Zeus Marine Service

Hull Thickness Gauging

Hull Thickness Gauging (Ultrasonic)

Zeus Marine Service — Chittagong Port, Bangladesh

1. Introduction

Hull Thickness Gauging (also called Ultrasonic Thickness Measurement or Ultrasonic Thickness Gauging, UTM / UTG) is a non‑destructive testing (NDT) technique used to measure the remaining steel plate thickness of a ship’s hull and structural members. By sending ultrasonic pulses and measuring the echo return, we can determine how much material has thinned over time, without cutting or damaging the structure.

This service is critical for condition monitoring, class surveys, maintenance planning, safety assurance, and regulatory compliance.

2. Why It’s Important

  • Corrosion detection: Marine environments cause corrosion and pitting. Early detection of thinning avoids failure.
  • Regulatory & class compliance: Required by classification societies (ABS, DNV, LR, BV, etc.) during special, intermediate, annual, or renewal surveys. (e.g. ACE Marine offers global deployment for such services) (Ace Marine Group)
  • Structural safety: Ensures that load‑bearing members have acceptable residual strength.
  • Maintenance planning & cost control: Allows predictive repairs or plating replacement rather than reactive failures.
  • Value protection: Demonstrates that the vessel is structurally sound to insurers, financiers, or buyers.

3. Scope of Our Services

Zeus Marine Service can carry out UTG on vessels of all types at Chittagong Port, whether berthed, anchored, or in repair yard. Our services include:

  • UTG for Special / ESP / CAP / CAS / Renewal Surveys
  • UTG for Annual / Intermediate / Condition Surveys
  • Rope access / close‑up inspections for hard‑to-reach areas
  • Rafting / diving / diver support for underwater areas
  • Steel thinning mapping and corrosion profile assessments
  • Pit gauging and local thinning evaluations
  • Preparation of dry-dock specifications and steel repair estimates
  • Reports accepted by major classification societies

We follow global best practice: UT‑based corrosion mapping (zero‑degree probes, raster scanning) is a standard method in many industries for deriving thickness maps.

4. Equipment & Technical Capabilities

  • Ultrasonic gauges / probes: High‑precision instruments (e.g. Cygnus, Krautkramer, GE, Olympus etc.) as per international NDT norms. (Many providers in marine NDT use these types)
  • Calibration & traceability: Instruments are calibrated regularly, traceable to standards, using echo‑to‑echo techniques to minimize coating error.
  • Certified personnel: Our inspectors hold certifications (ISO 9712, PCN, or relevant NDT credentials) and training in marine structural inspection.
  • Access methods: Rope access, scaffolding, rafts, diver support — whichever method is safest and practicable.
  • Data recording & software support: We log readings, map thinning, generate corrosion maps, and analyze against original thickness or allowable diminution.

5. Methodology / Workflow

  1. Pre‑survey planning & vessel briefing
    • Review plans, structural drawings, class requirements
    • Identify target areas (bilge, shell plating, bottom, reefs, welds, longitudinal girders)
  2. Surface preparation
    • Clean paint/dirt, remove marine growth or scale locally for proper coupling
    • Use coupling gel or suitable medium to ensure acoustic contact
  3. Measurement execution
    • Use zero‑degree probes for general thickness
    • Multiple readings at each grid point to reduce error
    • For pits or local thinning, take closer grid spacing or additional points
  4. Data capture & mapping
    • Label each point (frame, longitudinal, station)
    • Generate color‑coded thickness / corrosion maps
  5. Analysis & comparison
    • Compare measured thickness vs “as‑built” or nominal thickness
    • Calculate percentage diminution or loss
    • Assess whether any sections are beyond allowable class limits
  6. Reporting & recommendations
    • Deliver a comprehensive report with tables, maps, observed anomalies
    • Provide repair / reinforcement suggestions
    • Optionally, prepare dry‑dock steel replacement specification for yard use

6. Example Report Contents

  • Cover page, scope & terms
  • Vessel details (name, flag, class, drawing references)
  • Instrument calibration certificates
  • Survey plan and grid scheme
  • Tabulated readings by station / frame / section
  • Corrosion / thinning maps (color coded)
  • Highlighted critical zones
  • Diminution analysis & class compliance check
  • Photographs of measurement points / anomalies
  • Repair or reinforcement recommendations
  • Engineer’s signature & credentials

7. Pricing & Delivery

  • A nominal site mobilization / stand-by fee depending on vessel size and location within Chittagong port / anchorage
  • Per-hour / per-point measurement charges (depending on number of points, complexity, access method)
  • Report fee: included or separately itemized
  • If diving or specialized access is needed, extra charges may apply
  • Delivery of full report (PDF + hard copy) within 24 to 72 hours after survey completion

8. Why Choose Zeus Marine Service

  • Local expertise: Based at Chittagong, with deep familiarity with port conditions, tidal schedules, permits, etc.
  • Rapid response & 24/7 availability: We can mobilize survey teams at short notice.
  • Quality & accuracy: Use of calibrated instruments, certified inspectors, and robust methodologies.
  • Acceptance: Reports aligned with classification society standards for vessel audits, insurance, or sale.
  • Integrated marine services: If vessel needs structural repair, steel renewal, or other services, we can support or coordinate.

9. FAQs

Q: Do you need to remove paint or coating to measure?
A: You only need to remove a small patch so the ultrasonic probe can make direct contact. The majority of readings can be taken through paint if “coating compensation / echo-to-echo” methods are used.

Q: Can we measure underwater plating without dry docking?
A: Yes — using diversification methods (diver‑mounted UT, rope access, hull rafts). However, access and safety constraints may limit some areas.

Q: Will the classification society accept your report?
A: Yes, if the survey is conducted following relevant class rules, using calibrated instruments, and by certified personnel. Many marine NDT firms operate under these norms. (Ace Marine Group)

Q: How often should thickness gauging be done?
A: Depends on vessel age, corrosion environment, operational profile, and class society intervals (special surveys, 5‑year renewals, intermediate surveys, etc.).

Q: What is corrosion mapping?
A: It is plotting the thickness readings across the surface to visualize local thinning and corrosion zones. It is a standard practice in many industries.

10. Contact / Booking

If you wish to schedule a hull thickness gauging survey or request a quotation, please contact us:

Send us:

  • Vessel particulars (name, LOA, breadth, draft, class)
  • Preferred survey date & berth/anchorage location
  • Any class/flag requirements

We look forward to ensuring your vessel’s structural health and regulatory compliance with professional, accurate, and timely service.

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