New common IACS Rules for Tankers
IACS Joint Tanker Rules
Presentation/discussion with
Intertanko
Spetses 24-25 September 2004
2004.09.24
New common IACS Rules for Tankers
Items presented

Status of the JTP Rules
 Schedule
 Hearing
 Harmonisation in IACS
 Ongoing work
 Concerns and recommendations from Intertanko
 Consequences of the JTP Rules
 Calibration of the Rules
 Consequence in general terms
 Consequence in numbers

Open discussion
2004.09.24
New common IACS Rules for Tankers
Status of Joint Tanker Rules - Schedule
Publication
Internal Review
1
2
2004
3
4
5
6
7
Draft Rules
8
9 10 11 12 1
2
2005
3
4
5
6
7
IACS Adoption
IACS External Review
(Industry involvement)
Key dates
 30th September 04:
Closing date for hearing comments
 20th October 04:
Project reply to TC comments.
 1st January 05:
Publish Joint Tanker Rules
 1st July 05:
Rules come into force
2004.09.24
New common IACS Rules for Tankers
Status of Joint Tanker Rules
Hearing
 1800 questions/comments received
 3-4000 questions expected
 Replies available by 20 October 04
 FAQ list will be posted on the website
 Main concern so far is timing
Harmonisation
 Harmonisation of JTP and JBP has been initiated
 Differences and needs for adjustments are being worked out
in the small technical groups
 Way forward with corresponding schedule is being
discussed in IACS council.
2004.09.24
New common IACS Rules for Tankers
Status of Joint Tanker Rules
Ongoing work
 Review of comments
 Extended consequence evaluation
 Rule review with respect to possible loopholes
 Software comparison
 Improvements/adjustments
 Inclusion of Rule required seagoing and harbour still water
bending moments.
 Refinement of internal tank pressures
 Refinement of load combinations in terms of static and
dynamic loads
2004.09.24
New common IACS Rules for Tankers
Concerns and recommendations from Intertanko
Concern 3-1
More extensive comparative/ramification calculations should be presented.
Unfortunately, the comparative calculations presented into the JTP web
site are not conclusive, providing only the increment of the scantlings in
some areas but not defining into detail the base line design used. Is the
increment in scantlings as compared to the highest value of the three
societies’ existing rules? Is it related to an average value between the three
societies’ current rules values or is it related to the minimum of the three
societies current values? The comparative studies should be transparent
and include not only mid-ship sections but also the forward and aft bodies.
2004.09.24
New common IACS Rules for Tankers
Concerns and recommendations from Intertanko
Concern 3-2
We believe the corrosion margins proposed in the JTP rules are lower than
under the current designs on similar ships. It appears that the proposed
common rules have increased tnet to meet the buckling criteria but the tgrs
was not increased accordingly. This results in lower tcorr values than on
the current designs. Tanker owners and actually the receivers of such a
vessel believe this is (1) not in the spirit of the concept of a robust ship and
(2) would result in more frequent repairs and steel renewals and
therefore not acceptable. It is demonstrated that for long hauls, double hull
tankers receiving cargo at high temperature, would act as a thermos. The
corrosion margins for the cargo tanks and their adjacent ballast tanks of
such ships (i.e. tankers loading in tropical areas) should be higher. The
corrosion allowances should be even higher for cargo tanks with means for
cargo heating. Similar for ballast tanks adjacent to cargo tanks transported
heated cargo. we do not believe that the database on wastage used is
relevant if it could give such a result. (6/Table 6.3.3)
2004.09.24
New common IACS Rules for Tankers
Concerns and recommendations from Intertanko
Concern 3-3
Particular concern is with regard to the constant value of 0.5 mm for
tcorr(2.5) It has been assumed that 0,5 mm is a sufficient safety margin for
a period of 2 ½ years. This assumption is unrealistic and dangerous. There
is sufficient experience and Classification Societies should know best that a
number of ship, particular crude carriers but also other type of tankers
have experienced “super corrosion” rates in their cargo tanks, as high as 1
or 2 mm per year. As long as cargo tanks (particularly under deck and
bottom structures) are not protected against corrosion and as long as
negative tolerance of thicknesses of these structural elements is accepted, a
safety margin somewhere between 0.5 mm and 0.2 mm is totally
insufficient for a few months not for 2 ½ years. Concluding, the corrosion
margins, as presented do not seem to give a safety cushion to keep the ships
robust not only as new built but also when in service.
2004.09.24
New common IACS Rules for Tankers
Concerns and recommendations from Intertanko
Concern 3-4
The net scantling concept originally meant "gross thickness minus
corrosion addition" but is now changed to reflect "gross thickness minus
½ corrosion addition". This is considered a major philosophical change
that needs clarification (6/3.3.2.2).
2004.09.24
New common IACS Rules for Tankers
Concerns and recommendations from Intertanko
Concern 3-5
tcorr for bunker tanks with heated bunkers need to be higher than proposed
(6/Table 3.3.2)
2004.09.24
New common IACS Rules for Tankers
Concerns and recommendations from Intertanko
Concern 3-6
Tankers should not be designed with operational restrictions. to the contrary,
tankers should be designed to handle all the operating conditions that it could
reasonably be expected to face in normal commercial practice with a healthy
margin for operator error. (7/6) The common rules should allow:
(1) any transverse combination of cargo tanks across to be empty at or near design draft,
(2) a reasonable range of asymmetric cargo loads at full draft,
