ULTRASONIC THICKNESS
MEASUREMENT OF SHIPS
SEEN THROUGH
LEGISLATION
ACTION
REPORTING
ULTRASONIC THICKNESS
MEASUREMENT OF SHIPS
LEGISLATION
REASON
WHY?
•
The reason for this legislation/requirement is simple and obvious .
•
Ships, being of steel and operating in a marine environment ,are prone to corrosion.
•
Apart from very obvious cases that corrosion has led to extreme thinning of material ,
sometimes to actual holes on the material, the extent of corrosion is not and has not always
been easy to assess with the naked eye ,even at close-up distance, especially in case of
general corrosion, when it is evenly distributed over a surface.
•
There are three main types of corrosion, apart from the general corrosion:
- pitting corrosion
- grooving corrosion and
- edge corrosion .
•
Therefore, in addition to the basic visual examination of ships to assess the condition of their
structural elements, an additional technical method of structural element thickness
evaluation had to be adopted.
REASON
WHY?
REASON
WHY?
REASON
WHY?
REASON
WHY?
REASON
WHY?
REASON
WHY?
PITTING
REASON
WHY?
GROOVING-HOLES IN THE MATERIAL
REASON
WHY?
EDGE CORROSION
REASON
WHY?
REASON
WHY?
HISTORY OF LEGISLATION
• ORIGINAL REQUIREMENT - DRILLING
• It was a requirement of the Classification
Societies Rules, back in the 50s, that during
Special Surveys of certain types of ships the
thickness of structural elements at various
locations of the hull be ascertained via drilling.
• This had cost implications associated with the
practical problems that created, i.e. time
consumption, opening holes and closing up.
HISTORY OF LEGISLATION
HISTORY OF LEGISLATION
HISTORY OF LEGISLATION
HISTORY OF LEGISLATION
HISTORY OF LEGISLATION
HISTORY OF LEGISLATION
(associated with IACS)
It was n’ t until 1992 that IACS introduced Unified
Requirements for ultrasonic thickness
measurement of ships’ structures during class
surveys of Oil Tankers and Bulk Carriers under
U.R. Z10.1. and U.R. Z10.2 respectively.
Since then there have been 21 revisions to U.R.
Z10.1,the latest being in Jan. 2014, and 31
revisions to U.R.Z10.2, the latest being also in Jan.
2014.
HISTORY OF LEGISLATION
(IACS Formation)
•
•
•
•
•
•
•
IACS can trace its origins back to the International Load Line Convention of 1930 and its
recommendations. The Convention recommended collaboration between Classification Societies to
secure “as much uniformity as possible in the application of the standards of strength upon which
freeboard is based…".
Following the Convention, RINA hosted the first conference of major Societies in 1939 -also
attended by ABS, BV, DNV, GL, LR and NK -which agreed on further cooperation between the
Societies.
A second major Class Society conference, held in 1955, led to the creation of Working Parties on
specific topics and, in 1968, to the formation of IACS by seven leading Societies.
The value of their combined level of technical knowledge and experience was quickly recognized.
In 1969, IACS was given consultative status with the International Maritime Organization (IMO).
It remains the only non-governmental organization with Observer status which is able to develop
and apply Rules.
Today it comprises 12 member Classification Societies :
The current Members are:
ABS ,KR ,BV ,LR ,CCS ,NK ,CRS ,PRS ,DNV –GL ,RINA , RS ,IRS ,
•
Over the years certain Unified Requirements have been agreed by IACS Members and were
transposed into the individual Class Rules
HISTORY OF LEGISLATION
•
An ultrasonic thickness gauge, actually a measuring instrument, is the basis of
a nondestructive testing (NDT) method that evaluates the thickness of a
component by using ultrasonic waves, i.e. by measuring the time it takes for
sound to travel from the transducer through the material to the back end of a
component, and then measuring the time of reflection back to the transducer.
The gauge then determines the thickness based on the velocity of sound
through the material being tested. The standard frequency used by an
ultrasonic thickness gauge is 5MHz.
HISTORY OF LEGISLATION
(associated with IACS)
CURRENT REQUIREMENTS
HISTORY OF LEGISLATION
(associated with IACS)
CURRENT REQUIREMENTS
HISTORY & CURRENT LEGISLATION
(ADDITIONAL CURRENT IACS REQUIREMENTS)
• As it was said and it is known the original IACS requirements about
thickness measurements during periodical surveys referred only to
single-side skin Bulk Carriers and single hull Oil Tankers, the so
called ESP ships, as the requirement for an enhanced survey
program applied to these types of ships.
• The latest requirements refer not only to single-side skin Bulk
Carriers ,and single hull Oil Tankers, but also to double side- skin
Bulk Carriers , double hull Oil Tankers, Chemical Tankers , General
Dry Cargo Ships , Liquefied Gas Carriers.
• However, not all of the aforementioned are ESP ships.ESP ships are
those to which the ESP Code applies, i.e. Single-side and Double
side skin Bulk Carriers, Double hull Oil Tankers and Oil Tankers
other than Double hull , all 500 tons gross and above.
HISTORY & CURRENT LEGISLATION
(ADDITIONAL CURRENT IACS
REQUIREMENTS)
-
Single Hull Oil Tankers U.R.Z10.1
Single-side Skin Bulk Carriers U.R.Z10.2
Double Hull Oil Tankers U.R.Z10.4
Double-side Skin Bulk Carriers U.R.Z10.5
Chemical Tankers U.R.Z10.3
General Dry Cargo Ships U.R.Z7.1
Liquefied Gas Carriers U.R.Z7.2
HISTORY OF LEGISLATION
(associated with IMO)
•
In parallel, IMO introduced IMO Res. A. 744(18) , which was adopted on 04 Nov. 1993,
“GUIDELINES ON THE ENHANCED PROGRAMME OF INSPECTIONS DURING SURVEYS OF BULK CARRIERS & OIL
TANKERS”
emanating from
Res. A. 713(17) on Safety of Ships carrying solid bulk cargoes, by which it specified interim measures to be taken to
improve the Safety of Ships carrying solid bulk cargoes &
Reg. 13 G of MARPOL 1973 which states that Crude Oil Tankers of 20,000 tonnes deadweight and above & Product
Carriers of 30,000 tonnes deadweight and above shall be subject to the enhanced program of inspections the
scope & frequency of which shall at least comply with the guidelines of the Regulation.
•
On 30 Nov. 2011 the 2011 ESP Code was adopted by IMO Res.A.1049(27) and it was made mandatory via IMO Res.
MSC.325(90) which amended SOLAS Reg. XI-1/2 accordingly. Thus it became mandatory through SOLAS on
01.01.2014, superseding IMO Res. A.744.(18).
