Z7.1

Z7.1
Hull Surveys for General Dry Cargo Ships
Z7.1(June 2002

(cont’d)as Z10.6)(Rev.1
June 2003)(Rev.2June 2005)(Rev.3Jan. 2006)(Rev.4
Aug 2006)(Rev.5
Nov 2007)(Rev.6
Mar 2009)(Rev.7
July 2011)(Rev.8
Oct 2011)(Rev.9
May 2013)(Rev.10
Jan 2014)(Rev.11
Feb 2015)(Rev.12June 2016)(Rev.13
Aug 2017)(Rev.14
Jan 2018)(Rev.15
June 2019)(Corr.1
May 2024)

CONTENTS

1.
1.1
1.2
1.3
1.4
1.5

GeneralApplication
Definitions
Repairs
Thickness measurements and close-up surveys
Remote Inspection Techniques (RIT)

2.
2.1
2.2
2.2.1
2.2.2
2.2.3
2.2.4
2.3
2.4
2.5
2.6

Special Survey
Schedule
Scope
GeneralDry Dock Survey
Tank Protection
Hatch Covers and Coamings
Extent of Overall and Close-up Survey
Extent of Thickness Measurement
Extent of Tank Testing
Additional requirements for single hold cargo ships after determining compliance withSOLAS II-I/25

3.
3.1
3.2
3.2.1
3.2.2
3.2.3
3.2.4
3.2.5
3.2.6
3.3

Annual Survey
Schedule
Scope
GeneralExamination of the Hull
Examination of Hatch Covers and Coamings
Suspect Areas
Examination of Cargo Hold
Examination of Ballast Tanks
Additional requirements for single hold cargo ships after determining compliance withSOLAS II-I/25

4.
4.1
4.2
4.2.1
4.2.2
4.2.3
4.2.4

Intermediate Survey
Schedule
Scope
GeneralDry Cargo Ships 5 - 10 years of Age
Dry Cargo Ships 10 - 15 years of Age
Dry Cargo Ships Exceeding 15 years of Age

5.
5.1
5.2
5.3
5.4

Preparation for Survey
Conditions for Survey
Access to Structures
Equipment for Survey
Survey at Sea or at Anchorage

6.
6.1
6.2
6.3

Procedures for Thickness Measurements
GeneralCertification of Thickness Measurement Company
Reporting
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(cont’d)Note 1:

UR Z7.1 (Rev.1, June 2003) replaces ex-UR Z10.6(June 2002).

Note 2:

Changes introduced in Rev.2 are to be applied by all Members and Associatesfrom 1 July 2006.

Note 3:

Changes introduced in Rev.3 are to be uniformly applied by IACS Societies on
surveys commenced on or after 1 January 2007.

Note 4:

Changes introduced in Rev. 4 (paragraphs 1.1.1, 2.6 and 3.3) are to be uniformly
applied by IACS Societies at special and annual surveys, as applicable, carriedout after the ship has been made compliant with the requirements of SOLAS
II-1/23-3 and II-1/25, and commenced on or after 1 July 2007.

Note 5:

Changes introduced in Rev.5 are to be uniformly applied by IACS Societies forsurveys commenced on or after the 1 January 2009.

Note 6:

Changes introduced in Rev.6 are to be uniformly applied by IACS Societies forsurveys commenced on or after 1 July 2010.
As for the requirements regarding semi-hard coatings, these coatings, if alreadyapplied, will not be accepted from the next special or intermediate survey
commenced on or after 1 July 2010, whichever comes first, with respect towaiving the annual internal examination of the ballast tanks.

Note 7:

Changes introduced in Rev.7 are to be uniformly applied by IACS Societies forsurveys commenced on or after 1 July 2012.

Note 8:Changes introduced in Rev.8 are to be uniformly applied by IACS Societies forsurveys commenced on or after 1 January 2013.

Note 9:Changes introduced in Rev.9 are to be uniformly applied by IACS Societies forsurveys commenced on or after 1 July 2014.

Note 10:

Changes introduced in Rev.10 are to be uniformly applied by IACS Societies forsurveys commenced on or after 1 January 2015.

Note 11:

Changes introduced in Rev.11 are to be uniformly applied by IACS Societies forsurveys commenced on or after 1 July 2016.

Note 12:

Changes introduced in Rev.12 are to be uniformly applied by IACS Societies forsurveys commenced on or after 1 July 2017.

Note 13:

Changes introduced in Rev.13 are to be uniformly applied by IACS Societies forsurveys commenced on or after 1 January 2019.

Note 14:

Changes introduced in Rev.14 are to be uniformly applied by IACS Societies forsurveys commenced on or after 1 January 2019.

Note 15:

Changes introduced in Rev.15 are to be uniformly applied by IACS Societies forsurveys commenced on or after 1 July 2020.

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(cont’d)

ENCLOSURES:
Table I:

Minimum requirements for Close-up Surveys at Hull Special Surveys of General
Dry Cargo Ships.

Table II:

Minimum requirements to Thickness Measurements at Hull Special Surveys ofGeneral Dry Cargo Ships.

Table III:

Guidance for Additional Thickness Measurements in Way of Substantial
Corrosion.

Table IV:

Procedures for Certification of Firms Engaged in Thickness Measurement of Hull
Structures.

Figure 1:

Areas for Close-up Survey of General Dry Cargo Ships.

Figure 2:

Areas for Close-up Survey of General Dry Cargo Ships.

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Z7.1
(cont’d)1.

