Is LR's certification for ballast tank coatings and weathering steel more stringent than CCS's?

1. Preheating Requirements and Temperature Control

Elevated preheating is essential to mitigate hydrogen cracking risks in LR FH40 welding.

• Temperature Guidelines:

  • Base preheat: 100-150°C (increases to 150-200°C for thicknesses >40mm)

  • Interpass temperature must be maintained at 150-250°C

• Technical Basis:

  • Slows cooling rate to prevent martensite formation in HAZ

  • Allows hydrogen diffusion out of weld metal

• Practical Implementation:

  • Induction heating preferred for uniform temperature distribution

  • Continuous monitoring with thermocouples or infrared sensors

  • LR requires documented preheat procedures in WPS qualification

2. Welding Consumable Selection and Handling

Specialized low-hydrogen consumables are mandatory for FH40 applications.

• Electrode Requirements:

  • SMAW: AWS E11018-G or equivalent Ni-Cr-Mo alloyed electrodes

  • FCAW: AWS E81T1-Ni2 with 1.5-2.5% Ni content

• Hydrogen Control Measures:

  • Maximum diffusible hydrogen content: 5ml/100g (H5 classification)

  • Strict electrode storage (100-150°C holding ovens)

  • Rebaking protocol for exposed electrodes

• LR Certification:

  • Consumables must have LR type approval for FH40 grade

  • Batch-specific certification documents required

3. Heat Input Management and Welding Technique

Precise control of welding parameters is critical to maintain mechanical properties.

• Optimal Parameters:

  • Heat input range: 1.5-2.5 kJ/mm

  • Current type: DC+ for most applications

• Process Selection:

  • SAW preferred for long straight seams

  • Pulsed GMAW for better control in positional welding

• Technique Requirements:

  • Stringer bead technique preferred over weave

  • Controlled interpass temperature maintenance

  • LR mandates procedure qualification for each application

4. Post-Weld Heat Treatment Considerations

PWHT may be required depending on application and thickness.

• When Required:

  • Typically for thicknesses >50mm

  • High restraint joints

  • Critical structural components

• Treatment Parameters:

  • Temperature: 580-620°C

  • Soak time: 1 hour per 25mm thickness

  • Cooling rate: <200°C/hour

• Alternative Approaches:

  • Local stress relief for repairs

  • Temper bead welding technique

  • LR provides specific guidelines in Pt.3, Ch.4 of rules

5. Quality Assurance and NDT Requirements

Enhanced inspection protocols ensure weld integrity.

• NDT Methods:

  • 100% UT for full penetration welds

  • MT for all surface examination

  • PAUT recommended for thick sections

• Acceptance Criteria:

  • Zero tolerance for cracks

  • Maximum inclusion size: 4mm

  • Porosity limits per LR standards

• Documentation:

  • Complete traceability of welding parameters

  • NDT reports must be LR-approved format

  • Third-party verification often required