What are the permissible diminution limits for general dry cargo ships?

Which category the ship falls into, class by class

Before any number, the map. The defining fact about a general dry cargo ship is that it is in nobody's strictest category. Every society that sorts ships into tiers puts the tankers, the chemical carriers, the dry bulk carriers, the combination carriers and the gas ships in the top tier, and then puts everything else — including this ship — in the tier below. Get the tier wrong and every figure that follows is wrong, because the tiers are typically 5 to 10 percentage points apart on the same plate.

LR defines three categories for thickness measurement evaluation. Category 1 is a non-CSR oil tanker, chemical tanker, dry bulk cargo ship, combination carrier or liquefied gas ship of length L ≥ 90 m. Category 2 is every remaining ship type at L ≥ 90 m. Category 3 is every ship type at L < 90 m. The general dry cargo ship is read from §1.5.4, which is headed for general dry cargo ships and all other Category 2 and 3 type ships — one table for both categories, so the 90 m line does not change the figure at LR. LR TM Guidance §1.5 / §1.5.4 · older edition, Nov 2016

INSB uses the same three-category wording and reaches the same place by a different route. Its Category 1 list names liquefied gas ships, combination carriers, dry bulk cargo ships, chemical tankers and oil tankers at L ≥ 90 m; Category 2 is all remaining types at L ≥ 90 m; Category 3 is any type under 90 m. So a general dry cargo ship is Category 2 at or above 90 m and Category 3 below it — and INSB's Table C, the individual plate and stiffener table, prints one shared column headed Category 2 & 3 ships. The category split only bites in Table D, the topside and bottom area table, which does give Category 2 and Category 3 separate columns. INSB Pt I Ch 3 Sec 13, Tbl C / Tbl D note 5

ABS has no dry cargo column at all. Part 7 carries a tanker wastage table (Table 1A), an other-conventional-vessels table for ships of 90 m and over (Table 1C) and a short table for conventional vessels under 90 m (Table 2). Table 1C has six columns, and the named ones are non-CSR bulkers, ore carriers and OBOs, and containerships, split by contract date. The general dry cargo ship falls in the last column, headed "Vessels of all ages with a combination of transverse and longitudinal framing". There is no column for a longitudinally framed dry cargo ship of 90 m and over built after 1962; the fifth column covers longitudinally framed vessels built prior to 1962, transversely framed vessels of all ages, and dry cargo barges. Every ABS figure on this page is the combination-framing column, with the under-90 m Table 2 figure given alongside it. ABS 7-A1-4/35.3 Tbl 1C · Tbl 2

KR sorts by class rather than by category. Class I is a ship of 90 m and above, or a ship carrying liquid cargo, classed during construction after 1 July 1998; Class II is any other ship; Class III is high speed and light craft, where the limit is a flat 1 mm. A dry cargo ship of 90 m and above classed during construction after 1 July 1998 is therefore Class I, and a smaller ship, or one classed earlier, is Class II. Both the length and the class-during-construction date have to be checked; either one alone will put the ship in the wrong column. KR Guidance Pt 1 Annex 1-5 Tbl 1

BV and RINA both print a dedicated general cargo ship table, so nothing has to be borrowed: BV Part A Ch 2 App 3 Table 4 and RINA Part A Ch 2 App 2 Table 5. RINA splits its general cargo tables by contract date — Table 5 for ships contracted for construction on or after 1 June 2000, Table 6 for earlier ships — and the two are not the same. Every RINA figure below is Table 5 unless it says otherwise. BV Pt A Ch 2 App 3 Tbl 4 · RINA Pt A Ch 2 App 2 Tbl 5

CSR does not reach this ship type. The Common Structural Rules apply to bulk carriers and to double hull oil tankers, and to nothing else; a general dry cargo ship is not caught however new it is and however large. There is no t_ren, no corrosion addition table and no half-millimetre reserve band on this ship. If someone hands you a renewal-thickness column for a general cargo ship, it came from the owner or the builder, not from CSR. CSR Pt 1 Ch 1 Sec 1 [1.1.1] a)

