What does UR Z10.2 require for bulk carriers, in plain language?
UR Z10.2 is the enhanced survey requirement for bulk carriers that are not double skin. Table I fixes the close-up survey, Table II the thickness measurement, and both step up with the special survey number.
The short answer
- Who: all self-propelled bulk carriers other than double skin bulk carriers. On a hybrid ship the double-skin holds and their wing spaces go to Z10.5 instead.
- Close-up frames: 25% in the forward hold at SS1; all forward-hold frames plus 25% elsewhere at SS2 — 50% if 100,000 DWT and over; at SS3 all frames in the forward hold and in one other selected hold, plus 50% in each remaining hold; every frame at SS4.
- Gauging: suspect areas only at SS1; then 2 deck sections at SS2, 2 transverse sections at SS3, 3 plus every bottom plate at SS4.
- Substantial corrosion: Table VIII, five sheets, and the pattern is nearly always five points.
- Rev.37 applies to surveys commenced on or after 1 July 2024.
Which bulk carriers, and the hybrid rule
Check the revision first. The note at the front is explicit: IACS societies apply the Rev.37 changes uniformly to every survey that commences on or after 1 July 2024. A survey started before that date runs on Rev.36. The Rev.37 change a gauging technician meets on the ship is the ballast tank coating trigger: a tank whose hard coating is found in less than GOOD condition and is not renewed goes onto annual examination, where the earlier text used POOR as the threshold. UR Z10.2 Note 30
Z10.2 applies to all self-propelled bulk carriers other than double skin bulk carriers, the double-skin boundary being the one drawn in UR Z10.5. A bulk carrier here is a ship built generally with single deck, double bottom, topside tanks and hopper side tanks in the cargo spaces, meant mainly for dry bulk. Combination carriers are included; single skin combination carriers pick up further requirements from Z10.1. Inside the ship, Z10.2 governs the hull structure and the piping over the cargo holds, the cofferdams and pipe tunnels, and the void spaces and fuel oil tanks that lie inside the cargo length area, plus every ballast tank; the rest stays under Z7. UR Z10.2 §1.1.1–1.1.2
The hybrid case catches people out at the planning stage. Where a bulk carrier has some holds of single side skin and others of double side skin, the ship is not sent wholesale to one requirement or the other: the double side skin cargo holds and their associated wing spaces are worked to Z10.5, the rest of the ship stays on Z10.2. One survey programme then carries two sets of minimums, split by hold. Two further hooks matter for gauging — ships that must comply with UR S19 pick up Annex III for the corrugated bulkhead between holds 1 and 2, and ships that must comply with UR S31 pick up Annex V for the side shell frames and brackets. UR Z10.2 §1.1.4–1.1.6 A third hook sits on the annual survey rather than the special: a ship subject to SOLAS XII/9.1 — single side skin, 150 m in length and upwards, carrying solid bulk cargoes of density 1780 kg/m³ and above, contracted before 1 July 1999, and without enough transverse watertight bulkheads to stay afloat with the foremost hold flooded — carries the Annex IV additional annual survey of the foremost cargo hold. Over 5 years of age that means, at every annual survey, an overall survey of the foremost hold with close-up of sufficient extent, minimum 25% of frames, on the shell frames with their end attachments, adjacent shell plating and transverse bulkheads, plus suspect areas — and over 15 years all shell frames of that hold. Gauging follows the close-up, with suspect areas as the minimum, and may be dispensed with where the close-up shows no structural diminution and the coating remains effective. UR Z10.2 §3.3 / Ann.IV
Close-up survey: Table I, by special survey number
An overall survey of all tanks and spaces is done at every special survey; Table I sits on top of it. Five structural families run down the table: hold transverse frames, transverse webs and watertight bulkheads in ballast tanks, hold transverse bulkheads, hatch covers and coamings, and the deck plating and under-deck structure inside the line of hatch openings.
