I don't know if I would go to the trouble of installing balancing monitoring equipment to check the perfect balance of idlers.

However if one spends an idler and upon stopping the idler reverses rotation, the idler should be replaced... (please maintenance people this is my view).

A new idler must have some adquate balance specification. In long conveyors with large numbers of idlers, not paying attention to the idlers create an array of maintenance issues.

Since we are on the subject of idlers... Why is it that the main problem for maintenance of conveyors is the one that people cares less about when specifying a conveyor?

Regards

Antonio Reis

www.vitrom.com ■

Although it is possible to balance idlers, the cost makes it impractical -- especially if there is a likelihood of experiencing build-up on the idlers.

Unbalanced idlers are susceptible to early bearing fairure and are, therefore, likely to be replaced earlier than balanced ones. although unbalanced idlers can have an adverse affect on belt tracking, it is only minor (unless the idler stalls). The greater danger is with earl bearing failure that can cause the idler to stall, be strapped, and become a belt threatening double-bladed knife.

The recommendation by Mr. eis to replace idlers that move by themselves due to poor balancing is correct -- why wait for a mal-balanced idler to create problems when it can be replaced easily?

Regards, ■

Dear Sir

Idler balance is an issue if you want to run the belt and roll RPM above the published standards. Typical limits are around 700 RPM. Some manufacture's tubing and fab procedures allow for 800-850 RPM. Above these levels balance and concentricity are critical for bearing survival from imbalance forces and belt flap modal amplification factors. Overland conveyor upgrades are the pioneers in this area. SELBY in the UK is running ( at last count) at 8.4 m/s with balanced rolls (193mm dia), Lachhammer pit in Germany has a belt running at 10 m/s, KPC in Indonesia is/was running above 7 m/s, Aloca in Australia is/was toying with going to +9m/s from 7m/s using balanced rolls (see publication of David Morrison in IIR publication).

Lawrence Nordell

Conveyor Dynamics, Inc.

1111 West Holly St

Bellingham, WA 98225

USA

ph 360/671-2200

fx 360/671-8450

email nordell@conveyor-dynamics.com

website www.conveyor-dynaimcs.com reformated 1/2002 ■

So that there is no misunderstanding on the subject...

The issue here is related to inspection, detection etc, of unbalanced idlers and not if a balanced idler is required.

My opinion is that once an idler is placed in service, one has very limited options that make economical sense to determine its condition with respect to balance.

My argument is:

The time required to install portable vibration analyses equipment negates such Task.

The cost of permanent sensing on the block is too costly for the operation and adds another maintenance item and this one requiring skilled labor.

Timming/Probe lights only show the reaction of the idler in reference to the surface speed of the belt at one point. The ones using this technique play the lottery in determining the condition of an idler.

So in a sense after the idler is instaled balancing it is very difficult and not economically sound.

In view of the above, mandatory replacement of idlers at a predetermined time interval is the most efficient method of maintaining them. Once out of the line one can do whatever necessary.

Again my question put in different words.

Why does everyone talks and writes about the initial condition of the equipment and never consider the maintenance issues that this systems have?

Regards ■

Hi Baskar

An easy solution would be to use Poly / Plastic Rollers.

Off the shelf they are very close to perfectly balanced.

There are several manufactures and they seem to be very aggresive in regard to pricing etc.

If you would like further info please contact me. ■

Dear Shri Baskar,

If the customer is ready to pay for balancing, one can do that. However, practically indirect remedy / solution is to use tube of superior specification (i.e. lesser ovality, lesser variation in thickness and better straightness) and then manufacturing technique should be adopted such that it should not introduce imbalance.

Idlers of lesser imbalance are already used on belt weighers.

The issue of imbalance in the idlers will be of concern for high-speed conveyors.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyor.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 5882916 ■