MIL-HDBK-1027/1B
out. The duct system should have provisions for cleaning out
the PKP particulate which will settle out. Access doors and low
velocity areas should be used in long horizontal runs and at the
base of vertical runs. Provide a 50 mm trapped drain in the
duct section.
3.11.5
Dilution Air. Dilution air should be required to
protect the compartment environment from a buildup of products
of incomplete combustion, unburned fuel, and heat. Air
specifically for dilution is not needed. This requirement is
satisfied by secondary air.
3.11.6
Equipment
3.11.6.1 Louvers. Louvers should run continuously around the
perimeter of crawl spaces. They should be sized for a maximum
pressure drop of 25 Pa at the design "air in" flow and be a
minimum of 460 mm high. Louvers should be of corrosion-
resistant material and designed so they can be removed
individually for maintenance. Louvers should be designed to
meet the following additional criteria:
a) In areas where snow accumulation can be expected
on a regular basis, the design of the louver system should
prevent drifting snow from blocking the openings.
Caution: The structure should never be operated with
any portion of louver openings blocking the free
entrance of air. Unburned propane could easily build
to the LEL in pockets if ventilation is impeded.
b) In climates where the annual heating degree days
are greater than 1093 degrees C, perimeter louvers should be
provided with motorized dampers. Motorized dampers allow the
crawl space to be closed during unoccupied hours so the crawl
space can be maintained above freezing.
3.11.6.2 Dampers. Where more than one compartment is connected
to the exhaust fan system, the air from each duct should be
controlled by a motorized, modulating, floating point damper
from the instructor's station. In the "automatic" mode, the
damper should be controlled by the device computer. In the
56
Previous Page
