Page 337 - International safety guide for oil tankers and terminals

SAFETY AND FIRE PROTECTION
19.5.3.7
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Foam Systems
Foam concentrate should be properly proportioned and mixed
with water at some point downstream of fire water pumps, and
upstream of foam making equipment and application nozzles.
Fixed pipelines for expanded (aerated) foam are not
recommended because the fully developed foam cannot be
projected effectively due to loss of kinetic energy and high
frictional losses through such systems.
The type of foam concentrate selected, i.e. protein, fluoro-protein,
Aqueous Film Forming Foam (AFFF), or alcohol/polar solvent
resistant type concentrate (hydrocarbon surfactant type
concentrate), will depend upon the fuel type and formulation,
whether aspirating or non-aspirating equipment is installed and
ease of re-supply.
There are several systems that can be adopted for feeding foam
concentrate into foam making equipment at the berths. Some of
the principal systems are briefly described.
Direct Foam Pick-Up from Atmospheric Tanks
This method incorporates direct foam induction via a flexible
pick-up tube connecting a monitor to an adjacent foam storage
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tank at atmospheric pressure, a tank truck, portable trailer or
drum. One storage tank may be used to supply more than one
fixed monitor. Such monitors would be positioned near ground or
deck level.
Displacement Proportioner Foam Unit Utilising Pressure
Vessels
This unit may comprise foam concentrate in one large pressure
vessel, possibly of 4.5 cubic metres capacity, or two smaller
pressure vessels of 2.3 cubic metres. The foam proportioner unit
is positioned between the fire pumps and the downstream foam
making equipment. The system functions by utilising by-passed
fire-main water to pressurise the storage vessel and displace the
foam concentrate from the storage vessel into a foam-main.
Sufficient hydrants should be provided on the foam-main from
which portable foam making equipment, including monitors, can
be operated.
Dedicated ‘Foam Concentrate’ Pipeline System Using
Atmospheric Foam Tanks
This system comprises three main components:
1) Foam concentrate bulk storage in tanks or other vessels.
2) Foam pumps for delivering the foam concentrate into the foam
pipeline grid. The pumps may be electric motor or water
turbine driven using a bypass from the fire-main.
3) Pipeline grid, possibly of 75 mm diameter, traversing the berth
approach and the berth, providing numerous take-off points
for the attachment of foam induction hose for connecting
portable or fixed equipment.
Where pipelines for foam solution or concentrate are provided, the
lines should have a number of accessible take-off (hydrant) points
© ICS/OCIMF/IAPH 2006 303