•
It was also made mandatory through MARPOL Annex I on 1 October 2014, by the adopted IMO Res.
MEPC.236(65) which introduces amendments to CAS .
•
The purpose of the CAS (Condition Assessment Scheme) is verification that the structural condition of single-hull
oil tankers at the time of survey is acceptable and, provided subsequent periodical surveys are satisfactorily
completed and effective maintenance is carried out by the ship’s operator, she will continue to be acceptable for a
continued period of operation.
HISTORY OF LEGISLATION
(associated with IMO)
• It has always been recognized that the best way of improving safety
at sea is by developing international regulations that are followed
by all shipping nations and from the mid-19th century onwards a
number of such treaties were adopted. Several countries proposed
that a permanent international body should be established to
promote maritime safety more effectively, but it was not until the
establishment of the United Nations itself that this was realized. In
1948 an international conference in Geneva adopted a convention
formally establishing IMO (the original name was the InterGovernmental Maritime Consultative Organization or IMCO, but the
name was changed in 1982 to IMO).
• As a specialized agency of the United Nations, IMO is the global
standard-setting authority for the safety, security and
environmental performance of international shipping.
• IMO counts 170 Member States & 3 Associate Members. It is based
in U.K.
HISTORY OF LEGISLATION
(IMO Res.A.744(18))
HISTORY OF LEGISLATION
(IMO Res.A.744(18))
HISTORY OF LEGISLATION
ESP CODE
HISTORY OF LEGISLATION
ESP CODE
HISTORY OF LEGISLATION
(IMO Res.A.744(18))
HISTORY OF LEGISLATION
(IMO Res.A.744(18))
HISTORY OF LEGISLATION
ESP CODE
HISTORY OF LEGISLATION
ESP CODE
HISTORY OF LEGISLATION
ESP CODE
HISTORY OF LEGISLATION
ESP CODE
HISTORY & CURRENT LEGISLATION
The IACS / IMO requirements about ultrasonic thickness measurement of ships were incorporated into the Classification
Societies’ Rules as these are conventionally known, soon after their adoption by the two Bodies.
Later, however, the Common Structural Rules, separate for Tankers and Bulk Carriers (CSR) were formulated and adopted by
IACS and were entered into force in April 2006.
The Common Structural Rules for Double Hull Oil Tankers apply to Double Hull Oil Tankers of 150m length, L, and upward
classed with the Society .
The Common Structural Rules for Bulk Carriers apply to the hull structures of single side skin and double side skin bulk
carriers with unrestricted worldwide navigation, having length L of 90 m or above.
Soon afterwards, in view of certain drawbacks that were ascertained on applying these Rules, new common Rules were
developed by IACS in a single volume, The Harmonized Common Structural Rules for Bulk Carriers and Tankers (CSR-H),
which are to be entered into force on 1 July, 2015.
Both of these sets of Rules omit a specific requirement for Surveys and refer the reader to the IACS Requirements Z.10.1 ,
Z.10.2, and Z.10.5 which shall apply to ships that have been / will be built under these Rules.
However, both of these sets of Rules (one set not yet in force) specify the way that ultrasonic thickness measurements
should be evaluated and assessed against the original scantlings of the ships. This method of evaluation is totally different
to the conventionally known manner of assessment of existing scantlings during surveys (based on a percentage reduction
limit tolerance of the as built scantlings), which is of course due to the different philosophy of the structural design and
determination of scantlings of the types of ships in question adopted in accordance with these Rules (based on the renewal
scantlings as determined by the relevant formulae).
HISTORY OF LEGISLATION
HISTORY OF LEGISLATION
CURRENT LEGISLATION
CURRENT LEGISLATION
CURRENT LEGISLATION
FUTURE LEGISLATION
ULTRASONIC THICKNESS MEASUREMENT OF SHIPS
ACTION
PREPARATION FOR THICKNESS MEASUREMENTS
ACTION
PREPARATION FOR THICKNESS MEASUREMENTS
• Ultrasonic thickness measurement of ships has to
be carried out as a manner/means to detect,
monitor and hence deal with corrosion.
• There are benefits from it:
1) Ensures local ship strength is retained
2) Ensures global ship strength is retained
3) Identifies areas with corrosion which may
require more frequent inspection and
assessment
4) Provides data for corrosion trend analysis for
various types of ships
ACTION
PREPARATION FOR THICKNESS MEASUREMENTS
• UTM of ships is carried out with the involvement/
co-operation of three, or may say four parties:
1. Owners’ Representative
2. Class Surveyor
3. TM Company Representative
4. Dockyard or Shipyard Representative(Not
always)
• Before commencement of any TMs taken the
four or better say three parties shall gather into a
meeting, usually on board the vessel and plan/decide
the sequence and way that TMs are to be taken.
ACTION
PREPARATION FOR THICKNESS MEASUREMENTS
•
Each party has certain obligations emanating from its role and position :
Owners’ Rep.
- Arrange the initial meeting with the remaining parties
- Ensure that the TM Company that he has invited on board is approved by the ship’s Classification
Society
- As such, first to allow access to the ship, as no one can board the vessel without the Owners’
permission
- Have readily available for the Surveyor all ship documentation that is required (Survey Programme, in
case of a special survey, existing ESP documentation , all necessary structural plans) for the forthcoming
survey in question , and advise him of any possible damage to the ship after the last survey has been
held
- Ensure cleanliness of spaces that have to be surveyed/thickness measured.
- Provide means of access to all spaces /places that have to be close up surveyed and thickness
measured
- Ensure safety of access means
The means of access to be provided are :
- Staging
- Cherry Picker
- Rafting (IACS Recommendation 39 “Safe Use of rafts or Boats for Survey (1995) last revision Mar
2009”)
- Lifts and Movable Platforms
- Portable Ladders
depending on the survey circumstances
ACTION
PREPARATION FOR THICKNESS MEASUREMENTS
Classification Surveyor
- Shall be exclusive to the Classification Society that the ship is classed with
- In case of ESP ships two exclusive class Surveyors are required, one of whom shall be
preferably a Senior Surveyor, to jointly conduct the survey as follows:
-Single-skin side Bulk Carriers equal to or greater than 20,000 tons dwt at the 3rd
special and the remaining intermediate and special surveys thereafter
-Single-skin side Bulk carriers equal to or greater than 100,000 tons dwt at the
intermediate survey after the 2nd special survey and at subsequent surveys
-Double-side skin Bulk carriers, Double Hull Oil Tankers and Oil Tankers other than
Double Hull equal to or greater than 20,000 tons dwt at the 3rd special survey and
subsequent surveys
- Definitively be versatile with the Rule Requirements
-
Be aware of the ship’s history based on the information data available from the
ship’s classification records
ACTION
PREPARATION FOR THICKNESS MEASUREMENTS
Representative of the TM Company
- The TM Company shall be approved by the
ship’s Classification Society in accordance
with IACS UR Z.17. ESP Code and IACS documentation
refer to the requirement of the TM Company
certification.
