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ISO 19901-5-2016 Petroleum and natural gas industries. Specific requirements for offshore structures. Weight control during engineering and construction.pdf | Organización Internacional de Normalización | Comisión Electrotécnica Internacional
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BS EN ISO 19901-5:2016
gas industries Specific
Part 5: Weight control during engineering
and construction (ISO 19901-5:2016)
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Copyright European Committee for Standardization
Provided by IHS under license with CEN Licensee=OMV - Bucharest/5974190006, User=Nicolae, Dragos
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BS EN ISO 19901-5:2016 BRITISH STANDARD
19901-5:2016. It supersedes BS EN ISO 19901-5:2003 which is
Committee B/525/12, Design of offshore structures.
The British Standards Institution 2016.
ISBN 978 0 580 84453 9
Standards Policy and Strategy Committee on 30 June 2016.
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EUROPEAN STANDARD EN ISO 19901-5
EUROPISCHE NORM March 2016
ICS 75.180.10 Supersedes EN ISO 19901-5:2003
Petroleum and natural gas industries - Specific
requirements for offshore structures - Part 5: Weight
control during engineering and construction (ISO 19901-
5:2016)
Industries du ptrole et du gaz naturel - Exigences Erdl- und Erdgasindustrie - Besondere
spcifiques relatives aux structures en mer - Partie 5: Anforderungen an Offshore-Bauwerke - Teil 5:
Contrle des poids durant la conception et la Gewichtskontrolle whrend der Auslegung und
fabrication (ISO 19901-5:2016) Konstruktion (ISO 19901-5:2016)
This European Standard was approved by CEN on 30 January 2016.
2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 19901-5:2016 E
EN ISO 19901-5:2016 (E)
This document (EN ISO 19901-5:2016) has been prepared by Technical Committee ISO/TC 67
"Materials, equipment and offshore structures for petroleum, petrochemical and natural gas industries"
in collaboration with Technical Committee CEN/TC 12 Materials, equipment and offshore structures
for petroleum, petrochemical and natural gas industries the secretariat of which is held by NEN.
identical text or by endorsement, at the latest by September 2016, and conflicting national standards
shall be withdrawn at the latest by September 2016.
This document supersedes EN ISO 19901-5:2003.
Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
The text of ISO 19901-5:2016 has been approved by CEN as EN ISO 19901-5:2016 without any
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ISO 19901-5:2016(E)
0	Introduction.............................................................................................................................................................................................................. vi
4	Abbreviated terms............................................................................................................................................................................................... 8
5	Weight control classes..................................................................................................................................................................................... 8
5.1	General............................................................................................................................................................................................................ 8
5.2	Class A: High definition of weight and CoG..................................................................................................................... 8
5.3	Class B: Medium definition of weight and CoG............................................................................................................ 8
5.4	Class C: Low definition of weight and CoG....................................................................................................................... 9
5.5	Selection of class of weight control........................................................................................................................................ 9
6	Weight and load budget (WLB)...........................................................................................................................................................10
6.1	General......................................................................................................................................................................................................... 10
6.2	Requirements......................................................................................................................................................................................... 11
6.3	Content......................................................................................................................................................................................................... 11
6.3.1	General................................................................................................................................................................................... 11
6.3.2	Weight reserves.............................................................................................................................................................. 12
6.3.3	Future weights and loads....................................................................................................................................... 13
6.3.4	Loading conditions and parameters............................................................................................................. 13
6.3.5	Formats and levels....................................................................................................................................................... 14
6.3.6	CoG envelopes.................................................................................................................................................................. 14
7	Weight control procedure.........................................................................................................................................................................15
8	Weight reporting................................................................................................................................................................................................16
8.1	General......................................................................................................................................................................................................... 16
8.2	Weight report requirements..................................................................................................................................................... 17
9	Requirements for suppliers weight data and weighing of equipment and bulks.........................20
9.1	General......................................................................................................................................................................................................... 20
9.2	Provision of weight information............................................................................................................................................ 20
9.3	Weighing requirements................................................................................................................................................................. 20
9.4	Weighing equipment........................................................................................................................................................................ 21
9.5	Weighing procedure......................................................................................................................................................................... 21
9.6	Notification and witnessing of weighing........................................................................................................................ 22
9.7	Calibration of weighing equipment..................................................................................................................................... 22
9.8	Weighing operation........................................................................................................................................................................... 22
9.9	Temporaries during weighing.................................................................................................................................................. 23
9.10	Items not installed during weighing.................................................................................................................................. 23
10	Requirements for weighing of major assemblies.............................................................................................................23
10.1	Weighing procedure......................................................................................................................................................................... 23
10.2	Environmental conditions........................................................................................................................................................... 23
10.2.1	Light.......................................................................................................................................................................................... 23
10.2.2	Wind......................................................................................................................................................................................... 24
10.2.3	Temperature and humidity................................................................................................................................... 24
10.3	Weighing..................................................................................................................................................................................................... 25
10.3.1	Number and timing of weighing....................................................................................................................... 25
10.3.2	Weighing procedure.................................................................................................................................................... 25
10.3.3	Notification and witnessing of weighings................................................................................................ 26
10.3.4	Preparation of the weighing................................................................................................................................ 26
10.3.5	Weighing equipment.................................................................................................................................................. 27
10.3.6	Calibration of weighing system......................................................................................................................... 30
ISO 2016 All rights reserved
Copyright European Committee for Standardization iii
10.3.7	Weighing foundation and supports............................................................................................................... 30
10.3.8	Structural integrity...................................................................................................................................................... 31
10.3.9	Weighing operation..................................................................................................................................................... 31
10.3.10	CoG calculations............................................................................................................................................................. 32
10.3.11	Weighing certificate.................................................................................................................................................... 33
10.3.12	Weighing report.............................................................................................................................................................. 33
11	Requirements for as-built weight documentation.....................................................................................................34
AnnexA (informative) Weight data sheets Tagged equipment........................................................................................35
AnnexB (informative) Weighing certificates.............................................................................................................................................37
AnnexC (informative) Weight and load budget (WLB) formats and levels................................................................41
AnnexD (informative) Major elements of the weight displacement.................................................................................42
AnnexE (informative) Supplier weighing procedure.......................................................................................................................43
AnnexF (informative) Guidelines for displacement measurement of floaters......................................................45
AnnexG (informative) Requirements for weight control during operations...........................................................49
AnnexH (informative) Requirements for topside weight estimation New builds/green field......65
AnnexI (informative) Executive summary description..................................................................................................................70
AnnexJ (informative) Weighing result uncertainty............................................................................................................................72
AnnexK (informative) Weight control database structure.........................................................................................................73
Bibliography.............................................................................................................................................................................................................................. 75
Copyright European Committee for Standardization ISO 2016 All rights reserved
editorial rules of the ISO/IECDirectives, Part2 (seewww.iso.org/directives).
assessment, as well as information about ISOs adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC67, Materials,equipment and offshore structures
for petroleum, petrochemical and natural gas industries, Subcommittee SC7, Offshore structures.
This second edition cancels and replaces the first edition (ISO19901-5:2003), which has been technically
ISO19901 consists of the following parts, under the general title Petroleum and natural gas industries
Part 1: Metocean design and operating considerations
Part 2: Seismic design procedures and criteria
Part 3: Topsides structure
Part 4: Geotechnical and foundation design considerations
Part5: Weight control during engineering and construction
Part6: Marine operations
Part7: Stationkeeping systems for floating offshore structures and mobile offshore units
Part 8: Marine soil investigations
Part 9: Structural integrity management
Copyright European Committee for Standardization v
The International Standards ISO19900 to ISO19906 relating to offshore structures constitute a
common basis covering those aspects that address design requirements and assessments of all offshore
structures used by the petroleum and natural gas industries worldwide. Through their application the
intention is to achieve reliability levels appropriate for manned and unmanned offshore structures,
whatever the type of structure and the nature of the materials used.
It is important to recognize that structural integrity is an overall concept comprising models for
describing actions, structural analyses, design rules, safety elements, workmanship, quality control
procedures and national requirements, all of which are mutually dependent. The modification of one
aspect of design in isolation can disturb the balance of reliability inherent in the overall concept or
structural system. The implications involved in modifications, therefore, need to be considered in
relation to the overall reliability of all offshore structural systems.
ISO19900 to ISO19906 relating to offshore structures are intended to provide a wide latitude in the
choice of structural configurations, materials and techniques without hindering innovation. Sound
engineering judgement is therefore necessary in the use of these International Standards.
It is proposed to canvass the TC 67/SC7 member countries to widen the scope of this part of ISO19901
for the third edition. As a consequence, the title might change.
It is proposed to expand and re-structure this part of ISO 19901 to more comprehensively address
topsides weight engineering principles, roles, responsibilities and objectives for a complete platform
It is proposed to re-format into a more traditional ISO document layout.
The use of weight class A, B and C tables will be reviewed.
There will be an outline of how to control topside weight, and of the aims and expectations of a
Weight Review Panel (or similar).
A common topside operating philosophy will be included with a matrix of coincident drilling loads,
operating loads, and laydown / storage loads to be included in topside weight databases.
It is proposed to give guidance on applied design contractor allowances during detailed design, plus
the use of client operational and management reserves.
The weight and CoG accuracy expected from weighings will be addressed.
Separate clauses will be added to give clarity to specific requirements of floating structures and
The contents and terminology will be coordinated to interface with ISO 19902, Design of offshore
structures, and the forthcoming ISO19901-9, Structural integrity management (due to be published
It is proposed to give more guidance on a range of topics encountered during the phases of a platform
life cycle, typically:
a) Weight control principles
Overview of principles, aims and objectives
Deliverables for each project phase
Weight report contents
b) Floating structures and jackets
Specific requirements for floating structures
c) Concept and feasibility phase
Use of historical volumetric weight norms
Use of area based weight calculations
Use of footprint ratios
d) Front end engineering design phase
Design parameters to be fixed prior to setting Not-to-Exceed weights
e) Detailed design phase
Control of weight using a Weight Review Panel or similar
Use of contractor allowances
Use of client reserves
Discipline reporting responsibilities
Coincident operating loads
Coincident drilling loads
Coincident laydown and storage loads
Laydown and storage drawings and area signage
Vendor weighing requirements
f) Fabrication phase
Reporting of site run materials
Preparations for weighing
Expected weight and CoG accuracy from weighings
Predictions and witnessing of weighings
Post-weighing reconciliation and weighing corrections
g) Installation and hook-up phase
Reporting of hook-up weights
h) Operational phase
Control of weight and CoG for topside modifications
Copyright European Committee for Standardization vii
Interfaces with ISO 19901-9 and ISO 19902
i) Decommissioning phase
Some of the above proposed changes are outlined in Annex G of this document (informative).
It is proposed that preparation of the third edition of this part of ISO 19901 will begin immediately
after the issue of this edition with a target publication date of 2017.
viii ISO 2016 All rights reserved
INTERNATIONAL STANDARD ISO 19901-5:2016(E)
requirements for offshore structures
This part of ISO 19901 specifies requirements for controlling the weight and centre of gravity
(CoG) by means of mass management during the engineering and construction of structures for the
offshore environment. The provisions are applicable to offshore projects that include structures of all
types (fixed and floating) and materials. These structures can be complete new installations or the
modifications to existing installations. Maintaining the weight control of existing installations is not
part of the main body of this part of ISO19901, but some guidance on this is included in the AnnexG.
This part of ISO19901:
specifies quality requirements for reporting of weights and centres of gravity;
specifies requirements for weight reporting;
provides a basis for overall project weight reports or management reports for all weight control
specifies requirements for weight and load budgets;
specifies the methods and requirements for the weighing and the determination of weight and CoG
of major assemblies;
specifies requirements for weight information from suppliers, including weighing of equipment and
bulk materials for offshore installations.
as a basis for planning, evaluating and presenting the clients, contractors or fabricators weight
management and reporting system;
as a means of refining the structural analysis or model;
as a basis for costing, scheduling or determining suitable fabrication method(s) or location(s).
