Greetings from WA, USA:

This was an early sales pitch by Prok (Sandvik) for their drilling of a hole in the idler end disk. When the idler is in operation, the internal gas, within the roll chamber, heats up and the pressure drives the gas out of the roll chamber. When the conveyor is then parked, after running, and the ambient air cools, the gas returns to fill the roll chamber due to gas contraction. Without the hole in the end disk, the gas will pass through the bearing cavity along with contaminants such as fine grit and evaporated moisturee. Moisture will condense from cooling and deposit itself on internal surfaces (bearings). Aside from the moisture issue, gases may have entrained corrosive substances such as salt or product contaminants. The purpose of the hole is : a) to allow passage of the gas, in the roll chamber, without going through the bearing, and b) if the hole is placed downward, on the wing roll, this will aid in passing gas and condensate out the hole.

Another method is to fill the internal roll chamber wilth a solid, such as a foam, to eliminate the breathing. The expense is weighed against the environmental design factors. Others, have copied the Prok hole sale. And others have, filled the internal roll chamber when required to meet the design criteria.

Lorbrand, South Africa, has taken the hole idea to another step. They both drill the hole and seal the bearing chamber from both sides. This keeps grease lube in the bearing cavity and impedes the gas path through the bearing. They have been successful with this approach by customer accounting of dead rolls.

Viva la tinto (sic)

Lawrence Nordell

Conveyor Dynamics, Inc. ■

Greetings from WA, USA:

This was an early sales pitch by Prok (Sandvik) for their drilling of a hole in the idler end disk. When the idler is in operation, the internal gas, within the roll chamber, heats up and the pressure drives the gas out of the roll chamber. When the conveyor is then parked, after running, and the ambient air cools, the gas returns to fill the roll chamber due to gas contraction. Without the hole in the end disk, the gas will pass through the bearing cavity along with contaminants such as fine grit and evaporated moisturee. Moisture will condense from cooling and deposit itself on internal surfaces (bearings). Aside from the moisture issue, gases may have entrained corrosive substances such as salt or product contaminants. The purpose of the hole is : a) to allow passage of the gas, in the roll chamber, without going through the bearing, and b) if the hole is placed downward, on the wing roll, this will aid in passing gas and condensate out the hole.

Another method is to fill the internal roll chamber wilth a solid, such as a foam, to eliminate the breathing. The expense is weighed against the environmental design factors. Others, have copied the Prok hole sale. And others have, filled the internal roll chamber when required to meet the design criteria.

Lorbrand, South Africa, has taken the hole idea to another step. They both drill the hole and seal the bearing chamber from both sides. This keeps grease lube in the bearing cavity and impedes the gas path through the bearing. They have been successful with this approach by customer accounting of dead rolls.

Viva la tinto (sic)

Lawrence Nordell

Conveyor Dynamics, Inc. ■

After reading your inquiry and the solution of the hole, we think that even if the hole helps to avoid a moisture condensation it can be an entry of grit or different particles contaminants. Galda manufactures a rubber made flexible idler optimal to avoid this problem. The bearings are inside an iron made hook that avoid any particle or moisture from coming inside. To protect more the bearing a sealing gasket is inserted close to the bearing into the hook. This idler avoids corrosion and abrasion problems, allows a good alignment of the belt, resists aging. They are particularly recommended in oxidizables atmospheres (quarries, salt pits, fertilizers, mines). In case of needing more information you can visit galda’s web page: www.galdasl.es ■

After reading your inquiry and the solution of the hole, we think that even if the hole helps to avoid a moisture condensation it can be an entry of grit or different particles contaminants. Galda manufactures a rubber made flexible idler optimal to avoid this problem. The bearings are inside an iron made hook that avoid any particle or moisture from coming inside. To protect more the bearing a sealing gasket is inserted close to the bearing into the hook. This idler avoids corrosion and abrasion problems, allows a good alignment of the belt, resists aging. They are particularly recommended in oxidizables atmospheres (quarries, salt pits, fertilizers, mines). In case of needing more information you can visit galda’s web page: www.galdasl.es ■

This particular problem used to be something that idler manufacturers found very difficult to resolve. Piercing holes in the flanges of the steel bearing housings is certainly not the right way to approach this.

