The tractive force must overcome the affective net belt tension. With a tripper the effective net tension difference is the tension due to the idler losses along the tripped length plus the lift tension. With an extendable boom the necessary tractive force is approximatelly the sum of the top and bottom strand tensions. That will be much higher than the tripper values. Without exhorbitant ballast there will not be sufficient traction through the driven extending wheels. So: no: there is no other reasonable method of extending a conveyor boom by a reasonable distance. You could install dozens of driven wheels in line with modern 4WD thinking...but what would you gain besides high rail wear? ■

Dear All,

I would like to know in the movable head end

1. Weather we will be using the rail / wheel arrangmet for the to & fro movement.

If yes then how the skiding movement of the head end will be restricted when the position of the head end is at the exteme end as the belt tension will first result in skiding of the wheel over the rail & then the rotary motion. Even though the hydaulic brake will not help to restict this skiding movement.

2. If there is any other arrangment, kindly let me know.

Regards

Shrinivas Bartakke ■

Hi Sathish

There are basically two types of moving head.. balanced and un-balanced.

The latter simply has a moving discharge puley, which must be moved against the HT in the belt. For this you need a winch or a hydraulic cylinder, plus some sort of locking in position device.

The balanced type is like a flattened tripper, and only has to overcome all the frictions involved, inertias and possibly a rough pulley bearing.

The balanced type is often moved by winch, but can also be done by fixed chain with sprocket on the moving head, ladder-rack, hydraulic cylinder.

I have never used driven wheels on rails, the closest to this is the ladder rack which gives positive displacement

Cheers

LSL Tekpro ■

Originally Posted by sathish.hariharan

Dear Experts,

Should we have to provide only winch arrangement for movement of conveyor moving head?

Can we not provide wheel driven by geared motors similar to tripper conveyor?

Regards,

Sathish

There can be alternative solutions. We engineers have to weigh pros and cons of alternatives and choosee a solution. ■

What are you talking about? ■

Dear Sir,

Under the wagon tippler, one conveyor we are planning to provide with the capacity of 2000T/h, belt width of 1600 mm and speed of 3.5 m/s.

For this discharge end I have to feed into 3 conveyors. For this arrangment we are planning to go for 2 position shiftable header and one end discharge thru Head end.

In India this kind of arrangement is possible. Whether is it working any where such capacity.

Any vendor is there, please suggest. ■

Hi TK..

The answer is yes..

Here in South Africa, we have been doing multi-position moving heads for 35 years, at even more onerous duty than you describe, and I expect we were not the first.

Cheers

Taggart LSL Tekpro ■

Hello,

Shiftable head is always used for shifting (positioning) head end of conveyor to discharge either in mouth of chute-A or mouth of chute-B (both chute mouth are placed side by side, as common entity). Chute-A feeds to conveyor-A1 and chute-B feeds to conveyor-B1, etc.. The conveyor belt is always under tension, therefore head pulley is experiencing thrust towards tail all the time. So when shifting tends to increase conveyor length, then the shifting has to overcome force or work against the aforesaid thrust. Contrarily when shifting tends to shorten conveyor length, the shifting device is allowing (releasing) controlled movement towards tail. Shiftable head is generally equipped with:

- Mechanical actuator if thrust by belt is small.

- Rope and winch. The winch is firmly mounted on stationary structure. The winch drive can have Heli-worm gear box along with brake. The worm part to have self locking ratio i.e. it will not allow unwanted shifting (retracting) due to belt thrust. The brake is additional safety.

- Hydraulic piston - cylinder.

The simple travel drive (like tripper) will not work because the wheels, even if locked (braked by drive), will slide on guide / rail (friction grip due to self weight will not be adequate to counter belt thrust). In this case it will also require gears on drive wheel shaft, simultaneously engaging with the stationary rakes. The brake has to be part of drive, at gear box input shaft, for its manageable size. Mounting all these on head end carriage may not be convenient.

It seems winch would be economical and better option most of the time, unless belt tensions are small to suit mechanical actuator.

Ishwar G. Mulani

Author of Book : Engineering Science And Application Design For Belt Conveyors (new print November, 2012)

Author of Book : Belt Feeder Design And Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Pune, India.

Tel.: 0091 (0)20 25871916

Email: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■

Originally Posted by I G Mulani

Hello,

"The conveyor belt is always under tension, therefore head pulley is experiencing thrust towards tail all the time".

Actually, and with respect, this statement is not necessarily correct.

As I mentioned earlier, we have been using balanced moving heads on some of our conveyors for decades.

The balanced moving head uses three HT pulleys instead of one discharge pulley. Two pulleys are linked and move together as a pair, and the third one is in fixed position.

The forces on the two linked together moving pulleys are balanced out

As the moving head travels, the length of the belt remains the same.

You only have to overcome friction etc.., not the belt forces.

I commissioned another one of these as recently as last November, on a 2100mm wide overland conveyor.

Regards

Taggart LSL Tekpro ■

Hello,

Yes, I missed to mention the arrangement mentioned by Mr. Graham Spriggs. Thanks for the correcting additional information by him. In this arrangement three pulleys, one above the other will form two loops of belt. The upper two pulleys will be on shifting carriage. In this arrangement the shifting carriage does not have to counter belt thrust, but will require more head room. This arrangement is suitable for conveyor with screw / winch take-up as well as gravity take-up. The earlier arrangement mentioned by me can only be used for conveyor with gravity take-up (floating take-up).

If Mr. Graham Spriggs has other arrangement in mind, please elaborate.

The arrangement mentioned by me, I saw in Thailand and there is also similar arrangement in India, where minimum head room was the necessity.

Ishwar G. Mulani

Author of Book : Engineering Science And Application Design For Belt Conveyors (new print November, 2012)

Author of Book : Belt Feeder Design And Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Pune, India.

Tel.: 0091 (0)20 25871916

Email: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■

Originally Posted by I G Mulani

Hello,

"This arrangement is suitable for conveyor with screw / winch take-up as well as gravity take-up. The earlier arrangement mentioned by me can only be used for conveyor with gravity take-up (floating take-up)."

Hi there Mr Mulani..

Sorry to have to correct you again, but the balanced moving head is actually for the more major installations, with consequently higher tensions.

As such, the screw take-up would not be used on such major installations.

Also, with the balanced moving head, the gravity take-up invariably moves up and down during the travel of the head, albeit by only a small amount.

Because of this, the screw take up is unsuitable for conveyors with balanced moving heads.

Regards

Taggart LSL Tekpro ■