| Survey | Cargo hold shell frames | Ballast tank webs and bulkheads | Hold bulkheads, hatches, deck |
|---|---|---|---|
| SS1 age ≤ 5 | 25% in the forward hold at representative positions; selected frames in the other holds | One transverse web with its plating and longitudinals, in two representative ballast tanks of each type — topside, hopper side | Two selected hold transverse bulkheads with upper and lower stool internals; all hatch covers and coamings |
| SS2 5 < age ≤ 10 | All frames in the forward hold and 25% in each remaining hold, with end attachments and adjacent shell plating. At 100,000 DWT and above the figure is 50% | One transverse web in every ballast tank; forward and aft transverse bulkhead in one ballast tank with its stiffening | All hold transverse bulkheads; all hatch covers and coamings; every deck plate and the structure under it, inside the hatch opening line, between all cargo hold hatches |
| SS3 10 < age ≤ 15 | All frames in the forward hold and in one other selected hold, and 50% in each remaining hold | All transverse webs in every ballast tank; all transverse bulkheads in ballast tanks with their stiffening | As SS2 |
| SS4+ age > 15 | All frames in all cargo holds, with end attachments and adjacent shell plating | As SS3 | As SS3 |
Source for the whole table: UR Z10.2 Table I Hold transverse bulkheads are surveyed close-up at four levels: above the inner bottom and above the line of gussets or shedders; above and below the lower stool shelf plate; about mid-height; and below the upper deck plating next to the upper wing tank, or below the upper stool shelf plate.
The surveyor may extend the close-up survey, taking into account how the spaces have been maintained, the state of the corrosion prevention system, and any arrangement or detail that has given trouble in similar spaces or on similar ships. Where hard protective coating in a space is found in GOOD condition, the Table I extent may be specially considered. UR Z10.2 §2.3.3–2.3.4
Thickness measurement: Table II, by special survey number
At SS1 the gauging minimum is suspect areas and nothing else. From SS2 the deck starts, and it starts outside the line of the cargo hatch openings. The row that puts the Table I close-up members under the probe as well, for general assessment and recording of the corrosion pattern, runs from Special Survey No.2 onwards — the SS1 column carries suspect areas and nothing further. UR Z10.2 Table II
| Survey | Deck plating outside line of hatch openings | Sections | Wind-and-water strakes, bottom |
|---|---|---|---|
| SS1 | — | 0 | — (suspect areas only) |
| SS2 | Two transverse sections of deck plating | 2 deck | Strakes in way of those two sections, plus selected strakes outside the cargo length area |
| SS3 | Each deck plate | 2, one amidships | All wind-and-water strakes; selected strakes outside the cargo length area |
| SS4+ | Each deck plate | 3, one amidships | Each bottom plate; all wind-and-water strakes, full length |
Source for the whole table: UR Z10.2 Table II Suspect areas are gauged in every column; the Table I close-up members are gauged from Special Survey No.2 onwards. The table qualifies the deck plating and the transverse sections at SS3 and SS4 as outside the line of cargo hatch openings, and carries the pointers to Annex V from SS2 on and Annex III from SS3 on.
