Dear Rekhawar

It is difficult to specify norms for wastage . Percentage of wastage depends on following factors

1.0 material to be handled

2.0 system selected Pnumatic , belt conveyors, pipe conveyor , screw conveyor, chain convetc

3.0 proper design and selection of cleaning equipment, skirt plates , chutes

4.0 proper maintainance of system

5.0 provision and maintaince of dust supprssion and dust extraction system

6.0 provision of wind protection

7.0 Nos of transfer point in system

A R SINGH ■

Dear Mr. Rekhawar,

If it is restricted to handling loss only, we generally consider 2% maximum.Other losses depend based on the following.

1. As Stated by MR. Singh

2.Screening loss, if system requires

3. Moisture loss

Mr. Rekhawar, I have not come across any industrial standard so far.It is from the data collected from site only.

Regards.

A.Banerjee ■

It will come down to what is concidered acceptable by the end user.

If the cost of the product or quality of the product justifies the expense to install better systems to reduce the loss then they will make the decision to do so.

Take for example:

Dust collection in the cement industry can be reclaimed back into the product and increase saleable production. There by justifying capital cost for the equipment to do so.

Dust collection in the salt industry is usually too fine for good product and is concidered waste and not reclaimed. Therefore it cannot be justified to put the extra expense into the system.

There is no industry standard for loss as every system and every industry will be different.

Gary Blenkhorn ■

Regarding solids handling efficiency there is no "industry-wide standard", but for well-designed and operated plants a general rule of thumb is 100 ppm. This is based on a dust collection efficiency of 99.99% assuming accidental losses such as spillage are ignored.

Regards,

Amrit T. Agarwal

Consulting Engineer

Pneumatic Conveying Consulting Services

Email: polypcc@aol.com

Ph and Fax: 304 346 5125 ■

A picture may guide your evaluation, given that my math is correct.

Assume power plant coal (.8 t/cm) at 1000 t/h on 1000m belt with idlers pitched at 2.0m carry and 4.0 m return or 250 roll stations.

Assume the belt cleaner efficiency is 0.999 and carryback is equally distributed along each idler station and idlers clean off all coal over 800mm wide belt center.

What deposit will be acceptable at each idler assuming 24 hr operation?

The above will deposit each day a pile, at 35 deg. rilling angle

tons lost/day..24.0................2.4...................0.24 over 250 idlers

discharge ..0.0010............0.0001..............0.00001 inefficiency cm/day/idler.0.1200............0.0120............0.00120 loss

height........ 324 mm...........102 mm.................32 mm

width......... 926 mm............292 mm.................93 mm

length........ 800 mm............800 mm...............800 mm.

percentage 10% of 1%.......1% of1%.............0.1% of 1%

Not a good result for the noted efficiencies. The cleaners need turnovers and total efficiency should exceed 0.99999 or no more than 0.24 t/day. ■

Dear MR. Gary,

It is very nice & acceptable answar.

A.Banerjee ■

Dear Mr. Nordell,

Can you give some clear figure to be consider at the stage of making report for a steel plant.Please give me very tentative %.

Regards.

A.Banerjee ■

Dear Banerjee,

Your question is not clear. Be precise in the question, the answer you seek, and the obvious data required to formulate the answer. ■

Page 135 of the Foundations III book by Martin Engineering shows calculations for material spillage from belt conveyors. We also have an excell spread sheet one can use to calculate spiullage based on actual conditions. Both can be obtained by contacting Martin Engineering at 309-594-2384

The two main sources of spillage are carry back (material sticking to the belt on the return side, and load zone spillage. Both can be sustantial if not contained. ■