26 Sep 97
than the maximum water pressure, at the point of foam concentrate injection (proportioner).
Configure foam concentrate pumps in accordance with applicable provisions of NFPA 20,
Centrifugal Fire Pumps. Assure that power is in accordance with NFPA 20, 6-3. Pumping of
concentrate, as opposed to using a bladder tank, is mandatory when using in-line balanced-
pressure proportioners (ILBP's). Note: The use of a bladder tank and ILBP's as shown in the
appendix of NFPA 16A is not permitted.
10.2.5.1.1 Pump Control. Arrange foam concentrate pump for automatic starting of the primary
pump upon detection of flow within the fire protection system. In the event the primary pump
fails to start, the reserve pump should start. Provide necessary lockout to prevent both pumps
from running simultaneously. Also, arrange pump to start upon pressure drop within the foam
concentrate piping systems. Where the length of AFFF concentrate piping exceeds 50 feet from
the pump discharge to the proportioners, provide a pressure maintenance or jockey pump.
Arrange pumps to automatically stop upon actuation of a low-liquid level switch in the
10.2.5.2 Diaphragm Supply. With this arrangement, water from the fire protection water system
simultaneously supplies water to the proportioner and pressurizes the foam concentrate through
an elastomeric bladder which separates the foam concentrate from the water in the tank. Locate
bladder tank in close proximity to the proportioners it serves. Provide a single connection and
water line from the fire protection valve header to the bladder tank for pressurization of the
bladder. Include a check valve in the line to prevent backflow of AFFF concentrate into the water
system in the event of a bladder rupture. Arrange connection of bladder pressurization line to
avoid foam solution from entering or migrating into the piping and space between the bladder and
the tank after the system has operated.
10.2.5.3 Proportioners (Ratio Controllers). The term proportioner is used by some
manufacturers whereas ratio controller is used by others. The two terms are synonymous.
Proportioner is used throughout this technical letter.
10.2.5.3.1 Location and Arrangement. Locate foam proportioners in the fire protection
equipment room along with concentrate tanks and sprinkler and nozzles system risers and control
valves. Provide one proportioner in each sprinkler riser unless extenuating circumstances justify
using one proportioner for a single overhead sprinkler system and a nozzle system. This approach
may have merit for relatively small facilities with only one sprinkler system and one nozzle system.
10.2.5.3.2 Flow Range. All proportioners have a range over which they can be expected to
correctly proportion the foam concentrate with water in the correct ratio. Flow ranges for the
same size proportioner can vary significantly between manufacturers. For example, published
data of one major manufacturer's 150 mm (6-in) proportioner indicates a nominal flow range of
1136-9464 Lpm (300-2500 gpm) whereas another manufacturer's data indicates a range of 1136-