ISO/IECGuide98-3, Uncertainty of measurement Part 3: Guide to the expression of uncertainty in
Copyright European Committee for Standardization 1
designed and fabricated group of bulk and equipment items which form one unit
weight reference figures as defined in the weight and load budget and related to the initial or changed
component or arrangement of components defined as stock materials or of low complexity
Note1toentry:Bulk items support the equipment items by providing infrastructure around and between them.
average location of the weight of an item
Note1toentry:For assemblies, modules or topsides, the aggregate CoG is the mathematical weighted average
of the CoGs of the individual items (comprising the completed assembly, module or topsides) measured from a
organisation for which a weight report is prepared
Note 1 to entry: This is the project owner (oil company/operator, fabricator, engineering sub-contractor,
lift/transportation contractor, etc.).
client weight reserve
weight addition (usually a lump sum weight) controlled by the client and used to account for any orders
for variation to the contractual design concept
CoG envelope
defined constraint volume within which the centre of gravity (CoG) of an assembly shall remain
variable content that does not remain at a constant level due to consumption during the operation of an
EXAMPLE	Potable/service water, diesel fuel, crew provisions, bulk drilling powders for creation of mud
and/or cement.
fluids or bulk powders held within bulks (piping or structural tanks) or equipment at their normal
Note1toentry:Typical contents are hydrocarbons, cooling and heating mediums, chemicals, fuels, condensates,
seawater, fresh water, dry powders (drilling cement and mud additives), dry stores for workshops, sack stores,
etc. Fluids that are expected to be continuously installed in an item of equipment (e.g. coolants and lubricating
oils) are not to be considered as contents. See dry weight (3.16) for further explanation.
organization tasked with constructing a portion of, or an overall project facility
contractor weight reserve
additional weight (either a lump sum weight or percentage of a total weight) at a specified CoG,
controlled by the contactor and used to account for any design growth within their control
total carrying capacity of a floating structure
Note1to entry:Includes weight of crude oil, deck cargo, temporaries, water, snow and ice accumulations, marine
growth, ballast water, consumables, crew and their effects.
Note2to entry:See AnnexD.
discrete branch of engineering reflecting a single aspect in the project
EXAMPLE	Architectural, drilling, electrical, HVAC, instrumentation, loss control (safety), piping, structural
discipline check list
document detailing the weight items that are within the disciplines control
weight of the volume of water displaced by a floating structure
Note 1 to entry: The sum of lightweight and deadweight including mooring system load, appendences and/or
appurtenances e.g. structures outside the moulded hull
weight of a component, weight item or an assembly in its dry installed condition including permanent
Note1to entry:Examples of permanent utilities are gearbox oil, hydraulic oil, filter sand.
Note 2 to entry: Any content of operating fluid flowing through a component, weight item or an assembly is
component or arrangement of components, built for specific function(s)
Note1to entry:The component/assembly normally has unique documentation due to its function and complexity.
Note2to entry:Refer to tagged equipment (3.41) for further explanation.
weight determined based on previous experience
Copyright European Committee for Standardization 3
initial filling of specific contents in items of equipment or piping prior to start of operation of an offshore
Note1toentry:First fill typically takes place towards the end of site construction, prior to tow-out and prior to
filling for normal operations.
loading condition in which a major assembly is transferred from a dry construction site to become self-
weight of a component or an assembly to be installed after the start of production
steel structure, secured to the deck of a barge or vessel, designed to support the cargo and distribute
the loads between the cargo and the barge or vessel
sum of the net weight and weight allowances
installation of components or assemblies after the modules have been installed in their final position, to
connect to the existing installation
sum of component, assembly or module lift weight and lifting gear
<loading condition for an operating offshore facility> at the start of steady-state production
Note1toentry:All bulk and equipment items are present with contents at nominal operating levels.
equipment needed during a lifting operation
EXAMPLE	Slings, spreader bars, lifting frames, shackles.
weight of a component, assembly or a module, including temporaries and residual fluid content but
excluding lifting gear
dry and invariable weight of a floating unit, including minimum utility content to secure a safe condition
Note1toentry:See AnnexD.
defined event for which a weight and CoG need to be controlled
Note1to entry:For each loading condition, all weight items and variable loads that are known or predicted to
occur are identified, quantified and located.
Note2to entry:Typical loading conditions are dry installed offshore, float-out at assembly site, future operating
installed offshore, operating installed offshore, load-out to offshore transport vessel, transport to offshore field, etc.
transfer by way of horizontal movement of an assembly, module or topsides from its land-based
fabrication site onto a floating or grounded transport barge or vessel
Note1toentry:The following are typical load-out operations:
skidded:	load-out using a combination of skid-ways, skid-shoes or runners, propelled by towing engines,
jacks or winches;
trailer:	load-out using multi-axle trailers [self-propelled modular transporter (SPMT)].
project -specific database for control and management of technical data for tagged equipment
transfer of a major assembly supported on barge(s) or vessel(s) to a temporary or permanent support
major assembly of items forming a major building block which needs to be controlled with respect to
weight and CoG
calculated or estimated weight of an item excluding allowances
not-to-exceed weight
maximum acceptable weight for any given loading condition, with an associated limiting CoG envelope
sum of the dry weight and the content weight
<weight management> management personnel tasked with implementing weight policy, objectives and
content in bulks and equipment remaining after testing or commissioning, and being present during
the subsequent loading conditions up to the start of production
Copyright European Committee for Standardization 5
items used for temporary fastening to keep all items in position during transportation at sea
equipment identified and labelled in accordance with the project coding manual and tracked in MEL
items temporarily installed during a loading condition and removed afterwards
Note1toentry:Temporaries do not form part of a structures permanent dry or operating weight.
sum of the dry weight plus the content required to test the equipment or assembly
towing of a complete floating structure to the offshore installation site
<loading condition> transfer of an assembly or module from one inshore or at shore location to another
location, or to the offshore installation site
weight additions to account for expected general growth due to immaturity of the current project stage
and/or components which are not estimated in detail at the current project stage
weight and load budget
document defining the weight and CoG limits for each loading condition, major assembly (and disciplines
for the dry installed offshore load condition)
Note1toentry:The WLB are to act as a comparison reference for:
a)	weight, load and CoG control and reporting for the duration of the project through the engineering,
construction, installation and operation phases;
b)	structural capacity requirements for individual sections or modules and for the total topsides or supporting
c)	temporary and permanent bearing capacity and stability of the total facility;
d)	overall cost and schedule control.
item or collection of bulk and/or equipment, content or assembly identified for weight reporting
all planned and controlled activities which deal with:
definition and publication of the project weight procedures, objectives and policies;
identification of information about and evaluation of alternative design solutions;
selection and implementation of an optimal design with respect to weight, CoG, volume, functionality,
cost and progress;
monitoring and reporting weight data throughout the complete life cycle of an installation to assess
present and potential weight status
Note1toentry:Project management, engineering disciplines and weight control discipline shall cooperate and
participate to influence the weight management process by means of adequate working methods and tools.
defined set of engineering goals necessary to fulfil the project contractual weight/CoG requirements
and intentions in order to contribute to the correct design quality as defined by the management
weight phase code
code used to identify the loading conditions in which a weight item is present
statement from the project management, based on the weight objective, defining how the weight
objective is to be achieved
Note1toentry:As a minimum, the policy should include:
the importance of the weight objective to the project aims and results;
the priority, profile and control of weights at different levels in the project;
a philosophy for responsibility and authority within and between project groups engaged in weight matters
regularly issued project document that details the weight and CoG for required assemblies and load
conditions based on best available information
Note1toentry:This document provides the basic load case for the project Structural Integrity models.
weight status code
code, based on the maturity of the design, used to identify the level of accuracy of the weight of a
Note1toentry:The weight status code is often used to assess the value of the weight allowance applied. As a
design matures, the weight status code will change so that an items weight allowance is reduced.
Copyright European Committee for Standardization 7
4	Abbreviated terms
WLB Weight and Load Budget
WTO Weight Take-Off
5	Weight control classes
In order to select the most appropriate level for weight control and reporting according to the degree of
weight and/or CoG sensitivity of the project, three classes of weight control have been defined. These
classes may also be used to determine the level of effort required in the weight management activities
The tender documents and final contract shall specify the applicable weight control class, so that the
contractor can allocate the required resources.
5.2	Class A: High definition of weight and CoG
Class A shall apply if the project is weight and/or CoG sensitive for any of the anticipated loading cases,
or has many contractor interfaces.
Class A weight projects shall:
a)	regardless of the source, have full traceability of all weight and CoG data;
b)	record weight and CoG data using a relational database from the commencement of detail
engineering, with integration of suppliers, fabricators and weighing results into the system;
c)	verify the calculated weight and CoG of assemblies, modules or topsides by means of physical
weighings;
d)	update weight data per weight item produced during the design phases to as-built status during
5.3	Class B: Medium definition of weight and CoG
Class B shall apply to projects where the focus on weight and CoG is less critical for any of the anticipated
loading cases than for projects where ClassA is applicable.
Class B weight projects shall:
a)	based on the complexity of the project, determine whether a relational database or spread sheet
software is required for recording of weight and CoG data;
b)	verify the calculated weight and CoG of assemblies, modules or topsides by means of physical
c)	have less stringent requirements for updating as-built status during fabrication.
5.4	Class C: Low definition of weight and CoG
Class C shall apply to projects where requirements for updating as-built status during fabrication is
Class C weight projects shall:
a) as a minimum use a spread sheet software for recording weight and CoG data;
b) verify the calculated weight and CoG of assemblies, modules or topsides by means of physical
c) provide supporting weight and CoG documentation consisting of equipment weights and
summarized bulk weights by drawing;
d) have no requirements for updating as-built status during fabrication.
5.5	Selection of class of weight control
The design basis, NTE weight and CoG criteria, together with WLBs established at the close of the
concept phase, are major factors to be considered when selecting the class of weight control.
Potential weight and CoG problems, specific to the loading condition, also need to be assessed before
selecting the class of weight control.
Class selection may be made from examination of Table1, included as a guide for determining the
required degree of weight and CoG control for a project. The class of weight control selected should be
the highest class meeting any of the Project Parameters in Table1.
Table1 Guidance criteria for weight control class selection
Description ClassA ClassB ClassC
Concept type new partly known well known
Weight sensitivity high medium low
CoG sensitivity high medium low
Weight data processing requirement high medium low
Contract requirement detailed general none to minimal
Weight data external interfaces >6 4 to 6 1 to 3
(other contractors)
NOTE	Weight sensitivity may be a result of constraints established by installation method (i.e. capacity of lifting device)
or capacity of supporting structure (i.e. jacket, GBS, hull, etc.)
Copyright European Committee for Standardization 9
6	Weight and load budget (WLB)
For all offshore installations, weight and As ClassA. As ClassA, except that d) is not
CoG information for all loading condi- required.
tions shall be controlled from the start
of conceptual design. Budget weights and
CoG constraints shall be determined for
the modules, topsides and supporting
substructures (inclusive of temporaries
required for the appropriate loading con-
ditions). This shall be done in cooperation
with the structural and marine disciplines
as well as the project management. The
budget weights and CoG constraints shall
be presented in the project WLB as a ref-
erence point to be used during a project.
The WLB is to be reference point for:
a)	weight, load, and CoG control and
reporting during all phases of the project:
b)	structural capacity requirements
for assemblies, modules, topsides and
c)	bearing capacity and stability
of the total installation (temporary or
d)	control of overall cost and sched-
e)	ensuring that all loading condi-
tions are within the anticipated capacities.
6.2	Requirements
Each participant in a project (typically the As Class A. The contractor WLBs are estab-
client, contractor and sub-contractors) lished either by the client, and are
shall be allocated a separate WLB. included in the project contract, or
by the project contractor. Unless
The contractor WLBs shall be established
specified by the client, the format and
by either the client or the contractor.
complexity is left to the discretion
If established by the client, the WLBs
shall be included in the project contract
The project management or client shall
hold overall responsibility for deciding
the variations between the various WLBs.
WLBs for subcontractors and vendors
shall be established by the contractor.
Under normal circumstances, revisions to
WLBs shall not take place unless concept or
major changes to the design - which impact
the weight, load or CoG - are implemented
by the project management/client.
All participants in the project shall be
responsible for adherence to established
WLB values.
In the event that the project weight man-
agement detects the possibility of a sig-
nificant variation from the established
WLBs, corrective actions shall be initiated
by the project management in order that
weight or CoG variations do not occur, or
their impact is minimized.
6.3	Content
The WLB consists of different types of As ClassA. As ClassA.
weights, loads and associated CoGs, as
defined in Figure1.
Copyright European Committee for Standardization ISO 2016 All rights reserved 11
Figure1 Weights, loads and associated CoGs
6.3.2	Weight reserves
A contractor weight reserve including As ClassA. As ClassA.
CoG may be added on top of the WLB
In addition to the contractor weight re-
serve, the client may add a weight reserve
The value and location of the weight re-
serve will depend upon the concept type
and the project weight policy.
Any relevant variation orders issued by
the client after the contract has been
issued may affect the weight reserve and
may necessitate a WLB revision.
