Enhanced Survey Programme (ESP) Thickness Measurement and Close-Up Survey

ESP surveys under SOLAS XI-1/2, the 2011 ESP Code and IACS UR Z10

SOLAS chapter XI-1 regulation 2 makes an enhanced programme of inspections mandatory for bulk carriers and oil tankers, applying the 2011 ESP Code. IACS members implement it through a unified requirement for each ship type: UR Z10.1 and Z10.4 for oil tankers, the latter for double-hull designs; UR Z10.2 and Z10.5 for bulk carriers, the latter for double-skin designs; and UR Z10.3, through which class brings chemical tankers into the same regime.

Compared with an ordinary hull survey under UR Z7, ESP adds discipline in four places. The survey is planned in writing before it starts. Close-up survey and thickness measurement extents are defined for each renewal survey by age. Thickness measurement is carried out by a firm approved by the ship's classification society under UR Z17 and witnessed by its surveyor. And the results are filed on board, where the next surveyor reads them first. The table shows where gauging effort typically concentrates on each ESP ship type.

The survey planning meeting with class and the thickness measurement firm

Before any part of an ESP renewal or intermediate survey begins, the unified requirements call for a survey planning meeting between the attending surveyor, the owner's representative, the thickness measurement firm's representative where one is involved, and the master or an appropriately qualified person appointed by the master or the company. The agenda is laid down: the ship's schedule; arrangements for thickness measurement, including access, cleaning, lighting, ventilation and personal safety; the extent of measurement and the acceptance criteria; the extent of close-up survey and gauging in the light of coating condition and suspect areas; how the measurements will be executed, including representative readings where corrosion is uneven or pitted; the mapping of substantial corrosion; and how findings are communicated between the surveyor, the measurement operator and the owner's representative.

In practice the meeting decides whether a gauging job runs smoothly. It should settle the order in which tanks will be opened to match gas-freeing and ballast operations, who may call for additional points, how readings beyond limits reach the surveyor and the superintendent on the same day, and the format of daily results. One rule shapes the whole schedule: in areas subject to close-up survey, thickness measurement is carried out at the same time as the close-up survey, so the gauging team and the surveyor move through the tanks together rather than one after the other.

Suspect areas, critical structural areas and coating condition

Two categories of location recur in every ESP survey programme. Suspect areas are locations showing substantial corrosion, or considered by the surveyor to be prone to rapid wastage. Critical structural areas are locations identified from calculations as needing monitoring, or from the service history of the ship or similar and sister ships as sensitive to cracking, buckling or corrosion. Both are gauged at each survey, and both depend on the previous TM report to be found again, which is why point numbering carries over from one report to the next.

Coating condition is graded GOOD, FAIR or POOR under definitions in the unified requirements, and in ballast tanks it changes what happens at annual surveys. Under the double-hull tanker requirements, a ballast tank is examined at every subsequent annual survey where a hard protective coating was never applied, where a soft or semi-hard coating is in use, where substantial corrosion is found, or where the hard coating is less than GOOD and has not been repaired to the surveyor's satisfaction; the other ESP requirements use comparable triggers. Thickness measurement follows where the surveyor considers it necessary, so recording coating condition beside the readings gives the owner the evidence needed to plan coating repair before the tank falls into annual examination.

ESP thickness measurement reporting and verification

The unified requirements specify the report: measurement locations, measured and original thicknesses, dates, equipment, personnel and their qualifications, and the operator's signature, presented on the IACS forms for the ship type with sketches. The surveyor controlling the measurements on board verifies and signs it, and countersigns the cover page of the final report. The society then issues its executive hull summary to the owner, covering the extent of close-up survey, thickness measurements, tank protection, repairs, conditions of class and, for oil tankers where it applies, the longitudinal strength results.

ESP gauging credited to the survey must be carried out by a firm holding the approval of the ship's own classification society under IACS UR Z17, and is witnessed by that society's surveyor, who is on board to the extent needed to control the process. Ask us with the vessel's class named, so that the enquiry is answered on that basis. Not all ESP-related gauging is credited: an owner's gauging ahead of the survey to inform the survey programme and the steel estimate, and monitoring of suspect areas between surveys for the owner's own records, need no class approval.

Frequently asked questions