Standard for Certification 2.7-3: Portable offshore units

DNV GL © SAFER, SMARTER, GREENER DNV GL ©

2016 Technology Week

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DNVGL-ST-E273, April 2016 2.7-3 Portable Offshore Units

Mohsen Shavandi / Meindert van Mierlo

DNV GL ©

Agenda

Introduction / Safety Moment 1:00-1:15 pm Scope of DNVGL-ST-E273 1:15-1:30 pm Design Approval Process 1:30-1:45 pm Break 1:45-2:00 pm Certification Process 2:00–2:15 pm Design Requirements/ Subsea Application 2:15-2:45 pm Break 2:45-3:00 pm Manufacturing and Testing Requirements 3:00-3:30 pm Good/Bad Design Examples 3:30-3:45 pm Q & A 3:45-4:00 pm

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Introduction

3


Safety Moment

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Scope of DNVGL-ST-E273 , April 2016

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DNV GL ©

Scope

A “POU” (Portable Offshore Unit) is a package or unit intended for repeated or single offshore transportation and installation/lifting which may also be designed for subsea lifting.

POUs (2.7-3) are not Offshore Containers

- POUs typically carry equipment (or any kind of installation) intended for a service function offshore.

- PO Units are not intended to carry goods (general cargo) as their primary function but may be used for equipment that is impossible or too heavy (MGW > 25 tonnes) to transport in offshore containers.

- The maximum gross mass should normally not exceed 100 tonnes.

- Certification of PO Units with gross mass exceeding 100 tonnes could be agreed with DNV GL on a case by case basis.

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Scope Portable offshore unit

It is the intention that a POU that is certified by DNV GL according to this standard could be safely sea transported and lifted offshore including subsea anywhere in the world.

Standardized frames/ skids used for sea transport only may also be certified as a POU.

The PO Units shall meet the following requirements:

Be suitable for single or repeated use: • Material; • Protection; • Ease of repair and maintenance.

Be safe in use with regard to: • Life; • Environment; • Hazard to the vessel/ installation.

Therefore it is risk based

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Assumptions The requirements in this Standard for Certification are based on a number of assumptions highlighted in Section 1.1.3.

Lifted individually by one crane;

Any wave restriction for subsea lifting, if applicable, needs to be assessed for each POU;

The handling/lifting is carried out according to the agreed operational procedure, if any;

The POU is lifted with an adequate lifting set;

Can be lifted anywhere (world wide) by any crane with sufficient capacity and speed if not otherwise specified;

Stacking during transport on ships is not covered by this standard.

Cargo or loose installations are properly secured in the PO Unit.

Handled according to IMO CSS code, OSV code, or according to a special made transport procedure.

Handling and operation is in accordance with local regulations.

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Types of PO units

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Type A: Primary structure frame (including skids arranged with crash frames). Similar to a 2.7-1 frame with MGW > 25 tonnes and SE.

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Types of PO units

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Type B: Skid based installations without a primary structure frame (crash frame), due to size, shape or other considerations.

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Types of PO units

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Type C: lacks a dedicated skid or frame. May include integrated stand frame, skirt or support points. Examples: x-mas trees, reels, manifolds, pressure vessels with stools, etc.

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Types of PO units

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Type D: Shell constructions where the strength lies in the plate structure, not in a frame.

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Types of PO units

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Type E: POU that does neither fall into any of the PO Unit types A through D nor is a DNV 2.7-1 Offshore Container. It shall be agreed with DNV GL in each case if it is applicable to certify a Type E unit as a POU. Type E PO Units are typically used when it is not practical to use either a type C unit, where the load carrying structure of the PO Unit is also the structure of the equipment being transported, or a load carrying skid (Type B).

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Flowchart for Design Basis

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DNV offshore standards covering marine operations, i.e. DNV-OS-H101, DNV-OS-H102 and DNV-OS-H201 to DNV-OS-H206, are collectively referred to as the VMO Standard.

