What is the extent of thickness measurement at Special Survey No.3 for a bulk carrier?
The third special survey is the one that changes shape rather than size. Two things that were samples at ten years become complete at fifteen: the deck outside the hatch line, and the wind-and-water band. Everything else on this page follows from that.
The short answer
- Suspect areas, as at every survey.
- Every deck plate lying outside the hatch-opening line, for the length of the cargo area — no longer a sample.
- Two transverse sections outside that same line, one of them amidships.
- The whole wind-and-water band along the cargo area, plus a selection of the same strakes beyond it.
- The close-up members, gauged for general assessment and to record the corrosion pattern.
- Still not on the list: bottom plating, keel, and any full-length strake. Those wait for the fourth survey.
What changes at fifteen years
Read the second and third columns of UR Z10.2 Table II side by side and one thing stands out: the survey does not mostly get bigger, it gets complete. Two items that were samples at ten years are now the whole of their extent. UR Z10.2 R37
The deck. At the second survey the deck contribution was two transverse sections. Here it is every plate of the deck that lies outside the hatch-opening line, along the whole cargo area — and the two sections are still required on top of that. A planner who reads the third column as "the same two sections, one more time" has under-scoped the largest single item on the page.
The wind-and-water band. At the second survey it was the strakes in way of the two sections. Here it is the whole band for the length of the cargo area. Outside that length it stays a selection — and that split is worth holding onto, because it is the one place at this survey where a complete requirement and a sampled requirement sit inside the same sentence of the rule.
The statutory column reads the same way, item for item, and adds nothing at this stage that the UR does not carry. A.1049(27)
Where the two sections go — four documents, four wordings
Every document in this set asks for two sections and wants one of them near midships. None of them says it the same way, and the differences are not stylistic — they decide whether a chosen section is defensible.
| Document | How it fixes the section | Force |
|---|---|---|
| UR Z10.2 | One of the two in the amidship area — the area itself left undefined in the table. | Flat requirement |
| ESP Code | Same placement, written as should. | Mandatory instrument, permissive verb |
| DNV | At least one of them inside 0.5 L amidships — the area given a number. | Class rule |
| Lloyd's Register | A minimum of one of the two inside 0.5 L amidships — placement written as a count. | Class guidance |
Two of the four give the amidship area a boundary you can measure from a general arrangement; two do not. On a DNV or LR ship the answer to "is this section far enough aft" is arithmetic. Under the UR alone it is a conversation with the attending surveyor — and the UR does supply the other half of the test in its own text: sections are picked where the largest reductions are suspected, or where the deck readings have already shown them. UR Z10.2 §2.4.5 DNV Pt.7 Ch.1 Sec.4 LR Table 3.1.1
One further DNV point, easy to miss because it is a single adjective. DNV asks for two complete sections. Where the UR builds the section out of deck items, DNV puts the whole section in the column — so on a DNV ship the step up from the previous survey is the depth of each section rather than the count of them. DNV Table 12
The close-up scope, which is where the hours go
The last line of the systematic column sends you to the close-up table, so the size of the job is set there. For a single-side-skin hull at this survey:
- Shell frames — all of them in the forward hold and in a second hold the surveyor selects; half of them in each hold that is left. End attachments and the plating beside them come with the frames.
- Ballast tanks — every transverse web in every tank, with its plating and longitudinals; and every transverse bulkhead there, stiffening included.
- Holds and hatches — the transverse bulkheads, the hatch covers and coamings, and the deck inside the hatch line between hatches, carried over unchanged from the previous survey.
Against the previous survey the frame item moves twice over — a second whole hold enters, and the remainder goes from a quarter to a half. On a ship of 100,000 dwt and above the previous survey was already at a half, so for the biggest bulk carriers the change here is the second full hold alone. UR Z10.2 Table I
ABS and LR do not restate any of this in their measurement tables. Both point at their own close-up table and ask for readings on whatever it covers — the same construction the UR uses, which is why the close-up table has to be settled before the gauging plan can be drawn. ABS 7-A1-10
What three societies add — and they agree with each other, not with the UR
The peak tanks. DNV, ABS and ClassNK all put the internals of the fore and aft peak ballast tanks into the measurement column at this survey. The UR table has no such row at all. Three societies converging on an item the baseline omits is the clearest signal in this chapter that the UR column is a floor rather than a description of practice — and a programme drawn from the UR alone will be short of the peaks on any of those three ships. DNV · ABS · ClassNK
Hatch covers and coamings, as a gauging item. ABS and ClassNK both list the plating and stiffeners of the covers and coamings for measurement. The UR does carry them — but as a close-up area, from the first special survey, never as a line in the systematic column. The practical difference is what the report has to show: a close-up area produces readings where the survey finds cause, a systematic line produces readings because the table says so.
