Pump Repairs and Upgrades Standards
(starting with Vertical Turbines, VPRS,
Pump Repairs and Upgrades Standards
(starting with Vertical Turbines, VPRS, rev.2)
* When a customer needs a pump repaired, we usually go through an evaluation process before providing a quotation so we know exactly what it will cost for the repair/restoration. If I were in Purchasing, I would definitely go with the shop A (paper #1 = “Repair Standard for Vertical Pumps”, Pumps & Systems, February 2012, pp. 16-17) even though Level 1 is much more expensive than shop C. Considering this is basically a "blind" quote, I would have to consider the possibility that an overhaul might be necessary and it that event, I would have to go with Shop A's Level 3 quote as a measure to plan ahead, and not take the risk of spending $300,000 for what could have cost of $120,000.
Christi Prust, Magnatex Pumps, Engineering
* I would get a quote for all three levels (paper #1) of rebuild from all three repair companies. I would choose the repair shop that has the cheapest quote for level 3 repair, even if they are the highest price on a Level 1 rebuild. The difference in prices at level 1 are smaller than the difference in price at level 3. I think the payment department will be happy with that.
Pump School class attendee, February 2012, Georgia Power, Maintenance
* A pump user (maintenance/engineering) questions as to what type of a spider (column bearing retainer) retainer design to use? If not sure of the manner of columns-to-spiders design type, a concern may be regarding ability (by design) of proper alignment of the shaft centering within the columns, which can only be assured if all inner bores of bushings are very concentric from top to bottom. There are mainly three types of such designs used in the industry:
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option (a) option (b) option (c)
The first one (shown on left) has a spider clamped, with flanges not in contact, which makes it possible to over-torque the flanges and distort or break them. The portion of the flange surface in contact with the spider (radial and axial surfaces) must be machined very precisely, and the spider surface which contains the bushing itself, must also be very concentric to the spider OD. The non-contacting of the column flanges is a known industry concern.
The second option (in the middle) shows the spider sitting inside the column (welded to it), with flanges of the column in good contact, torques well with no concern of flanges distorted or broken. The column flanges themselves of course must be manufactured precisely, to make sure the radial fit is very tight (a few thousands), and the flanges surfaces must be machined flat and perpendicular to the radial surfaces. It is generally known as a better design in the industry.
The third option (on right) is usually used for the enclosed tube designs, but could occasional be used for the open shaft designs, where spider has an extended flange, sandwiched between the column flanges. All surfaces in contact must likewise be pricey, to ensure good centering, and no contact by the shaft to bushing.
Which of these options to use?
As we understand it, sometimes the end users had their installed design (a) changed/converted to option (b), to avoid problems they have been experiencing with repair shops not able to maintain these concentricity during repairs. Even though we understand that either options would (probably?) work fine when coming initially from the pump manufacturer as a brand new pump, but we also know the realities of the world, which are such that the next time the pumps gets repaired, option (a) may end up in more troubles, then option (b). We also wonder about option (c) because we feel that introduction of the extra sandwich in the middle between flanges of the columns adds another 2 surfaces to be worried about being concentric.
Thus, from the practical perspective, realizing that, should we have a (practical) concern for designs (a) and (c). We feel we do have a concern.
We would like to know the VPRS position on this, so that we can properly apply the best technical solution of a most reliable pump option.
Pump end user, March 2012