Contact the manufacturer and see what they would recommend.

If the manufacturer does not want to recommend anything, then as the designer you might want to recommend the installation of a clutch to disengage the idling drive (either friction or dog). It is additional equipment, but better to resolve things now that after it has been built.

It is not just the fluid coupling that is the issue here, but all the drive components. ■

Originally Posted by ambhad

Just to inform that it is a reversible stacker-cum-reclaimer.

Really, the simplest solution would be to have dog clutches on both drives with one engaged at any one time.

Thinking about it, there must be really compelling reasons for having a 400 KW drive set duplicated on a conveyor when only one set is required to operate at any one time.

Apart from the cost, there is the maintenance and electrical requirements for two drive sets.

I have been involved in the conveyor design of large stacker/reclaomers and I have never used two drives with one in use at any one time.

As a matter of interest, what are the details of the conveyor? ■

Originally Posted by ambhad

1. What happens to the fluid coupling if it runs in reverse direction when the power to the drive motor is disconnected ? Since power is not transmitted, fusible plug may not melt or otherwise ?

2. What might be the problem with the motor in above case ? Will it generate power and act as brake etc. ?

Have you actually bothered to discuss this with the component suppliers

If not, why not

Don't you think that motor, gearbox, fluid coupling makers probably have the answers

If they don't, change to suppliers who do know! ■

Originally Posted by ambhad

I am not going in to the details of the conveyor profile since it diverts our attention from the main points I am interested to know:

1. What happens to the fluid coupling if it runs in reverse direction when the power to the drive motor is disconnected ? Since power is not transmitted, fusible plug may not melt or otherwise ?

2. What might be the problem with the motor in above case ? Will it generate power and act as brake etc. ?

My reason for asking about the details of the conveyor profile was to get some sort of handle on the issue. But no problem.

On your point 1, the problem here is that the fluid coupling is not designed to be driven backwards. The turning vanes are generally biased to be driven one way. It may not drive efficiently and may actually brake the conveyor. This is apart from it generating some heat.

The other thing here is the gearbox. It is the first element in being driven backwards. What do the manufacturers say about this? After all, they are the ones providing a warranty or have they waived that?

On your point 2, chances are that you have a caged rotor motor. If the coils are not energised, then it should not generate any power out. This is the problem. The resistance is friction. At speed, the fluid coupling output section will be turned backwards at the normal driving speed.

As I said before, you really do need a clutch at both ends. Even here, you need the clutch on the output side of the gearbox so that when disengaged, it does not turn anything other than the pulley.

But here's another thought. You say that in one direction you need 250 kW and in the other direction 400 kW but the client wants the two drives to be the same, so why not have a 250 kW drive at each end and drive both motors? With two 250 kW motors you will have smaller gearboxes, couplings, shafts, bearings, wiring, etc. You will still need a fluid coupling capable of being driven in reverse, but it will be smaller than two couplings capable of transmitting 400 kW each. Your steady state power draw in one direction might be 250 kW, but with a 400 kW motor, you are going to get the locked rotor torque, the pull up torque and the starting torque of a 400 kW motor so it is going to cause a few issues with take ups etc.

Your client might want to do certain things, but you are the one who is supposed to know so you give your client all the information and make a recommendation. After all, if they knew it all, they would not have got you in in the first place. Trust me, no matter what they say, if there are problems, you know where they are going to come ■

Originally Posted by ambhad

One of the fluid coupling vendor has confirmed there will be no problem, if the fluid coupling runs in idle mode. By the way may I get some details about dog clutch required at coupling point between pulley shaft and gearbox output shaft ?

You could try companies like Renold http://www.renold.com or http://www.hilliardcorp.com/overrunning-clutch.html ■