Pump Alignment and Coupling Issues 2

[cleveland180]

Hello everyone,
I am looking for some input on a problem I am having with one of our pumps.
Every Lovejoy we have installed ends up being destroyed.

I think our issue is that fact that someone designed the counterbalance for the pump to be bolted to our lovejoy coupling. I think this is causing misalignment at speed, even though everything seems within spec. when the machine is off.
Does this sound reasonable?

Thanks,
David

 

[MikeHalloran]

No.

If I had to guess, and since you didn't tell us diddly-squat I'll have to, I'd guess that someone there didn't read or didn't understand the Lovejoy catalog, and picked the wrong coupling.

Why not start by telling us what kind of pump it is.

Mike Halloran
Pembroke Pines, FL, USA

 

[cleveland180]

Mike,

What we have is a three stage Methane compressor, each throw is oriented 90degrees from the other, so it looks like a "T".

At first we used a lovejoy that was far too small, and was a straight jaw. Then we upgraded the spider to a urethane, that ended up failing as well. Next we upgraded to a much larger straight jaw, and yet again the spider failed.

Since I started I have been troubleshooting all the old issues with this pump, and I want to use a curve jaw "zero backlash" coupling, since the compressor is constantly loading and unloading. I just have to convince my seniors it is worth a shot.

Thanks,
Dave

 

[macmil]

It might be worth while looking at a Magnadrive magnetic coupling.

 

[cleveland180]

Those are really cool couplings, sadly they do not make a coupling small enough for my application. I wish they did though.
My motor drive shaft is only 7/8" on this pump. I guess I can just keep on going to larger and larger lovejoys until I fill the inside of the housing...

 

[Strong]

What is the shaft speed and HP rating of the compressor?
What is the available space for a coupling? Length and Diameter/width

Walt

 

[cleveland180]

Motor is 2hp and runs at 1740rpm.

Length available is about 7 inches, Diameter is about 6 inches, if I had to guess.

The most recent coupling we used was a L100 and although that was somewhat large, we could possibly install a L110.

One thing that is really frustrating is every time I talk to a LJ rep I always get told a different story.

 

[TenPenny]

In what way is the coupling failing? 2 hp 1800 rpm seems awfully small to be having coupling issues.

 

[cleveland180]

It does seem like it should have no real issues... I used to work at a refinery and we had much more demanding pumps with less issues than this little compressor.

The issue is the spider (cushion) is getting completely chewed up by the constant loading and unloading, and ends up as dust in the bottom of our coupling housing ... The spider fingers that were under load are completely gone, and the ones not under load are flawless.

I have been told it was misalignment, but have a hard time believing that because the housing is designed to ensure alignment.

 

[MikeHalloran]

I agree it's not a misalignment problem, unless the shafts are actually at an angle. I'm assuming the housing interface is something like a C-face motor's. Correct me if I'm wrong.

>>>I just have to convince my seniors it is worth a shot.<<<
Huh? A complete Lovejoy jaw coupling in that size costs what, ten bucks, retail, delivered?

Can you work your way back from process conditions through the compressor crank geometry to get an idea of the maximum loads?

Since you give no hint of anyone, ever, having done any analysis of the problem, maybe the simplest quickest solution is to just go ahead and use the biggest coupling that will fit in the housing.






Mike Halloran
Pembroke Pines, FL, USA

 

[hydtools]

Looks like it is time to not trust the 'housing designed to ensure alignment'. The alignment may be changing under load.
Check alignment.
Try a urethane spider.

Ted

 

[cleveland180]

Mike,
We had our force analysis outsourced, so everything that is done already is simply a trust of their judgement. I wish I could just go ask whoever came up with this design, but they are unavailable.
And it's not the cost of the Lovejoy, but rather the cost of our assembly time. Also I have only been here for a month and a half, and I feel like every decision I make has to be sold to everyone before I can move forward (frustrating, but also encourages me to educate myself before spitting out an idea).

