Banda,

Contact the coupler manufacturer for this information. It would also be advisable to obtain their Operation & Maintenance Manual.

Regards, ■

Take care in assessing the motor and coupling torque curve compatabilities. The fluid coupling fill level cannot be allowed to generate a torque output that exceeds the motor torque at the same speed point between the curves.

This is a common misunderstanding with operators, that more fill is less likely to stall the drives acceleration cycle and that the only penalty for more fill is harsher acceleration.

Again, if the motor torque does not exceed the fluid coupling torque at all speedsover the acceleration cycle, then the motor will stall where the fluid couling torque curve crosses over the motor output torque.

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com ■

Good morning Banda..

As my learned friends have rightly advised, the starting point is to get the "correct oil fill" from the coupling supplier.

In addition though, what I have found in practice , is that this is to be used as an initial guide.

I like to adjust the oil fills down to give a really nice soft start, but not too little oil so as to over heat and blow the plugs, even if you start the conveyor several times an hour.

Here it is good to guard the coupling to contain the oil if a plug blows, but use the same guard as a cooling duct. The fluid coupling acts as a fan, and will cool itself as long as the guard has provision for the hot air to escape nicely at the end.

Remember also that you must have sufficient oil to be able to drive the conveyor in an overload situation. If overloaded with the coupling filled with too little oil, the conveyor slows down. This can overload the conveyor even more and slow it down until it stops. It is now extremely difficult to start the overloaded conveyor up again.

If you have multiple drives, it is often wise to balance out the powers by adjusting individual oil fills. A small variation in pulley diameters and motor speeds makes a huge difference in the absorbed powers. By adjusting this out, you avoid the usual.. one drive overloaded and doing all the work.

Regards

LSL Tekpro ■

The business of correct oil fill is always a tricky one. If we consider short plant conveyors (long overland ones are different)operating conditions can have quite an impact on the required fill. For example the type and fixing of the skirts, tighness and fixing of the scrapers, general operating condition of the conveyor and finally the loading conditions that the conveyor actually has to accommodate in daily use all have to be considered.

The power drawn under operating conditions of an older installation rarely equate to the original design calculations since the design criteria used for the selection of the equipment is often out of touch with the reality of what the conveyor is actualy doing.

The design criteria may call for tonnages and surplus power that the conveyor will never see. In this case the coulping manufacturer will oversize the coupling and give incorrect fills resulting in very harsh start ups.

The conveyor may also be operating at tonnages higher than the design criteria making the coupling border line and the oil fill critical. With extendable conveyors the oill fill should re-considered on each extension and should be minimal for the initial installation. This makes starting under load a problem.

Another hazard is checking the correct fill. It is very difficult to completely empty a coupling so draining and refilling will invariably result in an overfilled coupling.

If you are completely bewildered by the above or are battling with problematic short conveyors go to the basics. Run the belt empty and check the belt speed. Check the acceptable belt slip of the coupling with the supplier. Calulate the the loaded belt speed using that slip factor. Run the conveyor on full load and check the belt speed. if it is to high reduce the oil fill. If it is to low increase it. This will give you the optimum fill level. Mark the coupling with a new top dead centre andd you have the fill level that any maintenance man can check. DO NOT DO THIS FOR LONG OVERLANDS they need further investigation.

Engicon Systems (Pty) Ltd

+27-11-789-2102

+27-11-789-9664 ■

Banda,

The key is to get the fill/slip curves from the manufacturer so you can calculate what fill you should have. The general fill information provided in the sales literature doesn't tell you what you need to know. This can be hard to get but this is the informatin that we, as conveyor engineers, need to expect from our suppliers. ■

Dear Mr. Banda,

Quantity of oil to be filled in a fluid coupling can only be decided by the original designer / manufacturer of fluid coupling. At the user stage, issue could be marginal adjustment in the level recommended by the fluid coupling designer. In case such adjustment happens to be of larger magnitude, then fluid coupling manufacturer’s consent is essential, for adverse effects. The fluid coupling supplier maintenance manual mentions about the level and quantity of oil in fluid coupling.

Now, the complexities arise when conveyor is not designed properly. The conveyor design is often done with a tunnel vision taking one value of artificial conveying coefficient, unnecessarily large design capacity and not checking the conveyor response in varied situations. Suppose the conveyor has been over-designed unnecessarily and then this information is given to fluid coupling manufacturer. Also, sometimes, moment of inertia of various items is also not worked out with adequate care or these have unnecessary contingency for future replacement of items of larger size or different weight etc. Then, obviously there would be mismatch between the fluid coupling response to actual situation and then one is troubled with the oil level issue. So, in short, adequate attention should be given to proper designing of conveyor and overall average actual situation applicable to fluid coupling, instead of everything on maximum side.

Dear Mr. Bernard,

Regarding the effect of oil level on solder (fusible) plug, fluid coupling designers would be the right people to give specific answer. However, as I remember, if the oil level is less in fluid coupling, then there is more slip in the fluid coupling, which is appearing as an efficiency factor of fluid coupling. Thus, more slip infers as more energy loss in fluid coupling and this would appear as heat causing the temperature rise of the oil. Fusible plug will do its function when the oil temperature has exceeded its limit and thereby protect the fluid coupling and drive and indirectly the entire conveyor.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■