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Utility Line Insulation


Pipe Covering System
Utility lines are usually placed below the expected depth of frost penetration into the soil in order to prevent freezing of water in the lines. However, sometimes it is not possible to bury lines deep enough due to high water table, rocky outcrops, or soil conditions. Water lines for snow making equipment inevitably end up partly in a freezing environment. Lines may also be in the active layer of permafrost, or for other reasons it is known they will be in a freeze zone. Under these conditions the pipe can be insulated with PlastiSpan® HD pipe insulation covering at the time of installation to increase the time the pipe can store still water before freezing.

Utility lines may freeze after installation due to underestimation of frost penetration or due to removal of some of the protective soil covering. It is possible to eliminate the problem next season by placing a layer of PlastiSpan HD insulation above the utility line but under the ground level to raise the frost line above the utility line. This system is not usable where the utility line is installed in the active layer of permafrost.

Design Principles
The design principles to be used in determining the thickness of the pipe covering can be quite complex. Factors affecting the design are:

  1. Minimum temperature of soil or air around the pipe.
  2. Temperature and rate of flow of water through the pipe.
  3. Size of pipe and material from which pipe is made.

In order to provide a greater period of time before the pipes freeze, the following modifications can be made in utility lines in addition to the installation of insulation on the pipe:

  1. Increase the diameter of the pipe (particularly service
  2. Provide a heating plant at the pumping station so that the water enters the system at
    a higher temperature than from the reservoir.
  3. Loop all mains in the system so there is recirculation back to the pumps and still water in
    the mains is avoided.
  4. Trace lines with heating cable in combination with insulation of the line.




Recommended Insulation Thicknesses

The tables on the following pages indicate the time (in hours) that still water can remain in the pipe without the pipe
freezing.   The assumption is made that if half the cross section is frozen to slush the line will plug at a restriction such as
a fitting or a stop.  The tables assume that PlastiSpan HD insulation is used. The low temperature in the soil minimizes
decreases the mean temperature within the pipe insulation and minimizes water absorption into the insulation.

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Time (in hours) required to freeze still water in pipe
The chart below assumes a thermal conductivity of 0.039 W/m2•°C for the PlastiSpan HD insulation. The design is based on pipe buried in the soil but is conservative for pipe exposed to the atmosphere to the extent of thermal resistance of the surface air film.

