Page 229 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

HEAT TRANSFER, INSULATION, AND FREEZE PROTECTION

HEAT TRANSFER, INSULATION, AND FREEZE PROTECTION 5.13

5. Accessibility for the insulated pipe
6. Installed cost of the complete insulating system

Reasons for Using Insulation
There are four reasons to use insulation:
1. Condensation prevention
2. Reduction of heat loss
3. Personnel protection
4. Noise reduction

Condensation Prevention. Insulation applied to pipes carrying storm water, city water,
chilled water, and drinking water is done to prevent condensation. On pipes containing chilled
and drinking water, condensation prevention is the secondary consideration after heat gain
prevention. Each of the various insulating manufacturers has prepared charts giving the nec-
essary thickness of the insulation in question to prevent condensation. The design temperature
of the fluids is storm water, 35°F (2°C); domestic water, 60°F (15°C); and chilled water, 50°F
(10°C). The design ambient temperature is 90°F (32°C), the relative humidity, 90 percent.
A vapor barrier jacket is required on fiberglass, mineral wool, and calsil. It is not necessary
over rubber or cellular glass. The total system perm rating must be no more than 0.30.
For insulation thickness to prevent condensation, refer to Tables 5.1 and 5.2 for ser-
vice temperatures of 50°F (10°C) and 34°F (2°C), respectively. Find the pipe size, relative

TABLE 5.1 Insulation Thickness to Prevent Condensation, 50°F Service Temperature and 70°F
Ambient Temperature *

Relative humidity, %
Nom. Pipe 20 50 70 80 90
DN size, in TNK † HC ‡ ST § THK HG ST THK HG ST THK HG ST THK HG ST

15 0.50 0.5 2 66 0.5 2 66 0.5 2 66 1.0 2 68
20 0.75 0.5 2 67 0.5 2 67 0.5 2 67 0.5 2 67
25 1.00 0.5 3 66 0.5 3 66 0.5 3 66 1.0 2 68
32 1.25 0.5 3 66 0.5 3 66 0.5 3 66 1.0 3 67
40 1.50 0.5 4 65 0.5 4 65 0.5 4 65 1.0 3 67
50 2.00 0.5 5 66 0.5 5 66 0.5 5 66 1.0 3 67
65 2.50 0.5 5 65 0.5 5 65 0.5 5 65 1.0 4 67
75 3.00 0.5 7 65 0.5 7 65 0.5 7 65 1.0 4 67
90 3.50 Condensation 0.5 8 65 0.5 8 65 0.5 8 65 1.0 4 68
100 4.00 control not 0.5 8 65 0.5 8 65 0.5 8 65 1.0 5 67
125 5.00 required for this 0.5 10 65 0.5 10 65 0.5 10 65 1.0 6 67
150 6.00 condition 0.5 12 65 0.5 12 65 0.5 12 65 1.0 7 67
200 8.00 1.0 9 67 1.0 9 67 1.0 9 67 1.0 9 67
250 10.00 1.0 11 67 1.0 11 67 1.0 11 67 1.0 11 67
300 12.00 1.0 12 67 1.0 12 67 1.0 12 67 1.0 12 67
* 25 mm = 1 in.
† THK = Insulation thickness, inches.
‡ HG = Heat gain/lineal foot (pipe) 28 ft (flat), BTU.
§ ST = Surface temperature, °F.

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