UR Z7.1: the survey requirement, not the wastage allowance

These two things get run together constantly, and on this ship type the confusion is expensive. UR Z7.1 is the survey requirement. It says which spaces are opened, which structure is close-up surveyed, how many transverse sections are gauged and at what age. It is not the wastage allowance. The percentages on this page come from the class rules, not from Z7.1, and Z7.1 says so itself: the acceptance criteria for thickness measurements are those of the individual society's rules and of specific IACS URs depending on the ship's age and the structural elements concerned, naming UR S18 for the corrugated transverse bulkhead and UR S21 or UR S21A for cargo hatch covers and coamings on exposed decks. Not one diminution figure is printed anywhere in the 26 pages. UR Z7.1 §1.6

PRS says the same thing in its own implementation, which is why the PRS column of the grid is written as not published rather than left blank: Publication 62/P §1.5 sets the acceptance criteria by reference to the PRS Rules and the same IACS URs, and PRS Part I §5.1.3.6 does the same. PRS Part II — Hull, which carries the criteria, is not held, so nothing is quoted for PRS on this page. PRS Pub 62/P §1.5 · PRS Pt I §5.1.3.6

The second thing worth knowing about Z7.1 is which ships it catches, because the answer is narrower than "dry cargo ship". Three things have to be true at once: the ship is self-propelled, she carries solid cargo, and she is 500 gt or larger. Nine exclusions then cut back what is left. One of them takes out any ship the ESP series already reaches, through UR Z10.2 or UR Z10.5. Another takes out the dry cargo ship whose double side skin runs the full length of the cargo area and the full height of the hold up to the upper deck. The other seven are named types: dedicated cement carriers, dedicated wood chip carriers, refrigerated cargo ships, ro-ro cargo ships, dedicated container carriers, livestock carriers and deck cargo ships. On a hybrid ship — some holds single-side skin, some double — Z7.1 bites only on the structure serving the holds that are built with a single side skin. UR Z7.1 §1.1.1–§1.1.2

And the survey regime behind the allowance is not the ESP one. A general dry cargo ship is outside the Enhanced Survey Programme; Z7.1 sits alongside UR Z7, the general hull classification survey requirement, and not in the Z10 series that governs tankers and bulk carriers. That shows up in the gauging scope. At Special Survey No. 1 (age ≤ 5) Table II asks only for suspect areas. At No. 2 it adds one transverse section of deck plating in way of a cargo space within amidships 0.5 L, plus general-assessment measurement of whatever is under close-up survey. At No. 3 it is two transverse sections within amidships 0.5 L in way of two different cargo spaces, each deck plate outside the line of cargo hatch openings within the cargo length area, all wind and water strakes within the cargo length area and selected ones outside it. At No. 4 and subsequent it is a minimum of three transverse sections within amidships 0.5 L, each deck plate outside the line of hatch openings, each bottom plate including the lower turn of bilge, duct keel or pipe tunnel plating and internals, and all wind and water strakes full length. For ships under 100 m the three sections at No. 3 may drop to one and the sections at No. 4 and subsequent to two. UR Z7.1 Tbl II

Two more Z7.1 clauses that decide what happens to your readings. Substantial corrosion carries no figure of its own. Z7.1 pegs it to the allowance instead: read the corrosion pattern, and where that reading puts the wastage past 75% of the allowable margin while the member is still inside acceptable limits, the area counts as substantially corroded. It is three-quarters of whatever the table below allows, and nothing else. Find it and the gauging widens: §2.4.2 has the surveyor keep taking readings until the affected area is bounded, and Table III sets out a pattern for those extra readings — on plating, the suspect plate and the plates next to it, five points over one square metre; on stiffeners, the suspect area, three readings in line across the web and three across the flange. UR Z7.1 §1.2.9 · §2.4.2 · Tbl III

Seven schemes, and why they do not convert into one another

The figures below look like they belong on one axis. They do not. Seven different arithmetic schemes are in play, and a number lifted out of one and set beside a number from another is meaningless. Read the scheme first, then the number.