Pipe Material Metric Values Soil Temperature (°C)
Nominal Pipe Size PlastiSpan HD Insulating Thickness -40° -29° -18° -12° -7° -1°
Plastic, Steel
or Cast Iron
25 mm 38 mm 3.0 4.2 6.5 9.1 15.2 45.7
51 mm 3.6 4.9 7.7 10.8 18.0 54.0
76 mm 4.4 6.0 9.4 13.2 22.0 66.1
102 mm 5.0 6.9 10.8 15.1 25.2 75.7
38 mm 38 mm 5.7 7.8 12.3 17.2 28.6 85.8
51 mm 6.9 9.4 14.7 20.6 34.4 103.1
76 mm 8.6 11.8 18.5 25.9 43.1 129.3
102 mm 10.0 13.7 21.5 30.1 50.1 150.4
51 mm 38 mm 8.1 11.1 17.4 24.3 40.5 121.6
51 mm 9.8 13.4 21.1 29.5 49.2 147.7
76 mm 12.5 17.1 26.9 37.6 62.7 188.0
102 mm 14.7 20.1 31.5 44.2 73.6 220.8
64 mm 38 mm 10.1 13.8 21.7 30.4 50.7 152.0
51 mm 12.4 16.9 26.6 37.3 62.1 186.3
76 mm 16.0 21.8 34.3 48.0 80.0 240.1
102 mm 19.0 25.9 40.7 56.9 94.9 284.6
76 mm 38 mm 13.6 18.5 29.1 40.7 67.9 203.7
51 mm 16.8 22.9 36.0 50.4 84.0 252.1
76 mm 21.9 29.9 47.0 65.8 109.7 329.0
102 mm 26.2 35.8 56.2 78.7 131.2 393.7
102 mm 38 mm 19.3 26.3 41.4 58.0 96.6 289.8
51 mm 24.2 33.0 51.8 72.5 120.9 362.7
76 mm 32.1 43.7 68.7 96.2 160.4 481.1
102 mm 38.9 53.0 83.3 116.6 194.3 582.8
127 mm 38 mm 25.5 34.7 54.6 76.4 127.4 382.2
51 mm 32.2 43.9 69.0 96.6 160.9 482.8
76 mm 43.3 59.0 92.8 129.9 216.5 649.4
102 mm 53.0 72.3 113.6 159.0 265.0 795.1
152 mm 38 mm 31.9 43.5 68.4 95.8 159.6 478.8
51 mm 40.6 55.4 87.0 121.8 203.0 609.0
76 mm 55.2 75.2 118.2 165.5 275.9 827.7
102 mm 68.1 92.9 146.0 204.3 340.6 1021.7
178 mm 38 mm 38.1 51.9 81.5 114.2 190.3 570.8
51 mm 48.7 66.3 104.3 146.0 243.3 729.8
76 mm 66.7 90.9 142.8 200.0 333.3 999.9
102 mm 82.8 112.9 177.5 248.5 414.1 1242.3
203 mm 38 mm 44.3 60.3 94.8 132.8 221.3 663.8
51 mm 56.8 77.5 121.7 170.4 284.1 852.2
76 mm 78.4 106.9 167.9 235.1 391.8 1175.4
102 mm 97.9 133.5 209.8 293.7 489.5 1468.5
254 mm 38 mm 57.6 78.5 123.4 172.7 287.8 863.5
51 mm 74.4 101.5 159.5 223.3 372.1 1116.3
76 mm 103.8 141.5 222.4 311.4 519.0 1557.0
102 mm 130.9 178.5 280.5 392.7 654.6 1963.7
305 mm 38 mm 70.9 96.7 151.9 212.7 354.5 1063.4
51 mm 92.1 125.6 197.4 276.3 460.5 1381.5
76 mm 129.5 176.6 277.5 388.4 647.4 1942.2
102 mm 164.4 224.2 352.3 493.3 822.1 2466.3
356 mm 38 mm 79.5 108.3 170.3 238.4 397.3 1191.8
51 mm 103.5 141.1 221.7 310.4 517.3 1552.0
76 mm 146.1 199.2 313.0 438.2 730.3 2190.8
102 mm 186.1 253.8 398.8 558.4 930.6 2791.9

Time (in hours) required to freeze still water in pipe
The chart below assumes a thermal conductivity of 0.27 BTU•in/(ft2•h•°F) for the PlastiSpan HD insulation. The design is based on pipe buried in the soil but is conservative for pipe exposed to the air to the extent of thermal resistance of the surface air film. (See Page 6 for representative soil temperatures.)