- The TM operator shall be Grade 1 for ESP
ships
- Dockyard or yard representative (as per Rep.’s
decision and depending on the type of the survey and
the age of vessel)
ACTION
PREPARATION FOR THICKNESS MEASUREMENTS
Conclusion of Meeting
Time and sequence of survey, access arrangements , sequence of
availability of spaces required to be surveyed and thickness
measured, agreement between the TM Company and Surveyor as
to time and sequence of close-up surveys , bearing in mind that
when close-up surveys are required the thickness measurements
shall be taken at the same time as both require the availability of
access means, agreement that any deficiencies revealed by the TM
operator in absence of the Surveyor during thickness measurement
process shall immediately be brought to the attention of the
Surveyor and Owners’ Rep., so that necessary and timely action be
decided in order to avoid problems and delay of the ship , number
of Surveyors and TM operators , & may be the most important
ensure that all necessary plans of the ship are available.
ACTION
PREPARATION FOR THICKNESS MEASUREMENTS
As aforesaid during ESP surveys, and following
the agreement during the initial meeting, the
class Surveyor shall be in attendance during
thickness measurement procedure to the time
extent that is necessary for him to control the
process. Ideally two TM operators shall
collaborate during TM process, one taking
measurements and the other recording the
results .
ACTION
• Thickness measurements shall be taken as per the particular survey
requirements and under the guidance of the Surveyor, and the locations
that are selected shall provide the best representative sampling of areas
likely to be most exposed to corrosion, considering cargo and ballast
history and arrangement, and condition of protective coatings about all of
which at least the class Surveyor shall be informed by the ship’s Master or
the Owners’ Representative.
• In certain instances, in view of the ship’s commitments and in order to
shorten the time required for the survey, or to ascertain the condition of
the ship for themselves, the Owners may decide to arrange for thickness
measurements to be taken at sea and not necessarily under the
supervision of the Surveyor, in which case, mainly for ships not having
problems, the thickness measurements may be accepted PROVIDED these
are subsequently verified by spot thickness measurements and accepted
by a Surveyor during the required survey.
ACTION
• Four thickness measurements are required to be taken for each plate, two
forward and two aft, or two starboard and two port depending on plate
orientation.
ACTION
• General practical difficulties encountered during the
thickness measurement process:
-availability of spaces}Problems
-cleanliness of spaces}requiring solution
-access means}
by Owners
-coating/scaling/rusting} Surface material problems
-pitting}
requiring a solution
-grooving}
by Surveyor/TM
operator, Owner
may also be involved
ACTION
•
•
•
Availability of spaces problem is actually minimized on ESP ships during special
surveys by the Survey Programme proposing the sequence of survey as well as the
means of access to be provided, which is required to be submitted to the ship’s
class Society for agreement. This is agreed with or without amendments and
returned to the Owners for follow up and it is taken into consideration during the
initial meeting of the three/four parties. It has to be submitted at least six months
before the commencement of the survey.
Dependent on the above comes the cleanliness of spaces problem which has to be
dealt with by the ship’s Master/crew and/or shipyard/dockyard in co-ordination
with Owners’ Rep. Spaces offered for survey/TMs shall be sufficiently clean & free
from water, scale, dirt, oil residues e.t.c. to reveal corrosion and any other
structural problems as well as to enable TMs to be taken. Ideally , if necessary,
they shall be sand or hydro blasted, and certainly dry and clean with all sediments
removed, all loose coating and rust flakes removed. And definitely of paramount
importance is that all spaces shall be gas freed, ventilated as applicable, and
illuminated before any member of crew or any of the aforementioned parties
enters any space.
Safety of access means provided shall be ensured. No party shall make use of any
means that appear unsafe.
ACTION
• Scaling; Heavy scaling may be removed by hydro
or sand blasting and this has to be agreed
between the Surveyor and the Owner (and the
dockyard). In most cases this is done upon
Owners’ initiative.
• Rusting; If not heavy the area may be cleaned by
the TM operator at locations where TMs are
required to be taken
• Coating; to avoid impairing a good condition of
the coating , coating thickness gauges may be
used.
ACTION
EVALUATION OF RESULTS GENERAL CORROSION
Pre-CSR Ships built under the Classification Rules
ACTION
EVALUATION OF RESULTS
GENERAL CORROSION
•
On pre-CSR ships thickness measurements shall be assessed on the basis of a maximum acceptable
percentage diminution of the steel material which reflects the way the Rules were compiled which
has also been empirical, apart from scientific. This acceptable diminution is given as a percentage
of the original thickness of the structural member in question and it differs from structural member
to structural member and from location to location on board ships as well as from ship type to ship
type. To this end ships are categorized in three categories, 1, 2 and 3,depending on the ship type
and length . The above refers to a relatively even corrosion pattern over a surface.
•
Category 1: Non CSR Oil tankers, chemical tankers, dry bulk cargo ships, combination carriers and
liquefied gas ships having a length L equal to or greater than 90 metres.
Category 2:
All remaining ship types not included in Category 1 and having a length L equal to or greater than
90 metres.
Category 3:
All ship types having a length L less than 90 metres
•
•
•
•
•
Attention should be given to Suspect Areas which are locations showing Substantial Corrosion
and/or are considered by the Surveyor to be prone to rapid wastage. Also to Critical Structural
Areas which are locations which have been identified from calculations to require monitoring or
from the service history of the subject ship or from similar or sister ships (if available) to be
sensitive to cracking, buckling or corrosion which would impair the structural integrity of the ship.
ACTION
EVALUATION OF RESULTS
GENERAL CORROSION
Areas which are found with substantial corrosion (75% of acceptable diminution)
during surveys shall be under observation/re measured during annual surveys
and re-assessed.
IACS documents include all details for performing measurements of areas with
substantial corrosion.
Areas which are found with excessive diminution, i.e. greater than the allowable
values, shall be renewed with material of original thickness and grade.
In case a surface area/structural member is of a high grade , say high tensile steel
32 and the ship is in a port where such material grade is not available, steel of a
higher or lower grade may be used (i.e steel H36 or mild steel) of scantlings
equivalent to the original.
Similarly, in case of stiffeners, if the same profile and grade of steel is not
available, equivalent profiles and lower or higher grade of steel may be used in
lieu provided the renewal stiffeners have the same properties of section modulus
and inertia as the originally built ones, all to the Surveyor’s satisfaction.