VMO standard are not Standard for Certification

VMO Standards are being superseded by the new DNV GL Marine Warranty Standards, DNVGL-ST-N00x


Design Approval Process

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Certification Process

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Certification of components include:

Production Follow up Design Verification

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Design Approval

The design verification will include at least:

– Applied design loads

– Strength of main structure, including lift points

– Design details, if applicable – see sub-section 3.9.

– Material specifications

– Welding and other joining methods

Exclusions:

– Strength for in-place load conditions (e.g. of winch foundations).

– Strength of any equipment, including (empty) tanks in the unit.

– Secondary structures.

– Sea fastening arrangement.

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Required Design Documentation The following documentation shall be submitted for approval:

A) Design drawings of main (primary) structure including:

a) materials to be used, e.g. reference to the relevant material specifications,

b) dimensions and element properties,

c) joints and particulars of joining methods (welding, bolted and pinned connections),

d) NDT requirements,

B) Design drawings of lifting points and other design details subject to acceptance;

C) Design drawings of other elements considered as part of the primary structure;

D) Operational procedure;

E) Drawings of lifting set (if applicable) showing detailed information about:

a) dimensions and capacities,

b) materials,

c) each single component including reference to certificates,

d) certification scheme for lifting set.

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Required Design Documentation The following documentation shall be submitted for review/information:

F) General arrangement drawings showing:

a) any protruding parts

b) main dimensions

c) operational class

d) maximum gross weight (MGW), tare weight (T) and payload (P).

G) Lifting and transportation arrangement drawings showing:

a) sling angles

b) sling lengths

c) CoG location

d) lifting set components

e) seafastening layout

f) operational restrictions.

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Required Design Documentation The following documentation shall be submitted for review/information:

H) Design calculations including information and justification of:

a) selected operational class

b) applied weight and CoG

c) applied design loads for main structure and design details

d) lifting set details as maximum and minimum sling angles and shackles

e) if applicable; calculations for lifting set.

I) Information about intended use, as applicable:

a) single or multiple transports

b) any special handling restrictions and/or an operational procedure

c) equipment to be installed

d) service function

e) special loads to be applied.

J) Particulars of corrosion protection and painting (type, application, dry film thickness).

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Approval Scheme

Individual (case-by-case) approval:

– Single batch with limited number of PO Units (normally less than 20).

– The manufacturer must specify the number of PO Units covered by the approval.

– The approval is only valid for the actual project / installation / application

– The deliverable is Design Verification Report (DVR)

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Approval Scheme

Type Approval Certificate (TAC):

– Series production OR future orders of the same PO Unit.

– Type Approval process includes Design Assessment, Audit and Type Testing.

– The company applying for type approval of a POU type must be the owner of the design, or have a written acceptance from the owner of the design that the type approval certificate can be issued in the name of the company.

– The company must take the sole responsibility for the conformity of the product to the applicable requirements.

– When the POU design is manufactured at different places of manufacture, prototype testing shall normally be carried out at each manufacturing plant.

– TAC is valid for 5 Years.

– Type Approval process in DNV Standard for Certification 1.2.

Each POU manufactured according to a case-by-case or type approval shall be certified by DNV GL.

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Break

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Certification process

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Slide 27

Certification is relevant for products, processes, services or persons.

Certification: On the basis of a review and decision, a

written statement is issued, confirming that fulfillment of specified requirements has been demonstrated

Certification – Definition

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DNV GL

Deliver Product with DNV GL Certificate

- Perform certification - Deliver DNV GL Certificate

Oilcompany (Purchaser)

Order product with DNV Certificate

Manufacturer

Request DNV GL certification of product

Certification of Materials and components

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Slide 29

Certification of Components

Shall in most cases include Design Assessment

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+ Production Assessment

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”Case by case” Approval

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”Case by case” Approval

Production Assessment

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Slide 32

Request for certification

Qualified Manufacturer ?

Witness testing Perform survey

Compliance with requirements?

Mark product

Issue certificate

Design Assessment done ?

