SHIP ТО SHIP TRANSFER GUIDE (PETROLEUM)
(Third Edition 1997)
For Use with Crude
Oil and Petroleum Products
Chapter 2
Conditions and Requirements
2.1 SHIP COMPATIBILITY
When organisers are planning
an STS transfer operation they should ensure that the ships to be used are
compatible in design and equipment and that mooring operations, hose handling
and communications, can be conducted safely and efficiently. The initial
information required in Check List 1 of
Appendix 1 should be supplied to the organisers by the shipowners.
2.1.1 Cargo Handling Compatibility
The following should be determined prior to berthing:
• the size and number of manifolds to be used;
• the minimum and maximum expected height of the cargo
manifold from the waterline during the transfer operation;
• whether the cargo cranes or derricks are in a satisfactory
condition and of suitable Safe Working Load (SWL) to handle cargo hose and
fenders; and
• that hose supports, at the ship's side, are adequate to
prevent damage to hoses through chafing.
2.2 APPROVAL FROM AUTHORITIES
Where an STS transfer operation is to be arranged
within the territorial waters of a country, the organiser
should check local regulations and may need to gain local approval. This may
require the organiser and appropriate authority to
agree the transfer area to be used and to take into account other requirements.
At this time, matters pertaining to contingency plans should also be addressed
(see Section 10.1).
When an STS transfer operation is about to begin in
territorial waters, the organiser should notify the
local authorities and the government agencies concerned. This may be done
either directly by the organiser or, once local
requirements are known, by formally delegating the task to the person in
overall advisory control.
2.3 TRANSFER AREA
Transfer areas may be relatively large or quite small;
the space available will dictate the type of manoeuvre.
In the case of manoeuvres at sea, where it is
intended that both ships are to be underway, a relatively large transfer area
will be needed to accommodate the necessary manoeuvres.
Naturally, a ship approaching another ship at anchor will require a much
smaller overall area. Sometimes this can be within port limits, or in specified
approved offshore locations.
Points to be considered by organiser
when selecting the transfer area are:
• the destinations of the ships concerned to avoid unnecessary
ship deviation;
• the need to notify and obtain agreement of the applicable
coastal authority;
• the shelter provided from the weather, particularly from sea
and swell;
• present and forecast weather conditions;
• tidal current conditions;
• safe distances from offshore installations;
• the availability of a safe zone, free from small craft;
• the need for sufficient sea-room and water depth to be
available for manoeuvring during berthing and unberthing;
• the need for sufficient sea-room to be available to allow
for normal drift or steaming patterns when cargo transfer operations are
conducted underway;
• the selection of a safe anchorage with sufficiently good
holding ground; and
• the traffic density.
2.4 WEATHER CONDITIONS
It is impracticable to lay down limiting weather
conditions under which STS transfer operations can be carried out because much
will depend on the effect of the sea and swell on the fenders and the rolling
movements induced in the participating ships, taking into account their
relative freeboards.
If cargo transfer is to take place at anchor the
combined effect of current and weather conditions on the yawing movements of
the anchored ship and the ultimate strain on its anchor cable should be
considered.
All available weather forecasts for the area, should be obtained before and during operations.
Throughout any berthing operation the visibility
should be good enough for safe manoeuvring, taking
into account safe navigation and collision avoidance requirements. Manoeuvres should only start when relevant personnel are
satisfied that conditions are suitable for mooring and cargo transfer.