301. Cargo Piping Systems

Cargo piping systems are in general to comply with the relevant requirements in Pt 5, Rules for the Classification of Steel Ships.

1. Liquid Cargoes

(1) Combustible Liquid Cargoes

Ch 6 of

(A) For cargo fuel oil, base oil and oil-based liquid mud having a flashpoint exceeding 60℃,

the provisions in Pt 5, Ch 6 of Rules for the Classification of Steel Ships are appli- cable for cargo tank arrangements/protection, cargo transfer piping, tank level gauging, vent-

ing and heating systems. In addition, the following are to be complied with:

(a) Cargo pumps are to be certified in accordance with

Classification of Steel Ships

(b) An emergency means for pumping out the tanks is to

Pt 5, Ch 6 of Rules for the

be provided. For this purpose, a

portable pump, which can be used safely, may be accepted.

(c) A relief valve is to be installed in the discharge of each cargo and stripping pump. The

outlet from the relief valve is to be led to the suction side of the pump. This relief valve need not be fitted in the case where centrifugal pumps are installed and the pip- ing is designed to withstand the shut-off head of the pumps.

(d) Remote shutdown devices for all cargo pumps and similar equipment are to be fitted and capable of being activated from a dedicated cargo control location which is manned

at the time of cargo transfer and from at least one other location outside of the cargo area and at a safe distance from it.

(e) One pressure gauge for each pump is to be located at the pump discharge. Where pumps are operated at cargo control station remote from the cargo pumps, additional pressure gauges are to be installed at the cargo control station.

(f) Where cross-contamination either by cargoes or cargo residues causes safety hazards or marine pollution hazards, separation between cargo piping systems, is to be by means of spectacle flanges, spool pieces or equipment.

(2) Liquid Mud Cargo Tanks

Guidance for Offshore Support Vessels 2015 15

Ch 4 Offshore Supply Vessels Ch 4

Liquid mud cargo tanks are to be provided with vent pipes complying with Pt 5, Ch 6 of Rules for the Classification of Steel Ships. In order to prevent overpressure or under-pres- sure in the event of overflow into the vent pipe or clogging of the flame screen in the case of oil based mud, vents for liquid mud tanks are to also be provided with a suitable burst disc(s) rated below the mud tank design pressure. Spare burst discs are to be carried on board so that damage burst disc can be replaced. Suitable means of gauging the mud tanks such as a tank ul- lage method or level indicating devices may be fitted in lieu of sounding pipe.

2. Dry Cargo Piping Systems

(1) Dry cargo transfer piping systems are, in general, not to be led through machinery spaces.

However, when such design is impractical, piping systems may pass through machinery spaces, provided that all pipe connections located within the machinery space are welded and any de- tachable connections are arranged outside of the space. Any access door in the bulkhead is to be provided with a notice affixed to each such closing appliance to the effect that it is to be kept closed.

(2) Piping Scantlings

The minimum requirements for wall thicknesses of steel pipes in cement and dry mud system passing through machinery spaces are to be in accordance with following table.

3. Integrated Cargo Tank Piping System

For integrated cargo tanks, effective means are to be provided to prevent the use of compressed air as the primary means of discharge for combustible liquid cargoes.