Special Survey Thickness Measurement · Istanbul, Turkey
Third and Fourth Renewal Survey Gauging in Istanbul: From Anchor off Tuzla to the Dock
Istanbul owners tend to dock their older ships close to home, and the Tuzla yards on the Sea of Marmara handle most of those renewal surveys. The steel decisions are made quickly there, so the gauging has to be ahead of the yard rather than behind it. We mobilise a thickness measurement team from India to Istanbul, take readings at anchor off Tuzla or at the last cargo port before docking, and then measure in the dock as plating is exposed, keeping the superintendent's steel list a step ahead of the steelwork.
Steel list ahead of the steelwork
At Tuzla the yard's steel order follows the first readings. Gauging at anchor beforehand, then in dock as each area is released, keeps decisions area by area instead of crowding them into the last days of the stay.
Built for older Black Sea tonnage
Many Istanbul-managed Handysize and Supramax bulk carriers and small tankers reach their third and fourth renewal surveys here. Gauging is scoped for the wastage those ships typically carry after years of Black Sea and Mediterranean trading.
Several ships in one mobilisation
With many yards close together, a team that travels from India can gauge a ship at anchor, another in dock and a third alongside in the same visit, which suits managers with more than one ship due.
Why do Istanbul-managed ships dock at Tuzla for renewal surveys?
Istanbul is a shipowning city first. Turkish owners run large fleets of second-hand Handysize and Supramax bulk carriers, general cargo ships and small tankers, and their technical departments sit within reach of the yards. A superintendent can attend a docking daily at Tuzla, take decisions on the spot, and send a ship back to trade quickly. That convenience is why a repair centre on the Marmara shore keeps a steady queue of renewal surveys.
It also shapes the gauging. Superintendents here usually arrive with a sharp idea of where steel will be needed, based on years of experience with the same type of ship, and they want readings that confirm or correct that view quickly. A report that arrives after the steel has been ordered is of little use. The measurement plan is therefore built around the yard's schedule, with the first readings aimed at the areas that drive the largest renewals.
Is pre-docking gauging at anchor off Tuzla worth doing?
For most ships it is. A ship may wait at anchor off Tuzla for days before a dock is free, and that wait is a usable window: ballast tanks, hold frames and deck structure can be gauged by a team boarding from a launch. The readings tell the superintendent which members are likely to be renewed, so the yard's quotation is based on measured steel instead of an allowance.
Boarding at anchor depends on the weather on the Marmara and on the agent's launch. A strong wind can delay a visit, so the plan carries some float. When the dock date moves, which happens often, the team's visit can be moved with it as long as visa validity allows. The Istanbul agent, who handles the ship's entry to the yard, coordinates the sequence.
How is gauging sequenced once the ship is in a Tuzla dock?
Once the ship is docked and the hull is blasted, bottom and side shell plating become accessible and the yard begins its steel programme. The team's first task is the bottom and the shell, measured as strakes are cleaned, so that renewal marks can be made before steelwork starts on that area. Tanks follow as they are cleaned and certified: ballast tanks first for most ships, then cargo holds or cargo tanks depending on type.
On a chemical tanker, cargo tank readings depend on cleaning and gas-free certificates, which can be delayed by residual cargo or inspection schedules. On a bulk carrier, hold frames and hopper plating are accessible once holds are washed and staging is erected. We agree a daily summary with the superintendent and the attending surveyor, listing areas completed, readings beyond limits and areas still waiting, so everyone sees the same picture.
What do third and fourth renewal surveys usually show for older Istanbul ships?
By the third renewal survey the gauging extent has widened substantially, and by the fourth it covers most structural members in cargo and ballast spaces. On older bulk carriers, the usual findings are wasted hold frame ends, pitted tank tops, deep corrosion on hopper plating and thinning of the lower stools of corrugated bulkheads. Ships carrying steel products, scrap and bulk minerals on short Black Sea voyages often show abrasion damage to holds in addition to corrosion.
On general cargo ships and small tankers, ballast tank coatings that reached the end of their life years ago are a recurring source of heavy wastage, with grooving along weld lines and pitting on bottom plates. Deck plating and hatch coamings suffer on ships that load and discharge quickly with grabs. The report ranks members by remaining margin and by the likelihood of renewal, so the superintendent can set a steel budget from it.
Can several ships be gauged in one visit to Istanbul?
