Re: 90 Degree Trouhing Idlers
Dear Mr. Singh,
The 90 degree troughing angle mentioned by you, would mean that the belt bending at idlers kink will be 90 degree. Such large bending will reduce the life of belt, because it will put very high strain at the crease.
Generally, 45 degree is the limit for 3-roll idlers. One has to use 5-roll idlers for more troughing angle, but it will rarely exceed 55 degrees. Generally, there is a perception that higher troughing means superior version; this is not rue. Higher troughing implies more strain on the belt. So, one should use the troughing angle befitting to the application case. Higher troughing angle also demands longer length for transition.
Possibly, there are some manufacturers who manufacture special type of conveyor with 90 degree bend in cross section, but this has not been popular as a general belt conveyor.
Incidentally, pipe conveyor is a belt conveyor with 180 degree toughing ! (both side 180 degree).
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 ■
90 Degree Trughing Angle
Dear Shri I G Mulani
Thankyou vry much for sugestion for 5 roll idler. Infact with 3 roll idlers we can go upto 45 degree yroughing with 5 roll 90 degree angle is feasible seems to be feasible.
At each idler location belt will angle will be changed by 45 degree only whereas we are changing 60 degree at each roll location in pipe conveyor.
The idea is to devlop conveyor which can negotiate 4-5 degree more compared to conventional conveyor in any case troughing angle will not be more than 45 degree at loading point where maximum inclination will beof same range as per conventional conveyor
Troughing angle of conveyor will be changed by 5 roll adjustable idlers after loading point as we do by 3 rollers in pipe conveyor
I feel this typeof conveyor after formation of semi circular profile can negotiate 4-5 degree extra inclination as in case of pipe conveyors
For this application belt troufablity should be good so that 90 degree troughing can be achieved
Material will rest on semicircular profile at centre line of belt.
belt crossectional surchage angle will be good and chances of roll back will be less than conventional conveyor
Material cross section inside this conveyor will be similar to pipe conveyor which also have about 65 percent filling
This is just an idea i will make a small conveyor for experimental purpose in my shop to findout behavior of material from roll back point of view.
with regards
A R SINGH ■
Re: 90 Degree Trouhing Idlers
Dear Mr A R Singh
If you can trough to 35 degrees with 3 roll idlers, then you can trough to 2 x 35 degrees with 5 roll idlers, i.e. 70 degrees.
A Swedish company called Conveytech in Helsingborg did what they called a U-Con conveyor. This started out as a 90 degree wing roll arrangement as you mentioned.
They then squashed it further into the U-Con Delta which had a triangular cross section same as a bar of Toblerone chocolate, with the belt edges just touching at the top. This they used for fine materials where they had to load anywhere along the conveyors length, like from a ship unloader.
They then rolled it into a pipe and then squashed it into the final U-Con arrangement. This shape looks like the end view of you lap-top bag, and ran between two flat rollers.
This idea was it could go round pulleys even loaded in this shape and go vertical and go virtually anywhere. with horizontal and vertical radii of only a pulley radius.
Unfortunately, the rubber could not take the histerysis and the belts collapsed after only a couple of months operation.
I believe Conveytech went out of business.
Please note that the steeper the wing roll, the narrower the feed chute, which can cause problems.
Stick to 35 degree 3-roll and 45 degree 5 roll wherever possible
Regards
LSL Tekpro ■
90 Degree Troughing Idlers
Dear Sir
If you can trough to 45 degrees with 3 roll idlers, then you can trough to 2 x 45 degrees with 5 roll idlers, i.e. 900 degrees.In pipe conveyors at each location 60 degree troughing is provided
I understand you are talking about conveyor similar to sicon where radius of pulley dia is feasible
I appriciate your concern about belt regidity and life but special belt can be designed to suit the requirement.pipe conveyor is having 2x180 troughing and belts are devloped for that application.
I fully agree normal conveyors having 35 degree troughing angle are best as there is is no additional load on belt orwing rolls. However special conveyors like pipe conveyors are to be considered where layout or other local conditions does not permit use of conventional conveyor
Regards
A R SINGH ■
Re: 90 Degree Trouhing Idlers
Dear Mr Singh
You are quite correct about the 45 degree idlers..but I do avoid them for reasons you mentioned.
