Re: Selection Of Belt Rating
I believe you need to follow the starting tension.... ■
Re: Selection Of Belt Rating
Hello Shakee,
The belt is selected to suit minimum safety factor at belt joint, which is the weakest zone for the belt. The safety factor has 2 values, one for steady running situation and one for momentary state (starting / stopping).
DIN / ISO mentions following values, as an example:
For application condition standard / average; minimum safety factor during steady state operation should be 8 and minimum safety factor during momentary situation should be 5.4.
The chosen belt should suit both the requirements.
The safety factor is belt breaking strength divided by applicable working (occurring) tension during steady state or momentary state.
There are also other application conditions ‘favourable’ and ‘unfavourable’ for which there are different values of safety factors. Refer DIN / ISO or the standard you are following.
Regards,
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 ■
Belt Safety Factor
I find the comment by Mr. Mulani, hard to believe. Recommending SF=8:1 for running case and 5.4:1 for starting or stopping. These are values recommended 15-30 years ago, but, not today.
Most belt suppliers can guaranty SF = 5.5:1 running and 4.8:1 starting and stopping. Some modern designs take it further with SF=5.0:1 running and 4.5:1 starting and stopping. These limits assume:
1. Competent belt construction and core gum dynamic strength, as set by dynamic endurance testing
2. Proper splice pattern developed from modern analysis
3. Proper splice equipment and calibration
4. Proper splice preparation, construction, accuracy, hygiene
5. Proper splice kit storage
No large overland system would consider a SF=8:1 today with the associated penalties of capital and operating cost. These extreme values reflect a acquiesces to poor engineering and field practices, acceptance of substandard construction techniques, and poor quality belting. ■
Met The Numbers
Dear Sirs,
even if agreeing with the demand on modern technology, it is "in these here times" that such requirements on safety might be met in project specifications. The reason is obviously to allow for, i say, technically less sophisticated but pecuniarily more attractive supply offers and / or less developed maintenance culture which is not planned to be improved in the foreseeable future.
The whole picture is imo often more complex than just the technical matters.
There's also the opinion that higher safety margins make a longer useful life, and the calculation of power consumption is just not looked at.
It is rather quite difficult to convince the decisionmakers if the benefits of good tecnology show up only after more years than warranty lasts and there's only so many issues which allow to pull warranty at all.
These would be some really interesting points to get a broad picture about...! As, i allow myself the openness, there's so much cleverness in the markets, but i cannot make myself heard or accepted or my product bought because i try to follow the honest & safe and technical way and am to costly. Even if proposing something truly forward. Who wants to be the first one?
EOR.
So, dear Mr. Shakee, i think you got the point that both tension states have to be considered. It would be prudent to accept counsel if you are facing a real design issue, or to consult literature and standards on this matter. I feel that Mr. Nordell and Mr. Mulani gave you a very good and valuable briefing about the main topics which now must be filled in and detailed. Thank you for your understanding.
Have a nice sunday
Regards
R. ■
Selection of Belt Rating
Dear Experts,
Is selection of Belt rating based on Normal running tension is correct or Is selection of belt rating based on starting tension is correct?
Regards,
Shakee ■