look for the conveyor equipment manufacturers association.org ■

G'day!

These are the standards that I have come across so far which analyse the rolling resistance of conveyor idler roller:

DIN 22101

ISO 5048

CEMA 502 - 2004 (latest)

SABS 1313 - 1: 2002 also there is SABS 1313 - 1: 1998

My recommendation is the SABS 1313 - 1: 2002 or SABS 1313 - 1: 1998.

Regards,

Dhruv ■

Dear Mr. Trpimir,

The roller resistance for rotation comprises of following components.

1) Bearing frictional resistance. You can refer the bearing catalogue such as SKF, which informs the bearing friction coefficient with reference to the bore of the bearing. This friction coefficient is to be further reduces in the ratio of bore divided by roller outer diameter. This will also get affected by quality of the manufacture whether the fit at bore and outer periphery of the bearing is actually in accordance with the recommendation of the bearing manufacturer.

2) Seal resistance. This will be applicable if the seals are of rubbing type to the stationary component of the roller.

3) Grease shear resistance. This can only be decided by trial on actual rollers. It will vary according to the arrangement of the seals, their zigzag pattern, gap between two seals and roller rpm. Grease shear resistance will be less during lower rpm but it will increase as the rpm increases.

Reputed idler manufacturers published catalogue leaflet often mention the value of the roller resistance with reference to their construction and testing. If you want to use this data for conveyor design you can reply on the well known publications. If you are doing research on idlers, then it is a different subject.

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 ■

May I sugest you take a little more caution with the standards. First, they do not agree with each other such as CEMA with DIN or ISO. CEMA is based on two standard taper rollers (USA). DIN and ISO are a mix of ball bearing resistances. THen there are the other publications such as the excellent Precismeca idler catalog now out of print.

Today, ball bearing is the more preferred which is beyond the discussion.

WIthin ball bearings, thare are variations in drag due to notations summarized below and by which some have been noted by Mr. Mulani and others:

a) various sizes of ball and race such as series 62, 63, and 64,

b) various seal configurations including internal shields (one side or two of race),

c) labyrinth lube seal geometries which have contact or not and with differing pressures,

d) grease viscous variations betweeen mfgs which can produce large deviations as measured by ASME many years ago

e) temperature extremes which impact the various grease viscosities with different degrees of shear strength

f) ratio of race to shell diameter,

g) how the idler bearing is greased (ie. hand packed, pressurized gun) and degree or magnitude of greasing

h) if idlers are factory run it to pump out exess grease, and burnish seal contacts -- this can take months in the field

i) poor shell run-out tolerance or seam weld distortion that can in duce energy losses from vibration

j) poor installation design that induces belt vibration which appears to comsume unaccounted for power

k) location of installation were history has culled some of the un der performers due to enviromental or other perceived performance penalties

l) load magnitude and degree of shaft deflection

m) perceived loss due to roll alignment

The point to all this is that the manufacturers do differ for various reasons, some of them are well founded in good engineering. Caveat Emptor- know what and why in your purchase. ■

G'day everyone,

At present I am pursing a Final Yr. BEng. Mechanical Engineering Project titled "TEST RIG DESIGN FOR MEASURING ROLLING RESISTANCE OF CONVEYOR IDLER ROLLER". I am totally new to this field.

I have been also out for some information affilited to this topic.

The best information i have sourced out so far:

http://www.bulk.newcastle.edu.au/cbs/

Regards,

Dhruv ■

you should also look at the conveyor equipment manufacturing association web site as well. ■

Hello Trpimir...et al

I am always a little non-plussed when I hear that people want to measure the rolling resistance of an idler roll.

Like what will you do with it once you have got it?

It never stays the same, as a new roll is quite stiff to turn. When run-in, they spin quite freely, then stuff gets into the seals and the bearings start to go, and they get stiff again.

It varies with temperature, alignment.. etc.....etc.....

So what I do is ensure that I have sufficient power to always reliably be able to start a fully loaded conveyor, and forget the test results on an idler roll to several decimal places. As such, I have not had a problem over many (sheltered) years even though I have never measured a rolling resistance in my life.

Incidentally though.. I did manage to get a Melco return idler roll to spin for several minutes (but I reckon they took most of the seals out first)

Regards

LSL Tekpro ■

Thank you for that comment Graham. Not to detract from anyone's research, but after 28 years in this business, I was beginning to wonder how we ever built things before computers and calculators permitted multi-decimal place coefficiants to be generated and used with ease in calculation.

No-one here has mentioned the resistance of the belt and material burden flexing over the idler. According to my ancient empirical data, this resistance is often more than the idler rolling resistance. ■

Exactly so JD..!

Regards

LSL Tekpro ■

I fully agree idler rolling resistance is not very important at the time of roller manufacturing.