GENERAL

1.1

Application

1.1.1 The requirements apply to all self-propelled General Dry Cargo Ships of 500gt andabove carrying solid cargoes other than1:-ships subject to UR Z10.2 or UR Z10.5;
dedicated container carriers;
ro-ro cargo ships;
refrigerated cargo ships;
dedicated wood chip carriers;
dedicated cement carriers;
livestock carriers;
deck cargo ships2;
general dry cargo ships of double-side skin construction, with double-side skinextending for the length of the cargo area, and for the height of the cargo hold tothe upper deck3.

1.1.2 For General Dry Cargo Ships with hybrid cargo hold arrangements, e.g. with somecargo holds of single-side skin and others of double-side skin, the requirements of UR Z7.1
are to be applied only to structure in way of the single-side skin cargo hold region.
1.1.3 The requirements apply to surveys of hull structure and piping systems in way ofcargo holds, cofferdams, pipe tunnels, void spaces and fuel oil tanks within the cargo area
and all ballast tanks. The requirements are additional to the classification requirements
applicable to the remainder of the ship. Refer to Z7.
1.1.4 The requirements contain the minimum extent of examination, thickness
measurements and tank testing. The survey is to be extended when Substantial Corrosion
and/or structural defects are found and include additional Close-up Survey when necessary.
1.2

Definitions

1.2.1 Ballast Tank
A Ballast Tank is a tank that is being used primarily for salt water ballast.
1.2.2 Spaces
Spaces are separate compartments including holds and tanks.
1.2.3 Overall Survey
An Overall Survey is a survey intended to report on the overall condition of the hull structureand determine the extent of additional Close-up Surveys.
1

The requirements of paragraphs 2.6 and 3.3 also apply to those cargo ships, which, althoughbelonging to the ship types listed in 1.1.1 that are excluded from the application of this UR, are fittedwith a single cargo hold.

2

A deck cargo ship is a ship that is designed to carry cargo exclusively above deck without any
access for cargo below deck.

3

Special consideration may also be given to ships that are of double side-skin construction but withsingle skin in way of several frame spaces e.g. in way of a cargo hold entrance or in way offorebody hull form at the forward end of the foremost cargo hold.

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(cont’d)1.2.4 Close Up Survey
A Close-up Survey is a survey where the details of structural components are within the close
visual inspection range of the surveyor, i.e. normally within reach of hand.
1.2.5 Transverse Section
A Transverse Section includes all longitudinal members such as plating, longitudinals andgirders at the deck, sides, bottom, inner bottom and hopper side plating, longitudinalbulkheads and bottom plating in top wing tanks. For transversely framed vessels, atransverse section includes adjacent frames and their end connections in way of transverse
sections.
1.2.6 Representative Space
Representative Spaces are those which are expected to reflect the condition of other Spacesof similar type and service and with similar corrosion prevention systems. When selecting
Representative Spaces account is to be taken of the service and repair history on board andidentifiable Critical Structural Areas and/or Suspect Areas.
1.2.7 Critical Structural Area
Critical Structural Areas are locations which have been identified from calculations to requiremonitoring of from the service history of the subject ship or from similar ships or sister ships,
if applicable, to be sensitive to cracking, buckling or corrosion which would impair the
structural integrity of the ship.
1.2.8 Suspect Area
Suspect Areas are locations showing Substantial Corrosion and/or are considered by thesurveyor to be prone to rapid wastage.
1.2.9 Substantial Corrosion
Substantial Corrosion is an extent of corrosion such that assessment of corrosion patternindicates a wastage in excess of 75% of allowable margins, but within acceptable limits.
1.2.10 Corrosion Prevention System
A Corrosion Prevention System is normally considered a full hard protective coating.
Hard Protective Coating is usually to be epoxy coating or equivalent. Other coating systems,
which are neither soft nor semi-hard coatings, may be considered acceptable as alternatives
provided that they are applied and maintained in compliance with the manufacturer’s
specifications.
1.2.11 Coating Condition
Coating Condition is defined as follows:
GOOD

condition with only minor spot rusting.

FAIR

condition with local breakdown at edges of stiffeners and weld
connections and/or light rusting over 20% or more of areas underconsideration, but less than as defined for POOR condition.

POOR

condition with general breakdown of coating over 20% or more ofareas or hard scale at 10% or more of areas under consideration.

1.2.12 Cargo Length Area
Cargo Length Area is that part of the ship which contains all cargo holds and adjacent areas
including fuel tanks, cofferdams, ballast tanks and void spaces.
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(cont’d)1.2.13 Special Consideration
Special Consideration or specially considered (in connection with close-up surveys andthickness measurements) means sufficient close-up inspection and thickness
measurements are to be taken to confirm the actual average condition of the structure under
the coating.
1.2.14 Prompt and Thorough Repair
A Prompt and Through Repair is a permanent repair completed at the time of survey to thesatisfaction of the surveyor, therein removing the need for the imposition of any associatedcondition of classification.
1.2.15 Remote Inspection Techniques(RIT)
Remote Inspection Technique is a means of survey that enables examination of any part ofthe structure without the need for direct physical access of the surveyor(refer to Rec.42).
1.3

Repairs

1.3.1 Any damage in association with wastage over the allowable limits (including buckling,
grooving, detachment or fracture), or extensive areas of wastage over the allowable limits,which affects or, in the opinion of the Surveyor, will affect the vessel’s structural, watertight orweathertight integrity, is to be promptly and thoroughly (see 1.2.14) repaired. Areas to beconsidered include:-side shell frames, their end attachments and adjacent shell plating;deck structure and deck plating;bottom structure and bottom plating;watertight bulkheads;
hatch covers and hatch coamings.
items in 3.2.3.5, 3.2.3.6 and 3.2.3.8 of UR Z7.

