I dont believe these idlers are more economical compared to fixed idlers for the following reason

- if the shell in or bearing fails in one of the rollers the entire set needs to be replaced.

I know this can then be refurbished but there are associated costs such as replacement of roller,retrieval if underground,then transport to be refurbished

Regards

Shane ■

Dear Mr. Singh,

The garland idlers can only be used for conveyors which are primarily horizontal. These idlers are not recommended for use when belt conveyor is inclined to the horizontal. The garland idlers on inclined conveyor, will be in vertical plane, which would not be perpendicular to belt conveyor path. This will result in to continuous slippage between belt and side rollers. The degree of slippage will depend upon the inclination. However, shiftable conveyors often include these idlers for short length of inclined head end, where somewhat faster wear of the shell is expected and accepted.

The garland idlers are easy for replacement. They have flexible connection with the conveyor frame. In case of shiftable conveyor, this flexibility is very beneficial to provide flexibility to the entire frame.

Regards,

Ishwar G Mulani.

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

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Joy Rolller web site

http://www.conviber.com/productline...seidlers/main ■

Dear Mr Mulani

re garland idlers - I cn understand the reason why they are not preferred for inclided runs.

But, would U say that they will aslo act as forward tilt idlers and hence, contribute to tracking/training the belt.

We have them installed on a 2.2km belt with flat and inclined runs - presumably to save costs. I can say that the biggest issue is the correct location of the mounting holes in the stringer on each side is very important - both carry and return strands.

Cheers

James ■

Dear Mr. Singh,

We have extensive experience comparing conventional fixed roller with garland type suspended idler system. Syncrude Canada (SCL) contracted Conveyor Dynamics, Inc. (CDI) to assist in selecting a conveyor system for their $150 million dollar expansion plans starting in 1990. THis was to determine if a conventional trough conveyor, of a modern design, should be used to replace SCL's large garland idler.

THis became a 3 year project. A theory was developed for power consumption, the theory was tested, over the 3 years, in laboratory testing with special jigs, and later in field installations. Some of the methods were published in Bulk Solids Handling

Vol. 16, No.3 1996 entitled: "THe Power Of Rubber - Part i".

SCL replaced about $2 million, in garland idlers per year. Maintenance is very high, with the sticky tar sand and down to

-50C temperatures. A new ifixed idler frame and support structure was developed/installed/evaluated that showed a significant large savings over the garland replacement costs.

MAny field measurements were taken to evaluate roll and idler wear mechanisms as well as power consumption. The mechanisms of belt rtracking were investigated.

Alignment verses power consumption were theorectically developed and then measured in the field for verifcation. Programmed stringer offset were developed to include: a) normal shiftable errors, b) + and - 3 degrees variations in axial stringer alignment, and c) realigned to a high accuracy. These changes were introduced on a 2 km conveyor overland carrying up to 11,000 t/h. The instalation was measured with survey prisms to orient, in 3-dimensions, the position of the idlers.

We were able to differentiate the carry and return strand garland behavior on empty and loaded conveyors to measure and characterize garland forward tilt with changes in tonnage. Changes in belt tension were adjusted by the winch controlled take-up. Belt tension was also calculated using a special sag deflection jig installed after the head drive take-up and before the tail drive. These measurements were collected one year of operation with a range of temperatures.

Bottom line:

a) garland idlers are good for frequently shifted conveyor installations and where large + 600mm lump is transported.

b) in some cases garland have advantages in high impact load stations where controlled flow is not practiced.

b) they are not recommended for fixed stringer conveyor installations due to items noted in item (c).

c) tHey mistrack the belt , consume more power, cause more idler and belt wear, and have substantially higher maintenance costs ■

Dear Mr. R J Morish,

Please inform the inclination values in different zones of the conveyor i.e. starting from tail end, zone-1 length and inclination, next zone-2 length and inclination ………… This data would enable to formulate certain opinion concerning your installation. You have already installed the conveyor with garland idlers. If your inclinations are not very large, possibly you need not to worry unduly, because this is a fait accompli situation.

Regards,

Ishwar G Mulani.

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

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Dear Mr Mulani

It is 2.2kkm long and the last section is inclined at 12 deg. to provide a transfer to the shiploader.

It runs over reclaimed land/jetty..hence, the horizontal section goes up/down a little.

It is 25 yo and has only done 10,000hrs + due to demand and rate with most of the original Prok idlers installed.

I think that it was done on the cheap - combined stringer to support the garland idlers and also weather covers and suit the floating ground module design.

I can say that tracking - esp - on V return garlands - is very dependent on the setup/cross alignment of the garland idlers as we have proven when boilermakers replace the stringer without due regard for dimensions.

Is is what we have and not going to change.

Other than that we have seen centre roll shell wear - wave formation wear patterns in the shell near the edges...

Enough chit chat for now

James ■