Production assessment

Prepare for Survey

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Slide 33





Mark product Issue

certificate Make invoice



Prepare for Survey

•Define scope of work • Establish Contract

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Mark product

Issue certificate



Prepare for Survey

Check Qualifications • Quality system certified ? • Manufacturer approved ? • Procedures qualified ? • Personnel qualified ?

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Slide 35





Mark product

Issue certificate



Prepare for Survey

Check Design assessment • Drawings approved ? • Comments given ? •

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Mark product

Issue certificate



Prepare for Survey

• Understand issued approval comments Applicable Rules, IS and Checklist • Similar projects? •Testprogram esthalished?

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Slide 37





Mark product Issue

certificate Make invoice



Prepare for Survey

Survey and testing • Perform all required surveys • Witness all required testing • Check that all requirements are fulfilled • Check product vs approved design • Record results • Record corrective actions/repairs • Document progress of job

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Slide 38





Mark product

Issue certificate



Prepare for Survey

no • Reject Component

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Slide 39





Mark product

Issue certificate



Prepare for Survey

Completion of certification • Issue relevant certificate • Send certificate to manufacturer

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Certification

It is not DNV GL that requires offshore containers to be certified – DNV GL offers a certification service.

Requirements for certification come from:

- International regulations (IMO)

- National authorities

-Within the offshore industry (oil companies, supply vessel owners, organizations, etc.)

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Design Requirements

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Design

Design Condition

The structural integrity of PO Unit shall be verified for exposure to dynamic conditions that are common for an offshore transportation event involving:

sea voyages,

lifting onshore, inshore and on board vessels/platforms offshore,

Lifting to and from vessels offshore,

Lifting into and out of the sea (if applicable).

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Material

Design temperature

The minimum design temperature shall not be taken higher than the (statistically) lowest daily air temperature for the area where the PO Unit shall operate.

In the absence of a design temperature designation, the design temperature shall be -20° C.

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Material

Minimum material thickness

Applicable thicknesses for Type D POUs should be evaluated case by case.

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Material

Charpy requirements for steel

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Sy > 500 MPa T > 50 mm DNVGL-OS-B101 `

Average energy absorption for 3 base material specimens parallel to the final rolling direction single value >= 70% of average values

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Material

Charpy Impact Test Exemption (all of the following shall apply):

Normalized, killed, fine grain steel

Specified yield strength equal to or less than 345 MPa (50 ksi)

Minimum operating temperatures of 0°C or higher

Thickness of 25 mm or less.

Limitations: Steel with aging properties and steel with minimum yield strength above 690 MPa (100 ksi) should not be used.

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Material

Lift Points

References for acceptance criteria given in DNV-OS-B101, EN 10164 or a

compatible ASTM specification.

If the lifting load is transferred through the plate thickness (z axis), plates

with specified (documented) through thickness properties must be used.

All welds transferring load in tension shall be full penetration type.

Full penetration is also recommended for welds transferring loads in shear.

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Material

Steel bolts, nuts and pins

Bolts and pins considered essential for structural integrity and operating

safety shall conform to ISO 898 or other recognized code or standards.

Impact energy >= 42 J at -20°C

Nuts are normally exempt from toughness testing.

Bolts and pins for connection of padeyes and/or between a lifting tool

Type E PO Unit and the cargo should have individual fabrication

certificates.

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Operational aspects

All PO Units should be evaluated for any special consideration that may affect the design and procedures for the transportation.

In many cases operational aspects are adequate and covered by selecting Operational Class . The Operational Class shall be agreed with DNV for all PO Units.

In cases special design consideration are necessary for safe handling of a PO Unit an operation procedure shall be part of the design documentation.

The procedure should if requested be submitted to DNV for information/review.

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Operational Class

An operational class shall be assigned to each POU, based on the

following:

whether or not offshore lifting between vessels/platforms is intended;

Weight/mass;

Risk evaluation;

Type of POU.

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Operational Class

The following three Operational Classes with operational limiting significant wave height as indicated are used in this certification note:

– Class R60 – Lift from/to vessel in max Hs = 6.0m.