ACTION
EVALUATION OF RESULTS
GENERAL CORROSION-NON CSR SHIPS
•
Permissible Diminution Levels for Category 1 non-CSR Oil Tankers, Chemical Tankers and
Liquefied Gas Carriers
•
Hull Envelope
•
•
•
•
•
•
Strength deck plating
Side shell plating
Bottom shell plating
Forecastle deck plating
Poop deck plating
Superstructure deck plating
20%
20%
20%
25%
25%
25%
ACTION
EVALUATION OF RESULTS
GENERAL CORROSION-NON CSR SHIPS
•
General – Internal Structure
•
•
•
Transverse bulkhead plating
Transverse bulkhead stiffeners
Transverse bulkhead horizontal
stringer plating and face plates
Longitudinal bulkhead plating
Longitudinal bulkhead longitudinals
Strength deck longitudinals
Side shell longitudinals
Bottom shell longitudinals
Inner bottom plating
Inner bottom longitudinals
Horizontal girder (fabricated)
Horizontal girder face plate
Horizontal girder rolled section
•
•
•
•
•
•
•
•
•
•
25%
25%
25%
20%
25%
25%
25%
25%
20%
25%
20%
25%
25%
ACTION
EVALUATION OF RESULTS
GENERAL CORROSION-NON CSR SHIPS
•
•
•
•
•
•
•
•
•
•
•
Deck girder plating (fabricated)
30%
Deck girder face plates
25%
Deck girder (rolled section)
25%
Bottom girder plating (fabricated)
30%
Bottom girder plating (rolled section)
25%
Bottom girder face plates
25%
SWBT* & COT web frame plating
25%
SWBT* & COT web frame face plates
25%
SWBT* & COT web frame stiffeners
25%
SWBT* & COT web frame secondary structure 30%
*SWBT includes any tanks (including peak tanks, wing tanks, centre
tanks, double bottom tanks, side tanks and deep tanks) designated
for the use of salt water ballast.
ACTION
EVALUATION OF RESULTS
GENERAL CORROSION-NON CSR SHIPS
•
•
•
•
•
•
•
•
•
•
•
•
•
Centre tank deck transverse plating
Centre tank deck transverse face plate
Centre tank deck transverse stiffeners
Centre tank deck transverse secondary structure
Centre tank bottom transverse plating
Centre tank bottom transverse face plates
Centre tank bottom transverse stiffeners
Centre tank bottom transverse secondary structure
Peak tank longitudinal bulkhead plating
Peak tank longitudinal bulkhead stiffeners
Peak tank stringer plating
Plating of seachests
Shell plating in way of overboard discharges
25%
25%
25%
30%
25%
25%
25%
30%
30%
25%
30%
30%
30%
ACTION
EVALUATION OF RESULTS
GENERAL CORROSION-NON CSR SHIPS
•
Permissible Diminution Levels for General Dry Cargo Ship s and All Other Category 2 & 3 Type Ships
•
Hull Envelope
•
•
•
•
•
•
•
•
•
•
•
•
•
Strength deck plating
30%
Side shell plating
30%
Bottom shell plating
30%
Deck plating inside line of openings, where fitted 30%
Forecastle deck plating
30%
Poop deck plating
30%
Superstructure deck plating
30%
Miscellaneous & Internal Structure Strength deck longitudinals 25%
Side shell longitudinals
25%
Bottom shell longitudinals
25%
Transverse bulkhead plain plating
30%
Transverse bulkhead corrugated plating
25%
Transverse bulkhead stiffeners
25%
ACTION
EVALUATION OF RESULTS
GENERAL CORROSION
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Longitudinal bulkhead plating
Longitudinal bulkhead stiffeners
Inner bottom plating
Inner bottom longitudinals
Hopper sloping plating
Hopper sloping longitudinals
Topside sloping plating
Topside sloping longitudinals
SWBT frames or diaphragms
Cargo hold shell frame s and end brackets
Cargo hold hatch cover plating
Cargo hold hatch cover stiffeners
Cargo hold hatch coaming plating
Cargo hold hatch coaming stiffeners
SWDBT Floors
Web frame plating
Web frame face plates
Web frame secondary structure
Other miscellaneous plating
Other miscellaneous longitudinals or stiffeners
Plating of seachests
Shell plating in way of overboard discharges
30%
25%
30%
25%
30%
25%
30%
25%
25%
25%
30%
25%
30%
25%
25%
25%
25%
30%
30%
25%
30%
30%
ACTION
EVALUATION OF RESULTS
GENERAL CORROSION
•
Pre - CSR Tankers
For tankers having a length L of 90 metres or above, the thickness measurements
of upper deck, apart from satisfying the local diminution acceptable criteria ,shall
be checked for compliance with the deck plating residual buckling thickness
requirements according to the following equations:
1) tr = (to-1.5)mm
2) tr = s / Jr mm
The residual buckling thickness shall be the smaller of the above two values,
where :
tr = the residual buckling thickness
to = the original thickness
s = the spacing of the deck longitudinals
Jr a factor dependent on location and steel type, as given in the following table.
It is worth mentioning that in certain instances the residual buckling thickness may
be the limiting factor for tanker upper deck renewals.
ACTION
EVALUATION OF RESULTS
GENERAL CORROSION
ACTION
EVALUATION OF RESULTS
GENERAL CORROSION
• CSR SHIPS
• On CSR ships the minimum allowable thickness
diminution is linked to the net thickness philosophy that
has been adopted on developing CSR Rules. The strength
calculations carried out during the design stage are based
on the so called net scantlings. New building gross
scantlings requirements are calculated by the addition of
an allowance for the expected wastage during the design
life of the ship to the required net scantlings determined
in accordance with the Rule requirements. The net
scantlings are meant to remain / not to be reduced
throughout the life of the ship.
