SIGTTO issues guidance on the purging and disconnection of hard arms as follows:

As a result of concerns by members SIGTTO, working in collaboration with its members, has produced guidance on the purging and disconnection of hard arms. This document aims to develop a common understanding of safe purging and disconnection procedures.

This advice has been prepared following reports, from a number of members, that there appears to be confusion and misunderstanding among some
ship and jetty operators over the safe conduct of this operation.

This advice specifically pertains to terminals employing rigid transfer arms. (The basic principles are applicable for hose systems that may be used for
LNG ship-to-ship transfer, but there will be differences in the detail.)

Principal Objective

The principal objective is to disconnect the hard arms in a manner that eliminates any risk of liquid release and reduces the release of cargo vapour to the atmosphere to an absolute minimum. For this operation to be conducted safely and in a timely manner, it is essential that there is a carefully thought out procedure in place and that there is good communication between the ship's staff and the shore operational staff, both of whom bear responsibility for safe conduct of the operation.

The process has a number of logical steps

For more information click on Purging and Disconnection of Hard Arms

Source: SIGTTO