Dear Bharat

You have to give complete information for obtaining correct reply.

For calculating speed motor rpm is required

By chaging pulley from 630 to 1000 mm you have increased speed by about 50 percent

Capacity will be calculated based on speed

power consumption can not b calculated without length and lift.

A R SINGH ■

Dear Mr. Bharat,

increasing pulley diameter from 630 mm to 1000 mm will chg:

belt speed ................................. 1.73 m/s 2.75 m/s

belt power increase ................... 5.2 kW

Thus, if you demand power is close to nameplate power you may not be able to transport present tonnage even though your belt crossection will be reduced from about 54% to 34 %.

Your gearbox capacity will need to be reviewed to see that its rating is not exceeded. ■

Sorry for the typo

Belt speed will increase from 1.73 m/s to 2.75 m/s ■

I have a question, if he is not increasing the tonage per hour , just speeding the belt up with a larger pulley, that should not change anything other than belt speed. i understand he will have less starting torque. the total tons per hour are the same so horsepower should be the same also? ■

Dear KASEY,

The speed increase will increase belt power due to the increase in parasitic losses and increased idler indention hysteresis. Parasitic losses (columb drag) are like idlers, pulleys, skrtboards; belt cleaners.

Increasing speed at same drag constants will therefore increase power as in: kW = P x V , where P is pull or drag and V is change in belt speed.

Idler indention is the hysteresis loss of working the rubber cover in contact with idler roll. THis is more complex to explain in a few words. ■

Dear Bharat

In case you are having 4 pole motor with 1500 rpm 1.73 m/sc speed can be assumed.

When you change pulley to 1000 mm your speed will increase by about 1.0 m/sec

Without knowing conveyor length and lift horse power requirement and additional power cannot be accuratly calculated

By increasing speed by 1 m/sec conveyor horse power will increase as explained by Mr Nordell.

In simple explanation when you increase conveyor speed motor power will increase as more work is done by motor to carry / rotate the belt at higher speed.. Suppose belt weight is 12 kg/m , By increasing speed by 1 m/sec means additional weight of belt to be rotated per hour is equivalent to increased of capacity by 45 t/hr on carrying side and 45 t/hr on return side

A R SINGH ■

Dear Shri Bharat,

Originally you had a 630mm diameter pulley which you have replaced by 1000 mm diameter pulley. Kindly clarify the motive / purpose for using so large a pulley compared to original pulley. Whether this is for increased capacity or whether it is used because it is available.

If you have used larger diameter pulley for increasing the capacity, then complete conveyor is to be redesigned.

If you want to use larger diameter pulley without changing capacity, then you have to use higher reduction ratio gearbox.

If you are increasing the capacity of this conveyor, then it would have a chain reaction. It will need matching capacity of the feeding system and receiving system. What about this? The conveyor capacity cannot be manipulated in isolation.

If you are using bigger pulley and changing speed, capacity etc. then it is better that you take assistance from conveyor designer. In simple words, you can just not bigger wheels of a car, and that too by a ratio of nearly 1.5. Everything needs to be checked.

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 ■

Without getting into any equations on sag, you can assume the minimum sag tension needs to be increased in proportion to the change in idler spacing. So going from 4 to 4.5 ft spacing requires a sag control tension increase by 11% ((4.5-4.0)/4.0) all other things being equal. However, you may need to consider other factors. ■