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 insulation generally is not recommended for hoses subject to chafing in ser-
vice or to relatively frequent handling for connects/disconnects unless
absolutely necessary. The insulation is damaged easily, and therefore
requires more careful handling to avoid dragging it over abrasive surfaces
and obstructions. Also, insulated hoses are bulkier and require more storage
space.
13.5 ACTIVE FREEZE PREVENTION. These techniques require periodic personnel
servicing and/or the positive, continuous availability of electric, steam,
water, or compressed air hotel service. To date, no controlled field tests
under cold weather service conditions have been conducted. Therefore, no
specific recommendations relative to their use with sewage hoses can be made.
The techniques are presented here for possible consideration for use in ports
with extremely adverse weather, and where careful monitoring can be assured.
They are in commercial use but usually require specially designed and engi-
neered equipment and trained personnel.
13.5.1 HEAT TRACING. This technique normally is used in conjunction with
insulation. Either self-temperature-regulating electric heat tape or steam
jacketing provides the heat needed to compensate for the heat lost to the
atmosphere. The technique is very effective in any climate but consumes
energy, requires careful installation, and usually needs a source of well-
regulated steam or electricity to prevent overheating. However, where shore
steam normally is provided to a ship, the possibility of tying or wrapping
together the steam supply line and sewage discharge hose(s) could be consid-
ered.
13.5.2 AIR PURGE. After every pump-out and periodically or continuously
between pump-outs, compressed air purging of the hose can be used to force
out most residual wastewater, and to prevent any remaining water from pooling
and blocking the line if it freezes. This technique requires a modification
to the sewage hose inlet connection. It is not always effective, as com-
pressed air lines themselves often freeze during cold weather, due to the
presence of condensed moisture.
13.5.3 CONTINUOUS FLOW. A continuous flow of steam, steam condensate, or
water through a sewage hose between periods of wastewater pumping would pre-
vent freezing by providing both the addition of heat and fluid movement.
Implementation of this technique requires ship discharge station modifica-
tions to prevent sewage contamination of the supply lines for the purging
medium. The technique also increases the hydraulic load on shore receiving/
treatment facilities. Additional costs are required to supply and treat the
added fluid.
13-3
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