The practical consequence: k = 0.80 at DNV is not "20%", because the base is the gross offered thickness and not the as-built; 30 / 20 / 10 at BV is not "30%", because the three figures are three separate tests on three different reference areas; and a CCS 75% minimum renewed thickness is a floor, where an LR 30% is a ceiling on loss. None of these are converted into one another anywhere on this page or in the table. scheme definitions, all seven documents

One number CCS does publish for this ship type, and it is easy to miss because it sits outside the main criteria. The Guidelines state that no specific corrosion limit is defined in the CCS Rules for interior members of peak ballast tanks, and set one themselves: a minimum renewed thickness of 75% of as-built for structural members in fore peak and aft peak ballast tanks at L ≥ 90 m, and 70% below 90 m. Everything else in the CCS column is written as not published, against the clause that makes the referral: Chapter Three §I.1 sends the longitudinal strength criteria and §II.1 the local strength criteria to CCS Rules Part One Ch 5 Appendix 1, which is not held. CCS Ch 3 §I.1 · §II.1 · Tbl 3.1

One last piece of housekeeping before the numbers. Two societies attach a condition to the whole table rather than to a row. BV §4.3.6 allows the tabulated percentages to be increased by 5% for ships under 90 m, except for the deck and bottom zone figures, and the small-ship allowance and the allowance for structure outside the cargo area cannot both be applied at once. ABS Note 1 to Table 1C requires that internals included in longitudinal strength be continuous, or effectively developed at their ends, throughout amidships 0.4 L before the allowance in the internals row can be used at all, and Note 2 requires that the structure meet both the individual member thickness and the average wastage. BV §4.3.6 · ABS Tbl 1C notes 1–2

The hull envelope, member by member

Eight societies publish a figure for this ship type. PRS, CCS and CSR do not, for the reasons set out above — PRS refers the criteria out to its Rules Part II and to the IACS URs, CCS refers the local strength criteria out to CCS Rules Part One Ch 5 Appendix 1, and CSR does not apply to this ship at all. Those three positions hold for every member below and are not repeated in each table; where one of them does print something for a particular member, it is written into that member's table. The condition column is the part that matters most: a figure without its condition is not the requirement.

Strength deck plating, upper deck

Deck plating inside the line of hatch openings, where fitted

This is the row that separates a dry cargo ship from a tanker in the deck. Where a strake sits inside the line of the hatch openings it is not carrying hull girder bending in the same way, and three societies give it a wider allowance than the strength deck outside the line. Two do not print the row at all.

Sheer strake, side shell, bilge and bottom, keel

Three societies split the sheer strake from the side shell and three do not, so the four members are set out together. ABS is the one that separates them most sharply: sheer strake plates 20% in the combination framing column, but side shell plates, bilge strake plates and bottom plates all 25%. The keel plates row of Table 1C is left blank on purpose, and Note 7 takes over. It hands the keel no percentage of its own: the keel comes out once it has wasted down to whatever thickness the adjacent bottom plating is allowed to reach. Under Table 2, for vessels below 90 m, the figures are 25 % for the sheer strake, bilge strake, bottom and keel plating, and 30 % for side shell plating — so on a small ship the ABS side shell allowance is wider than the bottom, which is the reverse of the 90 m and over table. ABS Tbl 1C · note 7 · Tbl 2

BV and RINA print the same set. The sheer strake is not a line of its own — it is named inside item 2 with the upperdeck plating and the deck stringer plates, so it carries 30 / 20 / 10. Side shell plating is item 4 at 25 / 20 / 15, and bilge and bottom strakes and the keel plate are item 8 at 25 / 20 / 10. Those are the two envelope items the general cargo table puts below 30 % in the isolated area column; upperdeck plating with the deck stringer and sheer strake (item 2) and inner bottom plating (item 11) both stay at 30 %. RINA's figures are Table 5, for ships contracted for construction on or after 1 June 2000. BV Tbl 4 items 2/4/8 · RINA Tbl 5 items 2/4/8 · older edition

