TM 5-805-4/AFJMAN 32-1090
(2) When a pipe passes through the MER
ted with an exterior braided jacket to confine the
neoprene. These connections are useful when the
wall, a minimum l-inch clearance should be pro-
equipment is subject to fairly high-amplitude vi-
vided between the pipe and the hole in the wall.
bration, such as for reciprocating-type compressors.
The pipe should be supported on either side of the
Flexible connections generally are not necessary
hole, so that the pipe does not rest on the wall.
when the piping and its equipment are given
The clearance space should then be stuffed with
thorough and compatible vibration isolation. For
fibrous filler material and sealed with a nonhard-
serious pipe vibration problems, two flexible con-
ening caulking compound at both wall surfaces.
nections should be used, mounted 90 degrees to
(3) Vertical pipe chases through a building
each other. Inertial masses may be attached to the
should not be located beside acoustically critical
piping to add stability and help maintain pipe
areas. If they are located beside critical areas,
alignment.
pipes should be resiliently mounted from the walls
c. Nonvibrating equipment. When an MER is
of the pipe chase for a distance of at least 10 feet
located directly over or near a critical area, it is
beyond each such area, using both low-frequency
usually desirable to isolate most of the nonvibrat-
ing equipment with a simple mount made up of
and high-frequency isolation materials.
one or two pads of neoprene or a 1 inch or 2 inch
(4) Pipes to and from the cooling tower should
be resiliently supported for their full length be-
layer of compressed glass fiber. Heat exchangers,
hot water heaters, water storage tanks, large
tween the cooling tower and the associated MER.
Steam pipes should be resiliently supported for
ducts, and some large pipe stands may not them-
selves be noise sources, yet their pipes or their
their entire length of run inside the building.
connections to vibrating sources transmit small
Resilient mounts should have a static deflection of
at least 1/2 inch.
amounts of vibrational energy that they then may
transmit into the floor. A simple minimum isola-
(5) In highly critical areas, domestic water
tion pad will usually prevent this noise transfer.
pipes and waste lines can be isolated with the use
of 1/4-inch- to 1/2-inch-thick wrappings of felt pads
d. Summary. In this chapter, fairly complete
vibration isolation mounting are laid out for most
under the pipe strap or pipe clamp.
of the equipment included in an MER. Most of
(6) Whenever a steel spring isolator is used, it
these have been developed and proven over many
should be in series with a neoprene isolator. For
years of use. Although all the entries of the
ceiling hangers, a neoprene washer or grommet
accompanying tables have not been tested in ac-
should always be included; and if the pipe hangers
tual equipment installations, the schedules are
are near very critical areas, the hanger should be
fairly self consistent in terms of various locations
a combination hanger that contains both a steel
and degrees of required isolation. Hence, the
spring and a neoprene-in-shear mount.
mounting are considered realistic and reliable.
(7) During inspection, the hanger rods should
be checked to ensure they are not touching the
They are not extravagant when considered in the
light of the extremely low vibration levels re-
sides of the isolator housing and thereby shorting-
quired to achieve near inaudibility. The noise and
out the spring.
b. Flexible pipe connections. To be effective, a
vibration control methods given here are designed
to be simple to follow and to put into use. If these
flexible pipe connection should have a length that
methods and recommendations are carried out,
is approximately 6 to 10 times its diameter. Tie
with appropriate attention to detail, most equip-
rods should not be used to bolt the two end flanges
ment installations will be tailored to the specific
of a flexible connection together. Flexible connec-
needs of the building and will give very satisfac-
tions are either of the bellows type or are made up
tory results acoustically.
of wire-reinforced neoprene piping, sometimes fit-
8-11
Previous Page