– Class R00 – Lift onshore, inshore and on board vessels/platforms offshore, but not between vessels/platform offshore.

In addition the following notations shall be used if applicable:

– POU for Subsea use: Sxx, where xx is the limiting significant wave height in decimetre (e.g. 1.3 m would be written S13), see [3.11.4]. Alternatively for POUs without a pre-defined limiting wave height for subsea lifting: SXX.

– PO Unit for single event/transport only: SE.

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Operational Class

For example, for a R45 class POU for a single event and subsea use without any pre-defined wave height limitation for the subsea lifting (see [3.11.6]) the following identification applies:

DNV 2.7-3 R45-SXX-SE

In cases where a POU is designed for subsea handling only the operational class Rxx is not applicable and should be omitted. The notation used for such cases could e.g. be DNV 2.7-3 SXX-SE. This limitation should be clearly indicated in the certificate and also on the POU itself by e.g. the following text: “For Subsea Handling Only”.

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Selection of Operational Class By using Type, Risk and MGW as input, Table 3-3 could be used as guidance

for the Operational Class selection.

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The appropriate Operational Class for a POU should be selected based on a total evaluation and agreed with DNV GL

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Risk evaluation

The operational risk of PO Units defined as ‘Low’ or ‘High’. The following elements are considered to increase the risk and should at least be included in the risk evaluation:

Installed/transported equipment specially sensitive to impact loads.

Protruding parts

Lack of roof protection

Lift points in positions where they could be damaged by impacts.

Impact on primary structure

PO Units of large geometry or size.

Sling sets including (loose) spreader bar(s)

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Risk Evaluations (Continued)

If one of the elements above is clearly applicable or at least two elements are partly present the risk level should normally be defined as “High”.

In addition the following will influence the possible consequences and probability of an incident:

- Value of the PO Unit including equipment.

- Single or (number of) reoccurring transportation event(s).

An operational procedure could be used to reduce the risk level.

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Operational Procedures The operational procedure shall include all relevant information required for a safe

transport of the POU and normally include, as applicable:

– Any special assumptions made in the design phase. E.g. sling angle limitations;

– Any requirements/restrictions regarding support condition during sea transport;

– Any requirements/restrictions regarding positioning of the POU on vessel during sea transport;

– Sea fastening requirements/restrictions;

– Limitations with regards to stability;

– Limitations with regards to impact strength;

– Safe distances to other objects during lift-off and set-down;

– Safe handling of crane hook and sling set;

– Restrictions due to any sensitive equipment transported in the POU;

– Control of horizontal motions of the POU;

– Guidelines/restrictions for subsea lifts;

The need for a specific operational procedure shall be clearly identified on the POU.

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Analysis and acceptance criteria

Only the primary structure shall be included in the design calculations.

Strength of frame members may be calculated using classical hand calculation or finite element analysis.

The PO Unit shall be calculated/analyzed for all relevant load combinations.

Von-Mises equivalent stresses, σe, criteria: σe ≤ 0.85 × Re (yield strength).

All plates and members subject to compression stress should be verified for buckling. The maximum allowable utilization factor shall be taken as 0.85.

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Analysis and acceptance criteria

Essential and non-redundant primary structural members should be welded with full penetration welds

Weld strength shall be based on the nominal weld area.

The utilization factors is limited to :

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Case / Weld` Fillet Partial Penetration 1)

Single event 0.8 1

Multiple event 0.6 0.8

1) Also for partial penetration weld plus fillet weld where the throat area of the fillet weld is equal to or less than the stress area of the partial penetration weld.

PO Unit shall be checked for excessive deflection:

• Greater than the value specified by the owner/buyer.

• Affect safe handling of the PO Units.

• Deflected member (impact load) hit the cargo.

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Stability against tipping

The sea transport design loads (Section 3.7) should not cause uplift in any corner of the POU. If required uplift could be prevented by lashings.