LR gives 30% across the hull envelope — strength deck, side shell and bottom shell plating alike — and names no separate sheer strake, bilge or keel line. Where a plate is recorded by frame number and strake position, deck and sheer or bottom and side, Table 1.5.5 carries it, again at 30 % for Category 2 and 3 ships. Older edition, Ver 7.3, November 2016. INSB is a single hull envelope row at 30% for Category 2 and 3 covering deck, bottom and the wind and water strakes together. ClassNK treats sheer strake, side shell and bottom as shell plates and gives 20% of original + 1 mm with no separate keel line; the sheer strake is named on its own only for the flat bar longitudinal beams fitted on it. KR puts the sheer strake, the shell plating and the bottom shell plating in the first row at 20% (Class I) and 20% + 1 mm (Class II), also with no keel line. DNV reads them all as plating at k = 0.80, side and longitudinal bulkhead plating included; its table is by component type, not by strake name. LR · INSB · NK · KR · DNV, shell plating

Worth naming, because it is where the ship-type distinction shows: for the same side shell plate, the tanker figure at LR and INSB is 20% and the general cargo figure is 30%. That is a full half again as much steel gone before the same society calls for renewal. It is not a drafting accident and it is not a licence to gauge more loosely — it is the tier the ship is in, and it is written on the face of both tables.

Inner bottom plating

ABS 30% — the outermost strake of inner bottom and the other plates of inner bottom are both 30 % in the combination framing column, and Table 2 for vessels under 90 m carries no inner bottom line at all. BV and RINA 30 / 20 / 10, item 11, sitting in the bottom zone. LR 30% for the plating, with inner bottom longitudinals separately at 25%. ClassNK 20% of original + 1 mm, inner bottom plates named in the first band. DNV k = 0.80 — and note that the 0.75 line for inner bottom plate in the same table is for bulk carriers only and must not be read across to this ship. KR 20% (Class I) and 20% + 1 mm (Class II), inner bottom plating named in the first row. INSB 30% (Cat 2 & 3), longitudinal structural members, plating. inner bottom, eight documents

'Tweendeck plating

The 'tweendeck is where the documents disagree most, because half of them do not have the member. ABS prints nothing usable: the tween deck plates row shows ----- in the combination framing column and in all four bulker and containership columns, and prints 30 % only in the longitudinally-framed-pre-1962, transversely-framed and dry cargo barge column. BV and RINA do have the member — item 6, 'tweendeck plating, 30 / 20 / 15, in the neutral axis zone, with 'tweendeck longitudinals at web 30 / 20 and flange 25 / 15, group 15, and the 'tweendeck hatch girder at web 25 / 20 and flange 20 / 15, group 15. LR carries no 'tweendeck line; other miscellaneous plating is 30% and other miscellaneous longitudinals or stiffeners 25%, and that is where it lands. ClassNK gives 30% for effective deck plates — but the definition of effective deck sits in ClassNK Part C, outside the document held, so that is the nearest named item and not a 'tweendeck line. KR has the same problem in the same shape: effective deck plating, third row, 25% (Class I) and 30% (Class II), with the definition of effective deck in KR Pt 3 Ch 5, 103., outside the table. DNV's table is by component type and carries no 'tweendeck line, so the plate reads as plating at k = 0.80. INSB also carries no 'tweendeck line; the plate falls in miscellaneous structural members, plating, 30% (Cat 2 & 3). Before you record a 'tweendeck reading against a limit, confirm with the office which of these the attending society will actually apply. 'tweendeck, eight documents

