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RGf

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Reply with quote  #1 
Attached are a couple of pictures of a new KSB boiler feedpump Type HOC and the doweling arrangement. My question is what does the horizontal pin do for us? Is it required? I haven't seen this orientation of doweling before.  If we are going to use the dowel pins we would need to drill the new base in place which is a chore. I've read some of the older posts on the other board that discussed the pros and cons of doweling but I'm making the assumption here that everyone was discussing the "traditional" vertical pins. According to the KSB installation manual the dowel pins are installed to insure the alignment stays true.

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jpeg BFP_dowel1.jpg (118.26 KB, 56 views)
jpeg BFP_dowel2.jpg (117.13 KB, 55 views)

Danny Harvey

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Reply with quote  #2 
I've never seen that before but I guess it accomplishes the task of fixing the alignment of the pump. Are the pipes already in place and aligned?

I wouldn't want to try to drill that hole, either.
John from PA

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Reply with quote  #3 
I looked at the API pump spec with reasonable care and I can't find anything that addresses vertical baseplate dowels, let alone a horizontal type.  Machine components, like upper bearing to lower bearing alignment are covered.  

The use of dowels in general is an arguable practice, some people just don't use them and you can find references on the web discussing the topic (see http://vibralign.com/shaft-alignment/dowelling-machinery/).  I believe the practice dates back to the U. S. Navy.  A ship of course has some unique deflections to the hull in heavy seas so maintaining alignment is also a concern.
RGf

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Reply with quote  #4 
John-I have that paper also. I guess I will contact KSB and see if they have any technical info on these puppies. The standard response form the powers to be is of course they are required. As the bolting is G8 and the torque values are pretty hefty I'm thinking machine movement after alignment and torqueing would not be an issue. I'm inclined to suggest we forgo these pins but as any PdM/CBM guy knows-you can only recommend not demand.....
MachDiag

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Reply with quote  #5 

I performed a laser alignment on one of these (700 HP, Type HJC) for a customer yesterday.  Looks like your pump is brandy spanking new, no half dowel hole.  Mine was a rebuild and reinstalled on the same machine base.  When I arrived onsite the piping had all ready been reinstalled and the pump was hanging there on the piping, no way the pins would go back in without causing increased pipe strain.  The customer had two calls in to the KSB rep, but did not get a call back yesterday while the alignment was being done.  It was decided that the dowels would >>not<< be installed, and to proceed with the alignment.   

  Boiler Feed Water Pump.jpg

I came up with an idea to install a piece of ~1/2" x 2-1/2" (plus/minus) square stock at the front of the coupling side pump feet, welded to the base and to the pump foot on each side.  The idea of using the square stock is so the welds can be easily ground off and the piece removed without causing immediate distress to the surfaces of the pump and foot mounting areas. 

When I called the customer back today to suggest the installation of the square stock locking keys, he informed me that the KSB rep had just called him back.  The rep mentioned that the pins are not intended to be reinstalled after a rebuild and that it'd likely be difficult to reinstall them, based on how the pump in built in stages, etc.  The rep talked him about welding some pieces of key-stock to the pump base next to the pump feet on the suction side, but that it was considered optional.  My customer was somewhat pleased that I had more or less the same idea as what the KSB rep had in mind.      

Don't forget to measure the axial float of the pump shaft, set and try to maintain it during alignment, checking afterwards as well. 

