Subjective, releative to other locations on the belt / (plant?).

Regards,

Lyle ■

Various Standards quote pulley diameters based on percentage of belt rated tension.

For example, at 75-100% of belt rating, an ST2250 steel cord belt required a pulley diameter of 1219 mm.

At 50-75% the diameter is 914 mm and so on. Less than 50% of rated belt tension would be 610 mm pulley diameter (snubs etc).

See DIN 22101, 22131, Goodyear manuals etc.

A tension pulley would be one at 100% rated belt tension (Head pulley, high-tension snub)

A low tension pulley would be a snub or bend pulley with <50% rated belt tension.

You have to then look at the vector force on a pulley to rate its shaft and shell and bearings.

If the belt tension is Tmax, and the head pulley has a belt wrap of 180 degrees, then the pulley force is 2 x Tmax, or Tmax/pillow block.

So you need to rate the pulley and its design according to the belt vector force, as well as bending diameter for and belt stresses to satisfy belt supplier guarantees.

Thanks

Alex Harrison

Techanicaldesigner;76210]Are there criteria to classify pulleys as high tension or low tension ?

does exist ranges on Newtons for this?

or according of the location inside belt conveyor?

or perhaps according to the function or role within the belt?[/QUOTE] ■

Originally Posted by mechanicaldesigner

Are there criteria to classify pulleys as high tension or low tension ?

................

Tension is only one of the prevailing forces when the tension nearly approaches the limit for the belt.

There might be considerable torque applied to the shaft.

The answer should be NO because you need to classify tension itself as high or low. Good luck there because not even Sir Isaac Newton bothered to qualify force. He simply quantified it throughout the Universe. ■

Reply,

Didn't the original question ask for a criteria to classify high or low tension pulleys?

The answer given was that there are criteria, YES, which relates to belt forces (N).

There are Standards and industry-used limits, as discussed.

Maybe I overlooked seeing the word "torque" in your original question?

Perhaps you could try rewording the question : "how does one define high or low torque pulleys"?

There is no need to reply for this help.

Originally Posted by louispanjang

Tension is only one of the prevailing forces when the tension nearly approaches the limit for the belt.

There might be considerable torque applied to the shaft.

The answer should be NO because you need to classify tension itself as high or low. Good luck there because not even Sir Isaac Newton bothered to qualify force. He simply quantified it throughout the Universe.

■

Originally Posted by Alex Harrison

........................

You have to then look at the vector force on a pulley to rate its shaft and shell and bearings.

................

So you need to rate the pulley and its design according to the belt vector force, as well as bending diameter for and belt stresses to satisfy belt supplier guarantees.

Thanks

Alex Harrison

[/QUOTE]

You said it.

"There is no need to reply for this help." What help might that be? ■

Pulley diameters, for steel cord construction, are controlled by two properties:

1. Steel cord construction - internal wire arrangement that leads to variations in strength loss from bending and axial flux - differs with differing wire constructions

2. Rubber shear stress under the steel cord - ie. assumes the cord tension is proportional to the diameter squared (cord area)

I offer a qualitative note on considerations that extend beyond published belt supplier tables.

STEEL CORD CONSTRUCTION:

Wire group configurations ( 3x9x15; 7x7; 7x19; semi Warrington; ...) will impose differing Hertzian contact stress between wires that lead to their fatigue failure. Most often some belt manufactures will do flex testing of established steel cord construction to quantify the fatigue life. However, they do not factor in the influence of belt strength utilization (belt safety factor). The is important because the axial stress (tension component) differs from the bending stress component when the steel cord is bent over the pulley diameter. Different steel cord configurations produce different contact stress at the wire level due to bending. Some wire rope constructions have larger wire sizes for the same given steel cord size. In addition, some constructions have better rubber penetration that lower the hertz stress magnitude. In conclusion, steel cords with many smaller wires can utilize smaller pulleys, all things considered.

Belt manufacturers have not made a science of these features. Most of the wire rope fatigue science comes from wire rope testing programs such as the nuclear research industries, tire industry, et. al.

RUBBER STRESS:

Belt manufacturers do fatigue testing of selected belt constructions to study the rubber damage from the radial stress component under the cable as the belt is bent over a given pulley diameter. Recent findings show their is less rubber fatigue failure than first found from 1950-1960's testing. Modern rubbers have much better compound features than those of many years ago. Yet, the modern testing has been sporadic. In short, if you wish to use low safety factor belt construction, you must understand the added tensile and bending forces (stresses) should be tested for these conditions. This also becomes relevant with splice designs. ■

I will say that the pulley tension considers 2 major factors. They are the tensile strength of the material holding on the pulley i.e. the metal fatigue involved and the amount of stress incorporated. Rest is all observation in it. ■

elvira g caamal

You must have died your hair because on other forums you signed up on your pic is of a blond. If you want to peddle your martial arts classes please do it somewhere else as they are not welcomed on a technical forum such as this one.

Your reply clearly shows you do not understand the topic and therefore only posted to add your link to the post.

They will always be removed here so please move on.

BTW nice touch by using an email that can't be traced. Those sharklasers are nasty devils. ■

Hello Mechanical Designer,

Pulley diameters can be selected according to DIN22101 or ISO3684, which are primarily similar in nature. The pulley diameter depends upon following:

- Carcass type whether NN or EP or steel cord, etc.

- Carcass thickness (for steel cord belt cord diameter).

- Belt tension at pulley i.e. percentage utilisation of belt allowable (working) tension at pulley location.

The carcass bending around the pulley reduces its safety factor by certain margin (for which there is allotment of specific margin in belt safety factor being used). When the belt tension is high, the available reduction margin will be less. So it will need comparatively larger diameter pulley and vice versa.

For contractual application; one decides the pulley diameter as per DIN / ISO, so that belt performance guarantee gets agreed upon easily. Refer the aforesaid standard and calculate / decide pulley diameters accordingly. For regular in-plant belt conveyors, the pulley type A, B and C mentioned therein and belt operational tension range over 60% to 100%, over 30% to 60% and upto 30% are quite clear and does not need elaboration.

The pulley diameters for conveyor having drive at both the ends, or conveyor having multiple drives will present a special case because in such case belt high tension and low tension sides get blurred at some location of pulley. But even in such cases, it is found that the pulley diameter can be chosen from the information given in the aforesaid standards, by careful study. In such cases the designer can finally take concurrence from belt supplier, for the chosen diameters, in order to uphold the belt performance in conjunction with the pulley diameters being used.

The carcass bending at pulley creates alteration in stress distribution along carcass thickness, as per modulus of elasticity of carcass. This can be analysed, but the subject pertains to specialised activity. For conveyor usual designer, it may be out of touch subject, and finally issue about to have the agreement to such calculations and analyses.

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.

Pune, India.

Tel.: 0091 (0)20 25871916

Email: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■

Dear experts,

Is there any standardization done for pulleys as those for idlers? Say Pulley face width, Pulley diameters, shaft length, shaft diameters, bearing distance etc.,

Will it be possible to buy pulley, with out giving drawings as we can do for idlers ?

Regards, ■