UTM Ultrasonic Thickness Measurement Case Study
Independent ultrasonic thickness measurement and technical assessment of ship hull structures, supporting structural condition evaluation, classification surveys, corrosion assessment, maintenance planning and compliance with applicable marine inspection requirements.
Case Study Introduction
Ultrasonic Thickness Measurement (UTM) provides objective thickness data for evaluating the condition of hull structures and identifying areas affected by corrosion, wastage or structural deterioration.
This case study presents a structured approach to ultrasonic thickness measurement of ship structures, from inspection planning and measurement execution through technical assessment and reporting.
The approach is particularly relevant to surveys and inspections where reliable thickness data is required to support structural condition assessment, repair planning, classification requirements and statutory or regulatory oversight.
Case Study Scope
Vessel Structural Assessment
Assessment of accessible ship structural members through ultrasonic thickness measurements to establish the actual remaining material thickness.
Ultrasonic Thickness Measurement
Systematic UTM readings are obtained from selected structural locations in accordance with the applicable inspection scope, measurement plan and reporting requirements.
Corrosion & Wastage Evaluation
Recorded measurements are evaluated to identify areas where corrosion, wastage or other deterioration may require further investigation or engineering attention.
Technical Reporting
Measurement results are documented in a structured technical report providing traceable data for survey, condition assessment, repair and maintenance decisions.
Technical Objectives
The principal objective of the UTM case study is to establish reliable thickness information for ship structures and provide technically traceable data that can be used during structural assessment and marine survey activities.
- Establish actual remaining structural thickness.
- Identify areas of corrosion and material wastage.
- Support structural condition evaluation.
- Provide objective measurement data for survey activities.
- Support repair and maintenance planning.
- Provide documented technical evidence for classification and compliance activities.
Structural Areas Considered
Hull & Shell Structures
Thickness measurements may include accessible shell plating, bottom structures, side shell areas, longitudinal members and other relevant hull structural components.
Deck Structures
Selected deck plating, stiffeners and associated structural members may be examined where required by the inspection scope.
Internal Structures
Accessible internal structural members may be included to determine material condition and identify localized wastage.
Tanks & Cargo Areas
Where applicable and safely accessible, UTM may be performed in tanks, cargo spaces and other areas requiring structural thickness verification.
UTM Measurement Approach
Inspection Planning
The inspection scope is established according to the vessel, structural areas, survey requirements and intended technical assessment.
Surface & Access Assessment
Measurement locations are reviewed for accessibility, surface condition, coating condition and suitability for reliable ultrasonic measurement.
Thickness Readings
Ultrasonic measurements are taken at defined locations using suitable calibrated equipment and appropriate measurement procedures.
Results Documentation
Readings are recorded and organized so that the resulting thickness information can be traced to the relevant structural locations.
Measurement Limitations
Ultrasonic thickness measurement results depend on the condition of the structure, the accessibility of the measurement location, the surface condition and the suitability of the measurement equipment and procedure. These factors are considered when evaluating the reliability and representativeness of the recorded readings.
Surface Condition
Heavy corrosion, scale, marine growth, loose coating, surface irregularities or other contamination may affect the quality of ultrasonic coupling and measurement accuracy.
Accessibility
Restricted access, confined spaces, structural arrangements or unsafe locations may limit the available measurement points and require alternative access arrangements.
Material & Structural Condition
Localized corrosion, pitting, laminations, deformation or irregular structural conditions may require additional readings or further technical evaluation.
Measurement Coverage
The number and distribution of measurement points must be considered when interpreting the overall structural condition. Limited access or restricted measurement areas may affect the extent of available data.
Equipment & Calibration
Measurement reliability depends on suitable equipment, appropriate calibration and verification, correct probe selection and proper operating procedures.
Interpretation of Results
Individual thickness readings should be considered within the structural and survey context. Where necessary, additional measurements, surface preparation, other NDT techniques or engineering assessment may be required.
Where measurement conditions are unsuitable for obtaining reliable readings, the limitation is documented and appropriate corrective action or additional technical assessment may be recommended.
MSC.553(108) Firm Approval & Administration Audit
IMO Resolution MSC.553(108) amends the 2011 ESP Code procedures for the approval and certification of firms engaged in thickness measurement of hull structures. The amendment entered into force on 1 January 2026 and clarifies the role of the Administration in auditing such firms.
Following satisfactory review of the documents submitted for approval, the Administration is to audit the firm to ascertain that the firm is duly organized and managed in accordance with the submitted documents and is capable of conducting thickness measurement of the hull structure of ships.
Document Submission & Review
The approval process begins with submission and review of the documentation required by the applicable Administration for the thickness-measurement firm.
Firm Organization & Management
The firm's organizational and management arrangements should be consistent with the information submitted for approval and demonstrate an appropriately controlled thickness-measurement operation.
Technical Capability
The firm must be capable of conducting hull-structure thickness measurements using suitable personnel, procedures, equipment and technical controls.
Personnel Competence
Personnel involved in thickness measurement should have the appropriate technical experience, qualifications and competence required for the measurement activities being undertaken.
Equipment & Calibration
Thickness measurement equipment, maintenance arrangements and calibration or verification controls form an important part of demonstrating the firm's technical capability.
Measurement Procedures & Records
Controlled measurement procedures and suitable measurement records support consistent execution, traceability and technical review of the thickness-measurement operation.
MSC.553(108) therefore places greater emphasis on verification of the thickness-measurement firm's organization, management and capability, rather than treating approval solely as a document-review exercise. The Administration's audit provides an additional verification step before certification of the firm's thickness-measurement operation.