Bulkheads, internals and side frames

Longitudinal bulkhead plating, where fitted

Many general cargo ships do not have one; where there is one, four documents cover it and two do not. ABS 25% — the top strake, the bottom strake and the other plates of longitudinal bulkheads are all 25 % in the combination framing column. Table 2, for vessels under 90 m, has no bulkhead breakdown; it folds everything into internals and bulkheads at 30 %. BV and RINA print no longitudinal bulkhead item at all in the general cargo table — the bulk carrier and oil tanker tables have one, the general cargo table does not. LR 30% for the plating, with longitudinal bulkhead stiffeners separately at 25%. ClassNK splits by bulkhead type and not by orientation: a tight bulkhead of a deep tank takes 20% + 1 mm and watertight bulkhead plates take 25%, where a deep tank is defined in the table footnote as a tank used for the carriage of water, oil or other liquids forming part of the hull in holds or 'tween decks. KR does the same: bulkhead plating of a deep tank is in the first row, 20% (Class I) and 20% + 1 mm (Class II); watertight bulkhead plating other than a deep tank bulkhead is in the third row at 25% and 30%. DNV k = 0.80, side and longitudinal bulkhead plating. INSB 30% (Cat 2 & 3), longitudinal structural members, plating. So on this member the question you have to answer first is not "which society" but "is this bulkhead a deep tank boundary" — at ClassNK and KR that one fact moves the limit by five points and a millimetre. longitudinal bulkhead, eight documents

Transverse bulkhead plating, plain and corrugated

Two societies split plain from corrugated and the rest do not, and the corrugated figure is the tighter one where it exists.

Deck and bottom longitudinals, web and flange

ABS gives one figure, 25%, for one row that gathers the internals into a single heading — longitudinals, girders and transverses, struts, the webs and stringers of bulkheads, brackets, and hatch side girders — so the source does not split web from flange, and Note 1 conditions the whole row: internals included in longitudinal strength must be continuous or effectively developed at their ends throughout amidships 0,4 L. Table 2, for vessels under 90 m, gives 30 % for internals and bulkheads. BV and RINA give 30 / 20 on the web and 25 / 15 on the flange, group criterion 10 %, for items 3, 10 and 12 — deck, bilge and bottom, and inner bottom longitudinals. Here the general cargo table is the more generous of the three: the bulk carrier and oil tanker tables of the same document print 25 / 20 on the web and 20 / 15 on the flange, so in the isolated area column a general cargo longitudinal is allowed five points more wastage on the web and five more on the flange than the same member on a bulker or a tanker. The average-of-item figures are the same in all three tables; only the isolated area column moves. LR 25% — strength deck, side shell and bottom shell longitudinals alike. ClassNK 30% for longitudinal beams, stiffeners and brackets, but flat bar longitudinal beams on the sheer strake and the strength deck instead take 20% + 1 mm under the first band. DNV k = 0.75 for stiffeners, while girders and stringers take 0.80. KR 25% (Class I) and 30% (Class II) for the web, face and brackets of a secondary stiffener — meaning a member supported by a primary supporting member which does not itself support another reinforcement member — and again, longitudinals attached to the strength deck plating and the sheer strake fall in the first row instead, at 20 % for Class I. INSB 25%, and here the category makes no difference: the stiffener figure is 25 % in both the Category 1 and the Category 2 & 3 columns. Only the plating figure changes with category. The reduction is for the average thickness over the length between supports. longitudinals, eight documents

Side frames and end brackets, web and flange

On a single-side-skin dry cargo ship this is the member that gets found wasted, and it carries the one absolute floor in the whole set. KR reads 20% or 1,5 mm, whichever greater (Class I) and 25% or 2,5 mm, whichever greater (Class II) for the web, face and brackets of frames in a cargo hold or tank — the only row in the KR wear limit table that pairs a percentage with a millimetre floor, and on a thin frame web the millimetre is what governs. ABS folds frames and brackets into the internals row at 25% with no web/flange split; Table 2 gives 30 % under internals and bulkheads. BV and RINA item 19: web 30 / 20, flange 25 / 15, brackets 30 / 20 — with deck and 'tweendeck beams as a separate item 20, web 30 / 20 and flange 25 / 15. LR 25% for cargo hold shell frames and end brackets, and 25 % for salt water ballast tank frames or diaphragms too. ClassNK 25% for the web, face and bracket of hold frames, while frames other than hold frames take 30 % — read the space you are in before you pick the figure. DNV k = 0.75 on both web and flange. INSB 25% (Cat 2 & 3), cargo hold transverse frames and end brackets. And one absence worth stating plainly: PRS Publication 63/P, the side shell frame replacement document, does not reach this ship type — it covers single side skin bulk carriers and oil-bulk-ore carriers only. side frames, nine documents

