigue due to the transmission of wave loading through the supporting substructures. 9.12

Fire protection systems

Add after the second paragraph: Where the PFP can be wetted, the PFP shall be sealed to prevent water ingress and corrosion of the substrate. Where protection from jet fires is required, PFP products shall be specified that have been successfully tested to ISO 22899-1. Coat back lengths for secondary members attached to PFP protected primary members shall be determined to avoid potential system weaknesses. 9.13

Penetrations

Add after first paragraph: Where penetrations are required through a safety critical barrier, penetrations shall be designed such that the performance objectives of the barrier are not impaired. Detailing at penetrations shall minimise stress concentrations and corrosion development. 9.16

Actions due to drilling operations

Add after the first paragraph: Coincident drilling weights for Storm and Operating conditions shall be in conformance with ISO 19901-5 Annex Weight management during operations. 9.19

Muster areas and lifeboat stations

Add after the last paragraph: Dynamic impact factor applied to the loaded weight of the lifeboat shall comply with regulatory requirements.

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10

Materials

10.5

Fibre Reinforced Polymer (FRP) composite

Add after the third paragraph: FRP shall be considered as an alternative to steel for floor grating, hand railing and ladders, lightweight fire and explosion-resistant panels. Specific design requirements shall be included in assessing and selecting FRP elements. For example, for a floor grating, as a minimum, the following design requirements shall be: a) b) c) d) e) f) g) h) i) j) k) l)

layout requirements; spacing between load bearing bars; uniformly distributed loads and concentrated loads, including trolley wheel loads and wave uplift loads; span of grating and deflection limits; impact resistance; fire performance, including fire endurance, flame spread, smoke and toxic gas emissions, and residual strength following the exposure; skid resistance and durability of anti-slip surface; ultra-violet protection; chemical resistance; static electricity discharge; grating fixing details; cut-outs and penetrations.

Similarly, assessments shall be made for other product types (handrails, etc.). For locations where FRP does not meet all the performance requirements, a suitable steel grating shall be specified. Add at the end of the Clause: Primary escape routes shall not contain fibre-reinforced composites grating. 11

Fabrication, quality control, quality assurance and documentation

11.2

Welding

Add to the list of additional considerations: d) In general, DC 1, 2 and 3 steel member splices, connections to other members, and joints shall be full penetration welds. e) All partial penetration and fillet welds shall be designed and verified. f) Full penetration weld of a thicker member to a thinner member shall be avoided, e.g. by tapering at 1:4 or lower. 13

Loadout, transportation and installation

Add at the end of the Clause: Installation aid structures that are planned to be removed shall be designed taking safe and easy removal into account. Removal requirements of temporary attachments are provided in Clause 11.1.4. Verification of the deformation induced forces during loadout shall account for the stiffness and relative displacements of the structure being loaded out, the grillage structure, the trailers or skid beams, the barge and the quay soil. Differential deflections of the topsides structure during pre-service (fabrication, loadout, transportation and installation operations) shall be evaluated to verify equipment and piping serviceability and structures strength as required in Clauses 7.9.2, 9.2.3 and 9.2.4. Page 13 of 15

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Bibliography API RP 2FB

Recommended Practice for the Design of Offshore Facilities Against Fire and Blast Loading

ANSI/API RP 2TOP

ISO 19901-3:2010 (Modified), Petroleum and natural gas industries — Specific requirements for offshore structures — Part 3: Topsides structure

DNVGL-RP-C203

Fatigue design of offshore steel structures

ISO 19900

Petroleum and natural gas industries -- General requirements for offshore structures

ISO 19904-1

Petroleum and natural gas industries — Floating offshore structures — Part 1: Ship-shaped, semi-submersible, spar and shallow-draught cylindrical structures

ISO 22899-1

Determination of the resistance to jet fires of passive fire protection materials – Part 1: General requirements

UK HSE

Hazardous Installations Directorate (HID) Inspection Guide Offshore – Inspection of Temporary Refuge Integrity

END

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