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

 

[cleveland180]

Elliot,

I will be sure to give him a call, and I think the fact that you are on here, and actively helping your company out says a lot.
I hope I don't seem like a "Lovejoy Hater", I am not,your company has a great number of products and would be so big if the products were garbage. I am really hoping I wont have to step up to a SX80-4 coupling though... seeing as we are hoping to sell these compressors once we have the bugs worked out.

Thank you,
Dave

 

[cleveland180]

I meant the company WOULDN'T be so large, not would. My apologies

 

[btrueblood]

What temperature is the pump shaft running, or nearby pump housing? It's possible the temp. in a "sealed unit" could be high enough to fry the rubber spider?

 

[cleveland180]

btrueblood,

We actually did check that yesterday, We drilled a very small hole and slipped a thermocouple inside the housing, we found out that the temperature difference from the outside of the housing to the motor coupling was about 20 degrees F. Our coupling temp was close to 170F which is 20 degrees higher than Lovejoy recommends, but they said that we need to de-rate the spider at that point (150F). The current coupling should have been able to handle what needed it to do, so I am wondering if a jaw style coupling is a feasible option.I will talk to Charlie and see what he says.

 

[ElliotWilson]

Dave,
Glad to hear you’re not a hater, and that you called Charlie. ?
Charlie just swung by my office (we aren’t that large), and told me about your really cool application.
We are both cheering for you… and I know Charlie is ready to continue offering support through the duration.
Once everything is up and running, we’d love to see/share your application on our Facebook page (link found at the bottom of Lovejoy's homepage:

http://www.lovejoy-inc.com).

Best of luck!
-Elliot

 

[cleveland180]

Elliot,
I will be sure to let you guys know how things turn out! We are excited as well! Hopefully we can figure out this coupling deal soon, so we can move on to the fun stuff.

Thanks,
Dave

 

[racookpe1978]

And they lived happily ever after .....

8<)

OK, OK. So what did Lovejoy do to fix the problem? What other troubleshooting did you/they/the mechanics need to figure out what was going wrong?

(Inquiring readers want to know to know what to look for the next time ...) 8<)

 

[ElliotWilson]

Racookpe1978,

As I understand it, Dave was going to try out a curved jaw type coupling (in combination with several of the different polyurethane spiders available)... with the hope that one of these combinations would tune the coupling outside the system's natural frequency (which was unfortunately causing the previous elements to be destroyed).

Factors of safety and misalignment capability of the jaw coupling were well within limits... but, unfortunately, the coupling was sitting within the natural frequency of the system... leading to the spider overheating from within, then failing.

This failure type is seen most commonly with diesel engine applications, and Lovejoy does have a higher cost torsional coupling designed specifically for this type issue.

However, back in the real world... with production unit cost a major focus, Dave was reluctant to pursue any of the more expensive alternatives before exhaust his jaw options.

Given different spiders have different shore hardness, (speaking in lieu of any of his actual torsional data) it is possible that Dave will be able to construct a jaw coupling outside of his system's natural frequency that will meet his needs.

Hopefully he found a hub/spider combination that worked... but I haven't heard for sure.

 

[racookpe1978]

Thank you! I appreciate the troubleshooting.

 

[cleveland180]

We are currently using the curve jaw coupling with the yellow spider (92 shore I think). So far we have only been running the compressor at 1000psi, trying to get a baseline temperature on the coupling, but the temperature just keeps climbing. On a good note, we haven't noticed any shavings from the coupling, and hopefully can run a full range test soon .

Sorry I haven't been keeping up lately, I was T-boned by a Chevy Astro on Sunday and have been in and out of the hospital every day. I am too excited about work to stay away hahah!