An NDT written practice built around ASNT SNT-TC-1A for a fabrication shop or a refinery inspection department will not pass muster in front of an ABS, DNV, Lloyd's Register, or Bureau Veritas surveyor reviewing hull and structural NDT on a newbuild or an offshore unit. Not because SNT-TC-1A qualification is wrong — it remains the qualification basis Atlantis NDT trains and certifies personnel against — but because classification society rules layer additional, class-specific requirements on top of it: approved NDT procedures specific to the class society, surveyor witness-point requirements written into the newbuild inspection and test plan, and documentation formats the class society's own database expects. Marine and offshore NDT consulting exists in that gap, translating a shipyard's or offshore fabricator's existing NDT capability into a program a class surveyor will actually sign off without repeated procedure resubmissions that push a keel-laying or hull-erection schedule to the right.
Atlantis NDT's ASNT Level III consulting engagements in marine and offshore work most often come from EPC fabricators and shipyards building floating production units, jack-up rigs, semi-submersibles, or commercial hull sections for class-approved newbuilds, where the yard's existing NDT department is fully competent on API and ASME work but has never had to align a written practice and procedure set to IACS member rules — or has done it once, years ago, for a different class society than the current contract requires, and is now discovering that ABS, DNV, and Lloyd's Register do not treat procedure approvals as interchangeable.
The International Association of Classification Societies (IACS) does not itself certify NDT personnel or approve procedures — each member society (ABS, DNV, Lloyd's Register, Bureau Veritas, ClassNK, RINA, and others) maintains its own rules, though IACS Unified Requirements harmonize core structural and material requirements across members, including UR W-series requirements on welding and NDT of hull structures. In practice, three things vary by society and need to be tracked separately in a written practice serving multi-class work:
Offshore EPC fabricators and shipyards frequently work simultaneously under contracts for different class societies — an ABS-classed floating production unit hull section fabricated at the same yard building a DNV-classed offshore wind substation jacket, for example. Running two entirely separate, procedure-for-procedure NDT programs is expensive and increases the risk of a technician using the wrong approved procedure revision on the wrong job. The more defensible approach, and the one Atlantis Level III consultants typically build toward, is a core technique-qualification and equipment-calibration program that is class-agnostic — built to the more conservative requirements across the societies the yard regularly works with — with a thin layer of class-specific procedure cover sheets and witness-point documentation on top, referencing the shared core procedure by revision number. This keeps personnel qualification and equipment calibration records unified in one system rather than duplicated per class society, while still producing the class-specific paperwork each surveyor expects to see.
Marine and offshore structural NDT draws on the same core method set as onshore fabrication — visual testing (VT), magnetic particle testing (MT), ultrasonic testing (UT) and increasingly phased array UT (PAUT) for weld volumetric examination, and radiographic testing (RT) where geometry and access still favor film or digital radiography over PAUT — but with access and sequencing constraints specific to hull and topside fabrication:
Historically inspected primarily by RT, many yards and class societies now accept PAUT as an alternative or supplement, particularly for thicker plate on offshore hull structures where radiography exposure times and radiation-control logistics on an active fabrication yard floor are increasingly impractical. The written practice needs to specify, per class-approved procedure, which joint configurations and thicknesses PAUT is approved for versus where RT remains required.
MT is the primary surface method for accessible fillet welds on frames, stiffeners, and bulkhead connections; where subsurface examination of partial-penetration or full-penetration T-joints is required, UT techniques specific to T-joint geometry (distinct from simple butt-weld UT calibration blocks) are needed, and the written practice should call out T-joint-specific calibration reference blocks rather than assuming a standard butt-weld IIW block covers the geometry.
Process piping on a fixed platform, FPSO, or semi-submersible follows ASME B31.3 for construction and often API 570-derived in-service inspection philosophy once in operation, layered under the platform's overall class and flag-state survey regime — meaning a topside piping NDT program on an offshore asset typically needs to satisfy both the class society's structural/piping survey requirements and the operator's own process-safety inspection program, which are related but administered separately.
This is the point where Atlantis NDT is most precise with clients, because it is also where written practices most often go wrong. Atlantis trains and certifies personnel to ASNT SNT-TC-1A — an employer-based qualification program, not a third-party personnel certification scheme. Some class societies and some international contracts specify ISO 9712 or PCN (or a national equivalent) personnel certification as a requirement for NDT operators performing class-witnessed work, particularly on internationally contracted newbuilds. Where a contract requires that basis, the yard needs personnel holding that specific third-party certification — Atlantis does not deliver, administer, or issue ISO 9712 or PCN certification, and a written practice should never represent SNT-TC-1A qualification as satisfying an ISO 9712 or PCN contractual requirement, because a class surveyor checking certificates against the ITP will catch the mismatch immediately and reject the operator's qualification for that scope. What Atlantis Level III consulting does provide is the analysis of which scopes of a given contract actually require third-party certification versus which can proceed under the yard's own SNT-TC-1A written practice, so the yard invests in third-party certification only where the contract genuinely requires it, and builds everything else on the SNT-TC-1A foundation it already controls through in-house NDT training.
