Its not so much the idlers as it the flowability of the grease lubricant period, if the grease cannot flow the bearings will sieze up and you will lose idlers period. ■

Low temp grease is the key to low temp operation.

In this country -20C is nothing to get excited about. Only around -40 do you start to look at special steels & welding procedures.

Belts that are stiff like plywood at low temperature are a bigger problem, which is why they run on creep drives or are just left running all the time at low temp. ■

ANy API grease rated for low temperature use will work just be sure to spec the rating for your application.

Galvanizing your idlers will not help as it will wear off. ■

You ask:

However i am a bit skeptical about the shell and the shaft material for idlers. Wouldn't a carbon steel shell catch corrosion because of the excessive moisture in the sorrounding environment at -20 deg cel. So as the case with shaft material.

Can hot galvanizing of pipe be a solution for this ?

Reply is:

At sub-zero temperature humidity in surrounding air is zero. You need not worry about corrosion.

You have not mentioned normal operating temperature.

Forum members have already commented on other points raised by you. ■

As mentioned by others it is critical to use a suitable lubricant. Take care with the materials used for the sealing elements as many plastics become excessively brittle at low temperatures.

Steels up to -40 would not be a problem.

Regards,

adi Frittella ■

You should not use pipe construction for conveyor idlers. The shell tolerance is poor as is the TIR runout.

Many lubrication suppliers compound grease for -20 C operation.

A conventional steel idler can be applied in a -20C environment. There are ramifications of rolling drag of idler seal and bearing lubricant as is recognized by CEMA, DIN ahd ISO. THese points may be dominant if the conveyor is long or composed on many rollers.

There can be significant differences between seal designs and lubricants. We have had repeated difficulties with some manufacturers of idlers who assemble them with excessive rubbing friction. Sometimes 5-7 times the published drag. So, buyer beware.

One difficulty that is sometimes encountered - moisture and freezing of the seal assembly. ■

Dear Shri Yogesh,

Earlier respondents have already furnished adequate suggestions. I would only like to mention that -20 deg C temperature should not be an issue for the steel items of the idlers. It is the nylon or rubber components and greasing which needs to be given more thought. One can avoid nylon or rubber type or sealing by using zinc-aluminum alloy seals wherever possible. Plastic or rubber being used should be specifically suitable for their elasticity, flexibility and strength at the applicable temperature.

There are some regions in the world where winter temperature would be what you have mentioned but summer temp could be 35 to 40 deg C. In this situation please ensure that the components and lubrication remain suitable for such variation in temperature.

The applicable effect on the power for conveyor to be taken care appropriately as mentioned by others. Such power difference will be not by idlers alone but by other items also.

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 ■