Rolling resistance of roller is generally high due to excess grease present between labyrinth seals and close tolerances of labyrinth seal. Until and unless roller factory run / rotated for 1 –1.5 hors to pump out excess grease roller rolling resistance can not be reduced

In case of very good Tolerance between labyrinth seals with proper grease filling rolling resistance will be more initially however roller seals will be effective towards Dust and water ingress

On the other hand in case of more space between labyrinth seal and less grease between seals rolling resistance will be less at the cost of dust /water proof effectiveness of seal

I remember one of my client insisted for 100 gm weight for rotating 139 dia 25 mm bearing roller . We have shown roller rotating at 70 gm by simply not providing grease between seal lips

A R SINGH ■

Non-Plussed,

Certainly, someone has to disagree with the folly of GS's approach. I had already written on the matter which seems not to have made it into the forum yet.

Not taking into account the idler drag is admitting a low level engineering expertise. As rubber rolling resistance drops, the power idler drag plays on the design becomes significant. Presently, idler drag is around 15 % -20% of the overall rolling losses. In some cases, with very efficient low rolling resistant rubber cover, the idler drag influence can be > 30%.

Certainly, if you do not consider this fact you waste the client's money and allow the supply inferior products. ■

Gentlemen,

As indicated by Mr Nordell idler drag IS a large concern, especially for our more discerning clients. We spend many many hours every day testing and retesting idler rollers for drag figures.

However, even though we do many hours of testing I still believe it is a subject that should be investigated more thoroughly. For instance the testing done by ourselves (and I am sure other manufacturers) generally involves in only issuing out a single figure for roll drag resistance. In reality there are multiple drag figures for rollers. A combination of factors (many stated above) can combine to give a different result for the same roll i.e. temp, time, speed etc.

Having an accurate drag figure for rolls does aid a conveyor designer to more accurately predict the power requirements of the conveyor. I could (but wont for fear of retribution) name a number of conveyors where this figure has been overlooked and the conveyor has not performed satisfactorily. ■

Trpimir...You are most welcome...(especially since I obviously came out on top with this one)

Cheers

LSL Tekpro ■

Dear Chance,

Although what you say is true, its impact is small compared to the weight of belt and material over the idler span. "Seal" drag is usually the dominant drag component. ■

G'day

GSpriggs(Tekpro) has it correct, but for design use CEMA "Standard" values is a good start. On startup, the idler drag will be higher than when run-in some short time later but you need enough start torque to move the belt in the first place particularly if you plan to load it up soon after start-up. Otherwise run the belt empty for a while (some days) and watch the empty power come down on the PLCmeters.

Also see LNordell's reply again. ■

Dear Mr. Trpimir,

I had a discussion with Mr. Nordell of CDI,USA during his visit to our office wherein he stated that they developed idler with rolling friction is very very less. You may direclty write to Mr.Nordell regarding the same.

Regards.

A.Banerjee ■

I was involved in creating Rim Drag values for idler rolls and the following data on the rolls was obtained by using the simple test bench methods.

I believe the Manufacturer should have a spreadsheet which encompasses the following.

Rim Drag @ Fabrication (New)

[Rotational Break away values and running at 600 RPM and 1000 RPM]

Rim Drag @20 hours running[Rotational Break away values and Running values

at 600 RPM and 1000 RPM]

Rim Drag @50 hours running[Rotational Break away values and Running values

at 600 RPM and 1000 RPM]

Rim Drag @100 hours running[Rotational Break away values and Running values

at 600 RPM and 1000 RPM]

Rim Drag @150 hours running[Rotational Break away values and Running values

at 600 RPM and 1000 RPM]

Rim Drag @200 hours running[Rotational Break away values and Running values

at 600 RPM and 1000 RPM]

ETC.

(Any other information should be available)

Note:- Continental and Prok did their own testing and they placed the various aged hours rolls in a frame in a bank of 10 and a fine fishing cord from a small sheave horizontally onto the first roll and then wrapped 5 times on first roll and then to the top of the second roll and again 5 wraps then to the top of the next roll and so on until all rolls would rotate when the weight was on the cord tail off the last roll. The tail of the was then run over a small sheave so the line left the last roll top horizontally and down under a small sheave so the tail cord hung vertical with a loop and back to a sheave vertically under the lead start of the cord so as to make a complete loop of cord. A clamp on a slide with a calibrated tension gauge was affixed to the cord between the two small bottom sheaves and the Rim Drag was measured, and divided by 10 (Rolls), to obtain the breakaway values. The same rolls were then put into a small flat belt with a drive and tail pulley with known rotational Rim drag values. The increase in drag was calculated and divided again by 10(Rolls) to obtain the running Rim Drag values at the 600RPM and 1000RPM rotational speeds.

These test measurements can then be used to aid in conveyor design. ■

If I may below there is a sciencedirect link to full text of a paper titled "Laboratory Tests of Idlers Rotational Resistance – Selected Issues".

http://www.sciencedirect.com/science...7852201500363X

Best Regards! ■