For locations where adequate repair facilities are not available, consideration may be given to
allow the vessel to proceed directly to a repair facility. This may require discharging the cargo
and/or temporary repairs for the intended voyage.
1.3.2 Additionally, when a survey results in the identification of structural defects or corrosion,
either of which, in the opinion of the surveyor, will impair the vessel’s fitness for continued
service, remedial measures are to be implemented before the ship continues in service.
1.3.3 Where the damage found on structure mentioned in Para. 1.3.1 is isolated and of a
localised nature which does not affect the ship's structural integrity, consideration may be
given by the surveyor to allow an appropriate temporary repair to restore watertight orweather tight integrity and impose a condition of class in accordance with IACS PR 35, witha specific time limit.
1.4

Thickness measurements and close-up surveys

1.4.1 In any kind of survey, i.e. special, intermediate, annual or other surveys having thescope of the foregoing ones, thickness measurements, when required by Table II, of
structures in areas where close-up surveys are required, shall be carried out simultaneouslywith close-up surveys.
1.4.2 Consideration may be given by the attending Surveyor to allow use of Remote
Inspection Techniques (RIT) as an alternative to close-up survey. Surveys conducted using a
RIT are to be completed to the satisfaction of the attending Surveyor. When RIT is used for a
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(cont’d)close-up survey, temporary means of access for the corresponding thickness measurements
as specified in this UR is to be provided unless such RIT is also able to carry out the required
thickness measurements.
1.5

Remote Inspection Techniques (RIT)

1.5.1 The RIT is to provide the information normally obtained from a close-up survey. RIT
surveys are to be carried out in accordance with the requirements given here-in and therequirements of IACS Recommendation 42 ‘Guidelines for Use of Remote Inspection
Techniques for surveys’. These considerations are to be included in the proposals for use of
a RIT which are to be submitted in advance of the survey so that satisfactory arrangements
can be agreed with the Classification Society.
1.5.2 The equipment and procedure for observing and reporting the survey using a RIT are
to be discussed and agreed with the parties involved prior to the RIT survey, and suitable
time is to be allowed to set-up, calibrate and test all equipment beforehand.
1.5.3 When using a RIT as an alternative to close-up survey, if not carried out by theSociety itself, it is to be conducted by a firm approved as a service supplier according to UR
Z17 and is to be witnessed by an attending surveyor of the Society.
1.5.4 The structure to be examined using a RIT is to be sufficiently clean to permit
meaningful examination. Visibility is to be sufficient to allow for a meaningful examination.
The Classification Society is to be satisfied with the methods of orientation on the structure.
1.5.5 The Surveyor is to be satisfied with the method of data presentation including pictorial
representation, and a good two-way communication between the Surveyor and RIT operator
is to be provided.
1.5.6 If the RIT reveals damage or deterioration that requires attention, the Surveyor may
require traditional survey to be undertaken without the use of a RIT.
1.6

Thickness measurements Acceptance Criteria

The acceptance criteria for thickness measurements are according to the Rules of theindividual Classification Society and/or specific IACS URs depending on ship’s age andstructural elements concerned, e.g. UR S18 1 for corrugated transverse bulkhead, UR S213 or
UR S21A 2 for all cargo hatch covers and coamings on exposed decks.

1

UR S18 Revision 7 or subsequent revisions or corrigenda as applicable.

UR S21A applies for ships contracted for construction on or after 1 July 2012, Rev.1 of UR S21A applies forships contracted for construction on or after 1 July 2016. UR S21A was withdrawn from 1 July 2024 and replacedby UR S21 Rev.6.
2

3

UR S21 Revision 6 applies for ships contracted for construction on or after 1 July 2024.

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(cont’d)2.

SPECIAL SURVEY *2.1

Schedule

2.1.1 Special Surveys are to be carried out at 5 years intervals to renew the Classification
Certificate.
2.1.2 The first Special Survey is to be completed within 5 years from the date of the initialclassification survey and thereafter within 5 years from the credited date of the previous
Special Survey. However, an extension of class of 3 months maximum beyond the 5th year
can be granted in exceptional circumstances. In this case, the next period of class will startfrom the expiry date of the Special Survey before the extension was granted.
2.1.3 For surveys completed within 3 months before the expiry date of the Special Survey,
the next period of class will start from the expiry date of the Special Survey. For surveys
completed more than 3 months before the expiry date of the Special Survey, the period ofclass will start from the survey completion date. In cases where the vessel has been laid up
or has been out of service for a considerable period because of a major repair or modificationand the owner elects to only carry out the overdue surveys, the next period of class will startfrom the expiry date of the special survey. If the owner elects to carry out the next due special
survey, the period of class will start from the survey completion date.
2.1.4 The Special Survey may be commenced at the 4th Annual Survey and be progressedwith a view to completion by the 5th anniversary date. When the Special Survey iscommenced prior to the 4th Annual Survey, the entire survey is to be completed within 15
months if such work is to be credited to the Special Survey.
2.1.5 A survey planning meeting is to be held prior to the commencement of the survey.
2.1.6 Concurrent crediting to both Intermediate Survey (IS) and Special Survey (SS) for
surveys and thickness measurements of spaces are not acceptable.
2.2

Scope

2.2.1

General2.2.1.1 The Special Survey is to include, in addition to the requirements of the Annual
Surveys, examination, tests and checks of sufficient extent to ensure that the hull and related
piping, as required in 2.2.1.3, are in a satisfactory condition and fit for the intended purpose
for the new period of class of 5 years to be assigned, subject to proper maintenance andoperation and to periodical surveys being carried out at the due dates.
2.2.1.2 All cargo holds, ballast tanks, including double bottom tanks, pipe tunnels,
cofferdams and void spaces bounding cargo holds, decks and outer hull are to be examined,
and this examination is to be supplemented by thickness measurement and testing as
required in 2.4 and 2.5, to ensure that the structural integrity remains effective.
The aim of the examination is to discover Substantial Corrosion, significant deformation,
fractures, damages or other structural deterioration, that may be present.

