Hi Alex,

Have look at:

http://www.renold.com/nmsruntime/sav...ID=497&sID=467

Also important for your other thread.

The documentation on this website gives more and to the point information about the functioning of a fluid coupling in a drive train.

There are overload devices for fluid couplings, s.a. slip detection and remote temperature detection.

These instruments can switch off the e-motor in case of failure or stalling.

Have a nice day

Teus ■

In the old days of the National Coal Board they used to test above ground all equipment going underground. In the case of armoured face conveyors one of the tests was to "sprag" a running chain (with a large piece of I section). Nothing was supposed to happen until the fluid coupling blew it's fuseable plug. The film I saw was impressive, although I'd have liked to see it happen in the flesh!

Normally chain conveyors are fitted with rotation monitors on the non-drive shaft to switch off the supply in the case of the chain slowing down or stopping. Additionally all the fluid couplings I've ever used have had fuseable plugs to protect the coupling. ■

Originally Posted by alex-kaveh

Dear All,

Can we use fluid coupling in an application like drag-chain conveyor where there is a possibility of stalling? If stalling occurs what will happen to fluid coupling? over heating? ... if yes, does it mean that we can not use fluid couplings in the above mentioned applications?

Dear Mr.Alex,

Why don't you use speed sensor ( Zero Speed Switch) ?

Rgds, ■

You can happily use a fixed fill fluid coupling in this application, although I would suggest that you use one that does not have a delay chamber attached.

In fluid coupling terms, this is a constant torque application, so apart from offering the motor a no load start, the other primary function of the coupling would be drive train protection.

All fixed oil filled couplings have fusible plugs fitted to protect both the coupling and the drive train from damage. Due to the dynamics of the coupling design, the maximum amount of torque that can be delivered in a stall condition is limited, and when this situation does occur, the coupling fluid will quickly heat up, blow the plug, and empty the coupling of its driving medium. No damage is done to the coupling other than the fusible plug and oil.

All that needs to be done, is to remove the obstruction, refil the coupling with fresh clean oil, fit a new plug and you are on your way again.

Clearly this is messy, and sometimes, as Designer alludes to, the site will prefer to set the motor trips as the first line of defence, rather than rely on the coupling blowing its plug. The sprag test he refers too was to set the trip levels, once underground, the test was repeated periodically.

I can assue him the film of the sprag test is far better than the actual thing, it was not a pleasant experience when it went wrong!!! There are not many places to run, or in our case crawl on a coal face...

These days I am sure that the same results can be achieved without going to the levels of the sprag test.

Most good coupling manufacturers can give you an indication of the maximum full load torque of any of their couplings, and from this information it is possible to set the motor electrical trips appropriately. There will be a little bit of trial and error involved, but it is not rocket science to achieve. ■

Dear Experts,

Are there fluid couplings using water instead of oil? Other than cost ( a little bit to no environment effects ), what are the other advantages? Why do they prefer water ?

Thanks & regards, ■

Originally Posted by alex-kaveh

Dear All,

Can we use fluid coupling in an application like drag-chain conveyor where there is a possibility of stalling? If stalling occurs what will happen to fluid coupling? over heating? ... if yes, does it mean that we can not use fluid couplings in the above mentioned applications?

I would never use a fluid coupling as a means of coping with stalling.

Fluid couplings are designed to drive and not slip. Remember, it is designed to transmit the demand power (and more if you take into account the margin you have set for design load). The fluid used is a very heavy fluid. I have had to drain and re-fill a coupling and it takes hours to get the fluid out, even on a hot day.

On top of that, just think about the amount of energy you are going to be storing in the conveyor while it has stalled. What are you going to do once the stall condition is relieved?

I also noticed a comment on whether it could be use with water as the driving fluid. The short answer is NO. Even if someone designed a coupling that could use water, it would be more along the lines of a scoop controlled fluid coupling that also had a massive cooling system.

You need to use something else to cope with potential stalling, or eliminate the cause of stalling. ■

Originally Posted by waiwhite

I also noticed a comment on whether it could be use with water as the driving fluid. The short answer is NO.

The short answer is YES.

Well, if it's good enough for Voith it's good enough from me

http://www.voithturbo.com/satfluid-...p?id=6&LANG=en ■

Thank you Mr.Lyle & Mr.Designer.

Dear Mr.Waiwhite ,

The viscosity of fluid coupling oil is much less compared to other oil. i.e., they are lighter , not heavier.

Regards, ■

Originally Posted by Feco2008

You can happily use a fixed fill fluid coupling in this application, although I would suggest that you use one that does not have a delay chamber attached.

In fluid coupling terms, this is a constant torque application, so apart from offering the motor a no load start, the other primary function of the coupling would be drive train protection.

All fixed oil filled couplings have fusible plugs fitted to protect both the coupling and the drive train from damage. Due to the dynamics of the coupling design, the maximum amount of torque that can be delivered in a stall condition is limited, and when this situation does occur, the coupling fluid will quickly heat up, blow the plug, and empty the coupling of its driving medium. No damage is done to the coupling other than the fusible plug and oil.

All that needs to be done, is to remove the obstruction, refil the coupling with fresh clean oil, fit a new plug and you are on your way again.

Clearly this is messy, and sometimes, as Designer alludes to, the site will prefer to set the motor trips as the first line of defence, rather than rely on the coupling blowing its plug. The sprag test he refers too was to set the trip levels, once underground, the test was repeated periodically.

I can assue him the film of the sprag test is far better than the actual thing, it was not a pleasant experience when it went wrong!!! There are not many places to run, or in our case crawl on a coal face...

These days I am sure that the same results can be achieved without going to the levels of the sprag test.

Most good coupling manufacturers can give you an indication of the maximum full load torque of any of their couplings, and from this information it is possible to set the motor electrical trips appropriately. There will be a little bit of trial and error involved, but it is not rocket science to achieve.

Dear Experts,

I have come across an installation,Where a lot of O/M issues arises.

The drive is 900KW,6.6 KV, squirrel cage motor driving a bevel helical gearbox/pulley,through a fluid coupling.The fluid coupling is a delayed action fluid couplings with multidisc coupling on both the sides.

The disc of the coupling on both the sides disc breaks frequently and the vibration level of the system goes up.

Valuable opinion requested.

Rgds,

Narayanan Nalinakshan. ■

Originally Posted by Feco2008

....The sprag test he refers too was to set the trip levels, once underground, the test was repeated periodically.

I can assue him the film of the sprag test is far better than the actual thing, it was not a pleasant experience when it went wrong!!! There are not many places to run, or in our case crawl on a coal face...

These days I am sure that the same results can be achieved without going to the levels of the sprag test. .......

Dear experts,

1). Kindly request to explain about sprag test.

2). How to relate the oil quantity with the motor ampere ?

Regards, ■