Qualifying UTM Operators for Class Thickness Measurement Work

What a UTM operator must actually hold

IACS UR Z17 Annex 1, Section 1 sets two personnel requirements for firms engaged in thickness measurements. The responsible supervisor is qualified according to a recognised national or international industrial NDT standard, with ISO 9712 Level II given as the example. The operators carrying out the measurements are certified to a recognised national or international industrial standard, with ISO 9712 Level I as the example, and hold adequate knowledge of ship structures sufficient to select a representative position for each measurement.

Those are minima with a floor that societies can raise, and they do. Korean Register's published guidance for approval of service suppliers requires thickness measurement operators certified to ISO 9712 Level II — the level IACS names for the supervisor. A technician file built to the IACS example clears one society and fails another, on the same vessel type, doing the same work. Confirm the accepted scheme and level, in writing, per society, before the technician is assigned.

The general requirements add the part firms forget. Operators, technicians and inspectors must have had a minimum of one year of tutored on-the-job training, and where internal training is impossible a programme of external training is considered acceptable. Supervision must be provided for all services, and the responsible supervisor must have a minimum of two years of experience as an operator within the activity for which the supplier is approved.

Where SNT-TC-1A sits inside the class requirement

ASNT SNT-TC-1A is a recommended practice for employer-based certification, and it is the scheme almost every US inspection firm actually runs. Class does not name it in Annex 1 — the examples are ISO 9712 and the withdrawn EN 473 — but the requirement is written as 'a recognised national or international industrial standard', which leaves room for a national employer-based practice provided the firm can show the standard behind the certificate.

Showing it means producing the apparatus, not the card. A written practice that identifies the requirements for control and administration of training, examination and certification. Documented training hours and experience per method. General, specific and practical examinations that were prepared, administered and graded. Records that correlate to the examination sat. And the qualified Level III whose signature makes the certificate valid — the reason written practice development and Level III exam oversight are the first two workstreams in any class-approval project.

SNT-TC-1A also makes provision for limited certification, which is how UT thickness measurement is commonly certified — a Level II restricted to thickness gauging. That is legitimate when the limitation is described in the written practice and printed on the certification record. It becomes a finding when the certificate says Level II UT without limitation and the technician has only ever been trained and examined on thickness. The routes and their boundaries are set out on ASNT certification.

The ship-structure knowledge element nobody documents

The phrase in Annex 1 is doing real work: adequate knowledge of ship structures sufficient to select a representative position for each measurement. A thickness reading taken 200 millimetres from where class expected it is a different number. The operator is being asked to make a structural judgement in the moment, and Z17 makes the firm responsible for evidencing that the operator can.

Evidence looks like a training plan and a training record. Z17's companion categories spell out the expected content — minimum rule requirements for relevant ship and unit types, the ship's or unit's structure including internal structure, recognition of corrosion damage, buckling, cracking and deteriorated coatings, and use of the reporting system. Firms that document ultrasonic competence and nothing else have half a file, and the missing half is the half a class auditor can find in ten minutes.

This is the element that separates a general industrial UT technician from a UTM operator. The certificate transfers; the structural knowledge does not. A firm moving into class work from refinery or fabrication inspection needs a deliberate structures training programme with dated records per operator — the kind of gap maritime NDT consulting is engaged to close before the first witnessed job rather than during it.

The witnessed job: the surveyor signs each separate report

UR Z17 Annex 1 requires the supplier to have the surveyor's verification of each separate job, documented in the report by the attending surveyor's signature. That single clause changes the risk profile of the whole programme. Firm-level approval is audited on a three-year cycle; the technician file is inspected every time a surveyor attends. Expired certificates, stale vision records and unnamed supervisors surface at the gangway.

DNV states the expectation directly for its own scheme: evidence of valid qualifications and training for service technicians is presented to attending surveyors at the time the service is conducted. In practice that means the crew travels with the file, not with a promise that the file exists at head office. Firms that keep a per-technician evidence pack — certificate, vision record, OJT log, structures training record — clear the check without a phone call.

The demonstration requirement at approval works the same way. Certification is conditional on a practical demonstration of the specific service plus satisfactory reporting, and where a firm seeks several scopes each is demonstrated separately with its own service report. At renewal, evidence of performance verified by a class surveyor since the previous audit satisfies the requirement — which rewards a firm that has kept its signed reports filed by society and by date.