ACTION
EVALUATION OF RESULTS
CSR SHIPS
ACTION
EVALUATION OF RESULTS
GENERAL CORROSION
CSR – Double Hull Oil Tankers
For evenly distributed local corrosion the evaluation of thickness measurement results shall be based on the Renewal
thickness, where:
tren = tas-built-twas-town-tcorr-2.5
tren
:renewal thickness
tas-built :as built thickness
twas
: wastage thickness, given by the Rules, depending on the member and
space in question
town
: any voluntary Owners’ thickness that has been added during construction
tcorr-2.5 :=0.5 mm, wastage allowance in reserve for corrosion occurring in the 2 1/2
years between Intermediate and Special Survey
If
if
tmeasured > trenewal
tmeasured <trenewal
no action or other assessment is required
area concerned shall be renewed with material of a
repair thickness and same grade as the original
trepair=tas-built-town
Re-examination and additional thickness measurements at annual and intermediate surveys are required where the
measured thickness, tmeasured ,is less than the allowable thickness at annual survey, tannual, i.e
tmeasured < tannual ,where
tannual = tas-built – town - twas
ACTION
EVALUATION OF RESULTS
GENERAL CORROSION
•
CSR – Single - side skin and Double – side skin Bulk Carriers
At general corrosion,i.e. evenly distributed over the surface,
tmeasured < trenewal
where,
trenewal = tas-built-tc-tvoluntary addition
tc :corrosion addition
tvol.add. :Owners ’voluntary addition
Corrosion addition is as per CSR relevant table
Substantial corrosion in this case is an extent of corrosion such that assessment of
the corrosion pattern indicates a measured thickness such as
trenewal <tmeasured < trenewal + treserve
treserve ;is the reserve thickness to account for anticipated thickness diminution
that may occur during a survey interval of 2 ½ years and it is equal to 0.5 mm
In the above case coating may be applied over the affected area or annual gauging
may be adopted as an alternative to steel renewal
ACTION
EVALUATION OF RESULTS
GENERAL CORROSION
ACTION
EVALUATION OF RESULTS
GENERAL CORROSION
• CSR – Single - side skin and Double – side skin Bulk Carriers
and Double Hull Oil Tankers – Harmonized
The corrosion approach and the corrosion protection of the
ships have not been significantly changed from CSR-OT or
CSR-BC, but additional studies were performed to confirm
the corrosion addition values and the issue of protection
against corrosion in CSR-Harmonized.
The Harmonized CSR has been developed by blending the
requirements and philosophies of the existing CSR-OT and
CSR-BC and have benefitted from extensive review by
industry. The net thickness philosophy remains.
ACTION
EVALUATION OF RESULTS
GENERAL CORROSION
tdm is the Design Production margin, in mm, which is the difference
between offered gross thickness & required gross thickness
ACTION
EVALUATION OF RESULTS
GENERAL CORROSION
•
CSR-H Bulk Carriers and Tankers
At general corrosion evenly distributed over a surface:
trenewal = tas-built – tc –t voluntary addition
tc = corrosion addition = Round up 0.5(tc1+tc2) + t reserve ,where
tc1,tc2 ; corrosion addition in mm on one side of the considered structural member. Round up
0.5(t) means that the corrosion addition should be rounded to the upper half millimetre
t reserve = 0.5 m
Total corrosion addition tc shall not be taken less than 2mm except for web and face plate of
stiffeners or in way of internals in way of dry spaces where 1.5 mm is applicable
trepair = tas-built –tvol.add.
Alternative solutions may be adopted if
trenewal < or = tmeasured < trenewal+treserve
The as-built , the renewal, and any voluntary addition thicknesses shall be clearly stated on the
plans .
ACTION
EVALUATION OF RESULTS
GENERAL CORROSION
ACTION
EVALUATION OF RESULTS
LOCAL CORROSION - PITTING
•
Pitting is a problem mostly encountered on tankers. It is in fact heavy localized corrosion,
which forms the so called pits over a generally corroded area and it shall be differently dealt
with on ships built according to class Rules and ships built according to CSR or CSR-H.
•
To this effect a pit gauge may be required to measure the extent of pitting at pits, or
alternatively a miniature transducer (3-5mm dia.) – a conventional transducer is of 10mm
dia- .
•
In case the thickness of the remaining (sound) material at heavy pits is acceptable, depending
on the ship age, if the condition of the material area surrounding the pits in question is
acceptable, the pitted area may be repaired/filled in by
- welding
- coating with special material
and not renewed.
•
However, the condition of the surrounding area shall be carefully examined and verified by
numerous thickness measurements
•
INSERT SKETCH IF OBTAINED
ACTION
EVALUATION OF RESULTS
LOCAL CORROSION - PITTING
• Pre-CSR ships
On ships built in accordance with the
Classification Rules a pitted area may be repaired
and not renewed provided the thickness of the
remaining material in way of all pits is not less
than a certain value. For LR ships this thickness
value is confirmed at 6 mm. If the depth of pits
at any location is such that the thickness of
remaining material is less than , say, 6mm, the
plate in question has to be renewed.
ACTION
EVALUATION OF RESULTS
LOCAL CORROSION - PITTING
• CSR Double Hull Tankers (allowable pitting)
• “Pitting corrosion is defined as scattered corrosion spots/areas with local
material reductions which are greater than the general corrosion in the
surrounding area. “
(defn as per CSR)
On tankers built in accordance with the Common Structural Rules a pitted
area may be accepted and not renewed provided the thickness of the
remaining material in way of all pits is not less than the lesser of the
following values :
tmeasured >=0,7(tas-built – t Owners)
tmeasured >=trenewal-1 mm
and the pitting intensity of the considered area is less than 20%.
ACTION
EVALUATION OF RESULTS
LOCAL CORROSION – PITTING
CSR_ DOUBLE HULL TANKERS
ACTION
EVALUATION OF RESULTS
LOCAL CORROSION - PITTING
• CSR Bulk Carriers
For pitted areas the following shall apply:
- where the pitting intensity of the considered surface area is
less than 15%, the area in question may be coated without any thickness
measurements to be taken.
- where the pitting intensity of the concerned area is greater than 15%,
pit measurements shall be taken of the pitted area , about 5 over an area of
300mm diameter or more and the minimum remaining thickness in pits shall be greater than:
75% of the as-built thickness in the frame and
end brackets webs and flanges
70% of the as-built thickness in the side
shell , hopper side and topside tank plating attached
to the each side frame over a width up to 30mm each side
without being greater than trenewal
The average thickness across any cross section in the plating is not to be less than the renewal
criteria for general corrosion previously defined
ACTION
EVALUATION OF RESULTS
LOCAL CORROSION - PITTING
• CSR Bulk Carriers
ACTION
EVALUATION OF RESULTS
LOCAL CORROSION - GROOVING
“Grooving corrosion is typically local material loss adjacent to weld joints
along abutting stiffeners and at stiffener or plate butts or seams.”
ACTION
EVALUATION OF RESULT
GROOVING – EDGE CORROSION
• Grooving/edge corrosion form normal material
deterioration on pre-CSR ships.
• Depending on the severity of grooving this may be repaired
by filling the grooves with welding material.
• Edge corrosion around openings of girders / floor may be
dealt with by enlarging the opening in question down to
sound material by removing deteriorated material and
possibly stiffening it with a flat bar or a material ring all
around. Depending on the location of the structural
member in question the opening may be completely closed
by new material.
ACTION
EVALUATION OF RESULTS
LOCAL CORROSION - GROOVING
•
CSR – Double Hull Oil Tankers and Bulk Carriers – acceptance criteria
Where the groove breadth is a maximum of 15% of the web height, but not more
than 30mm, the measured thickness, tm, in the grooved area is to meet the lesser
of the following criteria:
t m ≥ 0.75 (tas-built - tvol add) mm
tm ≥ tren - 0.5 mm
but is not to be less than
tm = 6 mm where,
tm
: measured thickness
tas-built: as built thickness
tvol add : voluntary added corrosion
tren : renewal thickness as defined for general corrosion
Structural members with areas of grooving greater than those described above
are to be assessed based on the criteria for general corrosion of CSR using the
average measured thickness across the plating/stiffener.