Yes, and it is often the sensible way to use a team that travels from India. Managers with sister ships or ships scheduled in close succession can ask for a combined plan: one ship at anchor off Tuzla, one in dock, one alongside at a terminal. The sequence is arranged with the agent and the yards so the team moves between ships without gaps.
A combined plan also helps comparison. When a crack or a corrosion pattern is found on one ship of a class, the same detail can be checked on the sisters. Because the point numbering and report format are consistent, the superintendent can compare ships directly. Visa and travel arrangements are made once for the group, which reduces the planning burden when dock dates are firm.
What should be arranged for a renewal survey gauging job at Tuzla?
The yard arranges access and staging, the ship prepares tank cleaning and gas-free certificates, and the agent handles entry to the yard and terminals with crew lists and certificates sent ahead. Our team needs the class, the survey programme, the previous report and the dock dates; with those, the measurement plan and its split between anchor and dock can be agreed in advance.
Turkey requires a visa for Indian passport holders, so applications start as soon as the docking date is set, and the plan allows for a yard slot that may shift. We confirm in the plan which readings are owner's information and which a firm approved by the ship's class could take for the survey itself, so there is no surprise when the surveyor asks what is creditable.
Where special survey thickness measurement sits in the survey cycle
How much steel has to be gauged depends on which survey the ship is due for, its type and its age. The pattern below is the usual one under IACS unified requirements; the attending surveyor and the class rules for the ship decide the final extent. For a ship calling at Istanbul, we agree the programme with the class and the owner before the team mobilises.
| Survey | When it falls | What the thickness measurement usually covers |
|---|---|---|
| Annual survey | Every year, within three months of the anniversary date | General examination. Gauging where the surveyor finds suspect areas or where substantial corrosion was recorded at an earlier survey. |
| Intermediate survey | In place of the second or third annual survey | Suspect areas, and on older ships and ESP ships selected ballast and cargo spaces with close-up survey; the extent grows with age. |
| Renewal survey No. 1 | Around 5 years | The first full baseline: suspect areas and selected plating and stiffeners, usually with modest steel renewal. |
| Renewal survey No. 2 | Around 10 years | Wider gauging of deck, bottom and side plating, transverse sections across the cargo area on ESP ships, and more close-up survey. |
| Renewal survey No. 3 | Around 15 years | Extensive gauging of cargo and ballast tank structure and more transverse sections. The survey most likely to turn up steel renewal. |
| Renewal survey No. 4 and later | Around 20 and 25 years | Gauging extended to most structural members in cargo and ballast spaces. Charterers often add a Condition Assessment Programme. |
| Docking survey | Twice in each five-year period | Bottom and side shell, sea chests, rudder and stern area while the hull is dry; suspect bottom plating gauged. |
How the job runs at Istanbul
The sequence for a thickness measurement job at Istanbul is short and written down, so the yard, the surveyor and the superintendent know who arranges what.
- Send the vessel name or IMO number, ship type, class society, the survey due (annual, intermediate, renewal survey number, CAP or owner's condition survey), the port and dates, and the scope you expect.
- We confirm the scope against the class rules for that survey, prepare the thickness measurement plan with frame and section references, and say whether the measurement will be credited to a class survey.
- Mobilisation is planned around visa lead times and the vessel's schedule; the ship's agent arranges port access, and the yard or ship arranges staging, lighting, ventilation and gas-free certificates.
- Gauging with calibrated ultrasonic thickness gauges: through sound coatings only where the gauge's through-coating mode has been verified on a coated reference, otherwise on cleaned bare steel, with every reading tied to its frame, strake and location on the sketch.
- Readings are compared with original thicknesses as work proceeds; substantial and excessive corrosion and any cracks are reported to the attending surveyor and the superintendent the same day.
- The final report is issued on the class thickness-measurement formats with sketches, a summary of locations exceeding the allowable margins, piping tables where piping was in scope, and the gauge calibration and technician certificates.
Who does the work, and when class approval applies
We send the team from India to the ship for each job rather than keeping staff at the port, and plan the mobilisation around visas and the vessel's itinerary. The work is planned and supervised by the founder, our Responsible NDT Level III (ASNT NDT Level III in UT, RT, MT, PT and VT, with more than eleven years of international field experience). Technicians hold certification under the company's written practice to ASNT SNT-TC-1A; Atlantis is ISO 9001 and ISO 14001 certified.