Floors and bottom girders

ABS 25%, the internals row again, covering girders, transverses and struts; 30 % under Table 2 for vessels below 90 m. BV and RINA split them, and the split matters: bottom girders are item 9 at 25 / 20 / 10 and contribute to the bottom zone, while floors plating is item 21 at 30 / 20 and does not. LR 25% for salt water double bottom tank floors, with web frame plating and face plates also 25 % and web frame secondary structure 30 %. ClassNK 25% for floors and girders in the double bottom and for the web and face of primary members. DNV k = 0.80 on the web and 0.75 on the flange under Table 2 — except that a bottom girder contributing to longitudinal strength is taken at 0.80 under Table 1 instead. KR 20% (Class I) and 25% (Class II) for the floor and girder of the double bottom and the web and face of a primary supporting member — the tightest percentage of any internals row at KR. INSB 25% (Cat 2 & 3), transverse structural members in cargo oil and water ballast tanks. CCS is the one place a figure appears in an otherwise empty column: the Guidelines set a minimum renewed thickness of 75% of as-built for structural members in fore and aft peak ballast tanks at L ≥ 90 m and 70% below 90 m — peak tanks only, not the double bottom. floors and girders, nine documents

Hatch covers and coamings: a regime of their own

This is the one place on a general dry cargo ship where the wastage question is not answered by a percentage of the as-built. UR Z7.1 §1.6 names it directly: for all cargo hatch covers and coamings on exposed decks the acceptance criteria are UR S21, or UR S21A for the period in which that requirement was in force. UR S21A applies to ships contracted for construction on or after 1 July 2012, Rev.1 of S21A to ships contracted on or after 1 July 2016, and S21A was then withdrawn with effect from 1 July 2024, its place taken by UR S21 Rev.6, which applies to ships contracted on or after that date. Which of those a given ship falls under is decided by its contract date and nothing else. UR Z7.1 §1.6 fn 2–3

In practice the societies print that in two different forms, and both forms are in circulation for the same ship. A net-thickness rule, where the cover is judged against t_net + 0,5 mm with a corrosion addition per component; and a plain percentage, where the cover is judged like any other plate. Some documents print both and leave the reader to work out which applies.

The trap here is reading the percentage when the net-thickness rule is the one that applies, or the reverse. On a ship contracted after the S21A date the cover is judged against t_net + 0,5 mm, and on the same plate that can be a very different number from 30 % of as-built. The as-built thickness alone will not tell you which; the contract date will.

The hull girder

Every member limit above is a local test. Sitting over all of them is a global one, and on a ship whose deck is cut open along most of its length the global test is not a formality. Four societies express it as a section modulus percentage, two as a zone or area percentage, and one publishes neither.

