Page 62 - HVAC Pump Handbook

Rishel_CH03.qxd 20/4/06 5:35 PM Page 59

Piping System Friction
Piping System Friction 59

TABLE 3.12 K Factors for Miscellaneous Valves (100 percent open)

Angle valve
Screwed Ball Butterfly
Size, in check Screwed Flanged valve* valve
1
⁄ 2 5.6 — — — —
3
⁄ 4 3.7 5.5 — 0.11 —
1 3.0 4.7 5.0 0.10 —
1
1 ⁄ 4 2.7 3.8 3.7 0.09 —
1
1 ⁄ 2 2.5 3.0 3.0 0.09 —
2 2.3 2.2 2.5 0.08 —
1
2 ⁄ 2 2.2 1.7 2.3 0.07 3.5
3 2.2 1.4 2.2 0.07 3.0
4 2.2 1.0 2.2 0.06 1.5
6 — — 2.1 0.05 1.0
8 — — 2.1 0.05 0.8
10 — — 2.1 0.05 0.7
12 — — 2.1 0.04 0.7
14 — — 2.1 0.04 0.6
16 — — 2.1 0.04 0.6
18 — — 2.1 — —
20 — — 2.1 — —
NOTE: Flanged check valves are assumed to have a K factor of 2.0 for all sizes.

Reducing bushings and couplings. The K factor for reducing bushings
can vary from 0.05 to 2.0. Replace them wherever possible with
threaded tapered fittings.
Sudden enlargements. Sudden enlargements such as reducing flanges
can have a K factor as high as 1.0. Replace them with tapered fittings
wherever possible.

3.4.1 Tapered fittings
There are a number of tests and equations for computing the K fac-
tors for tapered fittings. Like other fitting calculations, they are, at
best, approximate. Two of the most accurate calculations seem to be
those included in Cameron Hydraulic Data.

Tapered reducing fittings

2
d 1 2
K 0.8 sin 1 (3.8)
2 d
2
where total angle of reduction
d smaller, leaving pipe diameter
1
d larger, entering pipe diameter
2

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