Gauge calibration evidence, per instrument

Z17 requires the supplier to keep a record of the equipment used, available on request, containing information on maintenance and the results of calibration and verifications. The word that matters is 'results'. A calibration certificate stapled to a folder is a document; the audit wants the values, the dates, the reference used, and the decision that followed. Records are kept per instrument, tied to the serial number that appears on the report.

Annex 1 also constrains the instrument itself. On coated surfaces, instruments using the pulsed echo technique — oscilloscope, or digital using multiple echo, single crystal technique — are required. Single echo instruments are permitted only on uncoated surfaces that have been cleaned and ground. A firm gauging over coating with a single-echo gauge is producing readings class will not accept, regardless of how well the technician is certified.

The consequence clause is the one to plan around. Where equipment is found not to conform to requirements, the Society assesses and records the validity of previous measuring results and takes appropriate action on the equipment affected. That is retrospective exposure across every report that instrument produced since its last good check. Daily function checks against an identified reference block, recorded and retained, are what bound the blast radius to one day rather than one year.

Vision, recertification and keeping the file current

Under ISO 9712 the certificate is valid for five years, and near-vision acuity is verified before certification and annually thereafter — a minimum of Jaeger number 1 or Times Roman N4.5 or equivalent at not less than 30 cm, with one or both eyes, corrected or uncorrected. Colour vision moved to a five-year demonstration under the 2022 edition. Under SNT-TC-1A's 2024 edition the recommended maximum recertification interval is five years for Levels I, II and III, near vision is Jaeger number 2 annually, and colour contrast is examined at initial certification and at five-year intervals.

Annual is the operative word for vision in both schemes, and it is the single most common expired item in a UTM technician file. A vision test taken thirteen months ago invalidates the technician for the job in front of the surveyor. Firms that batch vision testing on a fixed calendar month, and diary it, remove the most frequent gangway failure at essentially no cost.

Recertification is a scheduling problem, not a technical one. Five-year certificate cycles, three-year firm approval cycles and annual vision cycles run on different clocks, and none of them align. A single register showing every technician's certificate expiry, vision date, OJT completion and structures training, reviewed monthly, is what an outsourced ASNT Level III maintains for firms that do not have one internally — and the boundaries of that role are set out on what an outside Level III can and cannot do.

The TM report class expects: members, diminution, percentages

The thickness measurement report is a controlled form, not a free-text deliverable. The ESP report formats carry the name of the firm performing the measurement, the society that certified the firm, the certificate number, the certificate validity dates, and the qualification of the operator — printed identity fields that expose the whole approval chain on the first page. A firm without a certificate cannot complete the header, which is the point.

The measurement body identifies structure before it reports numbers: strake position, plate position and structural member, then original thickness in millimetres, gauged readings port and starboard, and diminution port and starboard expressed in both millimetres and per cent, against the maximum allowable diminution. Place of measurement is recorded and referenced to structural sketches. The report closes with the firm's official stamp and the surveyor's name and signature.

Those percentages carry the decision. IACS defines substantial corrosion as an extent of corrosion such that assessment of the corrosion pattern indicates wastage in excess of 75 per cent of allowable margins but within acceptable limits — the trigger for extended measurement at subsequent surveys. Reporting raw thickness without the diminution calculation moves that assessment onto the surveyor's desk, and firms that do it get asked to resubmit. Building the calculation into the reporting template is a one-off engineering job with a permanent return.

Why the technician file fails the audit before the procedure does

Procedures are written once, reviewed by a Level III, and improve with each revision. Technician files decay continuously — certificates expire, people leave, vision tests lapse, a new hire arrives with a certificate from a previous employer that the current firm has never verified. The asymmetry is why audit findings cluster in personnel records even at firms with excellent documented procedures.

Z17 tells the auditor exactly what to look for, which makes the finding easy to write. Personnel records shall contain information on age, formal education, training and experience for the services for which each person is approved. Four fields. Most firms hold one — the certificate — and assume the rest is implied. The tutored on-the-job training year is the second most common gap, because nobody logged it while it was happening.

Fix the file first, then the procedure. A firm-wide personnel record rebuilt to the four Z17 fields, plus an OJT log, structures training record, vision register and per-instrument calibration file, removes the majority of realistic findings before class sees the door. The procedures that sit on top of it are then worth writing properly, which is what NDT technical procedure development delivers, and the firm-level gate those procedures serve is covered on IACS UR Z17 service supplier approval.

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