(3) all ballast tanks to be 100% full for a full range of bunkers,
(4) the ship to ballast down to a reasonably deep draft without resorting to ballasting
cargo tanks
(5) any single ballast tank to be empty with all the other ballast tanks full,
(6) normal ballast exchange (not only flow through) sequence without restriction on
weather.
2004.09.24
New common IACS Rules for Tankers
Concerns and recommendations from Intertanko
Concern 3-7
Use a ballast and cargo specific gravity of 1.025 tonn/m3 for the fatigue
assessment; this will give flexibility in trading (2/5.1.7.1 & 7/3.5.4.1 - .3 &
7/4.2.2.3)
2004.09.24
New common IACS Rules for Tankers
Concerns and recommendations from Intertanko
Concern 3-8
The hull girder buckling strength to be extended to the entire hull.
(8/1.6.1)
2004.09.24
New common IACS Rules for Tankers
Concerns and recommendations from Intertanko
Concern 3-9
The FE analysis should cover the entire length of the ship (9/2.2.1.1)
2004.09.24
New common IACS Rules for Tankers
Concerns and recommendations from Intertanko
Concern 3-10
Permissible deflections – if deflection criteria are exceeded, then a detail
fatigue analysis is required (9.2.2.5)
2004.09.24
New common IACS Rules for Tankers
Concerns and recommendations from Intertanko
Concern 3-11
The rules apply exclusively to L>150m, whereas the existing unified
requirements apply to L>90m. Oil tankers 90>L<150m should be
considered
2004.09.24
New common IACS Rules for Tankers
Concerns and recommendations from Intertanko
Concern 3-12
The calculated probability level of 10-8 for a 20-year design life has not
been adjusted to 25 years. Why?
2004.09.24
New common IACS Rules for Tankers
Concerns and recommendations from Intertanko
Recommendation 2-1
Inclusion of a prescribed mandatory coating life, e.g. minimum of 15 years.
This is to support the assumption made by the rules that the coating will
remain undamaged for the first 20 years of the ship’s life (see C/1.4.4.20).
2004.09.24
New common IACS Rules for Tankers
Concerns and recommendations from Intertanko
Recommendation 2-2
Inclusion of a performance standard for coating application and coating
maintenance.
2004.09.24
New common IACS Rules for Tankers
Concerns and recommendations from Intertanko
Recommendation 2-3
Inclusion of the IACS Recommendation 47, Part A - Shipbuilding and
Repair Quality Standard for New Construction and not a National
standard. As a result, the JTP team should remove from the proposed
common rules the alternative of “surveyor discretion” with regard to
constructions standards. The IACS Standards should be applicable.
2004.09.24
New common IACS Rules for Tankers
Concerns and recommendations from Intertanko
Recommendation 2-4
Include new provisions to ensure the structural continuity, particularly
the inner bottom and double side stringers into the fore body and aft body.
2004.09.24
New common IACS Rules for Tankers
Concerns and recommendations from Intertanko
Recommendation 2-5
Include new provisions to address the hull flexing/deflection problems.
There is no rule that would limit hull optimisation which may lead to
increases in frame and web spacing and which lead to a decrease of the
stiffness of the hull girder. Deflection of the aft body is critical to the shaft
alignment.
2004.09.24
New common IACS Rules for Tankers
Concerns and recommendations from Intertanko
Recommendation 2-6
Include provisions to cover the Ice-Classed tankers. There are significant
differences between the current regulations of various Classification
Societies in this regard. Although this might not be the first priority for the
JTP team before implementing the new common rules, we would urge
them to add provisions for ice-classed tankers into the common rules as
soon as practical possible.
2004.09.24
New common IACS Rules for Tankers
Consequences of the JTP Rules
Rule changes and consequences in general terms
Minimum thicknesses
- Minimum thicknesses included similarly as today
 Baseline is at least as high as existing ships
Longitudinal strength
- IACS URS fully implemented
- Increased hull girder wave shear
- New advanced buckling check and hull girder ULS
 Deck is strengthened compared to existing ships
 Longitudinal bulkheads are strengthened towards tbhds
2004.09.24
New common IACS Rules for Tankers
Consequences of the JTP Rules
Rule changes and consequences in general terms
Prescriptive rules
- Increased load level
- Simultaneously acting loads
- Slamming/sloshing bow impact based on most onerous of the existing
three Rule sets
- Increased corrosion additions
 Similar or higher scantlings compared to existing ships
 Slightly higher increase in the midship compared with fwd/aft cargo
area.
2004.09.24
New common IACS Rules for Tankers
Consequences of the JTP Rules
Rule changes and consequences in general terms
FEM
- Increased load level
- Simultaneously acting loads
- Increased corrosion additions
- New method for buckling assessment
 Increases due to buckling and hull girder shear
 Main increase in bottom plating, side shell plating, hopper tank top,
transverse bulkhead plating, web frames and stringers
2004.09.24
New common IACS Rules for Tankers
Consequences of the JTP Rules
Rule changes and consequences in general terms
Fatigue
- North Atlantic wave environment
- 25 year design life
- Preliminary check included in longitudinal strength
 Significantly higher baseline standard compared to today
 Main increase in bottom longitudinals in the midship, and side
longitudinals in the cargo area.
 Difficult with high tensile 36 grade in deck
 Will for some vessels dictate the hull girder section modulus
2004.09.24
New common IACS Rules for Tankers
Consequences of the JTP Rules
Consequence in numbers – VLCC midship
1
2
2
4
2
5
2
3
3
1
3
1
0
2
0
2
2
1
2
4
9
1
9
1
1
2
1
8
5
7
1
8
1
7
Ref.
As. Bu.
[mm]