In special situations, if the chosen design
concept is declared too heavy and thus
subject to weight reductions, the weight
reserve will be negative. This will result
in a WLB weight below the current esti-
mated or reported weight.
6.3.3	Future weights and loads
Future weights and/or loads are not in- As ClassA. As ClassA.
cluded in the weight reserve, but shall be
identified separately in the WLBs.
6.3.4	Loading conditions and parameters
A set of relevant loading conditions and As ClassA. As ClassA.
associated weight/load parameters shall
be defined for weight control and weight
Corresponding WLBs shall be provided. Not required.
This shall be done in cooperation with
the structural and marine disciplines as
well as the project management.
Agreement between the client and the As ClassA.
contractor shall be reached for:
the necessary weight reserves;
the implication of free surface
effects on the stability for floating condi-
tions (either temporarily or permanently)
the variable loads, relevant max-
ima and associated positions.
Variable loads may include, but shall not
operating loads (stores, person-
nel etc.);
6.3.4.2	Loading condition selection
The necessary loading conditions shall be As ClassA. As ClassA.
dependent on the nature of the structure
as well as the fabrication and installation
Copyright European Committee for Standardization 13
6.3.5	Formats and levels
6.3.5.1	General
The format of the WLBs shall depend on As ClassA. Not required.
the selected weight control class.
All WLB values shall be recorded
The WLB format shall, as a minimum in the relational-type database/
requirement, present a maximum permis- spread sheet.
sible weight and a CoG for each assembly,
module or topsides.
The format may be further developed in
order to present a maximum permissible
weight for each main weight contributor
(e.g. structural steel, piping and equip-
ment) and one common figure for the rest
of the design. Individual values for both
bulk and equipment for all disciplines
may also be given. All values shall be
recorded in the relational-type database.
The weight report formats shall allow for
the inclusion of necessary WLB values.
6.3.5.2	Formats
An example of a WLB format is given in As ClassA. As ClassA.
AnnexC.
6.3.6	CoG envelopes
The WLB shall include CoG envelopes As ClassA. As ClassA.
for weight control and weight reporting
The CoG envelope shall be either two-di-
mensional or three-dimensional depend-
ing on the structure being controlled,
i.e. for a fixed structure, where lifting
operations are critical to the CoG, the CoG
envelope shall be on two-dimensional,
but for stability purposes of a floating
structure, the CoG envelope shall be
7	Weight control procedure
A weight control procedure shall be is- As ClassA. As ClassA.
sued to the client by the contractors
weight control discipline within 60days
of the contract award, or as stated in the
The procedure shall document the weight
reporting responsibilities of the engineer-
ing disciplines and contractors.
The procedure shall include require-
ments that:
a) all personnel carrying out work
of significance concerning weight shall
have the necessary qualifications and
background/experience of such work,
b) the contractor or responsible
organization shall establish and document
a plan, which clearly shows how different
tasks, responsibilities and authorities are
distributed between disciplines,
c) the contractor or responsible As ClassA. Not required.
organization shall produce weight doc-
Include weight plan to explain
uments to substantiate methods of ob-
the use of weight allowances vs.
taining the weight data at various stages
design maturity.
of the project. This documentation shall,
as a minimum, contain a description of:
the estimating method-
ology used at during the project phase(s)
covered by the procedure;
the level of weight allow-
ances/ contingencies applied at various
assessment of CoG for
the loading conditions;
for hook-up scope material (if applicable);
assessment of loading
1) weight management philosophies;
2) transfer of weight control re-
sponsibility through the various phases
of the project (if applicable).
d) define the following: As ClassA. As ClassA.
1) input requirements;
2) global coordinate system;
3) area designation system;
4) loading conditions to be reported;
5) all codes (installation, status,
weight allowance, etc.) utilized in the
weight control system;
6) discipline checklist.
Copyright European Committee for Standardization ISO 2016 All rights reserved 15
8	Weight reporting
Project weight reporting shall be the As ClassA. As ClassA.
result of systematic compilation and
documentation. Results are presented in
a project weight report. It shall be based
upon agreed project procedures and work
instructions, with the formal weight policy
and weight objective defined and adhered
to, forming the project weight-manage-
ment activities, and requirements.
The frequency and type of report shall be The frequency and type of report The frequency and type of report
dependent on the project requirements. shall be dependent on the project re- shall be dependent on the project re-
As a minimum frequency, weight report- quirements. As a minimum frequency, quirements. As a minimum frequency,
ing every two months is recommended. weight reporting every three-months weight reporting every four-months
8.2	Weight report requirements
The following text is the required content of a weight report.
EXECUTIVE SUMMARY As ClassA. As ClassA.
Shall contain a short summary of pro-
ject main focus areas (loading condition
weights and CoGs) and brief descriptions
of variations in weight and CoG and the
WLB since the previous weight report.
(See examples in AnnexI)
A description of the purpose of the
weight report.
for the project and the corresponding
scope/content of the weight report. In-
clude a description of the specific loading
conditions that are reported.
1.3	Loading conditions
A description of the loading conditions
2	Report basis
A listing of reference material used (i.e.
layout drawings, plot plans, MEL, disci-
pline input, etc. and issue dates) used
to create the weight report. Include the
cut-off date used for submission of the
discipline weight data.
2.2	Report assumptions
A list of the assumptions used to create
2.2	Estimates
A table showing weight data based on
estimates (not detailed weight take-offs)
and/or factored from weights determined
by detailed weight take-offs.
Copyright European Committee for Standardization ISO 2016 All rights reserved 17
3	Loading condition summaries
Include tables showing weight and CoG
summaries for assemblies, modules and
entire topsides as defined by project
requirements. The tables shall present
weight and CoG data for current and
previous weight reports along with
mathematical differences between the
two time frames.
As a minimum, summary data shall be
presented for the following loading con-
3.1	Dry installed loading condition.
3.2	Operating installed loading
3.3	Other loading conditions sum-
3.4	Weight summaries by discipline
for assemblies, modules and topsides.
Include tables of comparisons between
current weights and CoGs and those
established in the WLBs.
3.5	Description of dry and operat-
ing installed weight variations (since
the previous weight report) for dry and
operating loading conditions.
3.6A list of possible weight risks (in-
creases) and savings (reductions). List
includes possible changes to scope and
design that are to be processed through
a management of change process before
inclusion in the weight report.
4	Weight and CoG trend graphs
Weight and CoG trend graphs for all agreed
loading conditions showing the weight
development and CoG shift over time.
5	Attachments
A table showing the definition of expres-
sions used in the report.
A table to explain the abbreviations used
5.3	Area plan and global reference
Drawing or sketch indicating the main
area codes and global coordinate system.
5.4	Weight phase codes
A table showing the relevant weight phase
codes used in the weight database.
5.5	Weight status codes
A table showing the weight status code
A table showing the reference documents,
standards, procedures and specifications
etc. for the report.
5.7	Report schedule
A schedule indicating the planned cut-off
and issued dates for the report.
5.8	Design data
A configuration of the principal design
data for the project.
5.9	Other
9	Requirements for suppliers weight data and weighing of equipment and bulks
The supplier shall calculate the weight As ClassA. As ClassA.
and CoG as accurately as possible.
The supplier shall provide the following
weight and CoG data for his delivery:
as-installed dry weight and CoG
for each item as it will be installed, in-
cluding any auxiliaries;
weight of the items normal op-
erating fluid content;
weight of the item in normal
weight of any auxiliaries such as
lubricants, hydraulic oil, etc.;
transportation weight;
weighing certificate (see B.1).
9.2	Provision of weight information
The supplier shall provide weight and As ClassA. As ClassA.
CoG information as follows:
as a part of the bid documents;
order issue;
when the weight change exceeds
the agreed project magnitude value;
within one week after weighing.
The weighing certificate shall be attached.
NOTE	AnnexA provides an example of
a weight data sheet. AnnexB provides an
example of a weighing certificate.
For purpose-designed items, the weight
data sheet shall also include weight and
CoG data based upon approved construc-
tion drawings.
9.3	Weighing requirements
The supplier shall perform weighing As ClassA. Weighing of equipment is optional.
of all equipment weighing more than
10kN(1t). If there is identical equipment,
only a representative sample shall be
weighed. For items weighing less than
10kN(1t), catalogue data or suppliers
detailed weight calculation is acceptable.
9.4	Weighing equipment
The weighing equipment shall have a The weighing equipment shall have The weighing equipment shall have
maximum relative measurement uncer- a maximum relative measurement a maximum relative measurement
tainty of1%. uncertainty of2%. uncertainty of3%.
The readout of the weighing results shall As ClassA. As ClassA.
be easily accessible, and display the results
with the same degree of accuracy as that
of the weighing equipment.
For all equipment/bulk items weighing For all equipment/bulk items weigh- For all equipment/bulk items weigh-
100kN(10t) or above, electronic com- ing 150kN(15t) or above, electronic ing 200kN(20t) or above, electronic
pression load cells or equivalent shall compression load cells or equivalent compression load cells or equivalent
be used to establish the horizontal CoG. shall be used to establish the hori- shall be used to establish the hori-
zontal CoG. zontal CoG.
The weighing shall be planned in such a As ClassA. As ClassA.
way that the weighing equipment operates
below 80% and above 20% of its rated
capacity, to account for possible weight
underestimation and safety aspects.
Necessary spare parts shall be made
readily available in order to minimize
delays in the weighing operation as a
result of faulty weighing equipment.
9.5	Weighing procedure
The supplier shall submit a weighing As ClassA. As ClassA.
procedure (see AnnexE) to the purchaser
for approval within three months of pur-
chase-order issue. The procedure shall
name and address of any sub-
contractor involved in the weighing;
description of weighing method;
make, type, range, and accuracy
of weighing equipment;
name and address of calibration/
verification body;
Copyright European Committee for Standardization ISO 2016 All rights reserved 21
9.6	Notification and witnessing of weighing
The supplier shall notify the purchaser As ClassA. As ClassA.
in writing of the planned date, time and
location of the weighing operation at least
14days in advance. The supplier shall
notify the purchaser of the confirmed
date, time and location of the weighing
operation at least three working days
All weighings of items weighing more
than 100kN (10t) shall be witnessed by
the client if not otherwise agreed.
9.7	Calibration of weighing equipment
The weighing equipment shall be cali- The weighing equipment shall be cali- The weighing equipment shall
brated for its full range. The calibration of brated for its full range. The calibration of have a readout facility, which is
the weighing equipment shall be carried the weighing equipment shall be carried traceable to a national standard,
out by a competent laboratory that can out by a competent laboratory that can such as in the form of a production
ensure traceability and adequate proce- ensure traceability and adequate proce- end control at the manufacturer
dures, such as a laboratory that meets dures, such as a laboratory that meets or subsequent check at intervals
the requirements of ISO/IEC17025 or is the requirements of ISO/IEC17025 or is not longer than four years.
accredited by a national accreditation accredited by a national accreditation
body. For weighings less than 100kN (10t), body. For weighings less than 150kN
the weighing equipment shall have been (15t), the weighing equipment shall
calibrated within the last 12months, and have been calibrated within the last
for 100kN (10t) and above within the last 12months, and for 150kN (15t) and
six months. The calibration certificate(s) above within the last six months. The
shall be available for the purchasers calibration certificate(s) shall be availa-
inspection prior to start of weighing. ble for the purchasers inspection prior
to start of weighing.
9.8	Weighing operation
A minimum of three weighings shall be As ClassA. As ClassA.
performed. Additional weighings shall
be performed if one of the following
problems has arisen:
inconsistent weighing results;
mechanical/electrical fault or
overloading of the weighing
In these cases the contractor shall make
provision to replace or interchange load
cell positions if required.
9.9	Temporaries during weighing
Temporaries shall be kept to a mini- As ClassA. As ClassA.
mum during the weighing operation.
The weighing shall be performed prior
to the packing of the suppliers delivery.
For temporaries weighing 10kN(1t) or
less, the weight and CoG for all tempo-
raries included in the weighing shall be
calculated, specified and included on the
weighing certificate. The weighing result
shall be adjusted accordingly. Temporaries
weighing above 10kN (1t) each shall be
9.10	Items not installed during weighing
The weight and CoG for all items not As ClassA. As ClassA.
installed during weighing of the bulk/
equipment items shall be obtained indi-
vidually and separately by weighing or
by detailed calculation, and included in
the weighing certificate.
Items excluded which are above 10kN
(1t) each shall be weighed separately.
