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 operate and maintain. The following considerations apply in the design of
aboveground distribution systems.
(a) Spans. The maximum spans between pipe supports for straight pipe
runs depend on pipe size. Maximum spans for steel pipe and rigid copper
tubing are shown "in tab' e 5-1.
Pipes are usually held in place by U-shaped or
( b ) Pipe Supports
s i m i l a r type clips firmly secured to support structures. The support
structures may be walls columns, brackets, concrete pedestals, steel frames,
or treated wood frames. C l i p s fit closely around the pipe; however,
s u f f i c i e n t clearance is p e r m i t t e d to allow for longitudinal movement during.
normal expansion and contraction. At anchor points, t h e pipe is firmly
clamped to the structure. The hangers are rigid or braced, if necessary,
where piping hangs from ceiling beams. This reinforcement prevents "whipping"
of the pipe should a break occur while the line is under pressure.
( c ) Elevation Clearance. F o r distribution outside buildings,
aboveground overhead lines may be located as little as 12 inches or as much as
22 feet above grade. The clearance above roadways is from 14 to 16 feet for
a u t o m o b i l e and truck traffic. F o r railroad crossings, the clearance is
22 feet above grade. The minimum height for installations at low elevations
s h o u l d be sufficient to clear surface water.
(d) Pitch of Aboveground Lines. Air lines are pitched down a minimum of
3 inches per 100 feet of length, i n the direction of airflow, to low points
where the condensate is collected.
Maximum Span for Pipe
TABLE 5-1.
S t d . #t.
Copper
Steel Pipe
Tube Type
K
Diameter
40 s
( f e e t & inches)
(feet & inches)
(inches)
1/2
5'-0"
3'-9"
3/4
5'-9"
4'-3"
1
5'-0"
6'-6"
1 -1/2
7'-6"
5'-9"
8'-6"
6'-6"
2-1/2
9'-3"
7'-3"
3
10'-3"
7'-9"
3-1 /2
11'-0"
8'-3"
4
11'-6"
9'-0"
5
12'-9"
10'-0"
6
13'-9"
10'-9"
8
15'-6"
10
17'-0"
12
18'-3"
(1
inch
=
0.3048m)
5-6
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