Thickness measurement that a classification society credits to a class survey has to be carried out by a firm approved by that society under IACS UR Z17. Atlantis is in the process of obtaining UR Z17 approval from DNV, Lloyd's Register and ABS. Until a certificate is issued, the readings we take are for the owner's own decisions, not for credit to a class survey, so tell us the vessel's class and the survey due when you enquire and we set the scope for the right purpose. Owner's and charterer's condition gauging, pre-docking steel estimates, pre-purchase and on-hire or off-hire gauging, and scrubber and piping condition checks between surveys do not need class approval.
Governing codes and standards
- IACS UR Z7 for hull surveys and the gauging extents tied to each renewal survey
- IACS UR Z10.1, Z10.2 and Z10.4 for the enhanced survey of oil tankers, bulk carriers and chemical tankers
- IACS UR Z17 on which firms may measure thickness for credit to a class survey
- SOLAS chapter XI-1, regulation 2, and the 2011 ESP Code
- ASTM E797 for manual pulse-echo ultrasonic thickness measurement
- ASNT SNT-TC-1A for the qualification of the technicians who take the readings
What you receive
- Pre-docking readings from anchor with a steel renewal estimate for the yard
- In-dock bottom and side shell readings issued as each strake is released
- Tank and hold readings on the class formats with original thickness and allowable margin
- Daily summary of areas done, readings beyond limits and areas waiting
- Comparison tables across sister ships where several are gauged in one visit
- Gauge calibration records and technician certificates
Industries served
- Handysize and Supramax bulk carriers
- General cargo and multipurpose ships
- Chemical and product tankers
- Crude tankers
- Container ships
- Ro-ro ships
- Tugs and offshore vessels
Frequently asked questions
Can we gauge a ship at anchor off Tuzla before it enters the dock?
Yes. Ballast tanks, hold frames and deck structure can be measured by a team boarding from a launch while the ship waits for a dock. The readings give the yard a measured steel scope for its quotation. Weather on the Marmara can delay boarding, so the plan carries some float.
Is thickness gauging at Tuzla credited to the class renewal survey?
Only when taken by a firm approved by the ship's society as part of the survey. Atlantis is in the process of obtaining UR Z17 approval from DNV, Lloyd's Register and ABS, so for now our readings serve owner decisions and steel planning, not class credit. Tell us the class early and we set the scope accordingly.
How quickly do readings reach the superintendent during a Tuzla docking?
Results are passed on daily during the dock, with readings beyond limits flagged, so renewal marks can be made area by area. We agree the format with the superintendent and the attending surveyor beforehand, and the final report on the class formats follows when the gauging is complete.
What do third and fourth renewal surveys typically involve for a Black Sea bulk carrier?
Wide gauging of hold frames, hopper and topside tank plating, tank tops, corrugated bulkheads and ballast tanks, with close-up survey under the ESP rules. Typical findings are wasted frame ends, pitted tank tops and thinned lower stools. The extent is set by the class, and we confirm it before the team travels.
Can one team gauge several ships in the same Istanbul visit?
Yes. A combined plan can cover one ship at anchor, another in dock and a third alongside a terminal, with the sequence arranged through the agent and the yards. It suits managers with sister ships due close together, and lets the same cracks or corrosion patterns be checked across the group.
What do Indian technicians need to travel to Istanbul for a docking?
A Turkish visa, applied for once the docking date is known. Because yard slots can shift, we plan the application around the visa's validity and keep the owner informed of any change. The sooner we know the expected dates, the more reliably a team can be in place when gauging should start.
Can special survey thickness measurement at Istanbul be credited to a class survey?
Thickness measurement that a classification society credits to a class survey has to be carried out by a firm approved by that society under IACS UR Z17. Atlantis is in the process of obtaining UR Z17 approval from DNV, Lloyd's Register and ABS. Until a certificate is issued, the readings we take are for the owner's own decisions, not for credit to a class survey, so tell us the vessel's class and the survey due when you enquire and we set the scope for the right purpose. Owner's and charterer's condition gauging, pre-docking steel estimates, pre-purchase and on-hire or off-hire gauging, and scrubber and piping condition checks between surveys do not need class approval.
Planning a survey or a drydock?
Send the vessel name or IMO number, the class, the survey due and the port. We reply with the scope, the mobilisation plan and a quote for that vessel.
Request a QuoteRequest a ship gauging quote
Send the vessel name or IMO number, the class society, the survey due and the port. We reply with the scope, the mobilisation plan and a quote for that vessel.
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