Section 1 General

1.1 Applicability

1.1.1 The requirements of this Chapter apply to products and process piping, including vapour piping, gas fuel piping and vent lines of safety valves or similar piping. Auxiliary piping systems not containing cargo are exempt from the general requirements of this Chapter.

1.1.2 The requirements for Type C independent tanks provided in Pt 11, Ch 4 Cargo Containment may also apply to process pressure vessels. If so required, the term ‘pressure vessels’ as used in Pt 11, Ch 4 Cargo Containment, covers both Type C independent tanks and process pressure vessels.

1.1.3 Process pressure vessels include but are not limited to; surge vessels, heat exchangers and accumulators that store or treat liquid or vapour cargo.

1.1.4 Recognised standards for cryogenic process equipment are given in Pt 12, Ch 1 Recognised Codes and Standards.

1.2 System requirements

1.2.1 The cargo handling and cargo control systems shall be designed taking into account the following:

Prevention of an abnormal condition escalating to a release of liquid or vapour cargo;
The safe collection and disposal of cargo fluids released;
Prevention of the formation of flammable mixtures;
Prevention of ignition of flammable liquids or gases and vapours released;
Limiting the exposure of personnel to fire and other hazards.

1.2.2 Arrangements – General

Any piping system that may contain cargo liquid or vapour shall:
- be segregated from other piping systems, except where interconnections are required for cargo related operations such as purging, gas freeing or inerting. The requirements of Pt 11, Ch 9, 1.4 Inerting 1.4.4 shall be taken into account with regard to preventing back flow of cargo. In such cases, precautions shall be taken to ensure that cargo or cargo vapour cannot enter other piping systems through the interconnections;
- except as provided in Pt 11, Ch 16 Use of Cargo as Fuel, not pass through any accommodation space, service space or control station or through a machinery space other than a cargo machinery space;
- be connected to the cargo containment system directly from the weather decks except where pipes installed in a vertical trunkway or equivalent are used to traverse void spaces above a cargo containment system and except where pipes for drainage, venting or purging traverse cofferdams;
- be located in the cargo area above the weather deck except for bow or stern loading and unloading arrangements in accordance with Pt 11, Ch 3, 1.8 Tandem and side-by-side loading and unloading arrangements, emergency cargo jettisoning piping systems in accordance with Pt 11, Ch 3, 1.8 Tandem and side-by-side loading and unloading arrangements 1.8.1, turret compartment systems in accordance with Pt 11, Ch 3, 1.8 Tandem and side-by-side loading and unloading arrangements 1.8.3 and except in accordance with Pt 11, Ch 16 Use of Cargo as Fuel; and
- be located inboard of the transverse tank location requirements of Pt 11, Ch 2, 1.4 Location of cargo tanks 1.4.1 except for emergency cargo jettisoning piping systems.
Suitable means shall be provided to relieve the pressure and remove liquid cargo from discharging headers; likewise, any piping between the outermost discharge valves and loading arms or cargo hoses or any other location prior to the outermost valve that may be subject to pressurisation during discharging operations.
Piping systems carrying fluids for direct heating or cooling of cargo shall not be led outside the cargo area unless a suitable means is provided to prevent or detect the migration of cargo vapour outside the cargo area. (See also Pt 11, Ch 13, 1.6 Gas detection 1.6.2.(f) ).
Relief valves discharging liquid cargo from the piping system shall discharge into the cargo tanks. Alternatively, they may discharge to the flare system which is to be designed in accordance with API 521 Guide for Pressure-relieving and Depressuring Systems: Petroleum petrochemical and natural gas industries-Pressure relieving and depressuring systems. Where required to prevent overpressure in downstream piping, relief valves on cargo pumps shall discharge to the pump suction.

1.3 Arrangements for cargo piping outside the cargo area

1.3.1 Emergency cargo jettisoning

If fitted, an emergency cargo jettisoning piping system shall comply with Pt 11, Ch 5, 1.2 System requirements 1.2.2 as appropriate and may be led aft, external to accommodation spaces, service spaces or control stations or machinery spaces, but shall not pass through them. If an emergency cargo jettisoning piping system is permanently installed, a suitable means of isolating the piping system from the cargo piping shall be provided within the cargo area.

1.3.2 Bow and stern loading arrangements

Subject to the requirements of Pt 11, Ch 3, 1.8 Tandem and side-by-side loading and unloading arrangements, this Section and Pt 11, Ch 5, 4.3 Installation requirements for cargo piping outside the cargo area 4.3.1, cargo piping may be arranged to permit bow or stern loading and unloading.
1. Arrangements shall be made to allow such piping to be purged and gas freed after use. When not in use the spool pieces shall be removed and the pipe ends blank flanged. The vent pipes connected with the purge shall be located in the cargo area.

1.3.3 Turret compartment transfer systems

For the transfer of liquid or vapour cargo through an internal turret arrangement located, outside the cargo area, the piping serving this purpose shall comply with Pt 11, Ch 5, 1.2 System requirements 1.2.2 as applicable, Pt 11, Ch 5, 4.3 Installation requirements for cargo piping outside the cargo area 4.3.2 and the following;
1. Piping shall be located above the weather deck except for the connection to the turret.
2. Portable arrangements shall not be permitted.
3. Arrangements shall be made to allow such piping to be purged and gas freed after use. When not in use the spool pieces for isolation from the cargo piping shall be removed and the pipe ends blank flanged. The vent pipes connected with the purge shall be located in the cargo area.

1.4 Gas fuel piping systems

1.4.1 Gas fuel piping in machinery spaces shall comply with all applicable Sections of this Chapter in addition to the requirements of Pt 11, Ch 16 Use of Cargo as Fuel.