ACTION
EVALUATION OF RESULTS
LOCAL CORROSION – EDGE CORROSION
• CSR – Double Hull Tankers and Bulk Carriers –
“Edge corrosion is defined as local corrosion at the free edges of plates,
stiffeners, primary support members and around openings. An example of
edge corrosion is shown in the following Figure.”
ACTION
EVALUATION OF RESULTS
LOCAL CORROSION – EDGE CORROSION
•
CSR – Double Hull Tankers and Bulk Carriers – acceptance criteria
Provided that the overall corroded height of the edge corrosion of the flange, or web in
the case of flat bar stiffeners, is less than 25%, of the stiffener flange breadth or web
height, as applicable, the measured thickness, tm, is to meet the lesser of the following
criteria :
tmeas >= 0.70 (tas-built – town)
tmeas>= tren – 1 mm
The average measured thickness across the breadth or height of the stiffener is not to
be less than tren.
Plate edges at openings for manholes, lightening holes etc. may be below the minimum
renewal thickness provided that:
(a) the maximum extent of the reduced plate thickness, below the minimum tren, from
the opening edge is not more than 20% of the smallest dimension of the opening and
does not exceed 100mm
(b) rough or uneven edges may be cropped-back provided that the maximum
dimension of the opening is not increased by more than 10%.
ACTION
• It may be of interest to show how thickness
measurements shall be taken on side shell
frames of single-side skin Bulk Carriers in
order to ensure compliance with URS31. The
aim of URS 31 was to reinforce single-side skin
Bulk Carriers in respect of the aforesaid
structural members and it applies to ships
built before 01 July 1998.
ACTION
GAUGING OF SIDE SHELL FRAMES AND BRACKETS IN SINGLE SIDE
SKIN BULK CARRIERS REQUIRED TO COMPLY WITH UR S31
ACTION
GAUGING OF SIDE SHELL FRAMES AND BRACKETS IN SINGLE SIDE SKIN BULK
CARRIERS REQUIRED TO COMPLY WITH UR S31
For the purpose of steel renewal, sand blasting and coating, four zones A, B, C and
D are defined. Zones A & B are considered to be the most critical zones.
Pitting and grooving are the usual corrosion phenomena that may be found on
side shell frames, both at webs and face plates.
To ascertain compliance with the requirements of URS 31 pitting has to be
measured, and the remaining thickness material in way to be calculated and
assessed.
If pitting intensity is higher than 15% in an area , then thickness measurements are
to be taken to check the extent of the pitting corrosion. The 15% is based upon
pitting or grooving on only one side of the plate.
In cases where pitting is evidently exceeding 15 % then the thickness
measurements shall be taken as in the case of CSR Bulk Carriers
ACTION
GAUGING OF SIDE SHELL FRAMES AND BRACKETS IN SINGLE SIDE SKIN BULK
CARRIERS REQUIRED TO COMPLY WITH UR S31
• The number of side frames required to be measured are equivalent
to those of Special Survey or Intermediate Survey corresponding to
the ship’s age. Representative thickness measurements are to be
taken for each zone as specified in the relevant sketch.
• Special consideration to the extent of the thickness measurements
may be given by the Class Surveyor, if the structural members show
no thickness diminution with respect to the as built thicknesses and
the coating is found in "as-new" condition (i.e., without breakdown
or rusting).
• Where gauging readings close to the criteria are found, the number
of hold frames to be measured is to be increased.
• If renewal or other measures according to S31 are to be applied on
individual frames in a hold, then all frames in that hold are to be
gauged.
ACTION
GAUGING OF SIDE SHELL FRAMES AND BRACKETS IN SINGLE SIDE SKIN BULK CARRIERS REQUIRED
TO COMPLY WITH UR S31
For Zones A, B & D five measurements shall be taken. The five measurements shall be within
an area across the full depth of the web and vertically along the same distance. The average
reading shall be included in the thickness measurement report.
Depending upon the condition of the web in way of Zone C, the web may be measured by
taking three measurements over the length of Zone C and considering the average. The
average reading is to be compared with the allowable thickness. If the web plating is found
with general corrosion then five measurements shall be taken and the average value
assessed.
Additional measurements shall be taken at the lower bracket in case the lower bracket length
or depth does not meet the requirements in UR S12(Rev.3), at sections a) and b) to calculate
the actual section modulus required in UR S31. At least 2 readings on the flange or faceplate
shall be taken in way of each section. Also, at least one reading of the attached shell plating is
to be taken on each side of the frame (i.e. fore and aft) in way of section a) and section b).
ACTION
GAUGING OF SIDE SHELL FRAMES AND BRACKETS IN SINGLE SIDE
SKIN BULK CARRIERS REQUIRED TO COMPLY WITH UR S31
ACTION
EVALUATION OF LONGITUDINAL STRENGTH
• In addition to the local strength assessment
requirements during the service life of ships,
Classification Societies had also requirements
about global strength assessment.
• The longitudinal strength assessment
requirements were applicable to certain type of
ships only and at certain classification surveys.
• Evaluation of longitudinal strength of ships during
their service life is actually evaluation of sectional
properties (section modulus and inertia)of the
ship’s transverse sections within 0.4L mid ships.
ACTION
EVALUATION OF LONGITUDINAL STRENGTH
ACTION
EVALUATION OF LONGITUDINAL STRENGTH
ACTION
EVALUATION OF LONGITUDINAL STRENGTH
ACTION
EVALUATION OF LONGITUDINAL STRENGTH
ACTION
EVALUATION OF LONGITUDINAL STRENGTH
• Classification Societies carried out this evaluation not by calculating the
sectional properties of transverse sections within 0.4L , but for the
selected number of transverse sections (depending on the type of ship
and survey), by defining the Topside and Bottom areas and by adding up
the measured thickness of each strake and each longitudinal member
included therein and assessing these sums as a percentage of the sum of
the original thicknesses of the same areas.
• Top side and Bottom areas were defined as all continuous longitudinal
material from the deck to a distance 0.1Dmld meters below the molded
deck line at side and from the bottom to a distance 0.1Dmld meters above
the base line respectively.
• If the sum of measured thicknesses was more than 90% of the sum of the
original thicknesses, the properties of the section were considered
satisfactory and no further action was required.
• Otherwise steel renewal or reinforcement was required, as in the case of
local corrosion, and the aforementioned sums were reevaluated so as to
ensure compliance with the percentage criterion.