* Some member Societies use the term “Special Periodical Survey” others use the term “Class Renewal
Survey” instead of the term “Special Survey”.

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(cont’d)2.2.1.3 All piping systems within the above spaces are to be examined and operationallytested to working pressure to attending Surveyor’s satisfaction to ensure that tightness andcondition remain satisfactory.
2.2.1.4 The survey extent of ballast tanks converted to void spaces is to be speciallyconsidered in relation to the requirements for ballast tanks.
Note: For survey of automatic air pipes refer to 2.2.13 of UR Z7.
2.2.2 Dry Dock Survey
2.2.2.1 A survey in dry dock is to be a part of the Special Survey. The overall and close-up
surveys and thickness measurements, as applicable, of the lower portions of the cargo holds
and ballast tanks are to be carried out in accordance with the applicable requirements for
special surveys, if not already performed.
Note: Lower portions of the cargo holds and ballast tanks are considered to be the parts
below light ballast water line.
2.2.3 Tank Protection
2.2.3.1 Where provided, the condition of corrosion prevention system of ballast tanks is to be
examined. For ballast tanks, excluding double bottom tanks, where a hard protective coating
is found in POOR condition and it is not renewed, where soft or semi-hard coating has been
applied, or where a hard protective coating was not applied from time of construction, thetanks in question are to be examined at annual intervals. Thickness measurements are to be
carried out as deemed necessary by the surveyor.
When such breakdown of hard protective coating is found in double bottom ballast tanks andit is not renewed, where a soft or semi-hard coating has been applied, or where a hardprotective coating was not applied from the time of construction, the tanks in question may be
examined at annual intervals. When considered necessary by the surveyor, or where
extensive corrosion exists, thickness measurements are to be carried out.
2.2.3.2 Where the hard protective coating in tanks is found to be in a GOOD condition, theextent of close-up surveys and thickness measurements may be specially considered.
2.2.4 Hatch Covers and Coamings
The hatch covers and coamings are to be surveyed as follows:
2.2.4.1 A thorough inspection of the items listed in 3.2.3 is to be carried out.
2.2.4.2 Checking of the satisfactory operation of all mechanically operated hatch covers is to
be made, including:-stowage and securing in open condition;
proper fit and efficiency of sealing in closed conditions:operational testing of hydraulic and power components, wires, chains and link
drives.

2.2.4.3 Checking the effectiveness of sealing arrangements of all hatch covers by hosetesting or equivalent is to be carried out.

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(cont’d)2.2.4.4 Close-up survey and thickness measurement1 of the hatch cover and coaming plating
and stiffeners is to be carried out as given in Table I and Table II.
2.3

Extent of Overall and Close-up Survey

2.3.1 An Overall Survey of all tanks and spaces, excluding fuel oil, lube oil and fresh watertanks, is to be carried out at each Special Survey.
Note: For fuel oil, lube oil and fresh water tanks, reference is to be made to UR Z7, Table 3.
2.3.2 The minimum requirements for close-up surveys at special survey are given in Table I.
2.3.3 The Surveyor may extend the close-up survey as deemed necessary taking into
account the maintenance of the spaces under survey, the condition of the corrosion
prevention system and where spaces have structural arrangements or details which havesuffered defects in similar spaces or on similar ships according to available information.
2.3.4 For areas in spaces where hard protective coatings are found to be in a GOOD
condition, the extent of close-up surveys according to Table I may be specially considered.
Note: For examination of automatic air pipe heads, reference is to be made to UR Z7,
Table 4.
2.4

Extent of Thickness Measurement

2.4.1 The minimum requirements for thickness measurements at Special Survey are given in
Table II.
2.4.2 The Surveyor may extend the thickness measurements as deemed necessary. When
thickness measurements indicate substantial corrosion, the extent of thickness
measurements is to be increased to determine the extent of areas of substantial corrosion.
Table III may be used as guidance for these additional thickness measurements.
2.4.3 For areas in spaces where hard protective coatings are found to be in a GOOD
condition, the extent of thickness measurement according to Table II may be speciallyconsidered.
2.4.4 Transverse sections are to be chosen where the largest reductions are suspected tooccur or are revealed from deck plating measurements.

1

Subject to cargo hold hatch covers of approved design which structurally have no access to the internals,
close-up survey/thickness measurement shall be done of accessible parts of hatch covers structures.

