Page 226 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

HEAT TRANSFER, INSULATION, AND FREEZE PROTECTION

5.10 CHAPTER FIVE

S or Z configuration, or by sheet metal screws. The ends are overlapped 2 in and secured
with straps or screws (or nothing for the interlocking type). Since they are usually applied
over insulation, a variety of vapor barrier materials can be factory applied to the aluminum
jackets, which may be necessary if the insulation has any ingredient that causes galvanic or
corrosive attack on the aluminum, or if an additional vapor barrier is thought to be neces-
sary. Fittings are fabricated from roll material in the shop.
There are four different alloys of aluminum commonly used for jacketing material:
1100, 3003, 3105, and 5005. Although there are differences among them, it is not usually
necessary to specify which alloy is to be used. The properties of all types are so closely
matched that the service or performance of the material is not affected by different choices.
It is common practice for the fabricator of the jacket to interchange any of the four types
depending on availability and price. By specifying the ASTM code alone, the engineer is
allowing the contractor to use any of the types (since they are all acceptable), and avoids
the possibility of a delay caused by waiting for the particular alloy specified and the extra
cost involved.
One alloy, 1100, is mostly used for fittings because it is the most malleable of the four.
If the jacketing is used on a pipe that may expand and contract often because of system
operation, corrugated aluminum jackets should be used. These jackets easily expand and
contract.
Aluminum jackets have the following advantages:
1. Easy application in any weather
2. Easy formation into different shapes
3. Good resistance to abuse
4. Ready availability
Aluminum jackets have the following disadvantages:
1. Low resistance to pH ranging from 7 to 11
2. Low fire rating
3. Low emittance value
4. High initial cost
5. Low resistance to strong cleaning chemicals

Stainless Steel Jackets

Stainless steel jackets (ASTM A-240) are available in either flat or corrugated forms and
in standard thicknesses of 0.010, 0.016, and 0.019. They are secured in the same manner as
aluminum jackets. A factory applied moisture barrier can also be added.
The most commonly available alloys are types 301, 302, 303, 304, 305, and 316; 304
is the most popular. It is best to consult with the manufacturer for the criteria that will
help determine which alloy would be best for any particular application. Several types
of finishes are available, from polished to dull. Stainless steel jackets have the following
advantages:

1. Excellent fire rating
2. High resistance to mechanical abuse
3. Excellent corrosion and weather resistance
4. Easy application in any weather
5. Excellent hygienic characteristics

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