ClassNK, twice more. Its column adds the piping in the cargo holds, which no other document in this set gauges here. And it attaches a condition to the section itself that the UR table does not print: where the chosen section falls in transversely framed structure, the frames in way of it and their end connections are measured with it. That is a rule about how a section is taken, not about which one — and it can change the point count of a section materially. ClassNK Table B5.15
The corrugated bulkhead arrives here, by three different routes
This is the survey at which the vertically corrugated transverse watertight bulkhead between the first and second cargo holds enters the measurement scope. Every route leads to the same steel; none of them looks like the others in a document index.
- IACS reaches it through the escalation column, which calls in Annex III for ships caught by URs S19 and S23 — so the trigger is the ship's own structural requirements, not its age alone. UR Z10.2 Annex III
- ABS prints it as an ordinary numbered item of the survey column, continuing from the previous survey — no annex, no conditional. ABS 7-A1-10
- Lloyd's Register gets there through its own notations instead: on a ship carrying ESN Hold or ESN All Holds, the corrugated part of the after bulkhead of the forward hold is measured. A ship without the notation is not caught by that note. LR Table 3.1.1 notes
The statutory column adds a fourth route that is easy to miss because of where it is printed: the ESP Code carries a line for ships subject to SOLAS regulation XII/6.1, and prints it in the third and fourth columns only. UR Z10.2 Table II prints no equivalent line — the UR holds the same material in its annual survey text. On a ship caught by XII/6.1 both have to be read, and reading only the class table will not surface it. A.1049(27)
Double-side skin, and the ore carrier
For a double-side-skin hull the governing text is UR Z10.5, and its systematic column matches the single-skin answer item for item at this survey — the whole deck outside the hatch line, two sections with one amidships, the full wind-and-water band inside the cargo area and a selection beyond it. Bottom plating is not there either. UR Z10.5 R20
The close-up side diverges, and the divergence is not the one people expect. The frame sampling stays at a quarter — of the ordinary transverse frames, or of the longitudinals, on the side shell and on the inner side plating, taken forward, amidships and aft. What changes from the previous survey is not the percentage but the tanks it applies to: all double side tanks now, rather than the foremost ones. A planner who scaled the single-skin step — a quarter becoming a half — onto a double-skin ship has the wrong number and the wrong reason. UR Z10.5 Table I/1
An ore carrier shares the systematic column but has a close-up sheet of its own, and this is where its wing void spaces first appear: one complete web frame ring with the members beside it in each void, and further rings there where the society judges them necessary. Its ballast tanks are taken whole rather than sampled — every web frame ring, every transverse bulkhead complete with its girder system. The judgement clause on the voids is the only place in this column where the extent is not fixed in advance. UR Z10.5 Table I/2
What moves the answer
Substantial corrosion moves it out of the survey column and into the widened pattern — Table VIII in UR Z10.2, Table IV in UR Z10.5, annex 10 in the Code, Table 13 in DNV. The extra readings are finished before the survey is credited, not after.
Coating condition in a ballast tank puts that tank onto yearly examination with gauging as the surveyor judges necessary, and keeps it there until the coating is restored.
Side shell frames on a single-skin hull carry their own annex — Annex V in the UR, annex 15 in the Code — for ships within UR S31. It is a separate extent from the frame percentages above, and it does not replace them.
And what this survey establishes sets the next intermediate. The intermediate survey after the third special survey repeats the previous special survey's extent, in both age bands above ten years — with the fuel oil tanks and the pressure tests lifted out unless the attending surveyor wants them. Whatever is scoped here is scoped again in two and a half years, which is the practical argument for placing the two sections where they will still be the right sections then.
Sources
- UR Z10.2 Rev.37IACS — Hull surveys of bulk carriers, Feb 2023index entry →
- UR Z10.5 Rev.20IACS — Double-skin bulk carriers, Feb 2023official text ↗
- A.1049(27)IMO Res. A.1049(27) — 2011 ESP Codeofficial text ↗
- ABS Part 7ABS — Rules for Survey After Construction, Jul 2026official text ↗
- DNV Pt.7 Ch.1 Sec.4DNV — Rules for Classification: Ships, survey requirements, Jul 2022official text ↗
- LR TM GuidanceLloyd's Register — Thickness measurement and close-up survey guidance, Nov 2016official text ↗
- ClassNK Part BClassNK — Rules and Guidance for the Survey and Construction of Steel Ships, 2022official 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.