Pipe Material Imperial Values Soil Temperature (°F)
Nominal Pipe Size PlastiSpan HD Insulating Thickness -40° -20° 10° 20° 30°
Plastic, Steel
or Cast Iron
1" 1-1/2" 3.1 4.2 6.5 9.2 15.3 45.8
2" 3.6 4.9 7.7 10.8 18.0 53.9
3" 4.4 6.0 9.5 13.2 22.1 66.2
4" 5.0 6.9 10.8 15.1 25.2 75.6
1-1/2" 1-1/2" 5.7 7.8 12.3 17.2 28.7 86.0
2" 6.9 9.4 14.7 20.6 34.3 102.9
3" 8.6 11.8 18.5 25.9 43.2 129.5
4" 10.0 13.6 21.4 30.0 50.0 150.1
2" 1-1/2" 10.2 13.8 21.8 30.5 50.8 152.3
2" 9.8 13.4 21.1 29.5 49.1 147.4
3" 12.6 17.1 26.9 37.7 62.8 188.3
4" 14.7 20.0 31.5 44.1 73.5 220.5
2-1/2" 1-1/2" 10.2 13.8 21.8 30.5 50.8 152.3
2" 12.4 16.9 26.6 37.2 62.0 185.9
3" 16.0 21.9 34.4 48.1 80.2 240.6
4" 18.9 25.8 40.6 56.8 94.7 284.1
3" 1-1/2" 13.6 18.6 29.2 40.8 68.1 204.2
2" 16.8 22.9 35.9 50.3 83.8 251.5
3" 22.0 30.0 47.1 65.9 109.9 329.7
4" 26.2 35.7 56.1 78.6 131.0 392.9
4" 1-1/2" 19.4 26.4 41.5 58.1 96.8 290.5
2" 24.1 32.9 51.7 72.4 120.6 361.8
3" 32.1 43.8 68.9 96.4 160.7 482.2
4" 38.8 52.9 83.1 116.3 193.9 581.6
5" 1-1/2" 25.5 34.8 54.7 76.6 127.7 383.2
2" 32.1 43.8 68.8 96.3 160.5 481.6
3" 43.4 59.2 93.0 130.2 217.0 650.9
4" 52.9 72.1 113.3 158.7 264.5 793.4
6" 1-1/2" 32.0 43.6 68.6 96.0 160.0 480.0
2" 40.5 55.2 86.8 121.5 202.4 607.3
3" 55.3 75.4 118.5 165.9 276.5 829.6
4" 68.0 92.7 145.6 203.9 339.8 1019.4
7" 1-1/2" 38.2 52.0 81.8 114.5 190.8 572.3
2" 48.5 66.2 104.0 145.6 242.6 727.8
3" 66.8 91.1 143.2 200.5 334.1 1002.3
4" 82.6 112.7 177.0 247.9 413.1 1239.3
8" 1-1/2" 44.4 60.5 95.1 133.1 221.9 665.6
2" 56.7 77.3 121.4 170.0 283.3 849.8
3" 78.6 107.1 168.3 235.7 392.8 1178.3
4" 97.7 133.2 209.3 293.0 488.3 1464.9
10" 1-1/2" 57.7 78.7 123.7 173.2 288.6 865.8
2" 74.2 101.2 159.0 222.6 371.0 1113.0
3" 104.1 141.9 223.0 312.2 520.3 1561.0
4" 130.6 178.1 279.8 391.7 652.9 1958.6
12" 1-1/2"
71.1 96.9 152.3 213.3 355.5 1063.4
2" 91.8 125.2 197.4 275.5 459.1 1381.5
3" 129.8 177.0 277.5 389.4 649.1 1942.2
4" 164.0 223.6 352.3 491.0 819.9 2459.6
14" 1-1/2" 79.7 108.7 170.7 239.0 398.4 1195.2
2" 103.2 140.7 221.0 309.5 515.8 1547.3
3" 146.4 199.7 313.8 439.3 732.2 2196.6
4" 185.6 253.1 397.7 556.8 928.1 2784.2

Time (in hours) required to freeze still water in copper tube
The chart below assumes a thermal conductivity of 0.039 W/m2•°C for the PlastiSpan HD insulation. The design is based on pipe buried in the soil but is conservative for pipe exposed to the atmosphere to the extent of thermal resistance of the surface air film.

Metric Values Soil Temperature (°C)
Copper
Tubing
Nominal Pipe Size PlastiSpan HD Insulating Thickness -40° -29° -18° -12° -7° -1°
Copper
Type k
19 mm 38 mm 1.9 2.6 4.1 5.8 9.6 28.8
51 mm 2.2 3.0 4.8 6.7 11.1 33.4
76 mm 2.7 3.6 5.7 8.0 13.3 40.0
102 mm 3.0 4.1 6.4 9.0 15.0 45.1
25 mm 38 mm 3.0 4.1 6.4 9.0 15.0 44.9
51 mm 3.5 4.8 7.5 10.5 17.6 52.7
76 mm 4.3 5.8 9.1 12.8 21.3 64.0
102 mm 4.9 6.6 10.4 14.6 24.3 72.8
38 mm 38 mm 5.4 7.3 11.5 16.1 26.8 80.3
51 mm 6.4 8.7 13.7 19.1 31.9 95.7
76 mm 7.9 10.8 17.0 23.8 39.6 118.8
102 mm 9.1 12.5 19.6 27.4 45.7 137.2
51 mm 38 mm 7.8 10.7 16.8 23.5 39.2 117.6
51 mm 9.5 12.9 20.3 28.4 47.4 142.1
76 mm 12.0 16.3 25.7 35.9 59.9 179.6
102 mm 14.0 19.1 30.0 42.0 70.0 209.9
64 mm 38 mm 10.5 14.3 22.5 31.5 52.5 157.5
51 mm 12.8 17.5 27.5 38.5 64.1 192.3
76 mm 16.4 22.4 35.2 49.3 82.1 246.4
102 mm 19.4 26.4 41.5 58.2 96.9 290.8
76 mm 38 mm 13.2 18.0 28.4 39.7 66.2 198.5
51 mm 16.3 22.2 34.9 48.9 81.4 244.3
76 mm 21.1 28.8 45.2 63.3 105.5 316.6
102 mm 25.1 34.2 53.8 75.3 125.6 376.7
89 mm 38 mm 16.1 21.9 34.5 48.3 80.4 241.3
51 mm 19.9 27.2 42.7 59.8 99.7 299.2
76 mm 26.1 35.6 55.9 78.3 130.5 391.4
102 mm 31.3 42.6 67.0 93.8 156.4 469.1
102 mm 38 mm 18.9 25.8 40.6 56.8 94.7 284.2
51 mm 23.6 32.2 50.6 70.9 118.1 354.3
76 mm 31.2 42.5 66.8 93.5 155.8 467.5
102 mm 37.6 51.3 80.6 112.8 188.0 563.9
127 mm 38 mm 24.8 33.8 53.2 74.4 124.1 372.2
51 mm 31.2 42.6 66.9 93.7 156.2 468.5
76 mm 41.8 57.0 89.5 125.3 208.9 626.7
102 mm 50.9 69.5 109.1 152.8 254.7 760.0
152 mm 38 mm 30.5 41.6 65.4 91.5 152.5 457.6
51 mm 38.7 52.7 82.9 116.0 193.4 580.2
76 mm 52.3 71.4 112.1 157.0 261.7 785.0
102 mm 64.4 87.8 137.9 193.1 321.8 965.5

