Goulds Pumps 3420 - IOM - Manual (Page 112)

108
3420 IOM 8/09
Impeller Description WR
2
Model 3420
To determine the WR
(2)
of an impeller:
1. For bronze impellers and water service, select the appropriate “wet” value at the desired diameter
from Table II or III.
2. For impeller materials other than bronze, and/or liquids with a specific gravity less than 1.0, proceed
as follows:
A. Determine both “wet” and “dry” values from Table II.
B. Multiply the “dry” value by the ratio of specific gravities of the impeller material and bronze
(See Table I for material specific gravities).
“Dry” value x
Sp Gr of impeller material
Sp Gr of bronze
. .
. .
= Answer (B) __________
C. Subtract the “dry” value from the “wet” value.
WR
(2)
“wet” - WR
(2)
“dry” + __________Answer (C).
D. Multiply answer (C) by specific gravity of the liquid.
Answer (C) x Sp. Gr. = __________Answer (D)
E. Add answers (B) and (D). This is WR
(2)
of the impeller in Lb.-Ft.
(2)
TABLE I
Material
Specific Gravity Bronze
8.86 Cast Iron
7.20 316SS
7.90