The International Association of Classification Societies (IACS) has published the revised Unified Requirements for piping design, construction, and testing.
This document (UR P2 Oct 2023 CLN) has been published on 1 October 2023.
These requirements in this UR pertain to piping systems composed of carbon, carbon-manganese, alloy steels, or non-ferrous materials typically installed on ships for the services detailed in Table 1 (see the document below).
These criteria encompass various services such as air, vapor, gas (excluding those mentioned in P2.1.2.2 below), water, lubricating oil, fuel oil, hydraulic systems for steering gear, toxic gases and liquids, cargo oil, tank cleaning piping, as well as open-ended lines like drains, overflows, vents, and boiler escape pipes.
Pipes forming an integral part of a boiler are not included in these requirements.
Hydraulic fluid systems, except those for steering gear, require individual consideration by each Classification Society.
Piping systems intended for liquefied gases (cargo and process) are addressed in UR G3 and W1.
P2.1.2 The requirements of this UR do not apply to the following piping systems:
- Chemical cargo piping systems on ships subject to the IBC Code and shipboard hydrocarbon/chemical process piping systems.
- Gas cargo/fuel and process piping systems on ships subject to the IGC Code and gas fuel piping systems of ships subject to the IGF Code.
- Piping systems for other low flashpoint fuels as defined in SOLAS II-1/2.29.
The revised requirements of UR P2.1 (Rev.3 October 2023) must be uniformly implemented by IACS Societies for ships contracted for construction on or after January 1, 2025.
For more information, please see the document below (available only to subscribers):
Rules for Piping Design, Construction and Testing

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