Time (in hours) required to freeze still water in copper tube
The charts assume a thermal conductivity of 0.27 BTU•in/(ft2•h•°F) for the PlastiSpan HD insulation. The design is based on pipe buried in the soil but is conservative for pipe exposed to the atmosphere to the extent of thermal resistance of the surface air film.

Imperial Values Soil Temperature (°F)
Copper
Tubing
Nominal Pipe Size PlastiSpan HD Insulating Thickness -40° -20° 10° 20° 30°
Copper
Type k
3/4" 1-1/2" 1.9 2.6 4.1 5.8 9.6 28.9
2" 2.2 3.0 4.8 6.7 11.1 33.4
3" 2.7 3.6 5.7 8.0 13.4 40.1
4" 3.0 4.1 6.4 9.0 15.0 45.1
1" 1-1/2" 3.0 4.1 6.4 9.0 15.0 45.0
2" 3.5 4.8 7.5 10.5 17.5 52.6
3" 4.3 5.8 9.2 12.8 21.4 64.1
4" 4.8 6.6 10.4 14.5 24.2 72.7
1-1/2" 1-1/2" 5.4 7.3 11.5 16.1 26.8 80.5
2" 6.4 8.7 13.6 19.1 31.8 95.5
3" 7.9 10.8 17.0 23.8 39.7 119.0
4" 9.1 12.5 19.6 27.4 45.7 137.0
2" 1-1/2" 7.9 10.7 16.8 23.6 39.3 117.9
2" 9.5 12.9 20.3 28.4 47.3 141.8
3" 12.0 16.4 25.7 36.0 60.0 179.9
4" 14.0 19.1 29.9 41.9 69.9 209.6
2-1/2" 1-1/2" 10.5 14.4 22.6 31.6 52.6 157.9
2" 12.8 17.4 27.4 38.4 64.0 191.9
3" 16.5 22.4 35.3 49.4 82.3 246.8
4" 19.4 26.4 41.5 58.1 96.8 290.3
3" 1-1/2" 13.3 18.1 28.4 39.8 66.3 198.9
2" 16.3 22.2 34.8 48.8 81.3 243.8
3" 21.1 28.8 45.3 63.4 105.7 317.2
4" 25.1 34.2 53.7 75.2 125.4 376.1
3-1/2" 1-1/2" 16.1 22.0 34.6 48.4 80.6 241.9
2" 19.9 27.1 42.6 59.7 99.5 298.5
3" 26.1 35.7 56.0 78.4 130.7 392.2
4" 31.2 42.6 66.9 93.6 156.1 468.2
4" 1-1/2" 19.0 25.9 40.7 57.0 95.0 284.9
2" 23.6 32.1 50.5 70.7 117.8 353.5
3" 31.2 42.6 66.9 93.7 156.2 468.5
4" 37.5 51.2 80.4 112.6 187.6 562.8
5" 1-1/2" 24.9 33.9 53.3 74.6 124.4 373.2
2" 31.2 42.5 66.8 93.5 155.8 467.3
3" 41.9 57.1 89.7 125.6 209.4 628.1
4" 50.8 69.3 108.9 152.5 254.1 762.4
6" 1-1/2" 30.6 41.7 65.5 91.8 152.9 458.8
2" 38.6 52.6 82.7 115.7 192.9 578.7
3" 52.5 71.5 112.4 157.4 262.3 786.8
4" 64.2 87.6 137.6 192.7 321.1 963.3


