Frostproof insulation is generally constructed of
five layers of felt. There are three layers of pure wool
felt and two layers of asphalt-saturated asbestos felt.
Frostproof insulation is 1 l/4 inches thick and comes
in 3-foot lengths with a canvas cover.
The pipe coverings shown in this section are some
of the types of coverings that are installed easily,
primarily because each section is split in half and has
a canvas cover with a flap for quick sealing. Joint
collars are furnished to cover joint seams on insulation
exposed to outside conditions.
Cheesecloth is used on some types of insulation
instead of canvas. To install the cheesecloth, use a
paste to hold it in place. Allow enough cheesecloth to
extend over the end of each 3-foot section to cover the
After you have applied the cheesecloth and
smoothed it out, install metal straps to hold the
insulation firmly in place, as shown in view H, figure
Valves and Fittings
Cover with wool felt, magnesia cement, or mineral
wool cement of the same thickness as the pipe
covering. These materials are molded into shape to
conform with the rest of the insulation. When
magnesia or mineral wool cement insulation is used,
cover the insulation with cheesecloth to help bind and
hold it in place.
Boilers and Storage Tanks
If the boilers and storage tanks are unjacketed,
cover them with an approved insulation. Use only
insulation approved by the MIL-STD. Some of the
approved types of insulation for boilers and tanks are
magnesia, mineral wool, calcium silicate, cellular
glass, or other approved mineral insulation at least 2
inches thick. Insulation may be of either the block or
the blanket type and must be wired securely in place
in an approved manner. When applying insulation to
the outside of a boiler or storage tank, put it over 1
1/2-inch wire mesh. The mesh is held away from the
metal surface by metal spacers that provide an air
space of at least 1 inch. When you use blanket or block
material, fill the joints in the insulation with magnesia,
mineral wool, or other suitable cement. Cover the
surface of the insulation with a thin layer of
hard-finished cement, troweled smooth, and
reinforced with 1 l/2-inch wire mesh.
What minimum dosage of chlorine is required to
disinfect a well under normal conditions?
An 8-inch pipe contains how many gallons of
water per foot of pipe?
What velocity of water through a pipe is required
for proper scouring action?
What is the purpose of a thrust block?
SHORING AND SCAFFOLDING
LEARNING OBJECTIVE: Recognize safety
and construction requirements of shoring and
As a Utilitiesman, it is part of your job to see
whether there is a need for shoring or scaffolding on
the job. Most of the time, job problems and accidents
are a direct result of inadequate planning. As you plan
each job, ensure that you have provided the equipment
necessary to do the job safely. In this section, safety
and health requirements are addressed. For more
information, see the Safety and Health Requirements
Manual, EM 385-1-1, U.S. Army Corps of Engineers.
The need to protect personnel who work in
trenches is important. Following the ground
investigation, you should make a decision as to how
the sides of the trenches are to be protected. All
necessary materials must be obtained and delivered to
the site (figs. 4-25 through 4-28 and table 4-1). All
trenches deeper than 5 feet must have their sides
supported or protected by sloping or battering.
Trenches can sometimes be made in the case of hard
rock, when it becomes clear to experienced engineers
on the site (as the trench proceeds) that the rock is solid
and has no dangerous cleavage planes that could cause
the side of the trench to collapse. The requirements are
1. Banks more than 5 feet high should be shored,
laid back to a stable slope, or provided with other
equivalent protection whenever workers must move
around or are exposed to a cave-in. Trenches less than
5 feet in depth must be protected when examination of
the ground indicates that hazardous ground movement
may be expected. The safe angle of repose for soil
conditions and bracing systems should be determined
by a qualified person.