tanks.) Approved diaphragm tanks larger than 9.50 -
11.40 cu meters 2,500 - 3,000 gallonsare not readily
available.
**************************************************************************
**************************************************************************
NOTE: Designer must calculate foam tank capacity
based on maximum flow for maximum duration to
determine size of tank and space required. Do not
label foam tank capacity on drawing. Exact tank
size (which may be larger) will be determined by
Contractor's hydraulic calculations.
**************************************************************************
Tanks shall be cylindrical steel ASME INTERNATIONAL (ASME) pressure vessels
with a full Buna-N impregnated nylon inner tank or bladder designed to
contain AFFF concentrate and to be used in conjunction with the concentrate
ratio controller. Tanks shall be designed for working pressure of [1206
kPa (gage)] [175 psig] [_____] and hydrostatically tested at 1.5 times the
working pressure in accordance with ASME standards at the factory. Tanks
shall have UL or FM label and ASME stamp affixed to the vessel. Size tank
to provide sufficient AFFF concentrate for the time specified when the
system is discharging foam solution at total maximum system flow. Also
provide connected reserve tanks(s) of equal capacity. Permanently label
each tank with its capacity, type and percentage of concentrate, which
system(s) it serves, and whether it is a main or reserve tank.
Conspicuously post filling instructions near each group of tanks. Provide
a gage or unbreakable sight glass to permit visual determination of level
of tank contents. Prior to shop painting, abrasive blast clean tank
exterior surface in accordance with SSPC SP 6to a surface profile not to
exceed 0.05 mm 2.0 mils and provide a MIL-P-24441 or SSPC coating system to
the tank exterior. Prime tank exterior with one coat of MIL-P-24441/1,
Formula 150 or SSPC Paint 22 primer applied to a dry film thickness of
0.076 mm 3 mils and topcoat with one coat of MIL-P-24441/7 Formula 156
(red) or SSPC Paint 22 topcoat (red) applied to a dry film thickness of
0.076 mm 3 mils.
2.13.2
Concentrate Ratio Controller
Ratio controller shall be a modified venturi device with AFFF concentrate
feed line from diaphragm tank(s), and integral concentrate metering
orifice. Size for specified flow rate(s).
2.14
BALANCED PRESSURE PROPORTIONING SYSTEM
**************************************************************************
NOTE: Select the method of proportioning best
suited for the project.
Diaphragm pressure proportioning systems operate by
water pressure, require no electrical power, and
minimal control circuitry for automatic operation.
Maintenance requirements are minimal, however
refilling the tank is a difficult operation
requiring the services of a qualified technician to
avoid rupturing the diaphragm.
Balanced pressure proportioning systems require
reliable electrical power and more complex control
SECTION 13957N
Page 28
Previous Page
