ISO 23055:2020

Overview

ISO 23055:2020 - Ships and marine technology - Design requirements for international ballast water transfer connection flange - defines the material, dimensional and marking requirements for a standardized flange used to transfer ballast water between a ship and a shore reception facility or between ships. The standard specifies flat-faced steel (or equivalent) flanges, minimum pressure ratings, bolt arrangements and quality/installation expectations. It does not cover ship piping reconfiguration to reach the transfer point.

Key topics and technical requirements

• Flange construction: Flat-faced, steel or equivalent materials; galvanically compatible with connected piping; corrosion-resistant fasteners.
• Pressure rating: Minimum MAWP of 1 MPa (145 psig) - typically satisfied by PN 10 rated flanges.
• Standard dimensions:
  • DN 200 (typical transfer connection): Outside Ø 340 mm, inside Ø 218–222 mm, bolt circle Ø 295 mm, bolt hole Ø 22 mm, flange thickness ≥ 24 mm; supplied with 8 bolts (bolts Ø 20 mm).
  • DN 300 (higher capacity - Annex A): Outside Ø 445 mm, inside Ø 327.6 mm, bolt circle Ø 400 mm, bolt hole Ø 22 mm, thickness ≥ 26 mm; 12 bolts.
• Gaskets and non‑metallics: Materials suitable for the MAWP and seawater service.
• Accessories: Flanges supplied with matching bolts, nuts and washers. Alternative bolt‑hole notch design (Annex B) permits minor alignment adjustments.
• Workmanship & QA: Welding personnel and procedures to meet recognized standards; contractor responsible for inspections unless otherwise specified.
• Marking & ordering: Flanges must be permanently marked with manufacturer name, PN and DN (e.g., PN 10, DN 200) and a reference to ISO 23055. Orders should state PN, DN, flange design standard, end connection and preservation/coating.

Practical applications & users

ISO 23055 is intended for:

• Shipyards and marine engineers specifying shipboard ballast water transfer connections.
• Port and shore reception facilities designing intake hookups for ship-to-shore transfers.
• Manufacturers of flanges, fittings and ballast water transfer equipment seeking a globally compatible interface.
• Naval architects and regulatory authorities aligning installations with IMO guidelines (G5) for efficient ballast water handling.

Benefits include simplified ship/shore connectivity, reduced downtime during transfer operations, and consistent safety/pressure handling.

Related standards

ISO 23055 references compatibility with recognized flange design standards such as ASME B16.5, BS EN 1092, JIS B2220, DIN 2632/2633, GB/T 2501 and aligns with IMO Guidelines for Ballast Water Reception Facilities (MEPC.153(55) - G5).