Soil Temperatures1
Average Temperature of Coldest Month (Metric Values - °C)
Location Depth Of Bury
200 mm 500 mm 1,000 mm 1,500 mm 3,000 mm
Prince George, B.C. -0.6 1.3 - 4.2 -
Saanichton, B.C. 4.4 5.3 6.7 7.8 -
Summerland, B.C. 0.8 1.5 2.8 5.5 -
Vancouver, B.C. (UBC) 4.0 5.5 6.7 7.5 -
Haines Jct.,Yukon - 5.0 - 3.1 - 1.0 0.1 -
Baker Lake, NWT - 25.2 - 21.0 - 18.0 - 17.1 -
Fort Simpson, NWT - 7.8 - 4.7 - 1.7 - 0.3 -
Resolute, NWT - 20.9 - 20.1 - 19.3 - 18.4 -
Beaverlodge, Alberta - 2.9 - 1.7 0.1 0.8 -
Ellersie, Alberta (Edmonton) - 4.3 - 2.5 - 1.2 - 0.6 2.0
Fort Vermillion, Alberta - 3.8 - 2.2 - 0.1 1.0 -
Lethbridge, Alberta - 2.7 - 0.8 1.5 2.9 4.2
Peace River, Alberta - 3.8 - 3.7 - 1.6 0.2 2.7
Calgary, Alberta (U of C) - 4.0 - 2.3 - 0.6 0.7 3.6
Vauxhall, Alberta - 4.1 - 1.5 0.5 1.8 -
Vegreville, Alberta - 4.9 - 2.7 - 0.3 0.7 1.9
Broadview, Saskatchewan - 3.9 - 2.4 - 0.7 0.3 -
Estevan, Saskatchewan - 5.3 - 1.6 1.4 0.8 3.0
Hudson Bay, Saskatchewan - 2.1 - 1.1 0.6 1.2 -
La Ronge, Saskatchewan - 1.4 - 0.6 0.4 0.7 2.0
Outlook, Saskatchewan - 8.1 - 5.7 - 2.2 0.2 3.4
Regina, Saskatchewan - 6.2 - 3.9 - 1.2 - 0.4 2.1
Saskatoon, Saskatchewan - 7.9 - 4.1 - 0.9 0.5 2.1
Swift Current, Saskatchewan - 2.5 - 1.6 - 0.5 0.7 2.6
Wynard, Saskatchewan - 5.6 - 4.2 - 1.4 0.3 1.8
Glenlea Sta., Manitoba - 4.5 - 2.7 - 1.2 0.5 2.7
Winnipeg (Airport), Manitoba - 3.5 - 2.2 - 0.3 0.8 3.4
Atikokan, Ontario 0.0 0.6 1.6 2.5 4.6
Guelph, Ontario 0.0 1.1 2.1 3.0 -
Harrow, Ontario - 0.2 0.9 2.5 3.6 6.9
Kapuskasing, Ontario - 0.1 0.0 1.6 2.2 3.3
Ottawa, Ontario - 0.2 1.0 1.3 3.5 4.6
Toronto, Ontario - 1.1 0.5 2.0 4.2 6.5
Vineland, Ontario 0.7 1.9 2.8 3.9 5.2
Caplan, Quebec - 0.6 0.6 1.6 2.0 3.9
La Pocatiere, Quebec - 0.4 0.4 1.6 2.5 5.4
Montreal-Mirabel, Quebec - 4.0 - 0.6 1.0 0.9 2.9
Normandin, Quebec - 0.2 0.2 0.6 2.0 3.2
St. Augustine, Quebec - 0.2 0.7 2.0 2.6 4.6
Val D’or, Quebec - 0.5 - 0.1 0.6 1.2 3.4
Fredrickton, New Brunswick - 1.7 - 0.3 1.8 2.5 4.6
Kentville, Nova Scotia 0.2 0.9 2.0 2.8 4.3
Truro, Nova Scotia 0.0 0.8 1.9 2.6 4.2
Charlottetown, P.E.I. 0.2 0.8 1.8 2.4 3.9
Note: Soil temperatures in Imperial - ºF = ºC x 1.8 + 32.
Average Temperature of Coldest Month (Metric Values - °C)