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(cont’d)

2.5

Extent of Tank Testing

2.5.1 All boundaries of ballast tanks and deep tanks used for water ballast within the cargo
length area are to be pressure tested. For fuel oil tanks, the representative tanks are to bepressure tested.
2.5.2 The Surveyor may extend the tank testing as deemed necessary.
2.5.3 Tank testing of fuel oil tanks is to be carried out with a head of liquid to the highest
point that liquid will rise under service conditions. Tank testing of fuel oil tanks may be
specially considered based on a satisfactory external examination of the tank boundaries,
and a confirmation from the Master stating that the pressure testing has been carried out
according to the requirements with satisfactory results.
2.6
Additional requirements for single hold cargo ships (see Footnote 1 to 1.1.1)
after determining compliance with SOLAS II-I/25
2.6.1 For ships complying with the requirements of SOLAS II-I/25 for hold water level
detectors, the special survey is to include an examination and a test of the water ingress
detection system and their alarms.

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(cont’d)3.

ANNUAL SURVEY

3.1

Schedule

3.1.1 Annual Surveys are to be held within 3 months before or after anniversary date fromthe date of the initial classification survey or of the date credited for the last Special Survey.
3.2

Scope

3.2.1

General3.2.1.1 The survey is to consist of an examination for the purpose of ensuring, as far aspracticable, that the hull, hatch covers, coamings and piping are maintained in a satisfactory
condition.
3.2.2 Examination of the Hull
3.2.2.1 Examination of the hull plating and its closing appliances as far as can be seen.
3.2.2.2 Examination of watertight penetrations as far as practicable.
3.2.3 Examination of weather decks, hatch covers and coamings
3.2.3.1 Confirmation is to be obtained that no unapproved changes have been made to thehatch covers, hatch coamings and their securing and sealing devices since the last survey.
3.2.3.2 Where mechanically operated steel covers are fitted, checking the satisfactory
condition of:-hatch covers; including close-up survey of hatch cover plating;tightness devices of longitudinal, transverse and intermediate cross junctions(gaskets, gasket lips, compression bars, drainage channels);clamping devices, retaining bars, cleating;chain or rope pulleys;
guides;guide rails and track wheels;
stoppers, etc.;
wires, chains, gypsies, tensioning devices;
hydraulic system essential to closing and securing;safety locks and retaining devices.

Where portable covers, wooden or steel pontoons are fitted, checking the satisfactory
condition where applicable of:-wooden covers and portable beams, carriers or sockets for the portable beam,and their securing devices;
steel pontoons;tarpaulins;
cleats, battens and wedges;
hatch securing bars and their securing devices;loading pads/bars and the side plate edge;
guide plates and chocks;
compression bars, drainage channels and drain pipes (if any).

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(cont’d)3.2.3.3 Checking the satisfactory condition of hatch coaming plating and their stiffeners
including close-up survey.
3.2.3.4 Random checking of the satisfactory operation of mechanically operated hatch
covers is to be made including:- stowage and securing in open condition;- proper fit and efficiency of sealing in closed condition;- operational testing of hydraulic and power components, wires, chains, and link
drives.
Note: For survey of air pipes, flame screens on vents and ventilators refer to 3.2.3.5 to 3.2.3.8
of UR Z7.
3.2.4 Suspect Areas
Suspect Areas identified at previous surveys are to be examined. Thickness measurements
are to be taken of the areas of substantial corrosion and the extent of thickness
measurements is to be increased to determine the extent of areas of substantial corrosion.
Table III may be used as guidance for these additional thickness measurements. These
extended thickness measurements are to be carried out before the annual survey is credited
as completed.
3.2.5

Examination of Cargo Holds

3.2.5.1 For Ships 10-15 years of age, the following is to apply:a)Overall Survey of one forward and one after cargo hold and their associated tween
deck spaces.

b)

When considered necessary by the surveyor, or where extensive corrosion exists,
thickness measurement is to be carried out. If the results of these thickness
measurements indicate that Substantial Corrosion is found, then the extent of
thickness measurements is to be increased to determine the extent of areas of
substantial corrosion. Table III may be used as guidance for these additional
measurements. These extended thickness measurements are to be carried out before
the annual survey is credited as completed.

3.2.5.2 For Ships over 15 years of age, the following is to apply:a)Overall Survey of all cargo holds and tween deck spaces.

b)

Close-up examination of sufficient extent, minimum 25% of frames, to establish thecondition of the lower region of the shell frames including approx. lower one third
length of side frame at side shell and side frame end attachment and the adjacentshell plating in a forward lower cargo hold and one other selected lower cargo hold.
Where this level of survey reveals the need for remedial measures, the survey is to beextended to include a Close-up Survey of all of the shell frames and adjacent shell
plating of those cargo holds and associated tween deck spaces (as applicable) as well
as a Close-up Survey of sufficient extent of all remaining cargo holds and tween deck
spaces (as applicable).

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c)

When considered necessary by the surveyor, or where extensive corrosion exists,
thickness measurement is to be carried out. If the results of these thickness
measurements indicate that Substantial Corrosion is found, then the extent of
thickness measurements is to be increased to determine the extent of areas of
substantial corrosion. Table III may be used as guidance for these additional
measurements. These extended thickness measurements are to be carried out before
the annual survey is credited as completed.

d)Where the protective coating in cargo holds, as applicable, is found to be in GOOD
condition the extent of close-up surveys may be specially considered.

e)

All piping and penetrations in cargo holds, including overboard piping, are to be
examined.

(cont’d)3.2.6 Examination of Ballast Tanks
3.2.6.1 Examination of ballast tanks when required as a consequence of the results of theSpecial Survey and Intermediate Survey is to be carried out. When considered necessary by
the surveyor, or where extensive corrosion exists, thickness measurement is to be carriedout. If the results of these thickness measurements indicate that Substantial Corrosion isfound, then the extent of thickness measurements are to be increased to determine theextent of areas of substantial corrosion. Table III may be used as guidance for these
additional measurements. These extended thickness measurements are to be carried out
before the annual survey is credited as completed.
3.3
Additional requirements for single hold cargo ships (see Footnote 1 to 1.1.1)
after determining compliance with SOLAS II-I/25
3.3.1 For ships complying with the requirements of SOLAS II-I/25 for hold water level
detectors, the annual survey is to include an examination and a test, at random, of the water
ingress detection system and of their alarms.

