Page 232 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

HEAT TRANSFER, INSULATION, AND FREEZE PROTECTION

5.16 CHAPTER FIVE

Personnel Protection. If system economy is not a consideration for any particular piping
system, a hot pipe must be insulated to bring the surface temperature of the insulation to
120°F (48°C) or below, the point that would burn a person’s skin. Refer to Table 5.4 for
the thickness of fiberglass insulation necessary to achieve a surface temperature of 110°F
(43°C) with a conservative ambient temperature of 80°F (26°C). Enter the table with the
service temperature and size of the pipe. Read the required thickness and resulting surface
temperature for the thickness selected at the intersection of the appropriate columns. Use
the 250°F column for lower service piping temperatures.
Noise Reduction. Some types of insulation and/or special jackets can reduce the noise
that may be generated or transmitted by pipes, depending on the degree of reduction
desired. Manufacturers have compiled data on the reduction factors of various insulation
and jackets, which will aid in the selection of materials for that purpose.

Expected Temperature
The expected temperature of the pipe is an important factor in the selection of insulation
systems. For hot pipes, the highest expected temperature will affect the choice of thickness
and type of insulation and the adhesives used to adhere the insulation or jackets to the pipe
and itself. For cold pipes, the coldest expected temperature will affect the selection of the
insulation and vapor barrier required to stop condensation. The expansion of the pipe and
insulation should also be compared to see if the difference is excessive.

Location of Insulation

Where the insulated pipe or equipment is located may dictate the type of insulation, jacket,
or covering and the method used to attach it to the pipe. Factors such as outdoor instal-
lation, high humidity, and low ambient temperature will affect the selection of system
components.

Accessibility

There may be a need to remove portions of the insulation to allow maintenance, inspection,
or repair to a section of the piping system on a regular basis. Fiberglass and rubber are the
easiest to remove, simply by cutting the cover and insulation with a knife and removing
them. Putting them back is just as simple as installing them originally, and no harm is done
to the surrounding insulation and covering on either side. If this is to be done often or on a
regular basis, another popular method is to use a blanket insulation and wrap it with a wire
mesh that is secured with straps. This last method is limited to hot lines that are not subject
to any physical abuse whatsoever.

CALCULATION OF INSULATION THICKNESS

The following examples will illustrate the use of previously presented formulas of heat
transfer fundamentals involving practical solutions to selecting the actual thickness of the
insulation intended to be used for any specific project.
In all probability, there are charts and tables available to determine some of the heat loss
figures to be calculated. But, there are bound to be situations that will not allow the use of
standard conditions or standard figures. Also, most charts do not go into enough detail or

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