Page 136 - Centrifugal Pumps Design and Application

114 Centrifugal Pumps: Design and Application

Figure 9-1. Specific speed and impeller profiles.

Configurations

There are three primary types of vertical pump configurations that are
used for a broad range of applications.

Well Pumps

Designed to be installed in cased wells, these pumps consist of a multi-
stage pumping element or bowl assembly installed at sufficient depth be-
low the dynamic water level (the water level when the pump is operating)
and with sufficient NPSH to preclude cavitation. The subject of NPSH is
dealt with in detail Chapter 8. The bowl assembly, as illustrated in Figure
9-2, consists of a series of impellers mounted on a common shaft, and
located inside diffuser bowls. The number of stages is determined by the
height to which the liquid must be raised to the surface plus the design
pressure required at the surface. The bowl assembly is suspended from a
segmented column pipe mat directs the flow to the surface where the col-
umn pipe is attached to a discharge head. The column also houses the
lineshaft with bearings for transmitting the torque from the driver to the
bowl assembly. The discharge head, in addition to providing the required
connection to the customer's piping, also serves as the base for the driver.
The driver can either be a direct electric motor drive, typically of hollow
shaft construction, see Figure 9-3, or a right angle gear drive powered by
a horizontal engine or turbine. The discharge head must be supported on
a foundation adequate to carry the water-filled weight of the pumping
unit plus the driver weight. However, the hydraulic thrust developed by
the pump impellers is not transmitted to the foundation.