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(cont’d)4.

INTERMEDIATE SURVEY

4.1

Schedule

4.1.1 The Intermediate Survey is to be held at or between either the 2nd or 3rd Annual
Survey.
4.1.2 Those items which are additional to the requirements of the Annual Surveys may besurveyed either at or between the 2nd and 3rd Annual Survey.
4.1.3 A survey planning meeting is to be held prior to the commencement of the survey.
4.1.4 Concurrent crediting to both Intermediate Survey (IS) and Special Survey (SS)for surveys and thickness measurements of spaces are not acceptable.
4.2

Scope

4.2.1

General4.2.1.1 The survey extent is dependent on the age of the vessel as specified in 4.2.2 to4.2.4.
4.2.2

Ships 5 - 10 Years of Age, the following is to apply :4.2.2.1 Ballast tanksa)For ballast tanks, an Overall Survey of Representative Tanks selected by theSurveyor is to be carried out. If such overall survey reveals no visible structuraldefects, the examination may be limited to a verification that the corrosion prevention
system remains efficient.

b)

Where POOR coating condition, soft or semi-hard coating, corrosion or other defects
are found in ballast tanks or where a hard protective coating was not applied fromthe time of construction, the examination is to be extended to other ballast tanks ofthe same type.

c)

In ballast tanks other than double bottom tanks, where a hard protective coating isfound in POOR condition, and it is not renewed, where soft or semi-hard coating has
been applied, or where a hard protective coating was not applied from time of
construction, the tanks in question are to be examined and thickness measurements
carried out as considered necessary at annual intervals. When such breakdown of
hard protective coating is found in double bottom ballast tanks, where a soft or semihard coating has been applied, or where a hard protective coating has not been
applied, the tanks in question may be examined at annual intervals. Whenconsidered necessary by the surveyor, or where extensive corrosion exists,
thickness measurements are to be carried out.

d)In addition to the requirements above, areas found suspect at previous surveys areto be surveyed in accordance with the provisions indicated in 3.2.4.

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(cont’d)4.2.2.2 Cargo Holdsa)

An Overall Survey of one forward and one after cargo hold and their associated tween
deck spaces.

b)Areas found suspect at previous surveys are to be surveyed in accordance with theprovisions indicated in 3.2.4.

4.2.3 Ships 10-15 Years of Age, the following is to apply:
4.2.3.1

Ballast Tanksa)

For ballast tanks, an overall survey of all tanks is to be carried out.
If such overall survey reveals no visible structural defects, the examination may belimited to a verification that the corrosion prevention system remains efficient.

b)

The requirements of 4.2.2.1 c) and d) also apply.

4.2.3.2 Cargo Holdsa)

An Overall Survey of all cargo holds and tween deck spaces.

b)Areas found suspect at previous surveys are to be surveyed in accordance withthe provisions indicated in 3.2.4.

c)When considered necessary by the surveyor, or where extensive corrosion exists,
thickness measurement is to be carried out. If the results of these thickness
measurements indicate that Substantial Corrosion is found, then the extent of
thickness measurements is to be increased to determine the extent of areas of
substantial corrosion. Table III may be used as guidance for these additional
measurements. These extended thickness measurements are to be carried out before
the survey is credited as completed.

4.2.4

Ships over 15 Years of Age, the following is to apply :4.2.4.1 The requirements of the Intermediate Survey are to be to the same extent as theprevious Special Survey as required in 2, except for item 2c) in column 4 of Table II.
However, tank testing specified in 2.5, survey of automatic air pipe heads (see Notes in
2.2.1.4 and 2.3.4) and internal examination of fuel oil, lube oil and fresh water tanks (see2.3.1) are not required unless deemed necessary by the attending surveyor.
4.2.4.2 In application of 4.2.4.1, the intermediate survey may be commenced at the second
annual survey and be progressed during the succeeding year with a view to completion at thethird annual survey in lieu of the application of 2.1.4.
4.2.4.3 In lieu of the requirements of 2.2.2, an in water survey, according to the provisionsof item 3.1.3 of UR Z3, may be considered as equivalent.

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(cont’d)5

PREPARATION FOR SURVEY

5.1

Conditions of Survey

5.1.1 The Owner is to provide the necessary facilities for a safe execution of the survey.
5.1.2 Tanks and Spaces are to be safe for access, i.e. gas freed, ventilated and illuminated.
5.1.3 In preparation for survey and thickness measurements and to allow for a thoroughexamination, all spaces are to be cleaned including removal from surfaces of all loose
accumulated corrosion scale. Spaces are to be sufficiently clean and free from water, scale,dirt, oil residues etc. to reveal corrosion, deformation, fractures, damages, or other structural
deterioration. However, those areas of structure whose renewal has already been decided by
the owner need only be cleaned and descaled to the extent necessary to determine the limitsof the areas to be renewed.
5.1.4 Sufficient illumination is to be provided to reveal corrosion, deformation, fractures,
damages or other structural deterioration.
5.1.5 Where soft or semi-hard coatings have been applied, safe access is to be provided forthe surveyor to verify the effectiveness of the coating and to carry out an assessment of theconditions of internal structures which may include spot removal of the coating. When safe
access cannot be provided, the soft or semi-hard coating is to be removed.
5.2