10	Requirements for weighing of major assemblies
10.1	Weighing procedure
The contractor shall, as part of his scope As ClassA. As ClassA.
of work, prepare his own weighing pro-
cedure, which shall be subject to client
Refer to 10.3.2 for details.
10.2	Environmental conditions
10.2.1	Light
Whenever possible, the weighing should As ClassA. As ClassA.
be performed during daylight. If this is
not possible, the contractor shall pro-
vide lighting to give good visibility to all
working and inspection areas where the
weighing operation is carried out.
Copyright European Committee for Standardization 23
If weighing take place at wind speed If weighing take place at wind speed If weighing take place at wind speed
above 8m/s the effects of wind shall be above 11m/s the effects of wind shall above 14m/s the effects of wind shall
calculated. be calculated. be calculated.
Wind-measuring equipment shall be As ClassA. As ClassA.
10.2.3	Temperature and humidity
The acceptable range of temperature and As ClassA. As ClassA.
humidity in which the assemblies/mod-
ules may be weighed shall be within the
ranges specified for the specific weighing
equipment. Measurement uncertainty
specified in 10.3.5.4 shall be maintained.
10.3	Weighing
10.3.1	Number and timing of weighing
Major assemblies shall be weighed twice. Major assemblies shall be weighed The necessity of weighing shall be
The first weighing should be performed once. The weighing shall be per- considered depending on the as-
when the assembly is 70% to 85% com- formed immediately prior to load out. sembly criticality. However, a final
plete with respect to weight. The final weighing is recommended.
weighing shall be performed immediately
prior to load out. For simple structures,
e.g. bridges or flare booms, only the final
weighing is required.
The precise timing of each weighing As ClassA. As ClassA.
shall be subject to approval by the client
10.3.2	Weighing procedure
The contractor shall submit his proposed As ClassA. If a final weighing is performed, the
weighing procedure to the project for requirements shall be as for Class A.
approval at least two months in advance
of the planned weighing date.
The weighing procedure documentation
name of subcontract weighing
specialist, if applicable;
description of weighing equip-
ment and method;
documentation of the accuracy
of the weighing equipment;
list of spare parts readily available
for weighing equipment;
calibration authority;
samples of calibration certificates;
dimensioned sketches of the
arrangement and alignment of the as-
semblies for weighing;
expected load at each weighing
the contractors organizing of
the weighing operation.
Copyright European Committee for Standardization 25
10.3.3	Notification and witnessing of weighings
The contractor shall notify the client As ClassA. If a final weighing is performed, the
representative in writing of the planned requirements shall be as for Class A
operation 30 working days in advance.
The contractor shall notify the client of the
confirmed date, time and location of the
weighing operation at least 10 working
days in advance of the weighing operation.
The client shall decide either to witness
the weighing or to authorize the con-
tractor to perform the weighing at the
contractors own discretion.
10.3.4	Preparation of the weighing
10.3.4.1	Weighing prediction report
The contractor shall produce a preliminary As ClassA. If a final weighing is performed, the
weighing prediction report prior to the requirements shall be as for Class A
weighing operation. This report shall be
produced no later than 24h prior to the
weighing operation, with a final update
immediately prior to the weighing.
The report shall contain at least the fol-
a) total theoretical weight and CoG
for the assembly to be weighed;
b) listings with weight and CoG
summaries for all permanent items in-
cluded in the weighing;
c) listings with weight and CoG
summaries for all temporary items.
This can include, but shall not be
residual fluid content,
sea fastening,
lifting gear (rigging),
10.3.4.2	Temporaries during the weighing
Temporaries shall not exceed 10% of the Temporaries shall not exceed 10% If a final weighing is performed,
permanent weight for any intermediate of the permanent weight for any temporaries shall not exceed 10%
weighings and shall not exceed 1% of the intermediate weighings and shall of the permanent weight for any
permanent weight for the final weighing. not exceed 2% of the permanent intermediate weighings and shall
weight for the final weighing. not exceed 3% of the permanent
weight for the final weighing.
At least the following items shall be re- As ClassA. As ClassA.
moved/released from the assembly before
the final weighing, and should preferably
also be removed/released before any
intermediate weighings:
all scrap containers;
all items that are no longer re-
quired for performing contractors scope
all water, snow and ice accumu-
lations. If this is not practical, the amount
of water, snow and ice accumulations
present shall be determined and recorded
in the prediction report;
all items that cause undetermined
loads on the assembly;
all personnel not involved with
the weighing operation;
all scaffolding material not in
use during the weighing operation.
10.3.5	Weighing equipment
10.3.5.1	Load cells
The weighing system shall consist of As ClassA. If a final weighing is performed, the
electronic strain-gauge load cells. Other requirements shall be as for Class A
types of load cell may be used if approved
by the client representative.
The load cells shall be equipped with a
spherical seating, or equivalent, in order
to minimize horizontal forces and bending
moments and to reduce the uncertainty
of the coordinates for the reaction forces.
Copyright European Committee for Standardization ISO 2016 All rights reserved 27
10.3.5.2	Read-out equipment
The loads on each load cell shall be indi- As ClassA. If a final weighing is performed, the
cated on a digital display using a central requirements shall be as for Class A
Weights shall be reported with a reso-
lution of one third of the measurement
uncertainty or better, i.e. a resolution
of 1kN or better for a 600kN load cell
reading with 0,5% uncertainty.
For weighings where four or more cells
are applied, a display for remote reading
of each cell shall be used.
10.3.5.3	Jacking system
It is essential that the jacking system As ClassA. If a final weighing is performed, the
employed for the weighing operation be requirements shall be as for Class A.
able to produce uniform vertical move-
ment at all weighing points.
When the load cells are positioned adja-
cent to the jacks, the assembly shall be
lowered smoothly and uniformly on to
the load cells. This method of jacking/
weighing shall be used only for smaller
The assembly weight shall be applied
directly to the load cells, either by jack-
ing up and lowering onto the load cells
(where the load cells are adjacent to the
jacks) or by jacking the load cells up to
the assembly and then lifting (where the
load cells are on top of the jack or inside
the hollow piston of the jacks).
10.3.5.4	Accuracy of weighing system
Each individual load cell shall have a Each individual load cell shall have If a final weighing shall be performed,
measurement uncertainty within0,5%, a measurement uncertainty with- the requirements are as follows.
k=2 of rated capacity. The measurement in1,0%, k=2 of rated capacity.
Each individual load cell shall have
uncertainty shall be calculated and pre- The measurement uncertainty shall
a measurement uncertainty with-
sented by the calibration authority in be calculated and presented by the
in2,0%, k=2 of rated capacity.
accordance with ISO/IECGuide98-3, calibration authority in accordance
The measurement uncertainty shall
Uncertainty of measurement Part 3: with the Guide to the expression of
be calculated and presented by the
Guide to the expression of uncertainty in uncertainty in measurement (GUM)
calibration authority in accordance
measurement (GUM:1995) or a document or a document for determination of
with the guide to the expression of
for determination of uncertainty in force uncertainty in force measurements
measurements based on the GUM and based on the GUM and issued by a
or a document for determination of
issued by a member of International member of International Laboratory
uncertainty in force measurements
Laboratory Accreditation Cooperation Accreditation Cooperation (ILAC) or
based on the GUM and issued by a
(ILAC) or International Accreditation International Accreditation Forum,
member of International Laboratory
Forum, INC (IAF). INC (IAF).
Accreditation Cooperation (ILAC) or
The measurement uncertainty of the The measurement uncertainty of the International Accreditation Forum,
weighing system as a whole shall be weighing system as a whole shall INC (IAF).
within1,0%, k=2 of actual weighed be within2,0%, k=2, of actual
The measurement uncertainty of the
weight. The measurement uncertainty of weighed weight. The measurement
weighing system as a whole shall
the weighing result shall be calculated uncertainty of the weighing result
be within3,0%, k=2, of actual
after principles given in the GUM. shall be calculated after principles
weighed weight. The measurement
given in the GUM.
See AnnexJ for further information. uncertainty of the weighing result
See AnnexJ for further information. shall be calculated after principles
See AnnexJ for further information.
10.3.5.5	Load range
The weighing operation shall be planned As ClassA. If a final weighing is performed, the
in such a way that the load cells and requirements shall be as for Class A
jacking (lifting) equipment are operating
within 20% to 80% of the rated capacity
of the load cells as stated by the load cell
Copyright European Committee for Standardization 29
10.3.6	Calibration of weighing system
The calibration of the weighing equip- As ClassA. If a final weighing shall be performed,
ment shall be carried out by a competent the requirements shall be as fol-
laboratory that can ensure traceability lows. The calibration of the weighing
and adequate procedures, i.e. a laborato- equipment shall be carried out by a
ry that meets the requirements of ISO/ competent laboratory that can ensure
IEC17025 or is accredited by a national traceability to a national standard
accreditation body. The calibration shall and adequate procedure.
be carried out over the full range of the
capacity of equipment and documented
in the calibration certificates.
The calibration shall have been carried out The calibration shall be carried The calibration shall be carried
within six months prior to the weighing out within 12months of the date out within 18 months of the date
operation. The client representative shall of weighing. of weighing.
be notified in writing of the calibration
date and location at least two weeks in
The calibration shall be carried out in one As ClassA. If a final weighing is performed, the
of the following two ways, depending on requirements shall be as for Class A.
the output of the read-out unit:
a)	If the output on the read-out
unit is dependent on cable lengths, the
whole weighing system, i.e. the load cells,
cables, read-outs and amplifiers shall be
calibrated as one system.
b)	If the output on the read-out unit
is not dependent on the cable lengths, the
load cells shall be calibrated mechanically,
separately from the amplifiers, which
shall be calibrated electrically by using
a precision strain-gauge calibrator. Both
the calibrator and its read-out unit shall
have valid calibration certificates. Type,
serial number, accuracy of measurement,
and reference to the master load cell shall
be included on the calibration certificates.
Unless permitted by the project, calibrated As ClassA.
load cells shall not be used for any other
10.3.7	Weighing foundation and supports
The load cells and lifting equipment shall As ClassA. If a final weighing is performed, the
be positioned at approved weighing points. requirements shall be as for Class A.
The contractor shall ensure that the foun-
dations and supports are fully adequate
and stable to account for all loadings
that might occur during the weighing
10.3.8	Structural integrity
The contractor shall ensure that the weigh- As ClassA. If a final weighing is performed, the
ing causes no damage to the assembly requirements shall be as for Class A.
being weighed. This shall be documented
The contractor shall ensure that any local
strengthening at load cell support points
are undertaken prior to the weighting
10.3.9	Weighing operation
10.3.9.1	Number of lifts
Before commencing the weighing opera- As ClassA. If a final weighing is performed, the
tion, a test weighing shall be performed. requirements shall be as for Class A.
For each weighing operation, a minimum
of three lifts/weighings/readings are
required. A fourth and any subsequent
weighings may be carried out at the
discretion of the client representative.
Following each lift/weighing, when read- Following each lift, when readings If a final weighing is performed, the
ings have been noted and witnessed, the have been noted and witnessed, requirements shall be as for Class B.
load cells shall be completely unloaded, the load cells shall be completely
the reading and display reset to zero for unloaded, the reading and display
the next lift. reset to zero.
The fourth and any subsequent lifts/ As ClassA. If a final weighing is performed, the
weighings shall be performed if one of requirements shall be as for Class A.
the following problems has arisen:
In these cases, the contractor shall make
provision to replace the load cells or
interchange their positions if requested
--`,,,`,``,`,```,,,,``,
Copyright European Committee for Standardization 31
10.3.9.2	Readings of load cells and level criteria
The assembly shall be lifted clear of all As ClassA. If a final weighing is performed, the
supports with a minimum air gap of 3mm. requirements shall be as for Class A.
An acceptable load distribution shall
be maintained during the weighing op-
eration. The load cell readings shall be
taken simultaneously after the readings
have stabilized, level checked and wind
speeds taken.
After the load has been removed from the
load cells, any residual weights shown
on display units shall be recorded and
the weight result amended accordingly.
In the event of the residual amount being
excessive, the equipment shall be checked
and previous results shall be disregarded
10.3.9.3	Consistency of results
Discounting clearly inconsistent or er- Discounting clearly inconsistent or Discounting clearly inconsistent or
roneous results, the total weight of an erroneous results, the total weight erroneous results, the total weight
assembly as measured for each of the of an assembly as measured for each of an assembly as measured for each
lifts shall not vary from the average of of the lifts shall not vary from the of the lifts shall not vary from the
the total weight by more than 0,5%. average of the total weight by more average of the total weight by more
than 1,0%. than 2,0%.