PO Unit should normally be stable considering the following tilting angles:

- Operational Class R60: 30°




If the above criteria can not be met the operational procedure shall describe appropriate actions including maximum allowable tilting angle. The allowable tilting angle should not be greater than 1/2 of the design tilting angle.

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Maximum gross weight (MGW)

The maximum gross weight (mass), MGW, is defined as: MGW = T + P

– T: Maximum tare weight (mass) of the POU.

– P: Maximum allowable pay load.

The weight values should be found by weighing or documented by a reasonable conservative weight estimate.

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Application of loads and Boundary Conditions

The design loads and BC should be applied as exactly as possible. I.e. the loading shall be distributed to members and joints according to the mass distribution in the PO Unit.

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Example:

– Designed for 4-point Lift

– Wrong BC

– Compression in the upper beam is neglected

– Effect of slings shall be properly considered/modeled.

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Design loads - Lifting

The design load F is the greater of FAir and FSub (if applicable).

FAir = DF x MGW x g

For subsea PO Units: FSub =2.5 x MGW x g is normally adequate, but see also section 3.11.

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Design loads - Lifting

For some POUs Type E it is not relevant to calculate the design load based on MGW. For these POUs, e.g. running tools, pull-in heads, the maximum dynamic load, FDyn, shall be found by calculations/analysis.

Design Load:

The certification may be based on a defined FDyn that needs to be considered and verified when using the POU.

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Design loads - Lifting Resultant Sling Force:

Single lift point:

For 2, 3 or 4 leg sling arrangements without spreader bars:

– ν = the angle between the sling leg and vertical. For 2, 3 and 4 sling sets, where ν ≥ 30 degrees.

– SKL = Skew load factor. 1.33 for a 4 slings set and 1.1 for 2 and 3 slings sets (assuming that slinglengths are adequately controlled) .

– PL = Percent Loading of F (quasi-static calculations) in the most loaded padeye. Any significant uncertainty in CoG should be included in the PL calculation by assuming ‘extreme’ positions of the CoG.

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Padeyes – Out of Plane Loads Out of plane loads on padeyes are due to:

A. Design angle between sling- and padeye plate planes.

B. Inaccuracies in padeye fabrication and sling set

C. Angle difference between crane hoist line and the line from the hook center to the PO Unit CoG.

Case “A” should normally be avoided, otherwise considered.

For case “B” a 3% out of plane loading shall be applied

For case “C” the following minimum hoist line angels should normally be considered:

– Operational Class R60: 20 degrees




Out of plane load due to “C” may be disregarded for 3 and 4 slings sets if none of the slings become slack due to the considered angle.

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Padeyes – Out of Plane Loads Angle difference between crane hoist line and the line from the hook center to the PO Unit CoG.

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Design loads – Horizontal Impact The impact stress shall be combined with a lifting stress based on the

unfactored loads.

For corner posts and bottom rails/edge:

– R60 & R45: FHI = 0.08 × the test load

– R30: FHI = 0.05 × the test load

For structure and upper rails/edge:

– FHIR = 0.6 × FHI

For single transportation 50% of the above defined FHI and FHIR may be applied.

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Design loads – Vertical Impact POUs in Operational Class R45, R60 and R60-SE shall be capable of

withstanding an impact from lowering on one corner of the structure on a flat surface. This may be simulated by the test described in section 5.3 or by calculation.

– Guidance note: Normally non-linear dynamic FE analysis is required for the simulation of impact load testing by calculation. Analysis details should be agreed with DNV GL.

POUs shall also be verified for an impact load acting on on the bottom outer edge, due to lowering onto an uneven surface: FVI = 0.08 × F.

Some Type C and E units may not be structurally suitable for vertical impact resistance and the above design criteria do not apply to these units. The Operational Class should be selected accordingly and a proper operational procedure should be created.

