Originally Posted by mehdiohadi

could you help me which one is true : CEMA or ISO-5048

In absolute terms, NEITHER.

This is because, IMHO, belt conveyor calculations are not 100% accurate as they require assumptions to be made regarding a number of factors used in the calculations. ■

Neither is correct. CEMA is too low and ISO much too high.

Look at your lift force. It is over half of CEMA but only somewhat less a third of ISO. You also have other issues making the design an unlikely and costly candidate. ■

I recommend you rework your analysis based on directions in the manuals. You seemed to have misunderstood the text instructions.

Some clarity on idler selection, diameter, spacing, also take-up type, location, and mass or belt line tension would help us understand what you are doing wrong.

Why so slow or so wide a belt?

What ISO, DIN "f" factor or CEMA Ky factor have you used? ■

Tell us why you selected ISO f=0.030?

CEMA selection is a result of the design, if it is within CEMA parameters. However, the value Ky is only one friction loss value. You also need to add idler Kx (seals and bearing with lubricant). For total power, you need to add parasitic losses along the belt line such as: pulley drag, skirtboard, material acceleration, belt cleaners and plows. ■

Dear mehdiohadi,

The problem is more complex than either CEMA, ISO or DIN profess. As has been written many times now, the power loss is most heavily dependent on the rubber cover rheology and its contact Pressure(physics) with the idler roller surface.

Rubber hysteresis loss is the main DIN f factor. It contributes from 60-75% of the rolling loss. Idler bearing lubricant and seal losses contribute between 10-20% of the DIN f loss depending if the rubber is efficient or less so. Lower rubber hysteresis means a higher ratio of idler drag influence. Idler drag loss grows dramatically with higher belt speeds as does the rubber hysteresis.

Modern overland belt conveyors, with optimized design of idlers have DIN f values closer to f=0.010. Some lower and some higher with many dependencies on rubber and idler design. Applying a DIN f =0.030 for a design value can be correct for poor rubbers and sub-optimized designs. Unfortunately, these techniques are not found in Standards. You must read the literature to see who is developing the "now" and "next" generation of conveyor designs. ■

Originally Posted by mehdiohadi

Thanks for your attention

In Iso f = 0.03

In Cema Ky - 0.0175

I attached detail in Excel File

you can compare them

thanks

Attached file not opened.please check it. ■

Originally Posted by kundu09

Attached file not opened.please check it.

I opened it?? ■

Do not compare DIN or ISO "f" value with "ky". They are not equivalent. ■

Your situation is quite common.

CEMA recommendations are not a Standard; the website confirms this. However they are a good work.

ISO Standards are the legal falllback in most countries, and will take precedence over DIN..

So it simply depends on where you are and where your plant is. If there is a risk of CEMA design results not working adequately then due diligence has not been applied to the work according to the legal beagles.

That is a very sorry state of affairs. Mr Nordell and other very leaned parties have taken conveyor design to higher levels which can benefit the entire industry worldwide. The prevailing blame culture in our society hampers their efforts beyond reason. Standards bodies and Engineering Societies are at fault and should pay more attention to progress, consultation and the outside world and less to exotic venues etc.

Conveyors apart, my particular gripe is the exclusion of electron beam welding, and other similar technology, from all the process industry standards in general.

When engineering bodies are clearly seen to fall far behind technology then it is a sad day for us all.

Pass me a hankie.■

Originally Posted by louispanjang

Your situation is quite common.

CEMA recommendations are not a Standard; the website confirms this. However they are a good work.

ISO Standards are the legal falllback in most countries, and will take precedence over DIN.

I don't consider that conveyor design "standards" from ISO, EN, BS, DIN have any more value than CEMA. At the end of the day these "standards" are no better than the cobbled together compromised knowledge of the people who gave the input into them. After all most of the knowledge is provided by those who actually design and supply machines so they need to keep a competitive edge over those whose knowledge is limited to being able to read a standard. And the fact that standards may not updated for years means that the knowledge can be years out of date! ■

try the attached file save as excell rev.97-003

Attachments

book4 (ZIP)

■

Originally Posted by designer

I don't consider that conveyor design "standards" from ISO, EN, BS, DIN have any more value than CEMA. .................!

I agree with everything that you say. But we have to cover ourselves in law. If a party is injured by a conveyor then we must be able to prove that we have applied due diligence and that requires adherence to the legally enforceable standards.

Testicular discomfort indeed, but its the price we pay for living so long. ■

Dear Louispanjang,

I submit your argument should consider the following: Standards apply if they work for all cases where the boundary limits are known and the designs are within those limits.

In the case of conveyor design, there are cases today where the known limits exceed the stipulated standard practices. The specifications must be expanded or face contention in law. Furthermore, the standards may also create serious cost penalties and safety concerns.

The Standards give lip service to dynamics. Since such analysis is complex and not easily penned into a standard, they ignore its necessity rather than identify when, how, who, et al, it should be used.

Rubber and idler energy consumption is not treated in a scientific manner. This too is complex, but understood. So, complexity is considered an excuse for ignorance?

Vibration controls of syncopation between roll spin, belt resonance and structural resonance is ignored. Yet we can see large spans of steel and idler support frames damaged by such resonance. Does the lack of notation promote unsafe practices? Is this ignorance acceptable?

Control of shockwaves is also complex and necessary. The standards recognize it exists and say nothing more as to how it should be treated or give any guidance on its application. At least CEMA says to seek advice from a CEMA member. This is better but a little off the mark, since most CEMA members cannot offer direct assistance. They may be able to offer recommendations on who is able to help. Then again, they may not be sufficiently informed.

These comments also extend to component construction such as belts, pulleys, idlers, instruments, brakes, holdbacks, bearings, yada, yada, ..... I contend we can show how the belt safety factor is impractical for small and large conveyors for different reasons. For small, short and high lift, the safety factor may lead to unsafe practice. The same application for overlands of > 10 km is ridiculous in its conservatism in contrast to short high lift conveyors. Is ignorance and excuse for not applying known wisdom?

Take the ASTM boiler standards, they are pedantic in details. This is in sharp contrast to DIN, ISO, or CEMA conveyor design recommendations. ■

If we're talking 'elf 'n safety and belt conveyors then that is a different matter to design.

With the introduction of the Machinery Directive in the EU (the requirement for CE marking to indicate machinery is 'safe') a new raft of standards we introduced to cover 'machinery'. In particular -

EN 618:2002

Continuous handling equipment and systems - Safety and EMC requirements for the equipment for mechanical handling of bulk materials except fixed belt conveyors

EN 619:2002

Continuous handling equipment and systems. Safety and EMC requirements for equipment for mechanical handling of unit loads

EN620:2002

Continuous handling equipment and systems - Safety and EMC requirements for fixed belt conveyors for bulk materials

Because of their relationship to the Machinery Directive they do have a quasi-legal status in the EU. ■

Gents,

I agree with you on all points. The Standards are inadequate. For the thread starter I was pointing out that CEMA is not a Standard.

What we've all said in some form or another is that the Standards need to be brought up to date. Our problem is that those concerned with the updating process can look over their shoulders, see the new technology ready to overtake and regurgitate their conservatism to protect an imagined status quo.

I personally doubt that a perceived status quo exists in the business. There are plenty of good new ideas about.

A treasured textbook of mine states that after coal has been deposited on the belt it needs no further attention. Mind you it was traveling at 1.2m/s. Those were the days. ■