Centrifugal Pumps Design and Application 2nd ed - Val S. Lobanoff, Robert R. Ross (Butterworth-Heinemann, 1992)

36 Centrifugal Pumps: Design and Application
* Establish volute width. In determing the width of the volute, the need
to accommodate impellers of different diameter and ba must be considered.
Distance from the impeller shroud to the stationary casing
should be sufficient to allow for casting inaccuracies yet still maintain
a satisfactory minimum end play. The values shown in Table 3-1
reflect those published by Stepanoff and are reasonable guidelines,
Volute width = 1.09 x 1.75 = 1.9 in. (say 2 in.)
* Establish cutwater diameter. A minimum gap must be maintained
between the impeller diameter and volute lip to prevent noise, pulsation,
and vibration, particularly at vane passing frequency. From Table
3-2, D 3 = D 2 x 1.07 = IP/a x 1.07 = 12 7 /i6 in.
Impeller design data shown in this chapter are applicable to:
• Specific speeds from 400 to 3,600,
« Open or closed impellers.
» Volute-type or diffuser-type casings.
• Single- or multi-stage units.
« Vertical or horizontal pumps.
• Single suction or double suction impellers.
In establishing discharge geometry for double suction impellers, use
factors as given in this chapter. Do not divide the specific speed by
Table 3-1
Guidelines for Volute Width
Volute Width
Specific Speed
ba
Ns
2.0 b 2 < 1,000
1.75hz
1.6b 2
1,000-3,000
> 3,000
Table 3-2
Guidelines for Cutwater Diameter
Specific Speed
Cutwater Diameter
N s
D^
600-1000 D 2 xl.05
1000-1500 D 2 xl.06
1500-2500 D 2 xl.07
2500-4000 D 2 x 1.09