ACTION
EVALUATION OF LONGITUDINAL STRENGTH
• Insert TM8 form EXAMPLE
ACTION
EVALUATION OF LONGITUDINAL STRENGTH
•
•
•
•
•
In 1992 Annex 12 to IMO Res. A.744(18) was entered into force which required
that on oil tankers of 130 meters in length and upward (as defined in the Load Line
Convention in force)and of over 10 years of age, the longitudinal strength of the
ship’s hull girder should be evaluated in compliance with the requirements of the
Annex on the basis of the thickness measured, renewed or reinforced, as
appropriate, during the renewal Survey of the Cargo Ship Safety Construction
Certificate.
It was then that Classification Societies commenced evaluating the ship’s
longitudinal strength by evaluating also the sectional properties of three selected
transverse sections during her service life for survey purposes.
To this end they developed a suitable software, namely Lloyd’s Register developed
TMCalc ,via the required sectional properties were evaluated.
The three transverse sections selected for the evaluation of longitudinal strength
of tankers which were built under the classification Rules shall lie within 0.4L and
shall preferably include a section in way of a ballast tank, which is always the case
for a Double hull tanker but not necessarily for a conventional crude oil carrier.
Upon entry into force of the CSR Rules, slightly different global strength
requirements were entered into force, with different acceptance criteria and new
definitions:
ACTION
EVALUATION OF LONGITUDINAL STRENGTH
•
IACS formulates the current requirements as follows for Single Hull Tankers:
1. Ships regardless of the date of construction:
Transverse sectional areas of deck flange (deck plating and deck longitudinals) and
bottom flange (bottom shell plating and bottom longitudinals) of the ship’s hull girder
have been calculated by using the thickness measured, renewed or reinforced, as
appropriate, during the special survey most recently conducted after the ship reached
10 years of age, and found that the diminution of the transverse sectional area does not
exceed 10% of the as-built area.
2. Ships constructed on or after 1 July 2002:
Section moduli of transverse section of the ship’s hull girder have been calculated by
using the thickness of structural members measured, renewed or reinforced, as
appropriate, during the special survey most recently conducted after the ship reached
10 years of age , and are found to be within their diminution limits determined by the
Classification Society.
ACTION
EVALUATION OF LONGITUDINAL STRENGTH
3. Ships constructed before 1 July 2002: Section moduli of transverse section of the ship’s hull girder
have been calculated by using the thickness of structural members measured, renewed or
reinforced, as appropriate, during the special survey most recently conducted after the ship
reached 10 years of age in accordance with the provisions of paragraph 2.2.1.2 of Annex III, and
found to meet the criteria required by the Classification Society and that the actual modulus, Zact,
is not less than a minimum value,Zmc:
Zmc = cL2B (Cb + 0.7)k (cm3) where
L = Length of ships. L is the distance, in metres, on the summer load waterline from the fore side of
stem to the after side of the rudder post, or the centre of the rudder stock if there is no rudder
post. L is not to be less than 96%, and need not be greater than 97%, of the extreme length on the
summer load waterline. In ships with unusual stern and bow arrangement the length L may be
specially considered.
B = Greatest moulded breadth in metres.
Cb = Moulded block coefficient at draught d corresponding to summer load waterline, based on L
and B. Cb is not to be taken less than 0.60.
ACTION
EVALUATION OF LONGITUDINAL STRENGTH
Acceptance Criteria for the Hull Girder Strength
a) CSR and non CSR Deck and Bottom Zones: The measured sectional areas of the Deck Zone and of
the Bottom Zone which are the sum of the measured item areas of the considered zones are not to
be less than 90% of the sectional area of the corresponding zones determined with the gross
offered thicknesses (original Rule sectional area).
b) Non CSR Neutral axis Zone: The measured sectional area of the Neutral Axis Zone, which is the
sum of the measured plating areas of this zone, is not to be less than 85% of the sectional area of
the corresponding zone determined with the gross offered thicknesses (original Rule sectional
area).
c) CSR Neutral Axis Zone: The current sectional area of the neutral axis zone, which is the sum of
the measured plating areas of this zone, is not to be less than the sectional area of the neutral axis
zone calculated with the gross offered thickness minus 0.5 tc.
(Gauged Thickness) x (Plate/Profile Width/Height) >(Plate/Profile Width/Height) x (((As-Built
Thickness) – (Owners Voluntary Addition) – (Renewal Thickness)) / 2) + (Renewal Thickness))
ACTION
EVALUATION OF LONGITUDINAL STRENGTH
For the purposes of assessment, each Transverse Section is therefore divided into 3 zones:-
‐ Deck Zone
For Bulk Carriers, Ore Carriers and other ESP ships of similar configuration:
strength deck plating
deck stringer
sheer strake
side shell plating
top side tank sloped plating, including horizontal
and vertical strakes
longitudinal stiffeners connected to the above
mentioned plating
For Oil Tankers (including Chemical Tankers, Oil/Bulk/Ore and Ore/Oil Ships):
strength deck plating
deck longitudinals
For all other ship types:
continuous longitudinal elements above the level corresponding to 0.9Dmld (where Dmld =
Depth of ship) above the base line.
ACTION
EVALUATION OF LONGITUDINAL STRENGTH
-
Bottom zone
For Bulk Carriers, Ore Carriers (and other ESP ships of similar structural configuration):
elements up to the upper level of the hopper sloping plating or up to and including the inner bottom plating if
there is no hopper tank:
Keel plate
Bottom plating
Bilge plating
Bottom girders
Inner bottom plating
Hopper tank sloping plating, and horizontal plating, if
any
Side shell plating
Longitudinal stiffeners and girders connected to the above
mentioned plating.
For Oil Tankers (including Chemical Tankers, Oil/Bulk/Ore and Ore/Oil Ships):
Keel plate
Bottom plating
Bottom longitudinals and double bottom girders in way.
For all other ship types:
elements below the level corresponding to 0.1D (where D = Depth of ship) above the base line.
ACTION
EVALUATION OF LONGITUDINAL STRENGTH
-The neutral axis zone
For all ship types includes longitudinal
material between the deck zone and the
bottom zone, for example:
Side shell plating
Inner hull plating (longitudinal bulkheads and
attached longitudinals (if any)
Inner bottom plating and attached
longitudinals (for Tankers only)
ACTION
• Following the above it is clear that it is essential for the
TM operator to advise timely the Surveyor (if not
present at the time the measurements are taken) and
the Owners’ Rep. of any findings requiring rectification.
