ISO 4827:2022

Overview

ISO 4827:2022 - Ships and marine technology: Escorting and pull-back system for tankers specifies technical requirements and test methods for escorting and pull-back fittings installed on tankers of 20 000 DWT or more. It defines design arrangements, manufacturing materials, strength and material testing, and marking requirements for critical fittings-primarily chocks and strong points-used to connect tuglines for escorting and pulling operations.

Key topics and technical requirements

• Applicability: Escorting and pull-back systems for tankers ≥ 20 000 deadweight tonnes (DWT).
• Design arrangement: Minimum distance from strong point to chock L ≥ 4.0 m to ensure proper positioning of towing eye splice (exceptions for emergency towing arrangements noted).
• Chock requirements:
  • Minimum closed-type opening: ≥ 600 mm width × ≥ 300 mm height.
  • Strength to accommodate towline angles up to ±90° horizontally and 30° vertically downward.
  • Minimum Safe Working Load (SWL) and corresponding test loads:
    • 20 000 ≤ DWT < 50 000: 1 000 kN (≈102 t) SWL
    • DWT ≥ 50 000: 2 000 kN (≈204 t) SWL
  • Safety factor on yield: minimum 2.0 × SWL.
• Strong point requirements:
  • Configuration and loading consistent with the matching chock.
  • Minimum dimensions for profile features: diameter D ≥ 600 mm, height H ≥ 300 mm.
  • Combined designs permitted when also used as aft emergency towing arrangement.
• Materials and workmanship: Acceptable materials include weldable cast steel, forged steel, or rolled steel. Products must be free from defects (cracks, sand holes, pores).
• Testing methods:
  • Material inspections: physical/chemical tests; magnetic particle inspection for castings; ultrasonic detection for forgings (grade II).
  • Weld inspections: ultrasonic testing for main welds; welds must be smooth and defect-free.
  • Strength test: apply test load for 1 minute, followed by inspection (magnetic particle) to verify no critical defects.
• Marking: Chocks and strong points must be clearly marked with their SWL in tonnes (e.g., SWL102t) where it remains visible during operation.

Applications and users

This standard is intended for:

• Ship designers, naval architects and shipyards specifying or installing escorting and pull-back systems.
• OEMs and manufacturers of chocks and strong points.
• Classification societies, shipowners, operators and port/tug operators assessing equipment compliance.
• Surveyors and inspectors performing material and strength testing.

Practical uses include specifying safe fittings for escort/tug operations, ensuring compatibility with tuglines, and providing uniform test and marking practices for tanker safety and operational reliability.

Related standards and guidance

• ISO 4827:2022 contains no normative references. Users should also consult relevant classification society rules, vessel-specific towing emergency arrangements, and applicable IMO guidance for escorting and towage operations.