We have been manufacturing steel bearing housings for over thirty years and we are familiar with all of the arguments put forward by Prok, Lorbrand and others.

According to our researches and indeed now in the light of years of experience in the field by our customers - you definitely do NOT

need to incorporate so called " Breather Holes " in the flanges of the idler bearing housings. In our view, this increases the risk of internal contmination of the idler.

The solution we have found is to develop a sealing arrangement within the bearing housing which resolves the issue.

The internal contamination problem is traditionally associated with labyrinth seals, which by definition are " Gap Seals " - i.e there is always a clear pathway between the outside air and the bearing itself within the bearing housing. This is why some idler manufacturers are obliged to incorporate sme additional kind of contact or wiping seal within their labyrinth seals.

Our contact sealing arangement is simple in concept but very effective in practice and can resist the pressure differential between the outside air and the inner idler chamber, which is the reaon for the problem in the first place.

See additional information on our website at www.edwinlowe.com

Thanks for taking the time to read this!

Tony Cook. ■

This particular problem used to be something that idler manufacturers found very difficult to resolve. Piercing holes in the flanges of the steel bearing housings is certainly not the right way to approach this.

We have been manufacturing steel bearing housings for over thirty years and we are familiar with all of the arguments put forward by Prok, Lorbrand and others.

According to our researches and indeed now in the light of years of experience in the field by our customers - you definitely do NOT

need to incorporate so called " Breather Holes " in the flanges of the idler bearing housings. In our view, this increases the risk of internal contmination of the idler.

The solution we have found is to develop a sealing arrangement within the bearing housing which resolves the issue.

The internal contamination problem is traditionally associated with labyrinth seals, which by definition are " Gap Seals " - i.e there is always a clear pathway between the outside air and the bearing itself within the bearing housing. This is why some idler manufacturers are obliged to incorporate sme additional kind of contact or wiping seal within their labyrinth seals.

Our contact sealing arangement is simple in concept but very effective in practice and can resist the pressure differential between the outside air and the inner idler chamber, which is the reaon for the problem in the first place.

See additional information on our website at www.edwinlowe.com

Thanks for taking the time to read this!

Tony Cook. ■

K. R. Giridharan,

If you wish to have a breather hole with minimum of its adverse effects, it seems that the only solution is to have an inner tube slightly bigger than spindle diameter. This inner tube is located between two bearings and it isolates the bearings from the air in the roller shell. But this adds into cost.

Detailed engineering analysis of this issue is given in my book 'Engineering Science and Application Design for Belt Conveyors'. It analyses air exchange during static as well as dynamic condition of rollers, when there is no inner tube.

Calculations indicate that the number of air exchages is more when there is breathing hole (rotating condition and air pressure difference due to vortex).

Regards,

I G Mulani.

Author - Book on 'Engineering Science and Application Design for Belt Conveyors'.

parimul@pn2.vsnl.net.in ■

K. R. Giridharan,

If you wish to have a breather hole with minimum of its adverse effects, it seems that the only solution is to have an inner tube slightly bigger than spindle diameter. This inner tube is located between two bearings and it isolates the bearings from the air in the roller shell. But this adds into cost.

Detailed engineering analysis of this issue is given in my book 'Engineering Science and Application Design for Belt Conveyors'. It analyses air exchange during static as well as dynamic condition of rollers, when there is no inner tube.

Calculations indicate that the number of air exchages is more when there is breathing hole (rotating condition and air pressure difference due to vortex).

Regards,

I G Mulani.

Author - Book on 'Engineering Science and Application Design for Belt Conveyors'.

parimul@pn2.vsnl.net.in ■