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Design loads - Sea Transport The accelerations should be based on motions calculations for the actual

transport vessel(s), position

If such information is not available, the following combination should be used:

– FH = MGW × g, combined with both

– FVmax = 1.3 × MGW x g and FVmin = 0.7 × MGW x g

– Wind force of 1.0 kN/m2

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Design of Lift Points Possible Failure Modes:

– Material or welding failure

– Overloading

– Loading in unintended direction

– Damage, e.g. due to impact

– Inadequate fit of lifting equipment (shackles)

Padeye Geometry – The outside radius of the padeye shall not be less than the diameter of

the pin hole.

– The pad eye plate thickness at the hole, including cheek-plates, shall not be less than 75% the inside width of a shackle.

– For padeyes with out-of-plane loading greater than 10%, the shackle pin diameter should not be less than 94% of the padeye hole diameter.

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Design of Lift Points Padeye Radius:

Bearing Stress:

Tear-out Stress:

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Cheek plate welds

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Lifting Sets – Approval Requirements Local regulations to lifting sets may be stricter/different than the

requirements stated in this standard. This standard does not identify/consider such possible local requirements.

To include the lifting set in the certification process is optional.

Normally lifting slings (chain or wire rope) and the main components shall be type approved.

If type approved products are not available or the manufacturer has not received a type approval, a Product Certificate may be issued.

Lifting sets certified according to DNV 2.7-1 for equal or greater MGW could be used, if the shackles are not subject to out-of-plane loading.

Sling sets that are referred to in the POU certificate shall normally not be removed from the PO Units except for replacement.

When a POU is installed for an extended period on an offshore installation, the lifting set may be removed for the duration of the installation period.

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Lifting Sets – Design Consideration

Slings shall be rated for their intended angle of use (from vertical).

Normally the sling leg angle from vertical for two, three and four leg slings should be between 45° and 30°.

For master link that is connected to crane hook, the minimum internal dimensions of 270 × 140 mm is recommended.

The top link shall be reachable when the sling hangs over from the long side of PO unit (not more than 1.3 m from the floor).

When 2-legged slings are selected to function as a 4-legged sling, they shall be calculated as for a 4-legged sling. Care must be taken that the angle from vertical is not the same as the angle between the 2 parts.

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Lifting Sets – Sling Sizing

Sling capacity:

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Lifting Sets – Shackle Sizing

– Working Load Limit:

(SF≤6)

– Shackles that can experience significant out-of-plane loading, shall be adequate for such loading according to the manufacturer.

– Their WLL shall be de-rated according to the manufacturers’ specification.

– If manufactures specification regarding de-rating due to out-of-plane loading is not available:

– should be fulfilled for out-of-plane angels greater than 2 degrees, where “ang” is the out-of-plane angle in degrees.

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Spreader Bars

Spreader bars are normally not considered adequate for offshore lifting under adverse weather conditions.

My be used for lifts with detailed operational procedures including weather limitations.

Offshore lifting including spreader bars are normally limited to Operational Class R30.

Spreader bars shall be included in the POU load test, or (e.g. in case of replacement) they shall be tested separately with the corresponding test load.

The requirements to materials, fabrication and NDT in Section 4 apply.

Marking shall be in accordance with Sec.6

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Subsea Applications

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Subsea Application Main Assumptions:

The applied installation/lift procedure will ensure no slack slings.

The requirements do not cover the actual subsea use/function of the POU.

It may be found relevant to design to the POU for other conditions than indicated in [3.11.2]. In such case the design conditions may be based on DNV-OS-H206 and DNV-RP-H103.

Design condition

The effective weight of a POU and the dynamic amplification factor will vary during a subsea lift.

The calculation of maximum effective weight shall include possible trapped water (when lifted out of water) and possible suction when lifted from the sea bottom.

The worst realistic combination of effective and dynamic amplification shall be considered. The suggested design factor of 2.5 is based on:

• DAF = 2.0;

• Submerged weight = 0.9 × MGW;

• General design factor = 1.4.

The applied design condition always needs to be verified against the actual installation condition.

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Subsea Application

Design considerations

A. This standard does not explicitly indicate a limiting sea state for the subsea lift. However, the values in Table 3-7 may be used as a rough (normally conservative) guidance:

DAF = 2

MWG in tonnes

A is the PO Unit drag area in m2.

