3.25 Class 4, size 15-cfm, winterized. When specified (see 6.2), the compressor shall be
winterized for operation at minus 50 F. When the winterized compressor is specified, the
canvas cover, as specified in 3.24.1, shall not be furnished. The winterized compressor shall be
provided with the following items in addition to those specified in 3.24.
3.25.1 Enclosure. A metal enclosure shall be provided to completely enclose the top,
bottom, sides, and ends of the compressor assembly, to prevent the entry of blowing snow, rain,
and dust, and to maintain temperature while heating and operating the compressor at
minus 50 F. Provisions shall be made for opening side panels or doors and manually adjustable
louvers at the engine end to allow ventilation for the engine and compressor unit at 120 F
without excessive overheating as specified in MIL-STD-1300 for the engine, and exceed the
temperature ratings as specified by the compressor manufacture, for the compressor unit.
Weatherstripping shall be provided on all doors and panels. Weatherstripping shall have a
protective wear coating, and both the weatherstripping and protective wear coating shall be
flexible at minus 50 F. The weatherstripping shall conform to MIL-R-14328. The
weatherstripping shall not interfere with normal operation. Insulation shall be furnished on the
interior of the enclosure and shall be nonasbestos mastic type and not less than 3/32 inch thick.
3.25.2 Heater duct connection. A heater duct connection shall be provided on the enclosure
for connection of a 12-inch-diameter duct from a heater conforming to MIL-H-4607, class 3.
The duct connection and cover shall conform to MIL-H-7365, size A. The duct connection
cover shall be securely fastened to the enclosure by a keeperchain or other means to prevent loss
when removed. The heater duct connection shall not protrude beyond outer extremes of the
enclosure more than necessary to facilitate connection of the heater duct.
220.127.116.11 Ducting. Provisions shall be made for adequate ventilation and circulation of air for
the compressor, while preheating and operating under cold weather conditions. The heat from
the heater shall flow through the compartment in such a manner as to warm the entire engine and
compressor unit to permit starting of the compressor in not more than 30 minutes at minus 50 F.
Ducting or baffles shall be provided to divert heated air to the batteries and to all critical moving
parts which may be restricted due to ice or congealed oil or grease. The heat shall be exhausted
from the compartment through a manually operated louver in such a manner as to flow over the
receiver, hose rack, and hose, warming these parts prior to starting.
3.25.3 Doors, panels, and openings. Doors or panels shall be furnished with recessed latches
operable by personnel wearing heavy arctic mittens. The doors or side panels shall be of a size
and location to afford accessibility to the compressor unit, control equipment, and engine for
routine service, adjustment, and maintenance. Doors over 18 inches in vertical height shall be
hinged horizontally in two sections. Hinges shall be the continuous piano type with brass hinge
pins. The roof of the enclosure shall be removable so that installed components can be removed
or replaced vertically.