Re: Fluid Coupling & Vvvf Drive In One Conveyor

Posted on 28. Feb. 2011 - 07:54

If you understand the functioning of fluid couplings and variable frequency drives you'll understand that you only use one not both.

Lyle Brown
(not verified)

Re: Fluid Coupling & Vvvf Drive In One Conveyor

Posted on 1. Mar. 2011 - 10:25

Assuming you are referring to a drive with both VSD and a fluid coupling, this was discussed a while ago, though a reason was not obvious:

Maybe you have more than one drive on the conveyor, where one (or more) drive has a VSD, though one (or more) drives on the same conveyor has fluid couplings (for some reason)?



Re: Fluid Coupling & Vvvf Drive In One Conveyor

Posted on 3. Mar. 2011 - 09:32

Hello all

VSD's are good for long smooth start up times whilst also being motor friendly (electrical soft starts are not motor friendly and have no good track record on multiple drives)

Fluid couplings are the answer but only for low inertia inclined conveyors or overland generally less than about 4km due to the start up time limitation before they cook, hence the scoops and drain couplings, which have external oil cooling.

There was a fad where they combined elecrical soft start with fluid couplings. Fortunately this did not last long, but unfortunately the fad changed to putting VSD's on just about everything.

There has been lots of mis-information about the "savings" from using VSD's

It actually looks like there is more energy loss at the VSD unit itself than the 3% loss you get in a fluid coupling. Hence the massive air conditioning units for the rooms housing the VSD's

Then you have to pay for a very clever person to sort them out (fluid couplings just need oil!)

This man costs money, and so does the VSD which will have to be replace a few times over the life of the conveyor, just like I have to replace my laptop! Work it out... the overall costs using VSD's is huge.

And then there is all this mis-information about saving power by running the belt full whatever the capacity by using the VSD.

According to my research, this does not apply to any conveyor less than about a kilometre long, as the effect of sag on lower tension conveyors is huge and causes excessive power loss, and the idler imprint load drag increases exponentially as the load increases. So why on earth keep it maximum at all times!

I notice that when I was in Australia on a recent project, the tendancy now is to not go the VSD route, except where it is of actual benefit. I wonder how long it will be before it is generally taken that VSD's are no longer the flavour of the month.

Watch this space..

Anyway VSD plus fluid coupling...nnnope..


LSL Tekpro

Graham Spriggs

Re: Fluid Coupling & Vvvf Drive In One Conveyor

Posted on 3. Mar. 2011 - 10:14

Thank you all.

Here the fluid coupling mentioned is only a coupling having pump & turbine vanes in a chamber. It does not have any scoop type arrangement to vary the speed of the conveyor.

Though the fluid coupling is mentioned to avoid the initial high pulling load on the conveyor components, it is not visible ( unless it has scoop arrangement ). But in VVVFD, we have the advantage of both ramp up & down time which is good for the conveyor, which can be set as per user's requirements.

I have asked my electrical engineers to install VVFD for a vertical conveyor. They are purchasing VVFD with bypass facility. So if VVFD is inline, should I not have fluid coupling? I fear during slow speed of the motor, the bearings of the fluid coupling may wear out faster. When VVFD is bypassed, should I have fluid coupling, to get it's advantage?

Plant cannot afford to change the motors since heavy production loss can happen during the motors replacement, alignment etc.,

Hence I rasied this question. Hope to get your earliest replies.


Roland Heilmann
(not verified)


Posted on 3. Mar. 2011 - 01:01

Est. Mr. Ganesh,

what exactly do you mean by "vertical conveyor"?

Fluid couplings serve also other purposes than only startup facilitation. I.g. overload protection in cases, where sudden blockage of drive motion may occur : bucket elevators, dischargers under silo gates etc.

In case the drive unit was purchased, the opinion of the supplier may be sought. In case it's a homemade device, you may have to run a full mechanical & dynamical analysis of your drive config.

A backup - philosophy: VFD + fluid cplg. just for startup purposes seems uncommon, why bypass the VFD once it's there? Is there a significant difference between installed and required power you may want to safe upon?



Controlled Start Transmissions

Posted on 12. Mar. 2011 - 05:06

Check this type of variable speed Clutch(Brake Type) & Gearbox drive system. These units in Huo Ji Tu(Mongolia) are the drives I check & commissioned for the drift conveyors in 1998. The drive is a compact and extremely reliable and are much cheaper in the initial purchase when all the electrical componentry and cabling is included, about 20% cheaper than any other comparative drive unit as well as a low ongoing maintenance cost in comparison with others. I highly recommend these drive units provided the LCDs (Lowest Common Denominator) who service them are well trained to do the correct thing. At a particular mine that had a big turnover of personnel including maintenance crews. One untrained maintenance person used the wrong oil which caused havoc with one drive unit and as such, a gearbox was serviced with gear oil instead of the correct hydraulic oil of specified grade. Apart from that incident, these Reliance-Dodge CST's are one of the leading units to look after conveyors systems in terms of gentle operating conditions on the system from Tail to Jib pulley and all bits in-between and longevity of reliable ongoing service.

Mechanical Doctor There is No such thing as a PROBLEM, just an ISSUE requiring a SOLUTION email:- [email][/email] Patented conveyor Products DunnEasy Idler Assembly & Onefits conveyor Idler Roll [WINNER] Australian Broadcasters Corporation's TV 'The New Inventors' Episode 25 - 27th July 2011 [url][/url]

Fluid Coupling And Vfd Drive In One Conveyor

Posted on 12. Mar. 2011 - 07:07

The VFD drive control has come a long way and is now economical and very effective in controlling long smooth starts and stops and can run at varied continuous speeds. A fix fill fluid coupling is good for limiting max torque and inrush current during starting and they can be used on multiple drives to affect good load sharing. The idea of using both at a single conveyor is absurd but reluctantly had the occasion to participate in such an absurdity. We built one of our sandwich belt high angle conveyors by licensing a foreign partner who actually supplied it. Without our agreement that partner used a single VFD to control the DSI Snake conveyor speed at both belts and fluid couplings (one at each drive) to affect load sharing between the drives. The latter pretty well precluded the benefit of the former. The first time that they slowed the belt speed appreciably they overheated and blew the plug of a coupling. This was inevitable and a terrible idea.

Joe Dos Santos

Dos Santos International 531 Roselane St NW Suite 810 Marietta, GA 30060 USA Tel: 1 770 423 9895 Fax 1 866 473 2252 Email: jds@ Web Site: [url][/url]