Page 222 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

HEAT TRANSFER, INSULATION, AND FREEZE PROTECTION

5.6 CHAPTER FIVE

k factor that might fail because of a large difference in the rates of expansion between it
and the pipe will prove less economical over time than another insulation system with a
lower k factor.
When an insulated pipe is to be installed in a corrosive atmosphere, the insulation sys-
tem, particularly the jacket, must be capable of resisting whatever substance is causing that
corrosion.
Insulation that is used for the food-processing, chemical, cosmetics, and pharmaceuti-
cal industries (or in other similar operations) must have the ability to withstand cleaning or
sterilizing by a wide variety of methods. The important properties are:
1. Smooth finish
2. Resistance to fungus, bacteria, or mildew growth
3. Resistance to washing by detergents, steam, and chemicals
4. No chipping, cracking, or peeling
5. Nontoxicity and fire resistance

TYPES OF INSULATION

The following general designations are generic names of the materials. The individual
manufacturers have different trade names for each of them. For each of the separate types,
various properties will be compared, with the following properties common to all.
1. They must have been tested for fire-related values by the ASTM, NFPA, and UL as
previously discussed, and meet the minimum standard for a flame-spread of 25 and
smoke-developed rating of 50 or less except where otherwise noted.
2. The temperature at which the k and R figures have been calculated is 75°F (24°C).

Fiberglass
Fiberglass insulation (ASTM C 547) is fibrous glass, made either plain or with a heat-
resistant binder in order for the fiberglass to hold its shape. Typical values for material with
3
3
a density of 3 to 5 lb/ft (48 to 80 kg/m ) are k = 0.22 to 0.26 and R = 3.8 to 4.5.
Fiberglass is the most popular insulation, and it comes in many forms. Felted glass fiber
without any binder is available in rolls. Made with a thermosetting resin binder, it comes
in several different stiffnesses. In the form most commonly used for pipe, it is molded and
shaped into semicircular sections. The binder is the critical factor for the ultimate tempera-
ture for which it can be used.
Fiberglass by itself is not strong enough to stay permanently on a pipe without falling
off in layers. Since fiberglass is porous, there is no way to seal it to prevent water vapor
from flowing freely from the air to the pipe and then condensing on the pipe and saturat-
ing the fiberglass. In addition, there is no way to finish fiberglass that would be considered
pleasant to look at. For these reasons, a covering, or jacket, must be added to protect it from
physical damage, allow it to be firmly and permanently attached to the pipe, and prevent
the penetration of water vapor.
Fiberglass is recommended for temperatures ranging from 35 to 800°F (1.5 to 422°C).
It is available in thicknesses from 1/2 to 5 in (DN 15 to 125) for 1/2- to 33-in (DN 15 to
750) piping, with manufacturers providing various thicknesses for certain size pipes. For
insulating tanks, fiberglass is also available in boards 48 to 96 in (1200 to 2400 mm) long,
12 to 24 in (300 to 2400 mm) wide, and up to 4 in (100 mm) thick. A high temperature,
flexible blanket can be used with temperatures up to 1000°F (530°C).

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