The contractor may be required to perform
the weighing again if the requirements
in general are not met.
The contractor shall ensure that results As ClassA. If a final weighing is performed, the
are satisfactory to the client representative requirements shall be as for Class A.
before demobilizing the weighing system.
10.3.10	CoG calculations
The final CoG shall be calculated as an As ClassA. If a final weighing is performed, the
average, using the results from each requirements shall be as for Class A.
The datum lines utilized for the calcu-
lations of the CoG locations shall be as
agreed with the project management.
10.3.11	Weighing certificate
The results of the weighing operation shall As ClassA. If a final weighing is performed, the
be presented on a weighing certificate, requirements shall be as for Class A.
and signed by the weighing contractor,
contractor and client representative.
An example weighing certificate is given
in AnnexB. The weighing certificate shall
time, date and location of weighing;
dimensional sketch of load cell
recorded total weight and CoG
for the weighed assembly;
reference to the global coordinate
system for the weighed assembly;
identification of weighing equip-
ment and calibration.
10.3.12	Weighing report
Within seven days of the weighing, the As ClassA. If a final weighing is performed, the
contractor shall submit a report of the requirements shall be as for Class A.
weighing operation. The weighing report
weighing results;
final weighing correction;
calculations of CoG;
weighing contractor;
weather conditions incl. wind
client witness;
calibration certificates of weigh-
weighing certificate (fully signed);
list and summary of temporary
construction items (including their weight
and CoG);
detailed list of installed items;
final prediction report;
any deviation from the approved
Copyright European Committee for Standardization 33
11	Requirements for as-built weight documentation
a)	An electronic copy of the weight As ClassA. a)	An electronic copy of the
database containing a complete set of de- weight data, containing a complete
signed quantities, including unit weights, set of weights with CoG and specified
CoG and specified attribute information attribute information and descrip-
and descriptions, shall be provided. tions, shall be provided.
If a 3D model is applied for the project,
the quantities within the weight database
shall be consistent with those in the model
with corrections for non-modelled items.
The database fields, their format as
well as the coding, shall be in accordance
with contractual requirements.
b)	A detailed hard-copy weight b)	A detailed hard-copy b)	No specific hard-copy as-
dossier which includes weight dossier which includes built weight dossier is required.
Thus, the as-built documenta-
an as-built weight and CoG an as-built weight and
tion shall include
report, CoG report,
the latest weight and CoG
an as-built weight item list, an as-built weight item
an as-built master equip-
the latest weight item list.
ment list (MEL), an as-built MEL.
tag-mark drawings corre-
lating to the electronic database (if
In order to provide the level of docu- As ClassA. Not required.
mentation required, a thorough weight
control activity shall be maintained by
Weight data sheets Tagged equipment
Copyright European Committee for Standardization 35
Weighing certificates
B.1	Equipment and bulks weighing certificate
Copyright European Committee for Standardization ISO 2016 All rights reserved 37
B.2	Major assembly weighing certificate
Copyright European Committee for Standardization 39
A dimensional sketch showing the load cell positions, reference to the global coordinate system and
wind direction shall be attached to this certificate.
Weight and load budget (WLB) formats and levels
TableC.1 Topsides operating weight budget
Area Platform area Weight Contrac- Client Content Live, Total Centre of gravity
code estimate tor weight weight weight hook weight
reserve reserve and set
(Unit: ) (Unit: ) (Unit: ) (Unit: ) (Unit: ) (Unit: )
A Utilities area
B Mud module
C Derrick substr./
D Flare boom
E Living quarters
F Process deck 1
G Process deck 3,
4, 5 and pipe-
H Well bay
I Hook-up
CoG-envelope: East:..... m
North:..... m
Elevation:..... m
Copyright European Committee for Standardization 41
Major elements of the weight displacement
FigureD.1 Weight displacement summary, design operating condition
Supplier weighing procedure
Copyright European Committee for Standardization ISO 2016 All rights reserved 43
Guidelines for displacement measurement of floaters
F.1.1	Procedure for displacement measurement
This part of ISO19901 gives guidelines for the minimum requirements for a displacement measurement
in order to provide reliable and accurate results for weight control purposes. When formal inclining
experiments are performed, the individual requirements from the classification society in question
Data obtained from the lightweight survey and inclining experiment applied for safety reasons by the
classification society can be used by the weight discipline provided certain requirements are fulfilled.
This method gives a lower degree of accuracy as compared with weighing using load cells.
The contractor should prepare a displacement measurement procedure incorporating the classification
society requirements in question. The contractors procedure should be made available to the client
representative at least one month in advance of the planned displacement measurement date.
F.1.2	Displacement measurement subcontractor
The displacement measurement should be conducted by the contractor and/or classification society in
question. Both the client representative and the contractor should be present during the measurement.
F.2	Environmental conditions for displacement measurement
The following requirements should be implemented:
a)	a sheltered location should be found in which the measurement can be carried out;
b)	sufficient time, approximately 12h, should be allowed for the measurement operation;
c)	good weather should be forecast;
d)	the wind speed should be below 5m/s;
e)	there should be no significant swell;
f)	the maximum wave height should be 1,0m and there should be no substantial current;
g)	the floating structure should be free-floating;
h)	time and location should be indicated, as well as water depth.
F.3	Displacement measurement
F.3.1	Displacement measurement procedure
The contractor should submit his proposed displacement measurement procedure for approval at least
one month in advance of the planned measurement date.
Copyright European Committee for Standardization ISO 2016 All rights reserved 45
The displacement measurement procedure should cover at least the following subjects:
description of equipment and method;
assessment of measurement accuracy;
dimensional sketches of the measurement arrangement;
contractors organization of the measurement operation.
F.3.2	Notification
The client representative should be notified in writing of planned displacement measurement dates
15working days in advance.
F.3.3	Preparation of the displacement measurement
F.3.3.1	Displacement measurement prediction report
The contractor should make a preliminary displacement measurement prediction report prior to
the measurement. This report should be presented to the project no later than 24 h prior to the
measurement operation with a final update immediately prior to the displacement measurement.
The report should contain at least the following information:
total theoretical weight and CoG for the assembly to be measured;
expected draught on the measurement locations on both sides aft, forward and midships;
NOTE	For semi-submersibles, the measured draught in the measurement locations should be at all columns.
listings with weight and CoG summaries for all items included in the measurement;
general arrangement plan as-carried-out;
draught-mark position survey;
listing of weight of liquids in tanks, including CoG;
listing of permanent items temporarily located;
listing and summation of all temporary items including CoG, including any ballast and consumables.
F.3.3.2	Temporaries and foreign forces
anchors should be raked and the floating structure, if necessary, assisted by tugs;
floating structure should be free-floating;
the minimum number of personnel should be on board during test;
no fresh water should be consumed or produced during the measurement operation;
the minimum number of cables and hoses, etc. should be connected; those hoses which are connected
should be slack.
F.3.4	Equipment for displacement measurement
Any equipment directly affecting readout of measurement results should be calibrated and have a
known measurement uncertainty. This includes the following:
hydrometers (densitometers) for measuring specific gravity of the water in which the floating
structure is floating;
thermometer for measuring seawater temperature;
steel measuring tape or similar for checking draught marks and draught measurements;
throttled transparent plastic tube or other suitable water-level measuring device for draught
equipment for measuring wind velocity.
F.3.5	Displacement measurement operation
If an adequate draught-mark position survey is not available, the draught marks should be checked by
measuring against a known datum level on the vessel.
Two sets of draught measurements should be executed at a minimum of six locations in sequence. A
third set and any subsequent draught measurement sets may be needed if one of the following problems
inconsistent draught measurements;
The draught measurements are considered consistent if the total displacement based on each set of
draught measurements does not vary from the average by more than 0,5% and the horizontal shift in
CoG is less than 0,3% of the floating structures dimension in the same direction. In case of inconsistent
draught results, efforts should be made to identify any activity on board that might have caused
movement of significant weights.
F.3.6	Displacement measurement certificate
The displacement measurement result should be presented on a displacement measurement certificate,
and signed by a representative from the measurement contractor, contractor and client representative.
The displacement measurement certificate should contain at least the following information:
floating structure identification
time, date and location of measurement;
temperature, wind speed and wind direction;
water depth and estimated wave height;
dimensional sketch of draught measurement locations;
draught readings and time at which they were taken;
specific gravity of water in which the floating structure is floating;
recorded total weight and CoG for the measured assembly;
reference to the global coordinate system for the measured assembly;
identification of displacement measurement equipment used.
Copyright European Committee for Standardization ISO 2016 All rights reserved 47
F.3.7	Displacement measurement report
Within seven days of the displacement measurement operation, the contractor should submit a report
of the measurement operation, which should include:
calculation of CoG;
displacement measurement certificate (fully signed);
assessment of the accuracy of measurement results.
Requirements for weight control during operations
G.1	Foreword
AnnexG is a precursor for some of the topics that are proposed to be included in the next revision of
ISO19901-5.
Some of this informative information may tend to conflict with present normative text given elsewhere.
However, these topics will be further discussed in the next edition and the informative may become the
normative, if proposals to expand the scope of this part of ISO19901-5 are accepted.
Once finalised, caveats will be added to this part of ISO 19901-5 where necessary to clarify the
coincident operating loads on different types of facilities e.g. oil and gas producing, gas producing, not
normally manned, drilling and work over by jack-up rigs, floaters.
G.2	Weight control during platform operational life
G.2.1	General requirements
The dry and operating weight and centre of gravity (CoG) of an offshore installation shall be controlled
throughout its operational life. The output from a topside weight database shall be the prime document
used by client structural engineers and Structural Integrity Management (SIM) engineers when
conducting assessment or re-analyses of structures.
Regular assessment and re-analysis ensures local and global design parameters are not exceeded by
the weight impact of the numerous projects and modifications a facility undergoes in its operational
lifetime (often in excess of 2000).
The dry and operating weight and CoG data stored in a facilitys weight database may also be used for
the following operational phase activities:
provision of weight and CoG of equipment to assist deck crew with offshore movements and --`,,,`,``,`,```,,,,``,,`,,``,``-`-`,,`,,`,`,,`---
change-outs;
provision of weight and CoG data for future decommissioning of the installation;
provision of weight and CoG data for presentation to verification bodies and certifying authorities.
A high degree of confidence in the accuracy of a facilitys topside operating weight and CoG is required;
otherwise proposed load factors in ISO19902, Petroleum and natural gas industries Fixed steel
offshore structures and ISO19901-9, Petroleum and natural gas industries - Specific requirements for
offshore structures Part 9: Structural integrity management, become inadequate. It is therefore critical
that weight databases used in SIM models have:
the complete topsides dry and operating weight, with drilling modules and in-line drilling equipment
no significant dry and operating weight or CoG errors;
no significant omissions;
no consistent un-conservatism in the weight estimate of the items;
Copyright European Committee for Standardization 49
no consistent conservatism in the weight estimate of the items (for brownfield project viability);
no operating practices on the platform that lead to significantly higher loads than those reported in
the weight database.
ISO19902:2007, A.9.1, states The partial action factors provided in Clause9 are intended to cover
variations in the intensity of direct actions from the specified representative values and as far as appropriate
the uncertainties in predicting internal forces.
Put another way, the load factors in ISO19902 do not allow for any significant weight errors, or weight
omissions (often referred to as known unknowns, and unknown unknowns).
Recent studies show that in the past, a number of operating weights and drilling loads have been
omitted from topside weight databases, and hence the SIM models.
To ensure these types of omissions do not recur, it is proposed that ISO 19901-5 includes a common
operating philosophy with a prescriptive list of coincident operating weights that regularly occur on a
facility. These shall then be included in topside weight databases and linked to the G1, G2, Q1, Q2 Load
Factors listed in ISO19902, to forge a link between these ISO standards.
The above measures will help prevent the selective weight reporting and SIM modelling that has been
found in some quarters.
Given the above focus on the accuracy of topside operating weight, it is interesting to note the results of
a recent academic study of 10 UK sector platform weight databases. The sample included:
a range of ages;
a range of operators;
a range of design contractors;
a span of topside operating weights.
After applying the proposed common operating philosophy to each platform, the total platform
operating weights increased by an average of 14% with a CoG movement approaching 1,0m. If these
study findings prove typical, a concerted effort will be required to undertake weight health check audits
to correct the c. 8000 offshore platforms installed globally, and ensure SIM models are not deficient.
Weight update and SIM download
Discussions with ISO 19901-9 SIM committee show their preferred way forward is to have weight
databases automatically downloaded into SIM models in future. This will require the weight database
to be constantly updated throughout the platform lifecycle, as it will become the primary document
for updating SIM models. It is understood that discussions with leading structural integrity software
suppliers are well advanced to enable this.