V is the volume of the PO Unit + added (water) mass/volume in m3.

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Subsea Application

B. All air filled members shall be designed for the maximum hydrostatic pressure, or proper ventilation/ water filling.

C. Lift points below CoG should normally be avoided.

D. Proper draining when lifted out of the water (if applicable).

E. Lift points should be placed/designed in such a way that the risk of damage and/or accidental release of lifting set is negligible.

F. Extended subsea application and retrieval thereafter is not covered by the basic requirements in this standard, and additional requirements shall be considered.

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Subsea Application – Other Design Loads In addition to the basic lift load case, the following need to be considered:

Effect of horizontal wave loads (Tilt effect)

Local design for hydrodynamic loads, e.g. slamming loads;

Guiding system for final positioning;

Retrieval loads;

Hydrostatic pressure;

Cathodic Protection (CP);

Marin growth.

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This standard does not offer specific design values for the above loads and verification against these loads is hence not normally a part of the DNV GL POU certification.

However, the designer should consider these

loads and DNV GL will request calculations if considered critical for the feasibility of the intended use of the POU.

Upon request any of these loads and related design details may be included in the DNV GL certification

scope.

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Subsea Application – Operational Aspects

All operational limitations shall be clearly indicated in the POU design documentation.

Critical limitations should be indicated in the certificate and normally marked on the POU.

Such limitations could be:

– Installation wave height/periods.

The installation contractor needs to do a final assessment of the applicable operation limitations based on the actual installation vessel and –procedure.

– B) Special considerations, the POU should pass splash zone with inclination.

– C) Maximum allowable water depth.

– D) Maximum allowable loads on tugger points and guiding systems.

– E) Acceptable sling angles (range).

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Break

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Production Surveys - General

The survey should ensure by means or random inspections, that the product complies with the requirements stated in the Rules / Standards.

Before starting of fabrication, an audit may be performed at the fabricator to verify its Quality Management System, and manufacturing capability.

The fabricator shall present a quality plan for acceptance before fabrication commences, relevant production documentation should also be presented in advance.

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Production Surveys – Program

Initial visit, where applicable hold points should be agreed. The hold points usually could be:

– Verification of incoming materials.

– Welding preparation.

– After welding inspections.

– Load tests (prototype / production).

– Additional tests.

– Final Inspection.

Document review including confirmation that the module design is in accordance with approved design.

Survey: the agreed hold point and others if applicable.

Final release / Certification.

The survey program will base on the quality plan, and usually should include:

DNV GL ©

Production Surveys – Verification of materials

Verification of incoming materials should consist of the following steps:

Review of unit structure materials for compliance with: - design - Rules.

Agree on traceability system to be used.

For steels, material impact values – thickness vs design temperature.

DNV GL ©

Production Surveys – Primary Structure

Traceability marking

During Production, and on the finished product, it shall be possible to identify the materials used for the primary structure with the corresponding documentation.

If the marking is not visible on the finished product, a log shall be kept of the components, to identify and ensure traceability of the materials.

DNV GL ©

Production Surveys – Welding Preparation

Inspection of welding preparation should consist of inspection of fit-up as well as manufacturers readiness for welding. The following steps require attention:

Verification that the weld preparations comply with the drawings and the Rules requirements.

Verification If the fabricator in possess of WPSs in accordance with approved WPQTs according to Rules

(EN / ISO / ANSI/AWS / DNV GL Rules and other recognized standards

Are the welders qualified to the WPSs in question.

DNV GL ©

Production Surveys – In welding

In welding inspection consist of the following steps:

Verification if the fabricator is using qualified welders.

Verification if the fabricator is using proper WPSs.

- Are the welders using proper welding consumables ?

- Are the welders using proper welding parameters

- Are the welding positions correct ?

Verification if proper assembly and welding sequence is kept.

DNV GL ©

Production – After welding inspection

Inspection shall be carried out after any production testing.

After welding inspection consist of the following steps:

Welds shall be subject to visual inspection and non-destructive examination (NDE), all welds shall be subjected to 100% visual inspection.

