dnv 2.7 3 portable offshore units overview
DESCRIPTION
DNV 2.7 3 Portable Offshore Units OverviewTRANSCRIPT
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DNV 2.7-3 Portable Offshore Units
Subsea Lifting OperationsKranTeknisk Forening
Per ystein AlvrStavanger, 28 November 2007
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Det Norske Veritas AS. All rights reserved Slide 223 November 2007
2.7-3? What is that?
The intention of this lecture is to briefly answer: What is DNV Standard for Certification 2.7-3?
How should 2.7-3 be used?
This is done by: Clarifying why 2.7-3 has been issued
Giving a general overview of the content in 2.7-3 (June 2006)
Describing what will be updated in the next revision
Indicating application of 2.7-3 for subsea
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Det Norske Veritas AS. All rights reserved Slide 323 November 2007
International Regulations
IMOs MSC/Circ.860 Guidelines for the approval of offshore containers handled in open seas
proposed to IMO by Norway
states that the International Convention for Safe Containers (CSC) does not cover Offshore Containers
states that offshore containers should be approved by the competent authority or by organizations Duly authorized by the Administration
states that offshore containers should be inspected annually
Refers to other standards for detail requirements, those listed are DNV 2.7-1, DNV 2.7-2, EN 12079 and BS 7072 (withdrawn)
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Det Norske Veritas AS. All rights reserved Slide 423 November 2007
Why 2.7-3?
Experience has shown that Standard for Certification No 2.7-1 "Offshore Containers, is being used more and more in the industry today than ever before. As a consequence of this increased demand, DNV customershave voiced a strong requirement for a need to certify portable offshore Units that are not shaped like containers, according to Standard for Certification No 2.7-1.
As a result of this market demand Standard for Certification No 2.7-3 has been developed, which covers all other types of portable offshore Units, other than offshore containers. DNV firmly believes that this new standard will meet the customers need for these services and at the same time enable DNV to expand in this market segment.
This new Standard has been developed in close co-operation with the update of the Standard for Certification No 2.7-1.
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Det Norske Veritas AS. All rights reserved Slide 523 November 2007
Definition
Portable Offshore Units Definition in SfC 2.7-3: Portable Unit or package with a maximum gross
weight not exceeding 50 tonnes, for repeated or single use with a primary service function, handled in open seas, to, from or between fixed and/or floating offshore installations and ships.
Also: Could be lifted subsea!
4 types defined:- Type A, skids arranged with crash frames- Type B, skids without crash frames- Type C, no dedicated skid frame- Type D, stress skin design
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Det Norske Veritas AS. All rights reserved Slide 623 November 2007
Content in 2.7-3 GENERAL Scope Definitions List of symbols Documents for approval and information National authorities References
CERTIFICATION PROCEDURES Introduction Design Review Testing and inspection Certification of existing units Maintenance of certificate Summary of procedures
DESIGN Structural strength Welding Design details Units with tanks Materials Prototype Testing
MANUFACTURE General Welding Secondary structure Production documentation Production testing
MARKING Safety marking Identification markings Additional information markings (optional) Other marking
INFORMATION PLATES General Operational limitations Information plate Inspection plate
OPERATIONAL RESTRICTIONS PERIODIC EXAMINATION, TESTS AND REPAIRS General Inspection, test and repairs on units
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Det Norske Veritas AS. All rights reserved Slide 723 November 2007
Test if SfC 2.7-3 is applicable
Tests to define type A, B, C or D
Integrated service? Use 2.7-2
Container shaped & W
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Det Norske Veritas AS. All rights reserved Slide 823 November 2007
Procedure for Certification
Application sent to DNV.
Order confirmed and fees agreed.
Drawings, documentation and calculations reviewed and approval given by the approval office.
Prototype offshore Unit manufactured under supervision of the Society's Surveyor.
Unit tested according to prototype test requirements, witnessed by the Society's Surveyor.
Production proceeds according to the agreed Quality Plan or Manufacturing Survey Arrangement. Production tests according to list in Section 4.5.
DNV surveyor issues Portable Offshore Unit Certificate (form 49.06a) and affixes emblem.
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Det Norske Veritas AS. All rights reserved Slide 923 November 2007
Design Requirements - General
Design to promote means for safe handling and transportation.