Sections are chosen where the largest reductions are suspected or where the deck plating readings have already shown them, one of them in the amidships area. Separate from the table, the technician takes representative readings on the shell frames and their end attachments, in every cargo hold and every water ballast tank, far enough to show what general and local corrosion is doing there; the transverse bulkhead plating is read for the same purpose. That extent may be specially considered where the close-up survey satisfies the surveyor that there is no structural diminution and the hard protective coating, where it was applied, remains efficient. UR Z10.2 §2.4.4–2.4.6
Intermediate survey: how the extent grows with age
The intermediate survey is held at or between the 2nd or 3rd annual survey, and the items that go beyond the annual survey may be taken at or between those two. One line governs the planning: concurrent crediting of surveys and thickness measurements of a space to both the intermediate and the special survey is not acceptable. The extent then depends on the age of the ship. UR Z10.2 §4.1 / §4.2.1
At 5–10 years the cargo hold work is an overall survey of all cargo holds, and inside it enough close-up work — at least 25% of the frames — to settle the condition of three things in the forward hold and in one other hold the surveyor picks: the shell frames with their upper and lower end attachments, the shell plating next to them, and the transverse bulkheads. Areas that came up suspect at earlier surveys are covered as well. Where that overall and close-up survey gives the surveyor reason, the survey is extended to close-up of all the shell frames and adjacent shell plating of that hold, and to close-up of sufficient extent in all remaining holds. UR Z10.2 §4.2.2.2
The ballast tanks at the same age take an overall survey of representative spaces chosen by the surveyor, the selection to include the fore and aft peak tanks; where that survey shows no visible structural defects the examination may be limited to confirming the corrosion prevention system is still efficient. A hard coating found in less than GOOD condition, corrosion or other defects, or no hard coating from new, pushes the examination out to other ballast tanks of the same type; and in ballast tanks other than double bottom tanks the tanks in question are examined with gauging as the surveyor considers necessary. Suspect areas from previous surveys are surveyed overall and close-up. Gauging is to an extent sufficient to determine general and local corrosion at the areas under close-up survey, with the minimum being the areas found suspect at previous surveys; it may be specially considered where the close-up survey satisfies the surveyor that there is no structural diminution and the hard coatings are GOOD. Substantial corrosion here expands the readings under Table VIII, before the survey is credited. UR Z10.2 §4.2.2.1 / §4.2.2.3
Over 10 years the intermediate survey is to the same extent as the previous special survey, with internal examination of fuel tanks and pressure testing of all tanks dropped unless the attending surveyor calls for them; the survey may be commenced at the second annual and progressed through the following year for completion at the third annual. In the 10–15 year band an underwater survey may be considered in lieu of the bottom survey in dry dock. Over 15 years a survey in dry dock is part of the intermediate survey, and the overall and close-up surveys and thickness measurements of the lower portions of the cargo holds and water ballast tanks — the parts below the light ballast water line — are carried out to the intermediate survey requirements if they have not already been done. UR Z10.2 §4.2.3 / §4.2.4
Substantial corrosion: what Table VIII adds
On a pre-CSR bulk carrier, substantial corrosion is a corrosion pattern showing wastage in excess of 75% of allowable margins while still within acceptable limits. On a CSR-built ship it is a measured thickness between tren + 0.5 mm and tren. Find it and Table VIII takes over — five sheets, and the pattern is five points almost everywhere. The extended readings must be taken before the survey is credited as complete. UR Z10.2 §1.2.11 / §2.4.2 Representative rows:
- Bottom and side shell plating: the suspect plate plus the four adjacent plates, five points per panel between longitudinals. Longitudinals: minimum 3 in way, 3 readings across the web and 3 on the flange.
- Inner and double bottom plating: the suspect plate plus all adjacent plates, five points per panel between longitudinals over 1 m length, and three longitudinals where the plates are measured.
- Lower stool: a band within 25 mm of the welded connection to the inner bottom and another within 25 mm of the connection to the shelf plate, five points between stiffeners over 1 m on each.
- Transverse bulkhead: a band at about mid height and one on the part next to the upper deck or below the upper stool shelf plate, five points over 1 m² each.
- Hatch covers and coamings: side and end skirts at 3 locations each; 3 longitudinal bands on the cover, the two outboard strakes and the centreline strake; on each side coaming and each end coaming, one band on the lower 1/3 and one band on the upper 2/3 of the coaming, five points in each band.
- Side shell frames: the suspect frame and each frame either side — five points on web and flange at each end and mid span, plus five points within 25 mm of the welded attachment to the shell and to the lower slope plate.
Source: UR Z10.2 Table VIII On CSR ships the identified areas may instead be coated to the coating maker's requirements and examined annually to confirm the coating still holds, or else gauged at annual intervals.