DNV GL ©

Production – After welding inspection

NDE operators shall be certified according to a national certification scheme or have qualifications accepted by the Society to a similar level.

Unless otherwise agreed, NDE standards and criteria's shall be used according to DNV GL Rules.

NDE:

NDE methods should be chosen considering the joint geometry, the welding method used and the sensitivity of the test method employed.

DNV GL ©

Production Surveys – Load Tests

During Production, some modules shall be strength tested. An all-point lifting test shall be carried out.

The number of containers to be tested should be agreed in advance with the fabricator, and will depend upon the total number in the production series.

The module to be tested shall be chosen at random after the production of a batch is finished.

NDE is to be performed after the test.

DNV GL ©

Production Surveys – Final Inspection

- Verify corrosion protection. - Verify roof anti-slip.

PO units shall be suitable for the offshore environment by means of construction, use of suitable material and/or corrosion and paint protection.

All PO unit roofs, including those constructed from chequer plate, shall be coated with a permanent non-slip medium.

DNV GL ©

Production Surveys – Final Inspection

Verify information marking

Verify Information and Inspection Plates

Verify other marking

Verify sling set (if fitted).

Verify safety marking

DNV GL ©

Production Surveys – Documentation Requirements (for DNV GL)

The certification of each module shall be based on the following documentation:

- Type Approval Certificate or case by case approval. - Approved drawings, including a general arrangement drawing. - Structural calculations. - Material documentation including welding consumables. - Welding procedure qualifications (WPQTs). - Welding procedure specifications (WPSs). - Welder's qualification certificates. - Report on traceability of materials in the primary structure. - Report from manufacturing inspection. - Report from dimensional control. - Report from non-destructive examination (NDE). - Report from prototype testing. - Report from production testing - Report from final inspection. (FAT)

DNV GL ©

Dossier (for customer)

The "As Built" dossier should at least include: General arrangement drawing.

Material documentation. Specifications for welding procedures (WPS). Report on traceability of materials. Report from manufacturing inspection. Report from dimensional control. Report from non-destructive testing (NDE). Report from production testing. Report from final inspection. DNV GL’s certificate for Portable offshore units (form 49.01a).

The various reports may be combined as practical.

DNV GL © 2013

DRAFT

Bad design: padeyes

padeyes are welded with fillet welds on the ouside of the frame Padeye plate is not in the correct angle 2 shackles are joined together

105

DNV GL © 2013

DRAFT

Bad design: padeyes and ISO container

Padeye attached later on an ISO-container:

• padeye-construction gives lack in continuity between toprail and corner post

• ISO-containers are not suited for use offshore (for instance the top beam is only a thin L-beam

106

DNV GL © 2013

DRAFT

Good design: padeyes

To obtain full penetration welding with this design the base plate is slotted into the top frame. Padeye is being prepared and welded with full penetration. Base plate are to have ”Z”-quality.

108

DNV GL © 2013

DRAFT

Bad design: Fork lift pockets

Old PO Unit: Cracks in bottom frame due to not sufficient shear area above fork lift pockets

110

DNV GL © 2013

DRAFT

Good design: fork lift pockets

111

Alternative reinforcements above fork lift pockets (wall plates are thin secondary structure)

DNV GL ©

Deformation – Repair Criteria

Inspection/Repair Criteria derived from the IICL “Guide for Container Inspection, 5th Edition” ©

This book – made for ISO/CSC freight containers - may also be used as a guide for repair criteria for offshore containers.

DNV GL ©

Periodic Surveys – Modifications

Major Repairs are defined as rework which affects the Primary Structure.

Modifications are defined as alterations to the container that affect any of the original design parameters which are stated in the DNV GL Design

Review.

Rating Dimensions Material Grades and properties

Major Repairs or Modifications which may alter the certificate shall be approved by the Society.

Standard for Certification 2.7-3: Portable offshore units

Documents

Transcript of Standard for Certification 2.7-3: Portable offshore units