6. Noncorrosive, insoluble, and chemically
edges engage both working surfaces on the nut
inactive
and bolt or screw. Some have teeth on the inner
diameter for applications where teeth projecting
properties unchanged by temperatures at
beyond the nut are not desired. The most common
which it is to be used
type have teeth on the outer diameter. Washers
8. Once installed, should not cluster, become
with teeth on both inside and outside diameters
lumpy, disintegrate, or build up in masses
are used for soft materials and oversize holes. The
from vibration
teeth are twisted, so as the nut is installed and
9. Verminproof
torqued down, the rim of the washer supports the
10. Hygienically safe to handle
pressure. Any backing off of the nut or bolt
releases tension that allows the teeth to dig into
Insulating material is available in preformed
the working surfaces of the nut and bolt.
pipe coverings, blocks, batts, blankets, and felts.
Refer to Naval Ships' Technical Manual, Chapter
635, "Thermal, Fire, and Acoustic Insulation,"
INSULATION
for detailed information on insulating materials,
their application, and safety precautions.
The purpose of insulation is to retard the
transfer of heat FROM piping that is hotter than
The insulating cements are comprised of a
the surrounding atmosphere or TO piping that
variety of materials, differing widely among
is cooler than the surrounding atmosphere.
Insulation helps to maintain the desired
other physical characteristics. Typical of these
temperatures in all systems. In addition, it
variations are the asbestos substitute cements,
prevents sweating of piping that carries cool or
diatomaceous cements, and mineral and slag wool
cold fluids. Insulation also serves to protect
cements. These cements are less efficient than
personnel from being burned by coming in
other high-temperature insulating materials, but
contact with hot surfaces. Piping insulation
they are valuable for patchwork emergency repairs
represents the composite piping covering which
and for covering small irregular surfaces (valves,
consists of the insulating material, lagging, and
flanges, joints, and so forth). Additionally, the
fastening. The INSULATING MATERIAL
cements are used for a surface finish over block
or sheet forms of insulation, to seal joints
LAGGING, usually of painted canvas, is the
between the blocks, and to provide a smooth
protective and confining covering placed over the
finish over which asbestos substitute or glass cloth
insulating materials; and the FASTENING
lagging may be applied.
attaches the insulating material to the piping and
to the lagging.
Insulation covers a wide range of tempera-
REMOVABLE INSULATION
tures, from the extremely low temperatures of the
refrigerating plants to the very high temperatures
Removable insulation will be found on the
of the ship's waste heat boilers. No one material
bleed air systems and waste heat boiler systems.
could possibly be used to meet all the conditions
Removable insulation is also installed in the
with the same efficiency.
following locations:
Flange pipe joints adjacent to machinery
INSULATION MATERIALS
or equipment that must be broken when
units are opened for inspection or overhaul
The following QUALITY REQUIREMENTS
for the various insulating materials are taken
Valve bonnets of valves larger than
into consideration by the Navy in the stan-
2 inches internal pipe size (IPS) that
dardization of these materials:
operate at 300 psi and above or at 240F
and above
1.
2.
Noncombustibility
All pressure-reducing and pressure-
3.
Lightweight
regulating valves, pump pressure gov-
4.
Easy molding and installation capability
ernors, and strainer bonnets
5.
Moisture repellant
6-40