The impeller for one of N.Y.C. main sewage pumps was found "Practically Destroyed".
Possible Solutions:
Get a new impeller from the manufacturer. This involved a waiting period of
48 - 52 weeks, a good long term solution, which meant having the pump out of service for (1) one year.
Call in several vendors so that they could offer a more viable solution. Every vendor practically gave up; saying that since more than half of the impeller was missing, there was nothing that could be done.
Frontline’s Solution:
Rebuild the impeller as close as possible to the original dimension. The customer provided Frontline with a drawing of the impeller and we went to work. See detailed description below.
Click on the images
below to enlarge
This is what was left over of the 48"
diameter impeller.
We had a foundry cast a ring and set it at the right height following
a customer's
dimensional drawing.
Following the existing profile, we built a vane
made out of reinforced plaster. Then we cut out the
vane and sent it to a
foundry to be reproduced.
The
foundry cast
(4) four identical vanes (2-shown in photo).
We then trimmed off the existing impeller vanes uniformly.
The (4) four new vanes were carefully set in place
and welded to the ring and to the hub.
The I.D. and O D. of the
suction ring was then machined according to the manufacturer's specifications.
The impeller was then put thru
an extensive phase of hand grinding to bring the (4) four vanes to a uniform and dimensionally symmetric profile.
A stainless steel wear ring was then "shrunk on" and
pinned to the impeller.
The impeller was then secured to a shaft provided by the customer.
Impeller and shaft assembly being lifted and secured onto the balancing machine.
Operator getting ready to dynamically balance the rotor.
The Results Were:
The
entire job took only 5 1/2 weeks, allowing the customer
to put a very important piece of equipment back on line
at a fraction of the original cost estimate, and with
a much shorter downtime than originally anticipated.
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