[mm]
1
19
+2
400x12 +150x18
0
2
19
+2
400x12 + 150x18
0
3
19
+0.5
390x12 +130x15
+50%
4
20.5
+2.0
520x12 +170x20
+10%
5
20
0.0
620x12+200x20
+10%
6
20
0.0
580x12+200x20
+40%
7
19.5
+2
630x12+200x20
+20%
8
21
+2
580x12+200x20
+2%
9
17
+1.5
510x12+180x20
-6%
10
15
+2
400x12+130x20
+50%
11
21
+1
580x12+200x20
+2%
12
17
+2
550x12+180x20
-8%
13
16.5
+2
400x12+150x15
+50%
Change
%
As.Bu. Profile
6
2004.09.24
New common IACS Rules for Tankers
Consequences of the JTP Rules
Consequence in numbers – VLCC midship
1
2
2
4
2
5
2
3
3
1
3
1
0
1
6
2
0
2
2
1
2
1
5
1
9
1
4
1
1
2
1
4
9
8
5
7
1
8
1
7
Ref.
As. Bu.
[mm]

[mm]
14
21
+2
730x12.5+210x26
-23%
15
18
+2
730x12.5+210x26
-8%
16
14.5
0
730x12.5+210x15
-3%
17
19.5
+2
NA
NA
18
23
+1.5
NA
NA
19
23
0
NA
NA
20
14
+3
NA
NA
21
21
+1.5
NA
NA
22
13
+2
NA
NA
23
13
+2
NA
NA
24
13
0
NA
NA
25
14
+2
NA
NA
Change
%
As.Bu. Profile
6
2004.09.24
New common IACS Rules for Tankers
Consequences of the JTP Rules
Consequence in numbers – Aframax midship
1
2
4
2
3
1
3
2
2
5
3
1
0
2
0
1
2
2
1
9
4
1
9
1
1
8
2
1
5
7
1
7
1
8
6
Ref.
As. Bu.
[mm]

[mm]
1
17
0
300X90X11/16
+10%
2
17
0
300X90X11/16
+10%
3
16.5
+1
250X90X12/16
+25%
4
16.5
+2
400X100X13/18
+20%
5
15.5
0
425X11 + 140X14
+30%
6
20
+2
425X11 + 140X14
+35%
7
16
+1
425X11 + 140X14
+25%
8
18
+1.5
425X11 + 140X14
+30%
9
14
+1
350X100X12/17
0
10
17.5
+1
300X90X11/16
+30%
11
15.5
-0.5
350X100X12/17
+20%
12
14
+1
300X90X13/17
0
13
18.5
+1
300X90X11/16
0
Change
%
As.Bu. Profile
2004.09.24
New common IACS Rules for Tankers
Consequences of the JTP Rules
Consequence in numbers – Aframax midship
1
2
4
2
3
1
3
2
2
5
3
1
0
1
6
1
2
2
1
2
0
9
1
5
1
9
1
4
1
1
4
8
2
1
5
7
1
7
Ref.
As. Bu.
[mm]

[mm]
14
15
+2
425X11 + 150X18
0
15
13.5
+3
425X11 + 150X18
0
16
13
+1
425X11 + 150X18
0
17
14
+2
NA
NA
18
18
0
NA
NA
19
15
+2
NA
NA
20
12
+1
NA
NA
21
14
+2
NA
NA
22
12.5
+1
NA
NA
23
12.5
+1.5
NA
NA
24
12.5
0
NA
NA
25
12.5
0
NA
NA
Change
%
As.Bu. Profile
1
8
6
2004.09.24