G.2.2	Operational phase weight control procedure
An operational phase weight control procedure shall be produced that clearly defines the roles and
responsibilities of the client; the modification design contractor; the SIM engineers; and the weight
database custodian. It should include a simple weight control flow diagram showing implementation of
a modification and its weight change from inception; to weight database update; to SIM model update;
and final close-out.
Weight and CoG changes resulting from modifications undertaken during the operational phase shall
be recorded on weight control input sheets to be completed by the design contractor. These must be
included in design work packs, and issued to the weight database custodian for review and input.
Weight database custodian
The topside weight database shall be maintained by the appointed weight database custodian, and
kept regularly updated with all weight and CoG changes and modifications i.e. additions, relocations
and removals. The custodian shall check to ensure the topside weight database includes all coincident
drilling, laydown and operating loads, as shown in the common operating philosophy below.
The custodian shall keep the client and structural integrity management engineers regularly
informed of all proposed weight and CoG changes. In addition, the custodian should issue an annual
weight report to the client and SIM engineers for presentation to certifying authorities as part of
the inspection regime.
It is important that structural SIM models and topside weight databases are kept fully synchronised.
To ensure this, one of the primary SIM model load cases shall exactly mirror the dry and operating
weights and centre of gravity in the topside weight database.
G.2.3	References to operational weight control and SIM in other ISO standards
ISO19902, Petroleum and natural gas industries Fixed steel offshore structures
An up-to-date topside weight database is required in order to check whether the magnitude of weights
and CoG changes have triggered the need for a SIM reassessment of the facility in accordance with
ISO19902:2007, Clause24. A SIM system is recommended in ISO19902:2007, 23.1.
ISO19904 (all parts), Petroleum and natural gas industries Floating offshore structures
ISO19904-1:2006, 5.5.4 and 5.5.7 contain requirements for the update of the weight database for the
structures operational life.
ISO19901-9, Petroleum and natural gas industries - Specific requirements for offshore structures
Weight control during a facilitys operational life will also be addressed in ISO19901-9.
G.3	Coincident operating weights
G.3.1	Common topside operating philosophy
All topside weight databases shall adopt a common topside operating philosophy as stated below.
The topside weight database shall comprise an inventory of the dry and operating weight and CoG
of each component broken down by module and discipline. When summarized, these shall reflect a
snapshot impression of the maximum topside operating weight and CoG that may be experienced under
normal operational drilling conditions.
Movable items shall be located in logically fixed locations e.g. cranes in parked position, forklift in sack
store, drilling derrick, substructure and skid base located over a corner drill slot, etc.
The maximum in-place operating condition shall be a summation of the dry weights, plus operating
increases from men, equipment, bulks, fluids, powders, laydown areas, storage areas, setback area, and
fully laden pipe rack applied simultaneously.
Copyright European Committee for Standardization 51
The topside weight database shall not attempt to reflect the worst topside load case, as this requires
the application of a number of variable factors and environmental forces to be added to the SIM model
by the structural engineer e.g.
stuck casing (hook load),
drilling modules and moveable items in most onerous location,
worst combination of environmental forces,
worst combination of hydrotest,
ice and snow accretion.
Likewise, transient live loads shall be omitted, as they will already be taken account of elsewhere i.e.
men and luggage located in the accommodation module, and transient loads located on laydown and
The maximum topside operating weight occurs when coincident maximums of mud, brine, powders,
drill string, and the 9 5/8 casing are on board for drilling the longest well. At this time all laydown and
storage areas are commonly coincidentally full, and shall be reflected as such.
NOTE	A fact often overlooked is that the longest well (and maximum topside operating weight) may occur
early in a platform life cycle. Studies show the operating philosophy and drilling matrix are often not updated.
Hence, neither is the topside weight database, nor the structural SIM model. Failure to update these documents
can jeopardize viable brownfield re-development proposals if the engineering is based on out-of-date drilling
load combinations that cannot recur.
G.3.2	Common operating philosophy assumptions
The common operating philosophy reflects a common condition when operational drilling is underway.
The topside operating assumptions for a manned, operational drilling oil and gas facility are listed below.
Fully outfitted drilling substructure, derrick, skid base, and pipe bridge/cat walk shall be
positioned over a well slot most onerous to the structural design (corner slot). These drilling
modules should be reported separately, so they can be re-located over any well slot if required.
Moveable equipment such as hoists, gantry cranes, and forklift trucks shall be reflected in
mid-range of normal operating locations. These are assumed unladen as transient loads are
reflected on laydown and storage areas.
Pipe rack (longest 9 5/8 casing load + 5 % rejects), plus containers shall be assumed full.
Approximately 80% of hole length is normally cased with 9 5/8 casing. Refer to the Drilling
Setback area shall be assumed full (drill string + 5% rejects with Bottom Hole Assembly for
longest hole to be drilled). Refer to the Drilling Operations manual.
Hook load shall be zero (drill string and casing cannot be in two places at once).
Drill water and brine tanks shall be assumed full.
Active and reserve mud tanks shall be assumed full. Once drilling has commenced, and LP and
HP piping and equipment are operationally full, the mud tanks are usually topped up.
Trip tank shall be assumed full.
Mud gutters shall be assumed full.
Mud in shakers and mud cleaning systems shall be assumed full.
Cuttings cleaning systems shall be assumed full.
Cuttings re-injections system shall be assumed full.
Poorboy degasser shall be assumed full.
Drilling line reel shall be assumed full.
Powder tanks (P-tanks) shall be full with worst case combination of powders and densities.
P-tanks shall be full of aerated powder (not settled contents).
Sack store shall be assumed full.
Drilling risers and Christmas trees are supported directly from the seabed, and shall not be
Vessel trains including sand accumulation, plus oil and water shall be assumed full to normal
Caissons supported from the topside structure shall be included.
Diesel tanks shall be assumed full.
Main water tanks shall be assumed full.
Potable water tank shall be assumed full.
Chemical injection tanks shall be assumed full.
Laydown and storage: all areas shall be assumed coincidentally full (single stacked containers).
Stairs, walkways, escape routes and other free areas shall be unladen i.e. live loads shall not be
Platform cranes shall be assumed unladen in parked position as laydown areas are full.
Forklifts shall be assumed unladen as laydown areas are full.
All personnel and baggage shall be assumed located in living quarters: POB0,20 tonnes per man.
Fridges, freezers, stores and laundry shall be assumed full.
Vegetable and cold stores shall be assumed full.
Single helicopter (maximum take-off weight) shall be assumed on helideck.
Lifeboats shall be unladen as men are in accommodation module.
Wet process piping plus HP/LP drilling piping shall be assumed coincidentally full.
Copyright European Committee for Standardization ISO 2016 All rights reserved 53
Dry gas and air piping shall be assumed empty.
Foam systems shall be assumed full.
Scaffolding and paint store
Scaffold and paint stores shall be assumed full.
Operational scaffold shall be assumed deployed (there is normally 250 to 350 tonnes of scaffold
on a 15000 tonne operating topsides).
G.3.3	Coincident operating loads
The table below shows the coincident operating increases that shall be included in a topside weight
database for a typical manned oil and gas producing installation with a single drilling rig facility.
I S O 19 9 0 2: 20 0 7
Coincident operating loads (G1 and G2) and
Variable actions (Q1
and Q2)
Setback load (for longest hole including Bottom Hole Assembly +5% rejects) Q1
Pipe rack load (9 5/8 casing string for longest hole, +5% rejects) Q1
Containers on pipe rack (normally 100 to 200 tonnes) Q1
Loose drill floor tools (normally 10 tonnes) G1
P-tank powder storage for cement, bentonite, and baryte (full - aerated) Q1
Sack store (full) Q1
Mud in tankage (active and reserve tanks full) Q1
Drill water in brine tanks (full) Q1
Completions fluid storage (full) Q1
Mud in cuttings cleaning system (full) Q1
Cutting slurry in cuttings reinjection system (full) Q1
Mud in shakers and mud cleaning system (full) Q1
Mud in Poorboy degasser Q1
Mud in Trip tank Q1
Schlumberger wireline and tools in tool house (full) G1
Laydown and storage areas all areas coincidentally full (single stacked containers) Q1
Platform stores and spares (full) Q1
Tote tank and IBC areas (full) Q1
Diesel in storage tanks and day tanks Q1
Potable water in storage tanks Q1
Fluids in topside Equipment including Process separators, Test separator and KO drum full
to normal operational levels (including sand accumulation)
Water in Coolers and Radiators (full) Q1
Fluids in Degassers Q1
Water in Fire pumps Q1
Chemicals in injection package Q1
AFFF in storage tanks Q1
Methanol in methanol system Q1
Fluids in deluge system Q1
Hydraulic fluids in Power Packs and accumulators Q1
Water in seawater system Q1
Water in firewater system Q1
Fluids in process piping and valves Q1
Water in potable water system Q1
Water in produced water system Q1
Equipment inventory including gearbox fluids, lube oil, etc. G1
Platform cranes shall be assumed unladen in parked position as laydown areas are full Zero
Forklifts shall be assumed unladen as laydown areas are full Zero
Men and luggage (POB x 0.2te/man) located in Accommodation module(s) Q1
Lifeboats shall be unladen as men are in Accommodation module Zero
Contents of fridges, freezers and veg dry stores Q1
Helicopter (max take-off weight) Q1
Galley fluids and black drains Q1
Sewage in macerator Q1
Scaffold stores shall be assumed full
Operational scaffold shall be assumed to be deployed (there is normally 250 to 350 tonnes Q1
of scaffold on a 15,000 tonne operating topsides)
TRANSIENT LIVE LOADS
Transient live loads shall be omitted, as they will already be taken account of elsewhere
i.e. men and luggage located in Accommodation module and containers on laydown and Zero
Bridge reaction (if applicable) G1 + Q1
G.3.4	How weight database dry and operating weights interface with ISO19902:2007
permanent actions (G1 and G2) and variable actions (Q1 and Q2)
9.2.1 Permanent action G1 (dry weight)
G1 is the action imposed on the structure by the self-weight of the structure with associated equipment
and other objects. G1 includes the following:
a)	weight of the structure in air, including, where appropriate, the weight of piles, grout, and solid
b)	weight of equipment and other objects permanently mounted on the structure that do not change
with the mode of operation;
c)	hydrostatic actions acting on the structure below the waterline, including internal and external
pressure, and resulting buoyancy (not applicable to topside weight database items);
--`,,,`,``,`,```,,,,``,,`,,``
Copyright European Committee for Standardization ISO 2016 All rights reserved 55
d)	the weight of water enclosed in the structure, whether permanently installed or temporary ballast
(not applicable to topside weight database items).
The representative value of G1 is the value computed from nominal dimensions and mean values of
9.2.2 Permanent action G2 (dry weight)
G2 is the action imposed on the structure by the self-weight of equipment and other objects that remain
constant for long periods of time, but which can change from one mode of operation to another or
during a mode of operation. G2 includes the following:
a)	weight of drilling and production equipment that can be added to or removed from the structure;
b)	weight of living quarters, heliport and other life-support equipment, diving equipment, and utilities
equipment, which can be added to or removed from the structure.
The representative value of G2 is the estimated lift weight of the object plus any field installed
9.2.3 Variable action Q1 (operating weight)
Q1 is the action imposed on the structure by the weight of consumable supplies and fluids in pipes,
tanks and stores, the weight of transportable vessels and containers used for delivering supplies, and
the weight of personnel and their personal effects.
Where appropriate, the weight of marine fouling and ice shall be included in Q1 (not applicable to
topside weight database items).
The weight of scaffolding or other temporary access systems used during operations and maintenance
of the platform shall also be included in Q1.
The representative value of Q1 is computed from the nominal weight of the heaviest material and the
largest personnel capacity under the mode of operation considered (typically mud and powder weights).
9.2.4 Variable action Q2 (not applicable to weight database items)
Q2 is the short duration action imposed on the structure from operations, such as lifting of drill string,
lifting by cranes, machine operations, vessel mooring, and helicopters. The additional weight of liquids
used for testing of vessels and pipes is also included in Q2. The representative value of Q2 is computed
from the rated maximum capacity of the equipment involved and includes dynamic and impact effects.
9.10-1 Table of partial action factors for in-place situations
SIM engineers must check that G1, G2, Q1 and Q2 are the maximum values for each mode of operation.
