Page 40 - HVAC Pump Handbook

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Piping System Friction
Piping System Friction 37

TABLE 3.1 Maximum Water Capacities of Steel Pipe (in gal/min)

Maximum Hydraulic
Size, in Schedule flow, gal/min Velocity, ft/s Loss, ft/100 ft radius, in
02 40 00,045 4.3 3.85 0.5
1
02 ⁄ 2 40 00,075 5.0 4.10 0.6
03 40 00,130 5.6 3.92 0.8
04 40 00,260 6.6 4.03 1.0
06 40 00,800 8.9 4.03 1.5
08 40 01,600 10.3 3.82 2.0
10 40 03,000 12.2 4.06 2.5
12 40 04,700 13.4 3.98 3.0
14 40 06,000 14.2 3.95 3.3
16 40 08,000 14.5 3.49 3.8
18 40 10,000 14.3 2.97 4.2
20 40 12,000 13.8 2.44 4.5
24 40 18,000 14.4 2.10 5.7
30 20 30,000 14.6 1.61 7.3
36 36-in ID 45,000 14.1 1.18 9.0
42 42-in ID 60,000 13.9 0.95 10.5

TABLE 3.2 Total Owning Cost of Piping
Amortized first Annual Total annual
Pipe size, in cost per year operating cost owning cost
12 $12,000 $16,000 $28,000
14 14,000 12,000 26,000
16 17,000 10,000 27,000

Obviously, the total owning costs of the piping system should be gen-
erated for each application. The derivation of these data is beyond the
scope of this book, but there are programs available for computing
these costs in detail.

3.1.1 Maximum capacities and velocities
of actual piping
Table 3.2 is a general recommendation to designers for the maximum
capacity and pipe velocity for standard sizes of steel pipe. One basis
for this information comes from ASHRAE Design Study RP-450,
which researched the literature available on pipe velocities and result-
ing friction. This research paper is an excellent document for reviewing
the history of and literature on pipe friction and maximum allowable
water velocities.
It is obvious that Table 3.2 is but a preliminary road map for the
knowledgeable piping designer. With the present information avail-
able, the pipe designer must rely on actual, personal experience.

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