Dear Shri A K Bhatnagar,

Your conveyor is equipped with variable frequency drive, i.e. it is used as a variable speed drive. This implies the conveyor will have a wide range of speed. In this situation how about the conveying capacity MTPH? Are you referring to the situation where conveying capacity MTPH is constant and speed variation is in a very limited range. Or are you referring to a situation where capacity is changing in proportion to the speed?

Belt conveyor behaviour w.r.t. speed is generally well understood. It may be just putting into various formats depending upon the situation you are referring.

Regards,

Ishwar G Mulani.

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

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Dear Bhatnagar:

Your question: can VFD, 200-300 sec start time and ceramic lagging change the power consumption?

Simple answer is yes. How is it done?

1. VFD can idealize the starting/ acceleration ramp that minimizes peak belt tension and belt-to-pulley slip criteria that governs the slack side or T2 tension that is often the counterwieght tension. Thus, the overall belt tension can be reduced when compared with other starting methods, which reduces belt mass and power to move added belt mass. Degree is not an issue.

2. Why have you noted 200-300 seconds to start a 4 kim overland conveyor? The starting time selection is associated with:

a) time required to engage the complete mass and bring it to belt speed

b) mass can large or small which will alter start time

c) belt speed can be high(>6m/s) or low (<3 m/s) which will alter the selection

d) undulating terrain may require a significant dwell or slack tak-up time before engaging the acceleration cycle, such as cause by a low tension zone away from the drive station, otherwise unstable shockwaves may ocurr.



e) typical simple monotonically height increasing or flat overlands can use the rule-of-thumb acceleration cycle of 30 seconds/km which equates to a conservative 120 seconds. Some 10 km can start in 80 seconds, some may require more than 300 seconds. It is very dependent on the conveyor profice and use of verical and/or horizontal curves.

Your selection is, in general, extremely conservative. What are your criteria? Everything changes by degree. What degrees of change are you chasing 1%, 5%?

3. Ceramic Drive Pulley Lagging can lower the required T2 ( slack or take-up tension) which I am sure you are aware of. Thus, the lower take-up mass means a lower belt tension, Lower belt mass lowers the power required. The degree is not in question.

Are you just chasing academic interest? I believe you are more versed in conveyor design that your question potrays. To generate a meaningfull answer much more needs to be known. I would guess the question and answers are beyond the ability and interest of this forum. The subject is too vast.

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com ■

In Ontario's Aggregate Industry The Standard Is To Have 3 Carrier Rollers On A Roller Frame.

However, When You Increase The Number Of Carrier Rollers On A Roller Frame, You Decrease The Amount Of Energy Used To Power The Conveyor System.

Increasing The Carrier Rollers From 3 Per Frame To 4 Per Frame Shows It's Best Benifits With Long Conveyors.

I Don't Know If That Has Anything To Do With Your Inquiry Or Not, But I Hope It Helps. ■

Dear Strada,

How does a 4 roll idler set reduce power?

What long overland have shown this benefit? ■

Dear Mr. Yeo San,

I am keenly interested in your low power rubber. Has Bridgestone perfected a new low rolling resistant rubber compound that will save 20-30% beyond recent compounds?

How is the Channar upgrade working?

Is there a new Bridgestone rubber that is superior to Channar?

Can we see this new performer? ■

It Reduces Power, Because It Reduces Friction.

Instead of 6 Bearings your using 8 bearings, which allows for a smoother, easier flow of the belt, because there is less friction.

If You Would like to know more, email me:

NPhelan@stradaindustries.com and I can Speak to my Idler Specialist about the matter and get you more information. ■

Dear Strada,

I do no think you have the insite to argue the merits you expouse.

I do not think you have made any engineering or scientific study.

I can say, based on many field and laboratory measurements, the friction columb drag major factors show:

1. There is more drag with 8 bearings and seals than with 6.

2. Major rolling resistance losses are from rubber rheology of the belt cover indention and flexure with the idler rolls (~70%) than with idler bearing and seals losses(15-20%). ■

Dear Strada,

Are you taking about the 'low-energy' idler i.e. with two centre rolls parallel to each other and able to swivel in accordance with the angle produced by the sag in the belt? I believe this was reported on in Bulk Solids previously and the system was marketed by Svedala?. Is there definite proof that the system works? Larry says it right, the more bearings the more friction, the more power.

Adi Frittella

Afripp Projects CC ■

Dear Ash-bhatnagar et al..

Things that gobble up power on overland conveyors are:

- High speeds

- Areas of low belt tension

- Poor alignment

- Poor housekeeping

- Stiff idler seals

You mention a VSD. This will allow you to select the optimum speed to carry the load with the least power. Go too slow though, and you get belt sag and you are back to increasing the power again.

You will be amazed at how sag gobbles up the power, so keep the belt tension as high as you can for the class of belt selected if power is important to you.

If you have to train the belt by adjusting the idlers, then your conveyor has never been properly aligned, and will use more power.

All this other stuff about number of rolls only makes sense to me if you can reduce the number of seals in an idler set. Its the seals and not the bearings that are to blame, especially if they are full of the proverbial nasty brown stuff.

LSL Tekpro ■