when there are multiple hazards with widely varying
discharge rates which are to be supplied from the
same proportioning system, and any time it is
desired to proportion foam remotely at risers or
discharge devices instead of at the pump room. Their
disadvantage is the need for much more concentrate
piping in the field.
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Foam solution shall be produced by introducing AFFF concentrate into the
water stream by the balanced pressure proportioning method using a pump and
proportioner. [Provide proportioning system and storage tanks for hose
lines independent of main proportioning system and tanks.]
[2.16.1
Skid-Mounted Balanced Pressure Proportioning System
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NOTE: Choose this paragraph or the paragraph below
entitled "In-Line Balanced Pressure Proportioning
System.
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Self-contained, skid-mounted system, fully assembled at the factory and
delivered complete and ready for use. Field connections shall be limited
to water, electrical, and AFFF concentrate inputs, foam solution output,
and foam concentrate return line to storage tank. Size system for required
flow rate(s). The concentrate pump and all piping, valves, and fittings in
contact with foam concentrate shall be of materials resistant to the
corrosive effects of the AFFF concentrate. Concentrate pump shall be
electric motor driven, drip proof, 240/480 volts, 60 Hz AC. Activation and
operation of system shall be fully automatic, with manual over-ride and
manual shut-down. Provide permanent engraved rigid plastic or corrosion
resistant metal instruction plate for emergency manual operation, along
with a similarly constructed label for each control device.
][2.16.2
In-Line Balanced Pressure Proportioning System
Size system for required flow rates. AFFF concentrate pump shall be
positive displacement, electric motor driven, drip proof, 240/480 volts, 60
Hz AC. System operation shall be fully automatic, with manual over-ride
and manual shut-down. Provide a pressure regulating device in the AFFF
concentrate pump return line to maintain constant pressure on the
concentrate piping system at all AFFF solution flow rates. Provide an
in-line balanced pressure proportioning device at each system riser to
automatically balance the AFFF concentrate pressure with the water pressure
at the riser to provide correct proportioning over the range of flow rates
calculated for that riser. The pump and all piping, valves, and fittings
in contact with the foam concentrate shall be of materials resistant to the
corrosive effects of the AFFF concentrate. Provide permanent engraved
rigid plastic or corrosion-resistant metal instruction plate for emergency
manual operation, along with a similarly constructed label for each control
device.
]2.16.3
AFFF Concentrate Storage Tanks
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NOTE: Designer must calculate foam tank capacity
based on maximum flow for maximum duration to
determine size of tank and space required. Do not
SECTION 13958N
Page 32
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