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dmcmmc

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Reply with quote  #6 
Some rolls on my paper machine have bearing housing bases that are machined like that and use a round key to ensure proper alignment during roll changes. The use of a round key instead of a square one makes it easier to line up the key way and key because it kind of self aligns and doesn't have to be perfect when the roll is set down on the base plate.
RGf

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Reply with quote  #7 
MachDiag-great information -This is the way we are going to go after buy in from our pump guy. We will take care in welding as to not create excessive heat to prevent warping the feet and causing another issue. Found out that one of the bolts (ODE) on the old pump was bound up in the axial direction so it will be interesting to see how the new one goes in.
Walt Strong

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Reply with quote  #8 
I disagree with the concept of welding key stock to the pump base and to the support base. It would not achieve the same purpose as the original dowel pin. The horizontal dowel pin provides restraint perpendicular to the pin while allowing sliding in-line with the pin. I have seen various schemes for restraining a pump base while allowing for differential thermal movement in a controlled direction. It is surprising that the pump OEM would supply dowel pin for the new pump, but not require it for a replacement pump installation. I have used welded key stock, but the key was only welded to the support base and not to a bearing housing or to a pump base. I have seen some pump base bolts that were supposed to be loose and not tight, so it is highly recommended to check the OEM pump installation requirements.

Walt
RGf

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Reply with quote  #9 
"The horizontal dowel pin provides restraint perpendicular to the pin while allowing sliding in-line with the pin" this gets back to my original confusion or misunderstanding on what we have here. The installation instructions call for securing the pin end DE (suction) side of the pump by fully torqueing the base bolts while only tightening the ODE bolts so that you would need a hammer to move the shims. This allows the pump to grow away from the drive coupling which is perpendicular to the pin orientation. If the pins allow for movement in line with the pins then the pins have no effect on securing the alignment in the horizontal direction. Am I missing something here?  or am I dazed and confused due to the outage madness.........
Walt Strong

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Reply with quote  #10 
"If the pins allow for movement in line with the pins then the pins have no effect on securing the alignment in the horizontal direction."
That would be correct, but the OEM should provide a complete explanation of how the original pins worked. The OEM should also offer an alternative retrofit design with either pins or keys to comply with the original design requirements. I was surprised to see the photograph above with his shims placed on of the pump base that were apparently not there for the original installation.

Walt
MachDiag

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Reply with quote  #11 

Quote:
Originally Posted by Walt Strong
... I was surprised to see the photograph above with his shims placed on of the pump base that were apparently not there for the original installation. Walt

Without the stack of shims, the dowel hole would end up being a squished oval shape.  If the pin were in place without the shims, the pump foot would be supported only by the pin.  By appearance it'd seem the dowel hole was likely drilled with a stack of shims in place.  The re-used shims in my photo could be special OEM made, or European, but not typical US "B" shims and not hand cut.  The outside leg of each shim was shorter on the pin side, not sure it looked like a drill bit had made it shorter though.  The sister pump next to this one also has dowel pins and a stack of shims under each inboard pump foot. 

It does seem clear by appearance that these dowel pins offer good restraint for movement in an axial direction, with little to offer in a horizontal, side to side direction.  If this is intentional, I'm curious as to why the manufacturer would be okay with some horizontal, side to side movement?             

Ralph Stewart

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Reply with quote  #12 
Have you considered using the self fabricated  "pusher" type attachment?

They work well on most, but maybe not all situations. Depends on the equipment's design,

And have dual purposes at each foot, when installed correctly.

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Ralph Stewart
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MachDiag

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Reply with quote  #13 
Quote:
Originally Posted by Ralph Stewart
Have you considered using the self fabricated  "pusher" type attachment?...


Like as in a Jacking Screw?  Don't know why it slipped my mind, but there is a pair of opposing jacking screws that locate on a protruding boss on the bottom (centered at 6-o-clock position) of both the inboard and outboard end of the pump base.  You can see one of these in the first photo on the original post. After the alignment of my pump, I snugged up each one, and the accompanying jam nut as well.  The jam nut feature on each screw more clearly indicates to me now that the screws are intended to be positioned up against the boss to keep the >center line< of the pump in place. 

If like what I believe Walt is thinking, maybe it'd be best to weld the piece of key stock to the pump's base, but not the pump foot.  Let the lower jacking/locking screws keep the center line of the pump in place and allow the housing with mounting feet expand with thermal growth during operation if it wants to?
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