Page 328 - Centrifugal Pumps 2E

Chemical Pumps Metallic and Nonmetallic 293

Figure 15-9B. Partially scalloped open impeller.

Casings

Casings for the ANSI chemical pumps have centerline discharge and
suction both in the horizontal and vertical pumps. This makes it easier for
laying out the piping in a system as well as reducing the nozzle loading.
This is because the centerline nozzle eliminates the moment arm from the
centerline of the casing to the centerline of the nozzle that exists with
tangential discharge (Figures 15-10A and 15-1 OB).
On the horizontal casing, the centerline discharge results in a cutwater
being approximately 30° off the centerline allowing the casing to be self
venting. The casings are designed so that the rotor can be removed from
the back without disturbing the suction and discharge piping. The gaskets
of the casing are atmospheric confined so that the internal pressure can-
not push the gasket out, as could occur with a Ml, flatface gasket. The
flanges are 150 ASME flatface with an option of a raised face for steel
and alloy material casings. There is the option of 300 Ib. flanges for both
the suction and the discharge on the steel and alloy casings. In the chemi-