Depending on the seriousness of the material
deterioration and following an agreement between the
Surveyor and the Owners’ Rep. the affected material
area may be rectified by any of the following methods:
- Steel Coating
- Steel Reinforcement
- Steel Renewal
- Welding
- Coating with special material
ACTION
•
It is also essential that the longitudinal strength results are evaluated soon after the three section
measurements are taken so as to confirm whether there are any problems that require to be dealt
with. That is:
- Classification Rules Ships :
In case the deck area is found more than
7.5 per cent deteriorated from the original
deck area, two additional transverse
sections shall be selected and thickness
measured in order to ascertain the condition
of the ship.
In case the deck area is found above 10 per cent deteriorated , steel
renewal or steel reinforcement may be required as it will be agreed
between the Surveyor (class) and the Owners’ Rep.
-
CSR and CSR-Harmonized ships are to be longitudinal strength wise evaluated on a different
basis .
ACTION
• Upon completion of the thickness
measurements process and timely
communication of the results to the Surveyor
and the Owners’ Rep., the TM Operator shall
prepare a Draught Survey Report and submit
same to the Surveyor for his assessment. On
satisfactory assessment the Surveyor shall
advise the TM operator accordingly so that he
can proceed with the preparation of the Final
Thickness Measurement Report.
REPORTING
REPORTING
• Upon satisfactory acceptance of the Draught Survey Report
by the Surveyor, the Final Thickness Measurement Report
shall be compiled by the TM Operator for submission to the
Classification Society.
• The report is prepared using the Thickness Measurement
software developed by the Classification Society with which
the ship is classed and it includes and is based on the
Thickness Measurements Forms developed by IACS.
• It would be a serious omission not to mention that Lloyd’s
Register just recently (October 2014) launched its new
thickness measurement software under the name
“Argonaut” to be used for pre-CSR and CSR ships.
REPORTING
•
Main things that have to be considered when compiling the Report but also beforehand , during the
survey, upon evaluation of a particular ship area/structural member are:
- c.c. Notation;
In case the ship has a c.c. Notation, care shall be taken so that the
thickness measurements are compared and evaluated against the ship
scantlings before allowance for c.c. notation, and not against the “as
built” scantlings.
-
Owners’ extra
shall be ignored when
assessing thickness measurements
-
Re-assessment of scantlings.
In case a ship has been re-assessed thickness measurements shall be
assessed against the re-assessed scantlings and not the “as built”
scantlings.
The above apply to pre-CSR existing ships.
In case of CSR and CSR-H it is worth stressing that the original/as built scantlings are clearly shown
on the structural plans.
REPORTING
• Other items to be given attention by the TM Company/operator during
compilation of the Report are :
1. Correctness of original scantlings
2. Correctness of the thickness measurements given in the Report against
those included in the Draught Report which have been
verified/accepted by the attending Surveyor
3. Correctness of the type of Form used to include the readings for a
particular structural member
(all the above three aim at correct assessment of the
thickness measurements taken)
4. Completeness of the Report, i.e. ensure that all structural
members required to be thickness measured at that particular
survey have been included
5. All Ship and Survey identification particulars to be correctly included in
the Report
REPORTING
•
Non CSR TM Forms
•
•
TM1 is to be used for reporting the thickness measurement of deck plating, bottom shell plating and side shell plating within the cargo length area.
TM2~3 is to be used for reporting the thickness measurement of the transverse section longitudinal plating, girders and longitudinal frames and
stiffeners under the deck, bottom or neutral axis zones.
TM4 is to be used for reporting the thickness measurement of transverse structural members and all attached structure in water ballast tanks, deep
tanks, cargo tanks and void spaces. This excludes reporting of W.T. transverse bulkheads of any type in any location.
TM5 is to be used for reporting the thickness measurement of W.T. transverse bulkheads where appropriate. This excludes reporting of bulk carrier
W.T. transverse bulkheads subject to assessment derived by Unified Requirements Strength 18 and 19 (UR S18, UR S19).
TM5 UR S18 is to be used for reporting the thickness measurement of bulk carrier W.T. transverse bulkheads subject to assessment in accordance
with Unified Requirements Strength 18 (UR S18).
TM5 UR S19% is to be used for reporting the thickness measurement of bulk carrier W.T. transverse bulkheads subject to assessment in accordance
with Unified Requirements Strength 19 (UR S19).This form is to be used in case the approved bulkhead upgrade plan does not provide any additional
thickness measurement requirements, but requires applicability of Class Rules (diminution criteria) in order to assess the bulkhead during periodical
surveys.
TM5 UR S19 is to be used for reporting the thickness measurement of bulk carrier W.T. transverse bulkheads subject to assessment in accordance
with Unified Requirements Strength 19 (UR S19) and the approved bulkhead upgrade plan, with additional thickness measurement requirements to
conventional Class Rules(diminution criteria).
TM6 is to be used for reporting the thickness measurement of miscellaneous structural members. Also this form is to be used for reporting of any
critical areas or any additional survey areas outside the normal scope of survey that would require to be thickness measured. This form is also to be
used for reporting of the deck, shell and bottom plating outside the cargo length area.
TM6 UR S21 is to be used for reporting of Scantlings of Hatch Covers / Coamings of Bulk Carrier cargo holds assessed in accordance with Unified
Requirements Strength 21 (UR S21).
TM6 UR S21A is to be used for reporting of Scantlings of Hatch Covers / Coamings of cargo holds for all ships except Bulk Carriers, Ore Carriers and
Combination Carriers, assessed in accordance with Unified Requirements Strength 21A (UR S21A).
TM7 is to be used for reporting the thickness measurement of cargo hold/tank transverse frames where appropriate. The form may also be used for
reporting of any attached structure to the cargo hold/tank transverse frames, unless it has been fully reported onto an additional TM form e.g. TM6.
Insert forms TM from IACS
TM7 UR S31 is to be used for reporting the thickness measurement of cargo hold/tank transverse frames of bulk carriers assessed in accordance with
Unified Requirements Strength 31 (UR S31).
TM8 is to be used for reporting the transverse sectional area of the hull girder strength for deck, bottom and neutral axis zone. This form is
automatically generated in the LR software and cannot be generated by the user individually. This form will get updated by data reported onto
TM2~3 form, for each zone under consideration.
•
•
•
•
•
•
•
•
•
•
•
REPORTING
• On receipt of the Final Thickness
Measurement Report at the Classification
Society, the attending Surveyor examines the
Report for correctness of the thickness
measurements included therein against the
Draught report, the correctness of the
corresponding original scantlings and upon
satisfactory completion, he signs the report as
the attending Surveyor.
REPORTING
• Finally the Report is examined by the so called
authorizing surveyor and upon satisfactory
completion it is vetted and ready for record.
The Owners are advised accordingly upon
receipt of the ship’s Executive Summary which
has to be issued by the Classification Society
for ESP ships upon satisfactory completion of
the Survey , as reported by the Surveyor, and
the vetting of the Final Thickness
Measurement Report.
REPORTING