G.4	Allocation of design allowances and reserves
G.4.1	Suggested design allowances
A design allowance is an overall allowance added to a dry weight to account for uncertainties. The
following tables show the suggested range of design allowances to be applied to dry weights of different
disciplines at the various stages of design development.
It comprises a summation of the following three elements:
Item accuracy allowance
An allowance to account for inaccuracies in estimates, Weight take-off and vendor data that
experience shows will be used during normal design development. It is dependent on assessed
quality of available data - not project phase.
Design change allowance
An allowance to account for weight changes that experience shows will be used during normal
An allowance to account for fabrication tolerances and changes that experience shows will be used
from material substitutions, site run materials, and site queries.
An additional allowance of operating weight expressed as an overall tonnage that is reserved over
and above the management reserve to account for additional items added to a platform during its
operational life. These would typically include the following.
Minor modifications. History shows most platforms will have more than 2 000 in a 30-year
operational lifetime. These can amount to increases in excess of 1000 tonnes operating.
Major projects (increases in power generation, produced water capability, tie-ins to new wells and
Additional laydown and storage.
An additional allowance of operating weight expressed as an overall tonnage that shall be reserved
over and above the factored operating weights to account for any changes made to original contract
requirements by the client. The management reserve shall be released as appropriate by the project
Weight Review Panel, or similar body.
Design allowances P r e l i m i n a r y Catalogue or prelimi- Vendor weight Final ven- W e i g h e d
estimate nary vendor estimate (or from previous dor weight weight
Item accuracy 5%7% 5%7% 2%5% 2% 0%
Design change 5% 2% 0% 0% 0%
Fabrication 5% 5% 2% 2% 0%2%
Total allowance 15%17% 12%14% 4%7% 4% 0%2%
Copyright European Committee for Standardization 57
Discipline bulks
Preliminar y Intermediate Weig hed
Design allowances Preliminary MTO Final MTO
estimate MTO weight
Design change 5% 2% 2% 0% 0%
Fabrication 5% 5% 2%5% 2%5% 0%2%
Total allowance 15%17% 12%14% 6%12% 4%7% 0%2%
Preliminary es- P r e l i m i n a r y I n t e r m e d i a t e Weig hed
Design allowances Final MTO
timate MTO MTO weight
Item accuracy 5% 3% 2% 0% 0%
15% 10% 4%7% 2%5% 0%2%
Item accuracy 10% 5% 2% 0% 0%
Design change 5% 5% 3% 0% 0%
Fabrication 5% 5% 5% 2%5% 0%2%
20% 15% 10% 2%5% 0%2%
Item accuracy 0% 0% 0% 0% 0%
Design change 0% 0% 0% 0% 0%
Deck plate and grating
5% 5% 2%5% 2% 0%2%
Structural steelwork typically represents between 40 % and 55 % of a modules dry weight, and
rationalization of the allowances applied to each category (Primary, Secondary, Plate) can produce
Primary steelwork is usually reasonably well defined at an early stage of a project. A preliminary
structural analysis is normally undertaken during the conceptual design to confirm member sizes. As
such, lesser individual allowances are justified.
Secondary steelwork is by its nature less well defined and is usually subject to change throughout
FEED and detailed design due to revisions made by upstream disciplines. As such, higher individual
allowances are recommended.
Deck plate and grating usually contributes a high proportion of structural dry weight. However, once
the area of deck to be plated has been defined and the plate thickness selected, it is normally only
subject to weight change in respect of openings and cut-outs for penetrations. Consequently, only the
Fabrication allowance is justified.
Guidance on design allowances
Some of the individual design allowances shown above have been given an upper and lower value i.e.
10% to 15%. The value that shall be used is dependent upon:
demonstrated accuracy of weight data previously provided by the design contractor;
demonstrated accuracy of final weights achieved on previous projects.
Design allowances applied to individual items of weight shall not be dependent upon project phase,
drawing, or data sheet revision. Rather, they shall be dependent upon the datas demonstrable accuracy
at any given time. This principle gives flexibility to setting of design allowances, produces lower factors,
and optimises the platform load carrying capacity at an early stage. It prevents weight conscious
designs from being penalised and ensures that full utilization of the available topsides weight capacity
is made at the earliest stages of design development.
It is important that the design allowance is understood to be a measure of accuracy of the base dry
weight of an item, and not an allowance for omissions. The weight allowance should generally only
be applied to the base dry weight of each item, not the contents, as all operating increases should be
accurately defined early in the detailed design of a project.
Guidance on miscellaneous operating loads
By the start of detailed design the following operating increases should have a design allowance of zero
(0%), as these values should be accurately known.
Pipe rack load (9 5/8 casing string + 5% rejects) maximum depth of hole to be drilled will be
known, and the weight of the 9 5/8 casing string can be accurately calculated. Refer to the Drilling
Setback load (drill string + 5% rejects) maximum depth of hole to be drilled will be known, and
the weight of the drill string can be accurately calculated. Refer to the Drilling Operations manual.
Laydown and helicopter (maximum take-off weight) helicopter weight will be known.
Fluids and powders in tanks and vessels (normal operating levels) tank and equipment process
data sheets should be available.
Paint and weld added as a percentage of dry weight.
Slings and shackles added as a percentage of lift weight.
Environmental loads, e.g. wind, snow and ice accretion, should not be included in a topside weight
database. They should be calculated and applied separately to the SI analysis by structural engineers.
Likewise, local design live loads should not appear in a topside weight database, as these are
transient and accounted for elsewhere, i.e. on laydown and storage areas, and in the living quarters.
A drilling load combination matrix should be included in the weight report. One is attached below
Guidance on CAD
There have been widely experienced problems with weight and CoG and extraction from CAD systems
in the past. It should be remembered that if it is not modelled, the weight and CoG will not be calculated,
e.g. stiffeners, handrail, drain boxes, piping specials, and separate manual weight estimates must be
included for non-modelled items, while bearing in mind the status of the model.
Copyright European Committee for Standardization ISO 2016 All rights reserved 59
G.4.2	Allocation of topside allowances and reserves
FigureG.1 Allocation of topside allowances and reserves diagram
G.5	Drilling load matrix
See G.3.3 for coincident loads to be reflected in the topside weight database.
Drilling load and operating load combinations
Full 9 casing on Full 9 casing on
pipe rack pipe rack Stuck casing Stuck drill string
Storm Operating
Hook load (rated capacity of the derrick.
not listed in weight report applied by SI Zero Zero Xd Xd
Setback load (for longest hole including
X acg X ac X ac Zero f
Bottom Hole Assembly +5% rejects)
Pipe rack load (9 5/8 casing string for longest
Xa Xa Xe Xa
hole, +5% rejects)
Containers on pipe rack coincident with 9
5/8 casing load (normally 100 to 200 tonnes)
P-tank powder storage for cement, bentonite,
and baryte (full- aerated)
Extreme wind (not listed in topside weight
database applied by SI engineer)
Operating wind (not listed in topside weight
Snow and Ice accretion (not listed in topside
weight database applied by SI engineer)
Drill Water tanks (full) Xa Xa Xa Xa
Sack store (full) Xa Xa Xa Xa
Active and reserve mud tanks (HP and LP
systems full)
NOTE 1	All other operating loads will be 100% of those reported in the topside weight database.
NOTE 2	Attempts to rationalize drilling loads should be avoided, as these are common conditions.
NOTE 3	Full to normal operating level switches as shown on P&IDs.
NOTE 4	100% full of the normal operating fluid flowing through it.
a	100% of reported weight database loads
b	100% of reported weight database load for supply containers and fixed containers e.g. tea shack, tool house, paint store, laboratory.
c	Setback load represents the drill string for longest hole plus 5% rejects, plus Bottom Hole Assembly. It is stacked in 90 stands
(triples).
d	The hook load for a typical derrick rating i.e. 1000000 lbs.=454 te.
e	Calculated for a full load of 9 casing (approx. 80% of hole length) plus 5% rejects for the longest well. It is assumed 50% of
casing, plus supply and fixed containers remain on the pipe rack, while the remainder of the casing is hanging on the hook.
f	Assumed zero, as the drill string will be hanging on the hook.
g	If sufficient warning is received for an approaching 100-year return storm, it is possible the drill string in the setback area may
be run down the hole to reduce wind load profile.
h	These loads should not be listed in the weight database. They must be calculated and applied by the Structural Integrity engineer.
G.6	Laydown and storage
G.6.1	General
Topside weight reports shall include laydown and storage drawings for each deck level. The drawings
shall include tabulated values for maximum global load, maximum local and concentrated load, and
area in m2. These values shall be consistent with the operating loads shown in the topside weight
database. Permanent containerised offices, tea shacks, and stores shall not form part of the laydown
storage loads. They shall be separately itemised, and reported in the weight database as such.
G.6.2	Signage
Laydown and storage drawings shall form the basis of the platform signage to be displayed at these
areas offshore (see Figure G.2).
FigureG.2 Example of laydown and storage drawing
G.7	Accuracy of weighing predictions
G.7.1	General
The accuracy of a module or assembly weighing result compared with its pre-weighing prediction
should be within the following tolerances:
The accuracy of the pre-weighing weight prediction shall be within the following tolerances:
Preliminary weighing 3% of prediction
Intermediate weighing 2% of prediction
Final weighing 1% of prediction
Predicted CoG
The accuracy of a module CoG prediction shall be expected to fall within the following percentages of
its length and breadth (measured centre to centre of trusses or legs):
Weighing East North
Preliminary weighing 0,75% 0,75%
Intermediate weighing 0,50% 0,50%
Final weighing 0,50% 0,50%
Example for final weighing of module 20,000m long10,000m wide
The longitudinal CoG should be within 20,000m0,005% =100mm
The lateral CoG should be within 10,000m0,005% =50mm
G.7.2	Post weighing reconciliation
Any predicted values that fall outside the above weight and CoG accuracy ranges shall result in the
design contractor undertaking a post-weighing reconciliation of the pre-weighing predictions. This
shall begin immediately on completion of the weighing, and continue until the inaccuracies can be
sufficiently explained and resolved to the client representatives satisfaction.
Once the post-weighing reconciliations have been satisfactorily concluded, the necessary weight
and CoG corrections shall be added to the weight database in a separate discipline named weighing
G.8	Competence
Broadly defined, competence is the combination of the qualifications, understanding, experience and
skills needed by an engineer to be effective in their job.
The weight control process involves data gathering from many sources, including discipline weight
input from the main contractor, the drilling contractor, the accommodation contractor and equipment
vendors (see G.9). Generally, one individual does not have the time, background or skills to single-
handedly manage the whole process. Usually, a team of people, with the requisite skills and background,
is needed to implement an effective weight control facility. The engineer (or group of engineers)
involved in the process should be:
familiar with weight control principles and procedures;
knowledgeable about multi-discipline weights;
knowledgeable about CAD extractions and downloads;
familiar with drilling techniques and loads;
familiar with laydown and storage requirements;
familiar with equipment and module weighing requirements;
cognisant of requirements for difference design phases;
familiar with weight control requirements of offshore structural engineers.
Further description of competencies for each aspect of the weight control process is provided elsewhere.
Copyright European Committee for Standardization 63
G.9	Weight control information sources and flow diagram
FigureG.3 Flow diagram of information sources
Requirements for topside weight estimation New builds/
H.1	General
Topside weight estimation is an important activity in early phase concept development for new
offshore installations. Estimated weights for topside units are important input and basis for a number
1)	weight information is one of the main input parameters for cost estimating and planning;
2)	weight information is vital for transportation, lifting and installation analyses;
3)	weight information is vital for analysis of substructure capacity;
4)	weight information is vital for stability analysis, loading conditions and platform operations.
The objective for weight estimation is to predict, from an early stage in concept development, a topside
weight as close to the final as-built weight as possible.
This annex describes weight estimation activities to take place in the early phase development of a
project, covering screening/feasibility phase, concept selection phase and FEED phase prior to the
detail engineering and construction phase.
H.2	Topside weight estimation methodology
All estimated weights shall be given as values covering both the identified elements, as well as the
anticipated, but yet unidentified/unspecified elements, giving the assumed as-built weight for the
chosen concept.
Weight estimates are established by use of different methods:
a)	Simple analytical models calibrated against relevant previous projects are used in the early stages,
especially in screening and feasibility phases. Weights are then estimated from assumed functions
and capacities, and scaled based on earlier project experiences.
b)	When there is sufficient knowledge about main equipment, normally after the first process
simulations, the MEL will be used as basis for determining the weights of other disciplines by
application of experience weight factors. This method is normally used in feasibility and concept
phases, and also in FEED. Different ways to use the MEL information to establish weight estimates
are given in 1) and 2).
