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INSTALLATION INSTRUCTIONS
6
ITEM 1
Sharp Angle
ITEM 4
Long Radius Bend
ITEM 2
Rounded
Outer
Corner
ITEM 5
Splitters, or turning vanes
installed in sharp angle
bend
ITEM 3
Rounded
Corners
ITEM 6
Splitters in rounded
corner bend
EDDIES
EDDIES
ABRUPT EXPAN-
SION
SMALL
DUCT
EDDY
LOSSES
LARGE
DUCT
FIG. 2.9
Abrupt expansion results in excessive pressure losses.
R
W
D
R
W
RR =
Radius Ratio (RR)
or RR = 1.5
FIG. 2.4
PREFERRED
(Standard)
FAIR
POOR
NOT ACCEPTABLE
Various Elbows Showing Radius Ratios
FIG. 2.3
Rb
Ra
D
W
CR =
Ra
Rb
Curve Ration (CR)
Optimum Reading CR = .05
FIG. 2.5
Ra
R
Rb
Rb
Ra
1
R
R
2
1
CR =
R1 = 2 Ra
CR = .25
CR =
R1 = 2 Ra
R2 =
CR = .15
Ra
Rb
Ra
Rb
(Rb - R1)
2
+ Ra
FIG. 2.6
Using Splitters to reduce resistance.
FIG. 2.7
Different ways of making a 90 degree bend. Some
involve greater pressure losses than others.
FIG. 2.8
Pressure losses occur with abrupt reducing fittings.
ABRUPT
CONTRACTION
SMALL
DUCT
LARGE DUCT
EDDY
LOSSES