THERMACORTECHNICAL DATA

L

H

W

L L2L1 = L2

Calculation and DesignTDCD15.103

3.14.07EXPANSION CALCULATIONS AND LOOP SIZING

EXPANSION CALCULATIONS AND LOOP SIZINGIn a bonded system, the carrier pipe, foam insulation, and outer protective jacket are joined together forming one co-hesive unit that expands and contracts together. Thermal expansion of the carrier pipe during operation is therefore transferred to the polyurethane foam and outer jacket. These movements are naturally restricted to a certain ex-tent by the friction between the soil and jacket. In extreme cases, the force of friction can become so great that free expansion cannot occur and the unit becomes “fixed” into place. In such a case, the opposing force from thermal expansion can place impermissibly high stresses in the carrier pipe. Therefore, free expansion must be allowed to occur, but expansion must ultimately be compensated for through system design. The most common method is the inclusion of expansion elbows, loops, or z-bends.

Thermal expansion will occur between all fixed points in the piping system. If the system has the same covering height, natural fixed points will occur in the center of a line section between two expansion elbows. Unequal covering will cause the fixed point to be displaced due to varying frictional forces, and if there is any doubt, the fixed point should be set with an anchor. In all cases, this fixed point should be considered when calculating expansion.

GUIDELINES FOR LOOP SIZING1. The expansion loop is usually located on the side of

the hottest line.2. The expansion loop, as a rule, should be located in

the center of the distance between two anchors.3. The height of the expansion loop is normally twice the

width. The exception to this rule occurs when more than one line runs parallel in a common trench. The dimensions of the loops for the additional line must be increased to allow nesting of the loops.

CALCULATIONS1. The formula for calculating thermal expansion: ΔL = C x L x (Tf - Tg) x 12in./ ft. Coefficient of thermal expansion (C): Steel (C) = 6.5 x 10-6 in./ in.°F Copper (C) = 9.2 x 10-6 in./ in.°F Distance between fixed points (L) in feet. Temperature of fluid (Tf) Temperature of ground (Tg)2. After calculating the expansion, find the expansion

loop size from the charts for the applicable pipe or tube. Loop sizes are taken to the nearest half foot on the height and width.

Elbow

Z-Bend

Loop

EXPANSION COMPENSATION

NATURAL FIXED POINT

EXAMPLEFind the loop size for a 6” diameter steel pipe carrying 200°F heating water with 200 ft. between anchors and an average annual ground temperature of 50°F. Given: Steel (C) = 6.5 x 10-6 in./ in.°F Distance (L) = 200 ft. Temp. Diff. (ΔT) = (200°F - 50°F) = 150°F Pipe Diam. (D) = 6” Calculations: ΔL = C x L x (Tf - Tg) x 12in./ ft. ΔL = 6.5 x 10-6 x 200 x (200 - 50) x 12 ΔL = 2.34 in. (expansion)From the expansion loop chart for steel:Requires 5’x10’ expansion loop.

EXPANSION LOOP

THERMACORTECHNICAL DATA

Calculation and DesignEXPANSION LOOP SIZES

Expansion loop dimensions are for ASTM B-88 seamless cop-per tubing based on an allowable stress of 6,000 psi. as stated in the copper development association handbook for copper tubing. Pressure shall not exceed 150 psig.

PIPESIZE(IN)

3/4

1

1-1/4

1-1/2

2

2-1/2

3

4

5

6

ΔL(IN)

0.00 - 2.092.09 - 4.694.69 - 8.350.00 - 1.621.62 - 3.653.65 - 6.49

6.49 - 10.140.00 - 1.321.32 - 2.982.98 - 5.315.31 - 8.300.00 - 1.121.12 - 2.532.53 - 7.027.02 - 10.110.00 - 0.890.89 - 1.931.93 - 3.443.44 - 5.375.37 - 7.730.00 - 0.690.69 - 1.561.56 - 2.782.78 - 4.354.35 - 6.266.26 - 8.520.00 - 0.580.58 - 1.311.31 - 2.332.33 - 3.653.65 - 5.265.26 - 7.167.16 - 9.340.00 - 0.990.99 - 1.771.77 - 2.762.76 - 3.983.98 - 5.425.42 - 7.087.08 - 8.960.00 - 0.800.80 - 1.421.42 - 2.222.22 - 3.203.20 - 4.364.36 - 5.705.70 - 7.210.00 - 1.191.19 - 1.861.86 - 2.682.68 - 3.653.65 - 4.774.77 - 6.036.03 - 7.45

EXPANSION LOOP SIZES FOR STEEL PIPE EXPANSION LOOP SIZES FOR COPPER TUBINGExpansion loops are sized for A53 Grade B ERW steel pipe allowable stresses.

PIPESIZE(IN)

3/4

1

1-1/4

1-1/2

2

2-1/2

3

3-1/2

4

5

6

8

ΔL(IN)

0.00 - 1.501.50 - 6.000.00 - 1.001.00 - 4.140.00 - 0.930.93 - 3.333.33 - 5.560.00 - 0.880.88 - 2.752.75 - 4.750.00 - 0.850.85 - 2.382.38 - 4.000.00 - 0.780.78 - 2.142.14 - 3.713.71 - 5.310.00 - 0.720.72 - 1.781.78 - 3.003.00 - 4.350.00 - 0.680.68 - 1.351.35 - 2.702.70 - 3.843.84 - 5.000.00 - 0.630.63 - 1.451.45 -2.412.41 - 3.453.45 - 4.520.00 - 0.420.42 - 1.271.27 - 2.122.12 - 3.003.00 - 3.963.96 - 4.130.00 - 0.460.46 - 1.161.16 - 1.871.87 - 2.352.35 - 3.513.51 - 4.260.00 - 0.540.54 - 1.001.00 - 1.641.64 - 2.302.30 - 2.952.95 - 3.643.64 - 4.35

PIPESIZE(IN)

10

12&14

16

ΔL(IN)

0.00 - 0.420.42 - 0.910.91 - 1.441.44 - 2.002.00 - 2.572.57 - 3.163.16 - 3.803.80 - 4.140.00 - 0.390.39 - 0.870.87 - 1.341.34 - 1.881.88 - 2.432.43 - 3.003.00 - 3.573.57 - 4.140.00 - 0.410.41 - 0.850.85 - 1.321.32 - 1.831.83 - 2.342.34 - 2.862.86 - 3.433.43 - 4.00

LOOP SIZE(FT)

LOOP SIZE(FT)

LOOP SIZE(FT)

TDCD15.104

3.14.07

468468

10468

10468

10468

1012468

101214468

10121416468

1012141668

10121416188

101214161820

23423452345234523456234567234567823456783456789456789

10

H W468

1012141618468

1012141618468

1012141618

234567892345678923456789

H W4646468468468468

10468

10468

1012468

1012468

101214468

101214468

10121416

23232342342342345234523456234562345672345672345678

H W