1)	Based on MEL information, relevant topside area and volume requirements can be identified
and layout drawings can be established. Based on the layout drawings, weight for bulk and
structural can be estimated based on experience area/volume density factors.
2)	Based on MEL information, equipment weight per system can be established. Based on this,
weight for bulk and structural can be estimated based on experience factors for bulk and
structural per system.
Copyright European Committee for Standardization 65
c)	When the progress of engineering is sufficient for a Weight Take-Off (WTO) for certain disciplines,
WTOs can be used for determining the weight for these disciplines. Weight allowance should then
be added to account for items not yet identified. This method is applicable for some disciplines in
FEED in combination with experience factors. Reported weights based on WTO must always be
verified by experience factor estimates.
H.3	Recommended weight estimation requirements
1.	The equipment list and the 1.	The equipment list and the 1.	Weight estimate to be based
equipment layout should be basis for equipment layout should be basis for on experiences from earlier, compa-
the topside weight estimate. the topside weight estimate. rable projects.
2.	Weights should be distributed 2.	Weights should be distributed 2.	Weights should be split in
on areas (construction units). on areas (construction units). equipment, structural and bulk.
3.	Weights in each area should 3.	Weights in each area should 3.	Split between topside and
be split in equipment, structural and be split in equipment, structural and substructure should be defined.
bulk. bulk. Weights should be calculated for
both substructure and topside and
4.	Bulk should be split on dis- 4.	Bulk should be split on dis-
be given separately.
ciplines. ciplines.
4.	Weight accuracy and confi-
5.	Structural should be split in 5.	Structural should be split in
dence level for the established weight
primary, secondary and outfitting. primary, secondary and outfitting.
estimate should be given, based on the
6.	WTO for designed structure 6.	If possible, piping material chosen estimating method and level
should be prepared, based on 3D models. grades should be given. of details (i.e. weight accuracy25%
with a confidence level of 80%). May
7.	WTO for piping should be pre- 7.	Split between topside and be verified by statistical simulations.
pared, based on 3D models. Material substructure should be clearly defined.
grade should be given. Weights should be calculated for both 5.	SI-units should be used.
substructure and topside and be given
8.	Weight allowance should be
8.	Centre of gravity should be
9.	Split between topside and
substructure should be clearly defined.
Weights should be calculated for both 9.	Weight accuracy and confi-
substructure and topside and be given dence level for the established weight
separately. estimate should be given, based on the
chosen estimating method and level
10.	Centre of gravity should be
of details (i.e. weight accuracy15%
11.	Lift weight for each lifting item be verified by statistical simulations.
10.	Layout drawings and coordi-
12.	Source of weight data should be nate system should be given.
given (vendor information, calculated,
11.	SI-units should be used.
reference project etc.).
13.	Weight accuracy and confi-
of details (i.e. weight accuracy10%
be verified by statistical simulations.
14.	Layout drawings and coordi-
nate system should be given.
15.	SI-units should be used.
H.4	Master Equipment List (MEL)
The MEL is of vital importance in weight estimation. Irrespective of chosen weight estimation method,
MEL is the main input and basis for the weight estimate.
Copyright European Committee for Standardization 67
Weight for each listed equipment item must be given. Weight allowances should be used and clearly
stated in the equipment list. Weight allowance should be added based on concept development and
MEL must also include temporary equipment needed for any defined temporary operation. These items
should be marked as temporary.
H.5	Weight allowance
When weight estimates are based on MEL and WTOs, a weight allowance should be added to the
reported weights to account for inaccuracies and incompleteness in the definition of items. The amount
of weight allowance should be determined based on experience, judgment of concept maturity and
development of engineering. The amount of weight allowance added should always be specified.
When weights are estimated by comparative methods, scaling or by experience factor estimates, no
weight allowance is needed as the basis for these methods are determined from existing, complete
facilities, and the estimated weights are considered to be expected values.
H.6	Recommended content for weight estimation report, feasibility and
WEIGHT ESTIMATES As Class A WEIGHT ESTIMATES
Topside weight estimate Topside weight estimate
Report Basis Report Basis
Overall reporting basis Overall reporting basis
Report assumptions Report assumptions
Weight Summary Weight Summary
Dry installed weight Dry installed weight
Operating weight Operating weight
Other weight conditions if required Other weight conditions if required
Weight Estimation Method Weight Estimation Method
Detailed description of methods used Description of methods used to es-
to establish the weight estimate tablish the weight estimate
Disciplines Scope of Work Disciplines Scope of Work
Description of elements included in Description of elements included in
each technical discipline each technical discipline
Dry installed and operating Dry installed and operating
weight by discipline and area weight by discipline and area
Detailed weight matrix showing Weight matrix showing weight broken
weight broken down by discipline, area etc. down by discipline and area
Estimate Accuracy Estimate Accuracy
Evaluation and discussion regarding Evaluation and discussion regarding
the weight estimate accuracy the weight estimate accuracy
Area Plan Sub structure/hull weight
Area plan showing coordinate sys-
tem and area coding according to weight Presentation of weight, estimating
matrix breakdown construction units, method etc.
functional areas etc.
Sub structure/hull weight
Presentation of weight, estimating
method etc. References
Copyright European Committee for Standardization 69
I.1	General
The executive summary is a one page dashboard summary of the weight status and trends presented
in the report. The executive summary varies from project to project depending on the risks and
concerns for the project or customer. The summary should address 80% to 90% of the issues. A good
executive summary will use 10-point font for all text and should be something that is posted on project
An example is shown in Figure I.3.
FigureI.3 Example of an executive summary
I.2	Trend for weight and CoG
The trends are time-based trends of weight and CoG for the project. The CoG(s) that are plotted vary from
project to project, based on the issues. For a module or topside the CoG envelope may be presented. For
a ship or submersible hull the KG curve may be presented. Each trend chart should have a bold limiting
curve or line, with one or two trend lines shown. A future weight and CoG point should be plotted for
each trend line that shows the impact of the potential changes on the currently reported weight.
I.3	Comparison to budget
This is a simple table that shows overall weight changes since the beginning of the project. It presents
the weight budget by discipline (structure, piping, outfitting, equipment and electrical), current weight
allowance, and current gross weight.
I.4	Loading conditions
I.4.1	General
This is a table of the loading conditions using the current weight and CoG. The loading conditions are
a limited set of all the conditions developed by the naval architect. Typically the loading conditions
used to establish the WLB, construction and extreme operating conditions are used. The construction
conditions may include launch, integration, tow out, commissioning and inclining experiment. The
extreme conditions are those that are close to the edge of the KG limit or CoG envelope.
I.4.2	Management reserve analysis
This is a table of the current values of net allowance, and gross weight along with the CoGs. It compares
the gross weight to the not-to-exceed limits to determine the amount of management reserve.
I.4.3	Changes to this report
A list of the changes that is included in the report. A description, weight impact and CoG information
should be provided for each change.
I.4.4	Potential changes for next report
A list of the potential changes that could impact the weight or CoG presented in the trend charts.
Potentials include the impact of weight changes of drawing calculations that have not been completely
checked, design changes that have not been completed, rumoured weight changes from vendors, etc.
I.5	Additional summaries (depending on project)
a)	Additional loading conditions
b)	Construction modules weight summaries
c)	Lift weight summaries (including temporaries)
d)	Cost account weight summaries
e)	Material take-off weight summaries
f)	Summary of the weight and CoG history over the life of the project
I.6	Discipline by Area (DA) weight summary
The DA summary is a table of the weight for each discipline and area. The disciplines are usually those
identified on the organization chart or upon customer request by their definition of disciplines. These
are not usually the same. The weight should be rounded to the nearest whole number.
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Copyright European Committee for Standardization ISO 2016 All rights reserved 71
Weighing result uncertainty
According to the GUM (Clause2) any measurement is disturbed by some random influence, called the
measurement uncertainty. It is quantified by its standard deviation and its weight result uncertainty,
called the standard uncertainty, denoted u.
As the GUM requires that the coverage factor is given together with the measurement uncertainty one
can easily recalculate the expanded uncertainty to any wanted value of k. The two statements
W = 1000 tonne 1%, k = 2
W = 1000 tonne 1,5%, k = 3
in fact have the same quality as both have standard uncertainty u=0,5%.
For weighing complying to the1%, k=2 requirement for the Class A weighing in this standard, it is
reasonable to assume that the weighing result will not deviate more than 1% from the true weight in
95% of the weighings.
Calibration is a documented act of observing and documenting the output of a measuring device when it
measures a physical quantity at a set of values having known uncertainty. The set of quantities should
be large enough to enable reasonable assessment of the measurement uncertainty and should cover the
whole range for which the measuring device is intended used.
Standard uncertainty is the standard deviation of the measurement uncertainty, denoted u.
Expanded uncertainty is the standard uncertainty multiplied by the coverage factor, denoted u. The
result of the measurementu is expected to cover a large fraction of values that could reasonably be
attributed to the measured quantity.
Coverage factor is the factor used to multiply the standard uncertainty to obtain the expanded
uncertainty, denoted k.
Weight control database structure
Each record in the weight control database Each record in the weight control No specific requirements.
shall as a minimum contain the following database shall as a minimum con-
information in separate data fields: tain the following information in
separate data fields:
Discipline code: The discipline code ac- Discipline code: The discipline code
cording to the projects numbering system. according to the projects number-
System code: The system code according
to the projects numbering system
Area code: The area code according to the Area code: The area code according
projects numbering system. to the projects numbering system.
Drawing number: The drawing number Drawing number: The drawing
from which the weight has been identified number from which the weight has
or calculated. been identified or calculated.
Drawing revision: The revision of the Drawing revision: The revision of
drawing from which the weight has been the drawing from which the weight
identified or calculated. has been identified or calculated
Piece number: The unique piece within a Piece number: The unique piece
drawing number, e.g. plate girder M102356 within a drawing number, e.g. plate
shown on a structural deck drawing. The girder M102356 shown on a struc-
data field is a text field. tural deck drawing. The data field
is a text field.
Number off: Number of identical pieces.
Only integer numbers shall be used.
Size: The size of each piece, e.g. 2,350m
for the length of an HE200A beam.
Dry weight: The dry weight of each Dry weight: The dry weight of each
piece in kg, that is the product of Number piece in kg.
offSizeUnit weight, e.g. 12,35042,
3=99kg for one HE200A with a length of
2,350m.
Content: The weight of the content in kg Content: The weight of the content
in a piping line, vessel, tank etc. in kg in a piping line, vessel, tank etc.
Weight status code: A coding to identify Weight status code: A coding to
the level of accuracy of the weight data of identify the level of accuracy of the
each piece number. weight data of each piece number.
Weight phase code: A coding to identify Weight phase code: A coding to
during which phase a piece number will identify during which phase a piece
be installed and present. number will be installed and present.
Weight installation code: A coding to Weight installation code: A cod-
identify whether a piece is installed or not ing to identify whether a piece is
on a module/installation. installed or not on a module/in-
Copyright European Committee for Standardization 73
Coordinates: The coordinates in the plat- Coordinates: The coordinates in the
form north direction, the platform east platform north direction, the plat-
direction and elevation. form east direction and elevation.
Originator code: The originator code ac- Originator code: The originator
cording to the projects numbering system code according to the projects num-
of the organization or contractor who have bering system of the organization
calculated or revised the weight data for or contractor who have calculated
a piece number. or revised the weight data for a
Date: The date when a piece number was Date: The date when a piece number
entered or revised in the weight control was entered or revised in the weight
database. control database.
[1] ISO19901-9, Petroleum and natural gas industries Specific requirements for offshore
structures Part 9: Structural integrity management1)
[2] ISO19902:2007, Petroleum and natural gas industries Fixed steel offshore structures
[3] ISO19904-1:2006, Petroleum and natural gas industries Floating offshore structures Part1:
Monohulls, semi-submersibles and spars
[4] ISO/IEC17025, General requirements for the competence of testing and calibration laboratories
[5] ASTM Designation F132192: Standard Guide for Conducting a Stability Test (Lightweight Survey
and Inclining Experiment) to Determine the Light Ship Displacement and Centres of Gravity of a Vessel
[6] Det Norske Veritas: Classification Notes No. 20.2 Lightweight determination Ships (Inclining
test and lightweight survey). February1990
[7] Det Norske Veritas: Instruction to surveyors for classification of Mobile Offshore Units. Units under
construction. Hull and Equipment. No.I-B31 General Survey
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1) Under preparation.
Copyright European Committee for Standardization ISO 2016 All rights reserved 75
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