Selected criteria to cover a transportation event involving sea voyage and lifting offshore.
Acceptable stress, structural displacement and stiffness.
Units designed for dynamic forces generated when handled in a sea state of up to Hs = 6m, unless otherwise stated in operational limitations.
Units intended for repeated transportation events and to be mixed with other frequent handled goods shall be free from protruding parts outside the envelope of the Unit.
All Units in compliance with this Standard for Certification shall be evaluated with regard to the risk of uncontrolled skidding and overturning on a moving ship deck.
Consider type A, B, C or D as defined in section 1.1.
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Det Norske Veritas AS. All rights reserved Slide 1023 November 2007
Design - Structural Strength
Calculation Methods. Only the primary structure shall be included in the design calculations.
Allowable Stresses. Von Mises equivalent stresses, e = 0.85C. For steel: C = Re = minimum yield stress.
Design Lifting Loads:- Primary structure: F = 2.5 x MGW x g
- pad eye: Single padeye: RSF = 2 x F
Impact Loads:- Horizontal impact - Vertical impact (Drop test)- Minimum thicknesses
Welding- Red. factor: Fillet = 0.5, partial = 0.75 and full pen. = 1.0
)()1(2.1
CosnFRSF
=
SKL Sling angle
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Det Norske Veritas AS. All rights reserved Slide 1123 November 2007
Pad Eyes- Not outside unit- Dim requirements: Dhole < Rpadeye_pl Tpadeye > 75% Shackle inside width- Strength: Req. to combined stress on net area
Other details:- ISO-corner Castings- Drainage- Fork Lift Pockets- Walls- Equipment and Supports for equipment- Lashing- Tugger points- Doors and hatches- Coating and Corrosion Protection
Design Details
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Det Norske Veritas AS. All rights reserved Slide 1223 November 2007
Materials and Manufacture
Design temperature, normally -20 C
Steel quality requirements
Aluminium and other materials
Welding Qualification
Inspection of Welds
Secondary structure
Production documentation
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Det Norske Veritas AS. All rights reserved Slide 1323 November 2007
Testing Requirements
All point lifting test- Mandatory, maybe omitted for single
transports- Test load: 2.5 x MGW
2-point Lifting- DNV decide if necessary- May not pass calculations- Test load: 1.5 x MGW
Vertical Impact Test- Drop or lowering test- Could be substituted by calculations
less for MGW > 25t
less for MGW > 25t
Test conclusion: Spreader frame is required!
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Det Norske Veritas AS. All rights reserved Slide 1423 November 2007
Marking
Safety marking
Identification by Certificate number
Information Plate- Name of manufacturer.- Month/year of manufacture.- Manufacturer's serial number.- Maximum gross weight (kg) at design sling angle.- Design temperature.- DNVs Inspector Stamp (Ref. 4.4).- Operational restrictions (if any).
Inspection PlateThe International Convention for Safe Containers, CSC
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Det Norske Veritas AS. All rights reserved Slide 1523 November 2007
The need for stricter operational restrictions The need for stricter operational restrictions than the general restriction than the general restriction Hs = 6.0mHs = 6.0m for for the offshore lift shall be evaluated. the offshore lift shall be evaluated.
Limitations of sea state for the transport Limitations of sea state for the transport event could be applicable.event could be applicable.
A specially arranged procedure or A specially arranged procedure or arrangements for handling or sea fastening arrangements for handling or sea fastening could be required. could be required.
It is advised that an agreement on the It is advised that an agreement on the possible operational restrictions is possible operational restrictions is established with DNV in an early stage of established with DNV in an early stage of the enterprise. the enterprise.
Operational restrictions
Section 7 in SfC (Standard for Certification) 2.7-3 include a text that unfortunately is rather unclear, but it generally says:
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Det Norske Veritas AS. All rights reserved Slide 1623 November 2007
Plans for Next Revision Slide 1
Improve the definition of the border between 2.7-1 and 2.7-3 including limitations for units that can be certified according to 2.7-3.
It should be made mandatory to define clearly (upper) operation limitations. The revised CN shall include (specific) guidance on how to do this. One proposal is to categorize the units into, say 3 classes with lift limitations at 6m (as 2.7-1), 4m and 2.5m. The categorization should be based on the design (i.e. type A, B, C or D), single or multiple use and weight.