• ABS — the member-by-member allowances only stand while the hull girder holds. The section modulus has to stay at or above 90% of a benchmark, and the benchmark is whichever is larger: the modulus required when the ship was built, or the modulus the current rule reference calls for. Table 2, for vessels under 90 m, carries the same 90 % condition, and below 61 m it adds a ceiling of 20% on lost deck or bottom area against the area the rules require. ABS Tbl 1C note 4 · Tbl 2 notes 3–4
• BV and RINA — zone criteria instead of a modulus: deck zone 10%, neutral axis zone 15%, bottom zone 10%, each evaluated separately. A greater diminution than the group figure may be accepted for one group of items if the overall diminution of the zone still meets the zone criterion. BV §4.3.6 allows the 5 % increase for ships under 90 m except for the deck and bottom zone figures — those two never move. RINA's Table 6, for ships contracted before 1 June 2000, publishes deck 10 % and bottom 10 % and leaves the neutral axis zone blank. BV Tbl 4 zone · §4.3.5–4.3.6 · RINA Tbl 5 / Tbl 6 · older edition
• ClassNK — 90% of the rule-required hull section modulus for L_f ≥ 130 m under the current rule set; L_f ≤ 60 m takes 80%, interpolated between. Ships built to the 1964–1972 rule versions are held to the full rule requirement, with no 90 % relief at all. Older edition — 2014. NK App 4-5 6(1) Tbl 4 · older edition
• DNV — the reduced section modulus is to be at least 90% of the required section modulus and at least 90% of the minimum rule section modulus — two tests, not one. Outside 0,4 L amidships, Table 3 sets an acceptable average reduction in deck or bottom of 10% over 0,0–0,1 L and 0,9–1,0 L. Older edition — July 2022. DNV Sec.2 [3.1.3] · Tbl 3 · older edition
• INSB — Table D, and this is the one place where Category 2 and Category 3 part company. Category 2, over 0,5 L amidships: topside plating 10%, topside longitudinals 15%, bottom plating 10% single bottom and 15% double bottom, bottom longitudinals 15%; at 0,075 L from the ends the same five figures are 30 / 25 / 30 / 30 / 25%. Category 3, under 90 m, over 0,5 L amidships: 15 / 20 / 15 / 20 / 20%, and 30% flat at 0,075 L from the ends. Intermediate values are linearly interpolated. Note 4 allows a greater reduction over 0,5 L amidships for Categories 1 and 2, on condition that the modulus worked from the gauged thicknesses still stands at 90% or more of what the Rules give the ship as new — which means the Category 3 ship, the one under 90 m, gets no such relief. Note 6: where the reduction of topside or bottom area exceeds 0.75 of the tabulated value, additional transverse sections are to be measured. INSB Tbl D · notes 1–7
• LR, KR, PRS and CCS publish no figure this page can quote. LR's §1.5 and Tables 1.5.5–1.5.6 give a strength deck residual buckling thickness t_r but no hull girder section modulus or area percentage. KR Rules Pt 1 Ch 3 106. 1 (2) names oil tankers of 130 m and upwards and sets the criteria by separate requirements of the Society, which are not held. PRS refers out. CCS Chapter Three §I.1 refers the longitudinal strength criteria to CCS Rules Part One Ch 5 Appendix 1, which is not held. LR · KR · PRS · CCS, hull girder

The full grid

This page gives the reading — which category the ship is in, which scheme each society uses, and what the condition on each figure is. The table gives every cell: fifteen structural members against eleven societies, for this ship type and for oil tankers and bulk carriers alongside it, each cell carrying its document, its clause and its PDF page.

T01 — Permissible diminution, class by class →

Use the table when you need the cell; use this page when you need to know whether the cell applies to the ship in front of you. The two are kept in step: no figure appears here that is not in the table, and no figure here has been converted out of the scheme its document prints it in.

What this means when you fill the sheet

On a tanker or a bulk carrier the sheet mostly works because the categories are unambiguous. On this ship type the same sheet can be filled correctly and still be judged against the wrong column, because the ship's identity has to be established before any limit means anything. Four things belong on the header, and they are the four that decide which column the office reads.

• Length L, against the 90 m line. It moves the ship between LR Category 2 and Category 3, between INSB Category 2 and Category 3, between KR Class I and Class II, and between the ABS 90 m and over table and the under-90 m table — and at ABS and INSB the two tables carry genuinely different figures for the same member. At BV it turns on the 5 % small-ship allowance of §4.3.6.
• The framing system. ABS reads this ship out of the column headed vessels of all ages with a combination of transverse and longitudinal framing. A transversely framed ship of any age goes in the previous column, where several members are five points more permissive. Nobody in the office can work that out from the readings.
• Contract date, and date classed during construction. RINA splits its general cargo tables at 1 June 2000. KR's Class I turns on classification during construction after 1 July 1998. The hatch cover regime turns on 1 July 2012, 1 July 2016 and 1 July 2024. These are not background information; each one changes a number.
• The compartment either side of the plate. At ClassNK and KR, a bulkhead that bounds a deep tank carries a different limit from one that does not, and a hold frame carries a different limit from a frame elsewhere. Record the space you were standing in and the space on the other side.