Ted,
I have ordered an window to be cut in our coupling so that I can actually see what is happening under load.
Our first two ventures with the urethane ended poorly, as can be seen in the picture I attached.

Thank you everyone for your help so far!

----Dave

 

[MikeHalloran]

You also have "New Guy Mojo", which enables you to ask for and receive stuff that the old hands have been bitching about not having for years.

Use it while you have it; New Guy Mojo usually expires when the next new guy falls off the turnip truck.

This would be a good time to track down and study the report of the outsourced analysis. It may very well have predicted the problem you face, and been ignored, or more likely, not even read.



Mike Halloran
Pembroke Pines, FL, USA

 

[JJPellin]

I don't care much for assumptions. You know what they say about you and umption. I would check all of the following:

Are the shafts straight? Check run-out on the bare shafts. It should be less than 0.003”.
Is the fit between the hub and shaft correct? 0.001” to 0.002” loose should allow for easy installation and removal.
Are the hubs bored concentric? Check the run out on the installed hubs. It should be less than 0.003”
Is the alignment acceptable? Sweep concentricity from each shaft to the pilot fit that aligns them to each other.
Is the axial spacing correct? These couplings are supposed to have 1/16" to 1/8" axial space.
Is the spider material correct?
Does either shaft have axial play in service that is changing the axial spacing?

If this is a reciprocating compressor, the load oscillates and an elastomeric coupling might not be a good idea. Try a little gear coupling with a nylon sleeve. If you are set on a rubber element coupling, try a little Woods coupling with a rubber element.


Johnny Pellin

 

[TenPenny]

The Lovejoy catalog, under the table of service factors, says that reciprocating machines need factory assistance for selecting...

 

[cleveland180]

Mike,
Thanks for the advice, I will try to use my "New Guy Mojo" to get my hands on a LoveJoy sampler pack. I think I can get our machinist on my side, and I will start with a large curve jaw and work my way down until I find our proper coupling.
My only complaint is that you made me laugh when I read your post and our drafting guy gave me a dirty look. haha

 

[cleveland180]

TenPenny,

Yeah, That is what they say, and all three times I have called I have gotten a different opinion on what we "need" and we have broken all of them... with the exception of one engineer there I have been disappointed.


JJPellin,

I will make sure that the next time we have this comp apart that I get some time with it and a dial indicator. There is no axial play, both bearings in the compressor are brand new , as are the motor bearings, everything looks great. I will keep you guys posted on what I find as far as measurements go.
Since when our compressor and motor go together they form a sealed unit, the tolerances are pretty tight,that is why I am trusting the shafts to be aligned, but I don't see any harm in checking !

Thank you all!

 

[macmil]

Hello cleveland180,
check out the Magnadrive MGE-01
mac

 

[hydtools]

Maybe a Para-flex if you have misalignment that cannot be fixed.

http://www.dodge-pt.com/products/pt_components/couplings/paraflex_coupling.html

Ted

 

[ElliotWilson]

Cleveland180,

I'm terribly sorry to hear you have struggled to get good answers on troubled Lovejoy application. As an member/employee of Lovejoy, customer service is something we take great pride in... and is very much our internal #1 priority.

>> Yeah, That is what they say, and all three times I have called I have gotten a different opinion on what we "need" and we have broken all of them... with the exception of one engineer there I have been disappointed. <<

To address your immediate need, please call Lovejoy's main number (630) 852-0500, and ask to speak directly with Charlie Mudra. Charlie is Lovejoy's primary product manager for L-line couplings... and also knows the rest our products (and the industry inside and out). ...I have already told him to expect a call from you.

Looking towards the future, I would really appreciate you sharing with Charlie the pain points you experienced when trying to trouble shoot your problem... as well as any recommendations on how we could better serve you in the future.

Thank you for your patience... and, again, please accept my apology on behalf of Lovejoy.

Best regards,
Elliot Wilson