For (very) special units it should be stated that a handling procedure both for sea transport and offshore lift should be made and presented for review.
Criteria for sea transport are vaguely described. Design requirements for the transport to be included.
Design and documentation requirements to lifting sets should be included (at least) as an option.
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Det Norske Veritas AS. All rights reserved Slide 1723 November 2007
Plans for Next Revision Slide 2
Tables showing test lift weights will be revised/corrected.
Weld type requirements and some manufacturing requirements to bereviewed.
2.7-1 includes several appendices with useful information. It will be considered to include something similar in 2.7-3.
Include, as for 2.7-1, a tailor made certificate form.
Description of DNV 2.7-3 emblem, as for 2.7-1, to be included.
Several typing errors and incorrect references will be corrected.
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Det Norske Veritas AS. All rights reserved Slide 1823 November 2007
Next Revision: Chapter 3 Design Chapter 3 Design will be considerably updated, e.g.:
- The general design factor - 2.5 for lift, will be a function of, op. lim. Hs, weight and subsea or not.
- Specific design requirements for transport will be included, normally 1g
- Accept criteria for stress and stability to be clarified.
- Deflection accept criteria to be deleted/updated (clarified why).
- Recommendations for vertical impact calculations.
- Minimum thickness requirement modify considering weight & optional impact test.
- Padeye design criteria Clarify/update and include 2.7-1 formulae as option.
- Clarify requirements to equipment and equipment supports
- Lashing and tugger points rewrite requirements
- Include more guidance on when 2-point lift test & impact test are required.
- Subsea use (next slide)
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Det Norske Veritas AS. All rights reserved Slide 1923 November 2007
Subsea Design Factor, Lift
Design factor structure: 3.0 (2.8) This covers DAF and LF Additional factor for padeyes as for lift in air
The following design requirements will be included to cover subsea:
In order to ensure that the unit could be installed without too strict operational limitations the drag area and volume, including added volume/mass should be reasonably limited.
The revised 2.7-3 will include some guidance on how to obtain an unit that do not need any special procedures to be installed.
The recommendations will be further reviewed, but will be something like:
A/Ws < 1.0 where A is drag area and Ws is the submerged weight
V/Ws < 2.0 where V is the volume of the unit + added (water) mass
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Det Norske Veritas AS. All rights reserved Slide 2023 November 2007
Subsea Design Considerations
All air filled members shall be designed for the maximum hydrostatic pressure, or proper ventilation/water filling shall be ensured.
Placing of lift points below CoG is normally not acceptable.
Lift point should be placed/designed in such a way that the risk of damage and/or accidental release of rigging is neglectable.
Effect of horizontal wave loads. (tilt of object in splash zone).
Local design for slamming loads.
Tugger points for horizontal and rotational control.
Guiding system for final positioning.
Retrieval loads, if applicable.
A set of additional (for subsea) design considerations, as indicated in the list below, will be included.
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Det Norske Veritas AS. All rights reserved Slide 2123 November 2007
Subsea Operational Aspects
All assumed operational limitations shall be clearly marked on the unit. This could be: Installation wave height/periods (if evaluated/applicable) Special considerations, e.g. pass splash zone with inclination Maximum water depth Allowable loads on tugger points and guiding systems Sling angles
The installation contractor needs to do a final assessment of the applicable operation limitations based on the actual installation vessel and procedure.
Installation means on the unit, e.g. as marking, ROV grab bars, skids for monitoring systems/equipment, should be installed as agreed.
A set of additional (for subsea) operational aspects, as indicated in the list below, will be included.
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Det Norske Veritas AS. All rights reserved Slide 2223 November 2007
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Det Norske Veritas AS. All rights reserved Slide 2323 November 2007
DNV 2.7-3 Portable Offshore Units2.7-3? What is that?International RegulationsWhy 2.7-3?DefinitionContent in 2.7-3Test if SfC 2.7-3 is applicableProcedure for CertificationDesign Requirements - GeneralDesign - Structural Strength Design DetailsMaterials and ManufactureTesting RequirementsMarkingOperational restrictionsPlans for Next Revision Slide 1Plans for Next Revision Slide 2Next Revision: Chapter 3 DesignSubsea Design Factor, LiftSubsea Design ConsiderationsSubsea Operational Aspectshttp://webshop.dnv.com/global/