Jumbo conversions, life-extension projects, and major repairs on existing hull or topside structure trigger the same class NDT and written-practice requirements as newbuild work, with an added complication: existing steel condition, prior repair history, and sometimes decades-old original construction records of uncertain completeness. A yard taking on a hull conversion or an offshore platform life-extension project needs its written practice to address not only new-weld NDT but also baseline condition surveys on existing structure — thickness measurement to establish current condition against original as-built minimums, and MT or PAUT screening of existing welds and highly stressed structural details before new work is welded onto them. Class societies scrutinize life-extension and conversion NDT programs closely precisely because the baseline condition data quality determines whether the extended service life assessment is credible, and a written practice that treats a conversion project identically to new fabrication — without the baseline survey component — is one of the more common findings in class plan-approval review for this project type.
Shipyards and offshore EPC fabricators evaluating outside Level III support ahead of a new class-classed contract should expect a scope that includes: a review of the contract's ITP and class rules to identify which NDT scopes require witness points, procedure pre-approval, or third-party personnel certification; a gap analysis between the yard's existing SNT-TC-1A written practice and what the specific class society expects to see; harmonization of procedures across multiple class societies where the yard works under more than one; and a documentation workflow that produces class-submittable records without duplicating data entry across systems. The deliverable should leave the yard's own quality and NDT department able to run the program independently on the next contract, with the class-specific requirements built into their standing written practice rather than re-discovered project by project.
Because newbuild schedules are driven by fixed milestone dates — keel laying, hull erection, float-out, sail-away — a rejected or resubmitted NDT procedure late in a project carries real schedule and liquidated-damages exposure. Getting the written practice and procedure package aligned to the class society's expectations before fabrication starts, rather than discovering a mismatch mid-project, is consistently the highest-leverage point at which outside Level III review pays for itself. Pairing that written practice with inspection management software that tracks procedure approval status, witness-point scheduling, and operator qualification against each class society's requirements in one system — rather than a quality manager's personal tracking spreadsheet — keeps a multi-class fabrication program from quietly drifting out of compliance between class society audits.
Class involvement does not stop at sail-away or first oil. Vessels and floating offshore units remain under a periodic survey regime — annual, intermediate, and special/renewal surveys on roughly a five-year cycle for most class societies — that includes close-up structural surveys and thickness measurement surveys targeting known corrosion-prone areas: ballast tanks, cargo tank boundaries on tankers, and topside structural steel exposed to marine atmosphere on offshore platforms. Owners and operators of FPSOs, FSOs, and other long-life floating offshore assets increasingly negotiate risk-based survey schemes with their class society — ABS's dynamic survey scheduling or DNV's equivalent programs — which substitute a data-driven, condition-based thickness measurement and structural survey plan for the traditional fixed five-year cycle, provided the operator can demonstrate a mature in-service NDT and corrosion-monitoring program. Qualifying for a risk-based survey scheme requires exactly the same discipline described earlier for pipeline and refinery RBI programs: documented thickness trending over time, corrosion rate calculation against class-approved minimum thickness diminution limits, and an NDT program executed by qualified personnel under a written practice the class society has reviewed. Operators who invest in that program early recover the cost through reduced dry-docking frequency and shorter survey windows over the asset's life, which for a floating production unit can represent weeks of deferred production avoided per survey cycle.
On a high-throughput newbuild program — multiple hull blocks or topside modules progressing through fabrication simultaneously — the operational bottleneck is rarely NDT technician capacity; it is surveyor availability to witness hold points on the schedule the fabrication sequence actually needs. A written practice and quality plan that pre-schedules witness points against the fabrication sequence, and that gives the surveyor advance visibility into which welds will be ready for witness on which shift, measurably reduces the idle time welds spend sitting complete-but-unwitnessed while waiting for a surveyor visit to be arranged. This is a scheduling and documentation-system problem as much as an NDT technique problem, and it is where a digitized inspection record system that the surveyor can review remotely between visits — rather than requiring an on-site walk of physical report binders — measurably shortens the witness-scheduling cycle on a busy fabrication program.
\nAtlantis NDT pairs field expertise with software: NDT inspection management software — Atlantis ERP, a digital twin platform for asset integrity, and NDT reporting software. Build your team with NDT training & certification (ASNT SNT-TC-1A) and ASNT certification pathways, or bring in ASNT Level III consulting. Affordable, accessible, fully customizable — book a free consultation.
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