The commonly used angles of inclination for screw pumps are 30o, 35o and 38o. For screw pumps of relatively high lifting head, like over 6.5m, angle of inclination of 38o is normally used. However, for relatively lower head and high discharge requirement, angle of inclination of 30o shall be selected. In general, for a given capacity and lifting head, the screw pump diameter is smaller and its length is longer for a screw pump of 30o inclination when compared with a screw pump of 38o inclination.
To increase the discharge capacity of screw pumps, a larger number of flights should be selected. In fact, screw pumps with 2 flights are more economical that that with 3 flights in terms of efficiency and manufacturing cost. Moreover, the discharge capacity is also determined by the screw pump diameter and sizes of 300mm to 5000mm are available in current market.
This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.
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