Fluid Operating Temperature Range and Usage (°F) | Insulation Conductivity | Nominal Pipe or Tube Size (inches) | |||||
Conductivity Btu • in. /(h • ft2 • °F)b | Mean Rating Temperature, °F | < 1 | 1 to < 1-1/2 | 1-1/2 to < 4 | 4 to < 8 | ≥ 8 | |
˃ 350 | 0.32 - 0.34 | 250 | 4.5 | 5.0 | 5.0 | 5.0 | 5.0 |
251 - 350 | 0.29 - 0.32 | 200 | 3.0 | 4.0 | 4.5 | 4.5 | 4.5 |
201 - 250 | 0.27 - 0.30 | 150 | 2.5 | 2.5 | 2.5 | 3.0 | 3.0 |
141 - 200 | 0.25 - 0.29 | 125 | 1.5 | 1.5 | 2.0 | 2.0 | 2.0 |
105 - 140 | 0.21 - 0.28 | 100 | 1.0 | 1.0 | 1.5 | 1.5 | 1.5 |
40 - 60 | 0.21 - 0.27 | 75 | 0.5 | 0.5 | 1.0 | 1.0 | 1.0 |
< 40 | 0.20 - 0.26 | 75 | 0.5 | 1.0 | 1.0 | 1.0 | 1.5 |
a | For piping smaller than 1-1/2 inch (38 mm) and located in partitions within conditioned spaces, reduction of these thicknesses by 1 inch (25 mm) shall be permitted (before thickness adjustment required in footnote b) but not to a thickness less than 1 inch (25 mm). |
b | For insulation outside the stated conductivity range, the minimum thickness (T) shall be determined as follows: |
T | = | r{(1 + t/r)K/k - 1} | ||
Where: | ||||
T | = | Minimum insulation thickness, | ||
r | = | Actual outside radius of pipe, | ||
t | = | Insulation thickness listed in the table for applicable fluid temperature and pipe size, | ||
K | = | Conductivity of alternate material at mean rating temperature indicated for the applicable fluid temperature (Btu × in/h × ft2 × °F) and | ||
k | = | The upper value of the conductivity range listed in the table for the applicable fluid temperature. | ||
c | For direct-buried heating and hot water system piping, reduction of these thicknesses by 1-1/2 inches (38 mm) shall be permitted (before thickness adjustment required in footnote b but not to thicknesses less than 1 inch (25 mm). |