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The Practical Pumping Handbook ........ i iiiiiiiiiiiiiiiiiiiiiiii iiiiiii iiiiiiiiiiiii iiiiiiiiiiiiiiiii iiiiiiiiiiiiiiiiii iii ................... i

1. Check the casing register fit and gasket surface for concentricity,
parallelism and perpendicularity.
2. Skim the wear ring fit by 0.001 to 0.002 inches, to ensure
concentricity with the registered fits.
3. Machine a new wear ring with an OD of 0.002 to 0.003 inches.
larger than the casing bore.

4. Install the wear ring in the housing and lock it into place by either
tack welding in 3 or 4 locations, or by set screws. Once the set
screws are secured, peen the ring to prevent them from backing
out.
5. Machine the I.D. of the wear ring to ensure the necessary
clearance for the impeller in accordance with the manufacturer's
instructions.

6. Check the casing register to ensure the correct clearance of
0.0004 inches, or less between the casing register fit and the back
cover or frame adapter.
7. Check to ensure that the register fit is parallel to the register fit
centerline within 0.002 inches, or perpendicular to within 0.001
inches, as appropriate.
8. The gasket surface also should be cleaned up to have a maximum
of 0.003 inches of runout and be free from any pitting or
scratches in the sealing surface. In addition, it should be
perpendicular to the register fit centerline within 0.002 inches.
While a closed impeller pump is being reassembled, check the radial
clearance between the impeller and casing wear rings as this will provide
a good indicator of the assembled alignment between the mating parts.
The radial clearance should be equal to or within 0.001 inch around
the diameter.

12.6 Dismantling the back pull-out assembly

As the assembly is being dismantled, any shims under the beating
housing foot should be collected, marked and stored for inspection.
This also applies to the coupling hub and key.
When attempting to remove an impeller, it is important never to apply
heat as it may cause an explosion as a result of trapped fluid, possibly
causing severe personal injury and property damage. In addition it is
recommended that heavy work gloves be used when handling an open
impeller as the vane edges may be sharp enough to cut.

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