If you were to use 2 x 45 degree = 90, then you effectively have a U-Con which never caught on.
The reason is that the vertical belt flaps demand large vertical radii, and collapse inwards in convex curves. You are better off with a pipe conveyor or wherever possible, conventional ones.
Regards
LSL Tekpro ■
Re: 90 Degree Trouhing Idlers
Increased troughing will help. It has been shown by German researchers in the 1930's that the smaller the hydraulic radius, the steeper the angle of inclination attainable when handling bulk material. For reference, the hydraulic radius is the ratio of the bulk material cross-sectional area to the perimeter that touches the belt. The number of idlers to accomplish 90° troughing is a function of the belt construction and the belt width. A special belt can be done with 3 rolls while some belts will require 7 rolls. Only the belt's manufacturer can tell you exactly. ■
Re: 90 Degree Trouhing Idlers
All of the above have points to make. However, there is no discussion on: stress and strain in the belt's carcass. It is not proportional to the individual trough angles but is dependent on the junction location, fatigue flexure each junction will experience and on the list of other dependent factors noted below.
THe greatest stress and strain is in the first junction (trough joint) which has the maximum vertical pressure. subsequent junctions have significantly less strain and can take greater discontinuities subject to the carcass construction and idler configuration.
THe junction stress is highly dependent on carcass construction and on:
1. cover thickness and ratio of top & bottom (non-linear modulus)
2. carcass thickness
3. trough angles
4. idler roll lengths by location
5. idler spacing
6. idler diameter
7. material crossectional loading
8. material density
9. vertical and horizontal curves
10 belt width
11. carcass properties and construction
12. probably missed a couple
It is less stressful, on the belt, to have the first junction angle limited to less than the remaining angles.
CDI uses these factors in the design of all overland conveyors and pipe conveyors
Some use the conventional 35 - 45 trough angles and then bend to 90 degree (vertical) to contain material in the loading station. This does not overstress or fatigue the carcass.
A higher trough angle can increase the allowable incline slope angle. Its benefit is in reducing roll-back of material sluffing on the edges and in consolidation of the product as noted by Mr. Tapp.
Applying the higher angle should be considered with shortening the center roll to improve material consolidation (interlocking). ■
Re: 90 Degree Trouhing Idlers
The 90 degree x 5 roll trough idler has been used successfully at transfer points in South Africa (Optimum Colliery is an example). In the experimental section the use of this type of idler eliminated the need for skirts, as well as ensuring centralisation of load. This solution was implemented throughout the mine.
Adi Frittella
AFRIPP PROJECTS CC ■
90 Degree Troughing Idlers
Dear Adi Frittella
thank you very much for giving information The 90 degree x 5 roll trough idler has been used successfully at transfer points in South Africa &use of this type of idler eliminated the need for skirts
As indicated by Mr Graham Spriggs vertical curve will be difficult at vertical curve portion I feel troughing angle to be reduced to 65-70degree.
with 90 degree troughing horrizontal curve of smaller dia may be feasible and advantage of climbing at 5-6 degree higher inclination seems to be feasible.
Mr nordell sugession is also very good to reduce central roller length
A R SINGH ■
Re: 90 Degree Trouhing Idlers
In addition to my previous reply I would like to add that I failed to mention although the German researchers measured a definite advantange to a smaller "Hydraulic Radius", it was measureable and repeatable but not very much. A few degrees at most. Not something that would give much of a usable design advantage in actual applications. For higher inclinations than can be achieved with conventional conveyors with smooth top belts, you would best to go to one of the following depending on the inclination required: shallow moulded cleat belts like Georgia Ducks' Cleatlok, deep moulded cleat belts like Metso's Escort belt, Enclosed Conveyors like Pipe Conveyors, Sicon, Foldbelt, Corrugated Side Wall belts with cleats, a Continental HAC, etc. ■
90 degree trouhing idlers
Dear Sir,
It is commonly known higher troughing angle is useful for negotiating steep angles
whether 90 degree troughing idlers can be provided to negotiate higher inclination
A R SINGH ■