Water pipes expand or contract for every change of temperature to which they are subjected. To provide for this, in all tall buildings expansion loops are placed in both hot water and circulation pipe to permit the expansion and contraction of the lines without injury to the pipes. The loops are usually from 6 to 8 feet long, made as shown in Fig. 138, placed under floors and spaced about 50 feet apart. Usually hot water and circulation pipes are fastened midway between loops and allowed to expand both up and down. The length that water pipes will expand depends upon the degree to which they are heated and the material of the pipes.

Expansion Of Pipes 159

Fig. 138

Within ordinary ranges of temperature, cast iron pipe varies 1/162000 of its length for each degree Fahr., heated or cooled. Wrought iron pipe varies 1/1500000 of its length for each degree Fahr. heated or cooled, and brass pipe varies 1/100000 of its length for each degree Fahr., heated or cooled. Hence the expansion or contraction of any pipe, when the length and the temperature of water are known, can be found by the following rule:

Rule

Multiply the length of pipe in inches by the number of degrees Fahr. it is heated or cooled, and divide the product by the coefficient of expansion for the kind of pipe used.

Expressed as a formula: e=1h/ c when 1=length of pipe in inches h=degrees Fahr. the pipe is heated or cooled c=coefficient of expansion (1/ 162000 cast iron, 1/ 1500000 wrought iron and 1/ 100000 brass) e+elongation of pipe in inches

Example

What will be the expansion of a wrought iron pipe 100 feet long when heated from 60 to 212 degrees temperature ?

Solution

100 ft.X12 in. X152=182400/ 1500000=1.21 inches.

The following table of linear expansion of cast iron, wrought iron and brass pipe for each 100 feet length at different temperatures, will be found convenient for reference.

Table LVII - Expansion Of Cast Iron Pipe

Temperature of Air when Pipe is Fitted

Length of Pipe when

Fitted

Length of Pipe when heated to

215 Deg. Fahr.

265 Deg. Fahr.

297 Deg. Fahr.

338 Deg. Fahr.

Deg. Fahr

Feet

Feet

Inches

Feet

Inches

Feet

Inches

Feet

Inches

0

100

100

1.59

100

1.96

100

2.20

100

2.50

32

100

100

1.36

100

1.65

100

1.96

100

2.27

64

100

100

1.12

100

1.43

100

1.73

100

2.00

Table LVIII - Expansion Of Wrought Iron Pipe

Temperature of Air when Pipe is Fitted

Length of Pipe when

Fitted

Length of Pipe when heated to

215 Deg. Fahr.

265 Deg. Fahr.

297 Deg. Fahr.

338 Deg. Fahr.

Deg. Fahr.

Feet

Feet Inches

Feet Inches

Feet Inches

Feet Inches

0

100

100 1.72

100 2.21

100 2.31

100 2.70

32

100

100 1.47

100 1.78

100 2.12

100 2.45

64

100

100 1.21

100 1.61

100 1.87

100 2.19

Table LIX - Expansion of Brass Pipe

Temperature of Air when Pipe is Fitted

Length of Pipe when

Fitted

Length of Pipe when heated to

215 Deg. Fahr.

265 Deg. Fahr.

297 Deg. Fahr.

338 Deg. Fahr.

Deg. Fahr.

0 32 64

Feet

100 100 100

Feet Inches 100 2.58 100 2.19 100 1.81

Feet Inches

100 3.18 100 2.79 100 2.41

Feet Inches 100 3.56 100 3.18 100 2.79

Feet Inches 100 4.05 100 3.67 100 3.28

Table LX - Values Of Pipe Coverings

Name

Maker

B. T. U. loss per sq. ft. pipe surface per minute

Per cent. or ratio of loss to loss from bare pipe

Thickness in inches

Weight in ounces per ft. of length, 4 in. diam.

Nonpareil Cork Standard...

Nonpareil Cork Co

2.20

15.9

1.00

27

Nonpareil Cork Octagonal..

Nonpareil Cork Co___

2.38

17.2

.80

16

Manville High Pressure.....

Manville Covering Co.

2.38

17.2

1.25

54

Magnesia.....................

Keasby & Mattison Co. H. F. Watson..........

2.45 2.49

17.7 18.0

1.12 1.12

35 45

Imperial Asbestos

"W. B."......................

H. F. Watson..........

Asbestos Paper Co___

Manville Covering Co.

2.62 2.77 2.80

18.9 20 0 20.2

1.12 1.12 1.50

59 35

Asbestos Air Cell............

Manville Infusorial Earth...

Manville Low Pressure

Manville Covering Co.

2.87

20.7

1.25

Manville Magnesia Asbestos

Manville Covering Co.

2.88

20.8

1.50

65

Magnabestos.................

Keasby & Mattison Co.

2.91

21.0

1.12

48

Moulded Sectional

H. F. Watson..........

3.00

21.7

1.12

41

Asbestos Fire Board.........

Asbestos Paper Co___

Philip Carey Co.......

3.33

24.1

1.12

35

Calcite

3.61

26.1

1.12

66

Bare Pipe

13.84

100.