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The Practical Pumping Handbook . . . .

between the mating faces of the frame adaptor and the pump casing
that has the potential to permit uneven torquing of the bolts. In the
event of a higher-than-normal pressurization of the casing by the
process system, this may cause a fracture of the adaptor.
The API design in Figure 1.9 bolts the back cover directly to the casing
and uses a confined controlled compression gasket with metal to metal
fits. The adaptor is bolted independently to the back cover and does
not play a part in the pressure boundary of the pump casing.

1.3.3 Mounting feet
Another difference between the two pump styles is the configuration of
the mounting feet. All ANSI pump casings are mounted on feet
projecting from the underside of the casing and bolted to the baseplate.
If these pumps are used on high-temperature applications, the casing
will expand upwards from the mounting feet and cause severe thermal
stresses in the casing that will detrimentally affect the reliability of the
pump. Operation at lower temperatures will not be affected by this
feature.

On the other hand, API pumps are mounted at the horizontal
centerline of the casing on feet projecting from each side of the casing
and bolted to pedestals that form part of the baseplate. This
arrangement provides the API pump with the advantage of being able
to operate with pumpage at elevated temperatures. As the pump comes
up to temperature in such cases, any expansion of the metal will be
above and below the casing centerline, and will exert minimal amounts
of stress to the casing, thus contributing to optimum reliability of the
pump.
The ability to handle higher temperature services is also evident in the
bearing housings of the API pumps, which tend to be much more
robust in design and also accommodate cooling jackets with a greater
capacity of cooling water.

1.4 The impeller

The impeller is secured on a shaft by which it is rotated. The liquid is
delivered to the eye of that impeller through the suction nozzle located
at the end of the pump. After the liquid enters the eye of the impeller,
the rotation creates the centrifugal force which moves the liquid out
along the vanes to the perimeter. As the liquid moves towards the outer
diameter, its velocity increases to the maximum that it achieves when it
leaves the outer diameter of the impeller.
In order to produce different relationships between the flow rate and

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