Page 67 - HVAC Pump Handbook

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Piping System Friction
64 The Basic Tools

are five different test projects completed as of this date. Other tests
on copper fittings are under consideration.
Some of these data should supplant the information in Tables 3.8
through 3.13. However, these tables provide information on fittings
not included in these tests.

The completed ASHRAE tests are:

Project no. Fitting size, in Material
968-RP 2, 4 Iron and Steel
1034-RP 12, 16, 20, 24 Steel
1035-RP 4 Steel*
1116-RP 6, 8, 10 Steel
1193-RP 6, 8, 10 PVC, Sch. 80

*The purpose of this test was to determine the effect of closely con-
nected fittings. The tests consisted of connecting two welded steel elbows
in four different configurations, which were (1) in plane, “Z” connection,
(2) in plane, “U” connection, (3) out of plane, torsional connection, and (4)
out of plane, swing connection.

Some very significant findings resulted from these tests. The follow-
ing is a synopsis of them:

968 RP. The K factor for these fittings demonstrated an apprecia-
ble variation, as the velocity changed from 2 to 12 fps. This varia-
tion is described in Fig. 3.6 for standard 2 and 4 in steel elbows.
Reducing elbows of the 2 and 4 in sizes are shown in Fig. 3.7.
The actual K factors when compared with published data are
shown in Table 3.14. New data for reducing elbows are shown in
both the reducing and expansion modes.
1034 RP. The variation in K factor for these larger-sized fittings
was not as pronounced as for the smaller sizes. Table 3.14 describes
this variation and compares the test data with past values for these
fittings. Significant, new data are provided for reducing fittings in
both the reducing ad expansion modes.
1035 RP. These tests proved that there is a reduction in the in the
friction loss of fittings when they are closely connected. There has
been an erroneous belief that bunching fittings together increases
the overall friction loss. This belief has been disproved before on
pump test stands. This report provides specific information on this
subject and Fig. 3.5 is typical of these findings. These tests are very
important, as some people in the pump industry have resisted the
development of factory-assembled systems and have argued that
closely assembling pipe fittings increases the friction loss of the
pumping system. These projects demonstrated that there may be an

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