TM 5-852-9/AFR 88-19, Vol. IX
CHAPTER 4
MECHANICAL
4-1. General. Design and operation of mechanical systems in arctic and subarctic regions are basically similar
to those Systems used in the northern regions of the continental United States; however, extended periods
of extremely low temperatures and high wind conditions of the arctic can cause failures in systems that
function normally in other areas. Therefore, mechanical system design for arctic regions must utilize arctic-
type technical changes and economic considerations. Systems should be as simple as possible to avoid
operator confusion. Operation and maintenance considerations are important since expert technical assistance
may not be available at isolated arctic sites. Components should be standardized whenever possible to reduce
the inventory of repair materials necessary. Material in this chapter should be used to supplement applicable
technical manuals.
4-2. Heating.
a. General A satisfactory, reliable, and easy to maintain heating system is extremely important for
personnel comfort. Remote locations, severe climatic conditions, and short daylight hours which all tend to
confine personnel to the site are primary reasons for maintaining a good physical environment. Cold floors
and downdrafts from windows should be minimized by using adequate floor insulation and locating heating
units below windows. While constant circulating heat systems will usually provide more uniform room
temperatures, it is important that all available information be evaluated before selecting a system. To provide
further design guides, various types of heating systems are discussed in detail below. Noted are the
advantages or disadvantages of each when used in the arctic environment. Unless otherwise stated herein,
heating designs shall be in accordance with TM 5-810-1.
(1) Hot air heating. Hot air heating is one of the simplest and most widely used systems in arctic
areas. Major advantages are that it is less expensive to construct, is easily understood, and requires less
maintenance. Systems with extensive ductwork, however, are expensive to ship, difficult to install, and can
be difficult to balance. When reliable electrical power is available, forced-air heaters with gun type oil or gas
fired burners should be utilized as operation is more efficient and less costly. Forced-air heaters must be
separated from the rest of the building by a 1-hour fire rated partition. Low-cost ventilating can be provided
by bringing dampered outside air into the building through the furnace cold air return. Where large quantities
of fresh air are required, however, a split system should be used. Forced-air heating systems can utilize duct
mounted humidifiers to increase humidity, and filters to control dust. Blowers in hot air furnaces distribute
heat effectively and should be operated continuously for best results. Hot air supply outlets should be located
near the floor to induce increased circulation in office and living spaces and in buildings with many open
spaces and high ceilings. Fans to move the hot air from the ceiling toward the floor are extremely desirable.
Air systems are not generally damaged by freezing if power is lost, and little preventive maintenance is
necessary.
(2) Steam and hot water heating. Central steam and hot water heating systems are the most widely
used in arctic regions because of the simplicity of heat distribution. Heat storage in steam and water systems
can prevent freezing during short power failures; however, a rapid means of emergency drainage is essential.
These systems require immediate attention if a problem develops, therefore alarm systems should be installed.
The use of thermostat draindown valves developed for solar systems should be investigated. In addition to
heating, the steam and hot water systems can provide a practical and economical heat source for various
water treatment processes. Steam and hot water can also be used to melt snow for domestic water. Anti-
freeze keeps hot water systems from freezeup.
(a) Steam heating Systems. Steam is used extensively in heat distribution systems and in primary
building heating systems. Steam heating can be used for shops, hangars, and garage-type buildings where
system noise and wide ranging temperatures are not objectionable. Conversely, steam is undesirable in offices
and living spaces because of noise problems and lack of precise control. Steam can be piped long distances
where unavoidable pressure losses would be excessive if using a normal hot water system. Adequate
condensate and steam line slopes must be provided to avoid freezing damage during outages. Drip legs and
receivers also require protection from freezing. Provide automatic condensate drainage with steam traps such
as the thermostatic bellows-type. Good water treatment is required to reduce corrosion in the return lines.
Maintain control of pH between 6.7 and 7.7 to avoid excessive corrosion. Pure condensate (pH 7), however,
can cause rapid pipe deterioration.
4-1
Previous Page