Access to Structures

5.2.1 For Overall Survey, means are to be provided to enable the surveyor to examine thehull structure in a safe and practical way.
5.2.2 For Close-up Surveys, one or more of the following means for access, acceptable to
the Surveyor, is to be provided:-

permanent staging and passages through structures;
temporary staging, e.g. ladders, and passages through structures;
hydraulic arm vehicles such as conventional cherry pickers, lifts and movable
platforms
boats or rafts
other equivalent means

5.2.3 For Surveys conducted by use of a remote inspection technique, one or more of thefollowing means for access, acceptable to the Surveyor, is to be provided:-

Unmanned robot arm.
Remotely Operated Vehicles (ROV).
Unmanned Aerial Vehicles / Drones.
Other means acceptable to the Classification Society.

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(cont’d)5.3

Equipment for Survey

5.3.1 Thickness measurement is normally to be carried out by means of ultrasonic test
equipment. The accuracy of the equipment is to be proven to the Surveyor as required.
5.3.2 One or more of the following fracture detection procedures may be required if deemednecessary by the Surveyor:-

radiographic equipment
ultrasonic equipment
magnetic particle equipment
dye penetrant

5.4

Survey at Sea or at Anchorage

5.4.1 Survey at sea or at anchorage may be accepted provided the Surveyor is given thenecessary assistance from the personnel on board. Necessary precautions and proceduresfor carrying out the survey are to be in accordance with 5.1, 5.2, and 5.3.
5.4.2 A communication system is to be arranged between the survey party in the tank andthe responsible officer on deck. This system must also include the personnel in charge ofballast pump handling if boats or rafts are used.
5.4.3 When boats or rafts are used, appropriate life jackets are to be available for allparticipants. Boats or rafts are to have satisfactory residual buoyancy and stability even if one
chamber is ruptured. A safety checklist is to be provided.
5.4.4 Surveys of tanks by means of boats or rafts may only be undertaken at the sole
discretion of the Surveyor, who is to take into account the safety arrangements provided,
including weather forecasting and ship response in reasonable sea conditions.
See footnote** Reference is made to IACS Recommendation 39 - Guidelines for use of Boats or Rafts for Close-up surveys.

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6.

PROCEDURES FOR THICKNESS MEASUREMENTS

6.1

General6.1.1 The required thickness measurements, if not carried out by the Society itself, are to bewitnessed by a surveyor of the Society. The surveyor is to be on board to the extent
necessary to control the process.
6.1.2 The thickness measurement company is to be part of the survey planning meeting to
be held prior to commencing the survey.
6.1.3 Thickness measurements of structures in areas where close-up surveys are required
shall be carried out simultaneously with close-up surveys.
6.2

Certification of Thickness Measurement Company

6.2.1 The thickness measurements are to be carried out by a company certified by theClassification Society according to principles stated in Table IV.
6.3

Reporting

6.3.1 A thickness measurement report is to be prepared. The report is to give the location of
measurements, the thickness measured as well as corresponding original thickness.
Furthermore, the report is to give the date when the measurements were carried out, type ofmeasurement equipment, names of personnel and their qualifications and has to be signedby the operator.
6.3.2 The Surveyor is to review the final thickness measurement report and countersign the
cover page.

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TABLE I

(cont’d)

TABLE OF THE MINIMUM REQUIREMENTS FOR CLOSE-UP SURVEY AT HULL
SPECIAL SURVEYS OF GENERAL DRY CARGO SHIPS
Special Survey No.1
Age ≤ 5Special Survey No.2
5 < Age ≤ 10

Special Survey No. 3
10 < Age ≤ 15

(A) Selected shell frames
in one forward and one
aft cargo hold andassociated tween deck
spaces.

(A) Selected shell frames
in all cargo holds andtween deck spaces.

(A) All shell frames in theforward lower cargo holdand 25% frames in eachof the remaining cargoholds and tween deck
spaces including upperand lower end
attachments andadjacent shell plating.

(B) One selected cargohold transverse
bulkhead.
(D) All cargo hold hatch
covers and coamings(plating and stiffeners).

(B) One transverse
bulkhead in each cargo
hold.
(B) Forward and afttransverse bulkhead in
one side ballast tank,including stiffening
system.
(C) One transverse web
with associated plating
and framing in two
representative ballast
tanks of each type (i.e.
topside, hopper side,
side tank or double
bottom tank).
(D) All cargo hold hatch
covers and coamings(plating and stiffeners).
(E) Selected areas of alldeck plating andunderdeck structure
inside line of hatch
openings between
cargo hold hatches.
(F) Selected areas of inner
bottom plating.

(A)
(B)
(C)
(D)
(E)
(F)

Special Survey
No. 4
and Subsequent
Age > 15(A) All shell frames in all

cargo holds and tween
deck spaces including
upper and lower end
attachments andadjacent shell plating.

Areas (B –F) as for Special
Survey No. 3.

(B) All cargo hold transverse
bulkheads.
(B) All transverse bulkheads
in ballast tanks, including
stiffening system.
(C) All transverse webs withassociated plating andframing in each ballast
tanks.
(D) All cargo hold hatch
covers and coamings(plating and stiffeners).
(E) All deck plating andunderdeck structure
inside line of hatch
openings between cargohold hatches.
(F) All areas of inner bottom
plating.