Who may hold the probe, and where the points sit
The measurements are carried out by a qualified firm certified by the Classification Society on the principles in Table V. That table is the whole chain: the firm submits its organisation, its experience, its technicians' careers — operators qualified to a recognised industrial NDT standard — its equipment and calibration procedures, operator guide, training programmes and record format; it is audited; and certification is conditional on an onboard demonstration plus satisfactory reporting. The certificate is renewed or endorsed at intervals not exceeding 3 years, and approval can be cancelled where measurements were improperly carried out or improperly reported. Around that: the firm sits in the survey planning meeting; a surveyor witnesses the work unless the Society takes it itself; gauging in areas under close-up survey is done at the same time as that survey; and the report is reviewed by the surveyor, who countersigns the cover page. UR Z10.2 §7.2.1 / Tbl V
Where the points go is §7.3 — and read its first line before using it. Section 7.3 applies only to vessels built under the IACS Common Structural Rules. For a ship not built under CSR the number and locations come from the individual Classification Society's rules and from the specific IACS URs that fit the ship's age and the element in hand. For CSR ships, §7.3.3 hands over to Table 1 with Figures 4 to 9 behind it, and that is where the standing interpretations live: "selected" plates means at least a single point on one plate out of three; all deck, tank top and bottom plates and the wind-and-water strakes take at least two points each, at the 1/4 extremities or in areas of average corrosion; "selected frames" means at least 3 frames on each side of a hold; 25% of frames means one out of four along the hold on each side, and 50% one out of two. Where the rule says one transverse bulkhead per hold, the close-up and its gauging go on one side, chosen from what the overall survey of both sides showed. UR Z10.2 §7.3
Annex V frames, Annex III corrugations
Annex V covers side shell frames and brackets on single side skin bulk carriers that must comply with UR S31. It splits the frame into four zones A to D, with A and B — the lower bracket and the lower part of the frame — called out as the most critical. Zones A, B and D take a five-point pattern on the web over its depth, and the report carries the average. Zone C may be taken as 3 readings over its length, averaged, expanded to five points if the web plating has general corrosion. Where the lower bracket length or depth does not meet UR S12, extra gaugings at sections a) and b) give the actual section modulus: at least 2 readings on the flange or faceplate at each section, and at least 1 reading of the attached shell plating on each side of the frame, fore and aft. UR Z10.2 Ann.V §4
Two Annex V rules change the day's work. If renewal or other S31 measures are to be applied to individual frames in a hold, every frame in that hold is gauged; and where readings come out close to the criteria, the number of frames measured is increased. Pitting under coating blisters has to be exposed, and a normal 10 mm transducer will not read a pit — use a miniature transducer of 3 to 5 mm, or a pit gauge with the remaining thickness calculated. Above 15% pitting intensity, an area of 300 mm diameter or more at the worst-pitted part is cleaned to bare metal, the five deepest pits measured, and the least reading recorded. The floor is 75% of as-built in the frame web and flange, 70% in the shell, hopper and topside plating attached to the frame over a width up to 30 mm each side of it. UR Z10.2 Ann.V §3.1
Annex III covers the vertically corrugated transverse watertight bulkhead between holds 1 and 2 on ships that must comply with UR S19. Because S19 assesses that bulkhead on a buckling model, the readings go at fixed levels rather than wherever the corrosion looks worst, and on every corrugation the flange, web, shedder plate and gusset plate are all gauged. Level (a) for ships without a lower stool and level (b) for ships with one both sit low: mid-breadth of the corrugation flanges about 200 mm above the line of the shedder plates, the middle of the gusset plates between the flanges where fitted, the middle of the shedder plates, and mid-breadth of the corrugation webs about 200 mm above the shedder line. Level (c) applies either way, at mid-breadth of flanges and webs at about mid-height of the corrugation. Where thickness changes within one of these levels, the thinner plate is the one gauged. UR Z10.2 Ann.III
Sources
- UR Z10.2 Rev.37IACS — Hull Surveys of Bulk Carriers, Feb 2023official text ↗
- UR Z10.5IACS — Double skin bulk carriers; Z10.2 §1.1.1 and §1.1.6 defer to itofficial text ↗
- UR S31IACS — Renewal criteria for side shell frames and brackets, single side skin bulk carriersofficial text ↗
- UR S19 / UR S23IACS — Transverse watertight bulkhead between holds 1 and 2, and its compliance deadlinesofficial text ↗
- UR Z7IACS — Hull classification surveys, for the parts of the ship outside the Z10.2 scopeofficial 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.