Then the readings themselves. Two habits pay for themselves on this ship type:

• Report enough points to give an average, not just a worst point. LR Table 1.5.5 note 6 and INSB Table C note 3 both tie the maximum diminution to an average rather than to a point. Average the readings over the panel of plate; on a stiffener, average them along the span between its supports. BV's whole scheme is built on four averages at four different scales. A single low reading with nothing around it cannot be assessed against any of that; it can only be flagged.
• Record the as-built beside every reading, and say where it came from. Every scheme on this page except DNV's works from a thickness on a drawing, and DNV works from that thickness less the owner's voluntary addition. If the as-built came off the shell expansion, say so; if it came off a previous report, say that instead. On a forty-year-old dry cargo ship the as-built column is the part most often wrong, and it moves the limit one for one.
• Flag anything past 75% of the allowance as a suspect area on the sheet itself. That is the UR Z7.1 definition of substantial corrosion, and once it is found the extent of measurement is to be increased — five-point pattern over one square metre on the suspect plate and its neighbours, three measurements in line across web and flange on a stiffener. The technician who flags it during the survey saves a second attendance; the one who leaves it to the office does not.

Last thing, and it is the one that catches experienced people. The allowances on this ship are wider than on the tanker you gauged last week — 30 % where the tanker took 20 %, on the same strake, at the same society. That is the rule and it is not yours to tighten. But the survey regime behind it is lighter too: fewer transverse sections, no ESP close-up programme, and a hull whose deck is opened up along most of its length. The permissiveness in the table is not a statement that the structure matters less. Gauge it as if the number were the tanker's, and record the number the rule actually prints.

Sources

1. UR Z7.1IACS UR Z7.1 Rev.15 Corr.1 (2024) — Hull Surveys of General Dry Cargo Shipsofficial text ↗
2. ABS Pt 7ABS Rules for Survey After Construction, Part 7 — July 2026official text ↗
3. BV NR467 Pt ABV NR467 Rules for the Classification of Steel Ships, Part A — R26, July 2026official text ↗
4. LR TM Guidance Pt 1LR Thickness Measurement and Close-up Survey Guidance, Part 1 — Ver 7.3, November 2016 (older edition held)official text ↗
5. ClassNK GuidanceClassNK Guidance for Undergoing Class Maintenance Surveys — 2014 edition (older edition held)official text ↗
6. ClassNK Pt BClassNK Rules and Guidance for the Survey and Construction of Steel Ships, Part B — 2022 edition (older edition held)official text ↗
7. RINA Pt A Ch 2 App 2RINA Rules for the Classification of Ships, Part A Ch 2 App 2 — 1 July 2024 interactive set (older edition held)official text ↗
8. DNV-CG-0182DNV-CG-0182 Allowable thickness diminution for hull structure — Edition July 2022 (older edition held)official text ↗
9. KR Pt 1KR Rules and Guidance for the Classification of Steel Ships, Part 1 — 2026 editionofficial text ↗
10. PRS Pt IPRS Rules for the Classification and Construction of Sea-going Ships, Part I — January 2026official text ↗
11. PRS Pub 62/PPRS Publication 62/P — Hull Surveys of General Dry Cargo Ships, January 2025official text ↗
12. INSB Pt IINSB Rules and Regulations, Part I — Issue 04 Rev.03, December 2024official text ↗
13. CCS TM GuidelinesCCS Guidelines for Thickness Measurement of Hull — Ver 6.6, March 2025official text ↗
14. CSR Pt 1 Ch 1 Sec 1IACS Common Structural Rules for Bulk Carriers and Oil Tankers — 1 January 2024 versionofficial text ↗

Class-society and IMO documents are indexed and linked, never re-hosted. Where a class rule is stricter than the IACS baseline, the class rule governs.

Related questions

• How do I read a thickness limit?K5.1
• What counts as substantial corrosion in each class?K5.2
• What are the permissible diminution limits for oil tankers, class by class?K5.3
• What are the permissible diminution limits for bulk carriers, class by class?K5.4
• What are the pitting acceptance criteria in each class?K5.6
• At what thickness must steel be renewed on a CSR ship?K5.7
• What thickness limits apply to ships under 90 m?K5.8
• What changes for thickness measurement on CSR ships?K3.9