DO MAG-COUPLINGS SLIP?
DO MAG-COUPLINGS SLIP?
(OP)
I am working at a gold mine in Alaska. We have recently installed several mag-couplings on certain pumps which pump processing chemicals, gland water, potable water. They are installed on pumps with vfd's and without. My question is very general in nature; Does the mag-coupling have a certain amount of slippage on the output to the pump or is this "rock solid" technology" and if you know of a reference I could study on these I would appreciate that as well.
Thank You.
Thank You.





RE: DO MAG-COUPLINGS SLIP?
The amount of slip will increase with torque through the coupling.
I will search for something for your reference.
Adrian
RE: DO MAG-COUPLINGS SLIP?
RE: DO MAG-COUPLINGS SLIP?
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RE: DO MAG-COUPLINGS SLIP?
These couplings actually have an air gap, between the faces on the coupling halves.
RE: DO MAG-COUPLINGS SLIP?
In variable applications where the magnets are pulled away from the induction ring, the slip increase is non-linear.
RE: DO MAG-COUPLINGS SLIP?
RE: DO MAG-COUPLINGS SLIP?
An eddy current clutch / eddy current coupling has slip as a fundamental part of its operating principle. The eddy current devices are sometimes used as variable speed controls and can put up with outrageous levels of abuse, but are very lossy and run at blistering temperatures.
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If we learn from our mistakes I'm getting a great education!
RE: DO MAG-COUPLINGS SLIP?
There is no physical connection or mechanical connection between pump and motor. a magnet floats between two circular faces which is slipped on the end of each shaft. There is an air gap between the magnet and the faces. In some cases I have noticed some slight reduced flow. I am wondering if I decrease the air gap would that in fact increase my torque?
RE: DO MAG-COUPLINGS SLIP?
We are more connected to everyone in the world than we've ever been before, except to the person sitting next to us. Lisa Gansky
RE: DO MAG-COUPLINGS SLIP?
Yes, I noticed a 45 gpm loss in a water circuit that treats underground mine water. It is pumped through a sand filter and discharged to the river. Sand filtering is just one portion of the system. The filters go through several back flush cycles and the sand gets periodically changed. At this point in the process we are dealing with very clean water anyway, however the filters pose a restriction of flow and when I reinstalled the rigid coupling the flow came back up @45 gpm. I am pumping about 400 gpm. I strobed the two shafts and recently found a 181 rpm difference between motor and pump shafts. Without any literature at all on this coupling I was wondering if reducing the air gap would be worth my efforts to decrease the slippage.
RE: DO MAG-COUPLINGS SLIP?
I had a feeling that you wern't getting the whole truth about mag couplings not slipping. Every liquid, solid and gas is compressible, everything deflects under load and ... everything slips. It might not be much, but you know that it has to. Nothing is perfect. In fact I believe that you have almost proven as much with the 181 rpm difference between the pump and motor rpm that you have observed. If the motor speed was the same with both the mag and rigid couplings, we can find out how much slip there acually was. What were the motor speeds and the pump speeds with each type of coupling?
We are more connected to everyone in the world than we've ever been before, except to the person sitting next to us. Lisa Gansky
RE: DO MAG-COUPLINGS SLIP?
Magnetic couplings have slip!!!
We have a patented pump design for a variable flow pump. There is a magnet array on one side of a membrane and an induction ring on the other. The induction ring is attached to the impeller.
We vary the flow by moving the magnets away from the induction ring. The bigger the air gap, the slower the impeller.
Even when the air gap is reduced to its minimum, there is about 6-8% slip.
The neodymium magnets are sized to allows an amount of torque. If that torque level is exceeded, the slip increases.
So, even in the synchronous position...magnetic couplings do slip.
Adrian
RE: DO MAG-COUPLINGS SLIP?
Yes, it is obvious there is slip. I am truly getting familiar with what applications I can run these couplings and not have it affect certain pump circuits. The information you supplied me will help to research this further.
Thank You,
Scott
RE: DO MAG-COUPLINGS SLIP?
SOME magnetic couplings slip. Some do not.
Google magnetic coupling synchronous which will bring up a multitude of synchronous types.
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If we learn from our mistakes I'm getting a great education!
RE: DO MAG-COUPLINGS SLIP?
To prove this it will be probably be enough to monitor the temperature of the pump in the magnetic coupling area because the slippage generates heat
RE: DO MAG-COUPLINGS SLIP?
The other type, and an older design, is the 'slip ring' type of which were developed as the very first couplings, they are still available, butvtend tonne used for special applications such as hot liquids which become more viscous when cold which start up with slip to the impeller to ease the start up process. These are still quite rare in the current Market and very few manufacturers still make this type due to the very high costs and reducing marketplace.
Hope this clarifies things ?
Ash Fenn
www.cdrpumps.co.uk
RE: DO MAG-COUPLINGS SLIP?
So, with no mention in the original question of load or type of coupling, we can assume that we are all correct..can't we??
RE: DO MAG-COUPLINGS SLIP?
Perhaps the EEs out there see things through more of a binary mask.
Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso
RE: DO MAG-COUPLINGS SLIP?
Do we need to go back to basics and put a definition on "slip"?
For our magnetic clutch, 5% slip is good considering the amount of neodymium iron boron we use. More would reduce the slip, but its not cheap.
I guess for some 0.0001% may be excessive.
RE: DO MAG-COUPLINGS SLIP?
Magnetic couplings which consist of pairs of permanent magnets DO NOT SLIP. They rotate at the same speed until they de-couple.
RE: DO MAG-COUPLINGS SLIP?
So what does de-couple mean? If the flux breaks down between the rotating magnet pairs during transient torque loads, could that not be considered as slip. There would be a speed differential between the two halves of the coupling.
In the context of the original question, where slip is evident. It is safe to assume that the application features a coupling that does have an element of slip. Other applications that have massive permanent magnets and low torque would have no apparent slip.
RE: DO MAG-COUPLINGS SLIP?
are being used. No pipe strain to worry about, no precision alignments to worry about, less energy to run. But always carry a good strobe light...haha as I have found out.
http://www.youtube.com/watch?v=TtIkYbReMbk
Yes, we are talking about slip and how to accurately work with it.
Thanks all!!!....Scott
RE: DO MAG-COUPLINGS SLIP?
BigInch,
I'm an analogue guy.
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If we learn from our mistakes I'm getting a great education!
RE: DO MAG-COUPLINGS SLIP?
Scotty, I fear that there's few of you left out there.
Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso
RE: DO MAG-COUPLINGS SLIP?
Reducing the air gap will increase the torque handling of the coupling but.... there is a compromise as the wall of the can sit in the air gap and that has to hold the pressure. so pressure and wall thickness of the can will ditatate the minium air gap.
Is it decoupling at start up use a soft start. If it is decoupling when loaded check the can and bearings for particulate build up. Or use a bigger coupling size.