Cargo hold transverse frames.
Cargo hold transverse bulkhead plating, stiffeners and girders.
Transverse web frame or watertight transverse bulkhead in ballast tanks.
Cargo hold hatch covers and coamings. Subject to cargo hold hatch covers of approved design which
structurally have no access to the internals, close-up survey/thickness measurement shall be done ofaccessible parts of hatch covers structures.
Deck plating and underdeck structure inside line of hatch openings between cargo hold hatches.
Inner bottom plating.

See Figs 1 and 2 for the areas corresponding to (A), (B), (C), (D), (E) and (F).
Note:-

Close-up survey of cargo hold transverse bulkheads to carried out at the following levels:
Immediately above the inner bottom and immediately above the tween decks, as applicable.
Mid-height of the bulkheads for holds without tween decks.
Immediately below the main deck plating and tween deck plating.

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TABLE II

(cont’d)

TABLE OF MINIMUM REQUIREMENTS FOR THE THICKNESS MEASUREMENT AT
HULL SPECIAL SURVEYS OF GENERAL DRY CARGO SHIPS
Special Survey No. 1
Age ≤ 5

1. Suspect areas.

Special Survey No. 2
5 < Age ≤ 10

Special Survey No. 3
10 < Age ≤ 15

Special Survey No. 4
and Subsequent
Age >15

1. Suspect areas.

1. Suspect areas.

1. Suspect areas.

2. One transverse sectionof deck plating in way of
a cargo space within theamidships 0.5L.

2. Two transverse sections
within the amidships 0.5L
in way of two different
cargo spaces.

2. Within the cargo lengtharea:

3. Measurement for general 3. Measurement for general
assessment andassessment and recording
recording of corrosionof corrosion pattern ofpattern of those
those structural members
structural members
subject to close-up survey
subject to close-up
according to Table I.
survey according toTable I.
4. Within the cargo lengtharea, each deck plateoutside line of cargo hatch
openings.
5. All wind and water strakes
within the cargo lengtharea.
6. Selected wind and water
strakes outside the cargo
length area.

a) A minimum of threetransverse sections
within the amidships
0.5L.
b) each deck plateoutside line of cargo
hatch openings.
c) Each bottom plate,including lower turnof bilge.
d) Duct keel or pipetunnel plating andinternals.
3. Measurement for general
assessment andrecording of corrosion
pattern of thosestructural members
subject to close-up
survey according toTable I.
4. All wind and water
strakes full length

Notes:
1.

Thickness measurement locations should be selected to provide the best representative sampling of areas
likely to be most exposed to corrosion, considering cargo and ballast history and arrangement and conditionof protective coatings.

2.

For ships less than 100 metres in length, the number of transverse sections required at Special survey No. 3
may be reduced to one and the number of transverse sections at Special Survey No. 4 and subsequent
surveys may be reduced to two.

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TABLE III(cont’d)

GUIDANCE FOR ADDITIONAL THICKNESS MEASUREMENTS IN WAY OF
SUBSTANTIAL CORROSION
Structural Member

Extent of Measurement

Pattern of Measurement

Plating

Suspect area and adjacentplates.
Suspect area.

5 point pattern over 1
square meter.
3 measurements each inline across web and flange.

Stiffeners

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TABLE IV

(cont’d)

PROCEDURES FOR CERTIFICATION OF FIRMS ENGAGED IN THICKNESSMEASUREMENT OF HULL STRUCTURES
1.

Application
This guidance applies for certification of the firms which intend to engage in the
thickness measurement of hull structures of the vessels. UR Z17 also applies.

2.

Procedures for Certification(1)

Submission of Documents:
Following documents are to be submitted to the society for approval;
a)
b)
c)
d)
e)
f)

Outline of firms, e.g. organization and management structure.
Experiences of the firms on thickness measurement inter alia of hull structuresof the vessels.
Technicians careers, i.e. experiences of technicians as thickness
measurement operators, technical knowledge of hull structure etc. Operators,
are to be qualified according to a recognized industrial NDT Standard.
Equipment used for thickness measurement such as ultra-sonic testingmachines and its maintenance/calibration procedures.
A guide for thickness measurement operators.
Training programmes of technicians for thickness measurement.

(2)

Auditing of the firms:
Upon reviewing the documents submitted with satisfactory results, the firm is audited
in order to ascertain that the firm is duly organised and managed in accordance withthe documents submitted, and eventually is capable of conducting thickness
measurement of the hull construction of the ships.

(3)

Certification is conditional on an onboard demonstration at thickness measurements
as well as satisfactory reporting.

3.

Certification(1)

Upon satisfactory results of both the audit of the firm in 2(2) and the demonstration
tests in 2(3) above, the Society will issue a Certificate of Approval as well as a noticeto the effect that the thickness measurement operation system of the firm has beencertified by the Society.

(2)

Renewal/endorsement of the Certificate is to be made at intervals not exceeding 3
years by verification that original conditions are maintained.

4.

Information of any alteration to the Certified Thickness Measurement Operation
SystemIn case where any alteration to the certified thickness measurement operation systemof the firm is made, such an alteration is to be immediately informed to the Society.
Re-audit is made where deemed necessary by the Society.

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(cont’d)5.

Cancellation of Approval
Approval may be cancelled in the following cases:(1)

Where the measurements were improperly carried out or the results were improperly
reported.

(2)

Where the Society's surveyor found any deficiencies in the approved thickness
measurement operation systems of the firm.

(3)

Where the firm failed to inform of any alteration in 4 above to the Society.

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(cont’d)

End ofDocument
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