Operation and Design
A marine loading arm is an alternative to direct hose hookups that is particularly useful for larger vessels and transfers at higher loading rates and pressures. Controlled manually or hydraulically, a loading arm employs swivel joints and can, to some extent, follow the movement of a moored vessel. Many loading arm systems feature quick-connect fittings. Gasket or o-ring arrangements are required to make a secure seal to the ship's manifold flange. A loading arm must be drained or closed off before the connection is broken off. This is usually done in two ways. For fuels such as gas oil and diesel, the lines can be blown out with high pressure air. In the case of fuels such as kerosene or petrol, the lines can be stripped with pumps.
Loading arms can handle both liquids and gases, in a wide range of viscosities and temperatures. Cargoes from liquid sulphur to liquefied natural gas are moved through marine loading arms. Loading arms service vessels in a wide range of sizes, from small river barges to the largest supertankers.
Various designs exist, and specific installations can be tailored for a given port based on considerations such as vessel size, cargo flow rate and cargo temperature. Environmental constraints, such as the range of tide, wind conditions, and earthquake tolerance can also affect choice of loading arm. A loading arm installation may include add-ons such as hydraulic or manual quick connect couplers, position monitoring systems, emergency release systems, and piggyback vapor return lines.
Compared to cargo hoses, the loading arm's main drawback is its comparative lack of flexibility.
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