Technical Assessment of Measurement Results
Recorded UTM data is reviewed in relation to the relevant structural locations and the purpose of the inspection. The assessment considers observed thickness loss, corrosion patterns, localized wastage and other relevant structural observations.
The measurement data provides objective technical information that can assist surveyors, owners, operators and technical managers in assessing the condition of the vessel's structure and determining appropriate follow-up actions.
UTM readings are measurement data and should be interpreted within the applicable survey, structural and classification context. Where structural significance cannot be established from thickness data alone, further engineering or survey assessment may be required.
Case Study Outcome
Objective Measurement Data
Provides documented thickness readings that establish the measured condition of selected structural locations.
Condition Assessment Support
Supports evaluation of corrosion, wastage and remaining structural thickness.
Survey & Compliance Support
Provides technical measurement information that can support applicable classification, statutory and survey activities.
Maintenance & Repair Planning
Helps identify areas requiring further inspection, maintenance, repair or engineering evaluation.
Independent Technical Approach
PAMS Pacific Admiralty Maritime Services applies an independent technical approach to marine inspection and consultancy activities, with emphasis on objective measurement data, traceable reporting and practical technical assessment.
UTM results can be incorporated into wider marine survey, structural inspection, classification and technical consultancy activities where required by the vessel's condition, survey scope or project requirements.
Classification & Certification Context
UTM activities may be required in connection with classification surveys, structural condition assessments, special surveys, dry-docking, maintenance planning and other marine inspection requirements.
PAMS provides UTM technical services with experience supporting measurement and inspection requirements associated with major classification and marine inspection frameworks, including:
- American Bureau of Shipping (ABS)
- DNV
- Lloyd's Register (LR)
- Bureau Veritas (BV)
Classification or statutory acceptance remains subject to the requirements and decisions of the applicable Administration, recognized organization or classification society.
UTM Case Study FAQ
What is Ultrasonic Thickness Measurement (UTM)?
Ultrasonic Thickness Measurement (UTM) is a non-destructive testing method used to determine the remaining thickness of suitable materials, including ship hull plating and marine structural components, without destructive removal of the inspected structure.
What is UTM used for on ships?
UTM is used to determine the remaining thickness of ship structural components and to support structural condition assessment, corrosion monitoring, classification and statutory survey preparation, dry-docking, repair planning, technical due diligence and damage or deterioration investigations.
When is ultrasonic thickness measurement required?
Ultrasonic thickness measurement may be required or requested for classification and statutory surveys, special or renewal surveys, dry-docking, condition assessments, damage investigations, repair planning, pre-purchase inspections and other applicable marine inspection requirements, depending on the vessel, survey scope and governing requirements.
What structures can be measured using UTM?
Depending on the inspection scope and accessibility, UTM can be used on hull and shell plating, decks, bottom and side shell structures, frames, floors, girders, stiffeners, bulkheads, tanks, cargo holds, ballast tanks and other accessible marine structural components.
What is MSC.553(108)?
MSC.553(108) is an IMO resolution adopted on 23 May 2024 that introduces amendments to the 2011 ESP Code concerning procedures for approval and certification of firms engaged in thickness measurement of hull structures of bulk carriers and oil tankers. The amendments entered into force on 1 January 2026.
How does MSC.553(108) affect thickness measurement firms?
Under the amended 2011 ESP Code, after reviewing the documents submitted by a thickness measurement firm with satisfactory results, the Administration audits the firm to ascertain that it is duly organized and managed in accordance with the submitted documents and is capable of conducting thickness measurement of the hull structure of ships.
What does a thickness measurement firm need to demonstrate?
The approval and certification process requires the firm to demonstrate appropriate organization and management and the capability to conduct thickness measurement of hull structures. The applicable approval process may also address personnel competence, equipment, procedures, technical capability, records and reporting according to the Administration and applicable requirements.
Are UTM measurements affected by surface condition?
Yes. Surface condition can affect measurement reliability and accessibility. Surface preparation, coatings, corrosion, scale and other conditions may need to be considered when planning and performing measurements and evaluating the resulting data.
Are UTM measurements affected by accessibility?
Yes. Accessibility can affect the measurement scope, locations and practical execution of UTM. The inspection plan should consider safe access, structural configuration, surface condition and any limitations that could affect measurement coverage or reliability.
Can UTM results support classification surveys?
Yes. UTM results can support classification and statutory survey activities by providing objective thickness data for structural assessment. Acceptance of measurements and reports remains subject to the applicable classification society, Administration and survey requirements.
Which classification societies are relevant to UTM services?
UTM work may be relevant to requirements of classification societies including ABS, DNV, Lloyd's Register and Bureau Veritas, depending on the vessel, class status, survey scope and applicable approval or certification requirements.
Can UTM results be used for repair planning?
Yes. UTM results provide thickness information that can assist technical teams in evaluating corrosion wastage and structural condition and in planning steel renewal, repairs and maintenance during dry-docking or other technical interventions.
UTM Case Study Resources
UTM Services
Detailed information about PAMS ultrasonic thickness measurement services and technical scope.
View UTM ServicesMSC.553(108) Article
Stricter oversight on thickness measurement firms and the regulatory changes introduced by MSC.553(108).
Read the ArticleDiscuss Your UTM Requirements
Contact PAMS Pacific Admiralty Maritime Services for independent ultrasonic thickness measurement, marine structural inspection and technical consultancy support.
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