Page 221 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

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5.8 Materials of Construction 183

EXAMPLE 5.13 FREEZING INDEX AND FROST DEPTH REQUIREMENT IN NORTH AMERICA
In the absence of daily readings, the value of freezing index F may be approximated by equa-
tions 5.12a and 5.12b, using the U.S. customary units and the SI units, respectively. Determine
the freezing index of a northern state in the U.S. assuming the coldest monthly temperatures
recorded are:

T m , F T m , C
December 23 5
January 26 3.33
February 24 4.44
March 31 0.55

Solution 1 (U.S. Customary System):
©T m = 23 + 26 + 24 + 31 = 104
F = (32n -©T m ) * 30.2
= (32 * 4 - 104) * 30.2
= 724.8
d = 1.65F 0.468
= 1.65(724.8) 0.468
= 35.98 in. 7 12 in. Select 36 in. of fill material

Solution 2 (SI System):
©T m =-5 - 3.33 - 4.44 - 0.55 =-13.32
F = [0 -©T m ] * 30.2
= [0 - (-13.32)] * 30.2
= 402.26
d = 55.18F 0.468
= 55.18(402.26) 0.468
= 913.46 mm 7 305 mm. Select 1 m of fill material

5.8 MATERIALS OF CONSTRUCTION

Selection of pipeline materials is based on carrying capacity, strength, life or durability,
ease of transportation, handling and laying, safety, availability, cost in place, and cost of
maintenance. Various types of iron, steel, reinforced concrete, and fiberglass are most used
for water transmission pipes, but plastic pipes are now being made in the smaller sizes.
Other materials may come into use in the future.

5.8.1 Carrying Capacity
The initial value of the Hazen-Williams coefficient C hovers around 140 for all types of
well-laid pipelines but tends to be somewhat higher for reinforced-concrete and fiberglass
lines and to drop to a normal value of about 130 for unlined cast-iron pipe. Cast-iron and