11th April 2002, 14:09
Most overland & stockyard conveyors are satisfactorily grounded on concrete sleepers. Is it then safe to conclude that overland conveyor idler frames can be satisfactorily seated on concrete frameworks? From a structural point of view the support frames carry less load than the sleepers. Strength is no problem, durability would be better, maintenance less, installation easier, ground pressure reduced and manufacturing costs also reduced. Moulds could be designed to provide pleasant finishes to complement the terrain e.g. dry stone walls in the British Isles & bamboo in SE Asia. Even a newly built conveyor is an ugly animal and when it has been in service a few months it becomes uglier still. This must be down to the steel (what else?) which is expensive & even more so when design time is added to the equation. Lets face it, if steel construction is so accurate why are we always finding slotted holes on every bit of kit, idlers, stringer connection plates, bearing sole plates… everywhere? If we rely on survey techniques for setting out & final alignment then what is the point of shop made steelwork in between? All site works involve some measure of grouting to meet location criteria. There are no reasonable site arguments against casting the frames. Sleepers are already cast on a lot of sites.
Dear Mr. Johngateley,
Your comments are very interesting. I too have observed that facilities in our industry are typically unnecessarily ugly. I have attributed this to poor rationalization of the framing systems and equipment, resulting in ugly clutter. The typical eyesore atop an otherwise graceful machine (typically of box construction) is the chiken house (electrical house). It take little expense to intigrate the electrical house with bold corrugated siding and simple clean perimeter lines.
Simple awareness of aesthetics will lead any designer to produce more attractive systems. Rationalization of framing systems and equipment will result in a more attractive uncluttered and efficient system.
The use of concrete for conveyor framing is very interesting since it is completely moldable and can be made very attractive. I am curious about the cost implications. Some times cost is dictated by use and familiarity. I look forward to following your progress in promoting concrete framing systems for overland conveyors.
Joseph A. Dos Santos, PE
Dos Santos International
531 Roselane St NW
Marietta, GA 30060
Tel: 1 770 423 9895
Fax 1 866 473 2252
Email: jds@ dossantosintl.com
Web Site: www.dossantosintl.com
There is progress being made to combine ergonometrics, esthetic style, and economy. For examples visit our website Warkworth, Muja, et.al. Over 350 km installed to our teams' design standards. The supports are called "belt friendly" meaning belt protective. They are lighter, quicker to install, more accurately aligned, no slotted holes, no stringer post-installation hammering of of idler frames, lower overturning moment on footings, footings with more accurate positioning and so on. Further, we have developed and installed a completely new frame assembly that we will put on the website in the near future. Idler spacing is pitched at 4-5m on the carry side and in horiz. curves. These comments refer to overland, tunnel and stockyard conveyors. We win over 65% of overland conveyors we bid with our world-wide associates MGS in Brazil, Barclay Mowlem in Australia, Bateman in South Africa (now disolved), and Krupp Canada in Chile. We continue to seek partners with our goals, vision, and intensity to succeed.
The elevated structures are also undergoing significant changes along with maintenance methods. As the overland is increasing in single flight length (now 17 km is comming) economies of competition ever pressures us to find better ways. Measure efficiency by: a) $$/ton/km, b)kg/m of steel work, and c)hours to install and commision +3 km overland. Each new system is advanced from the one before: better rubber rolling efficiency, lfewer idlers with larger diameters, lower cost per ton to transport, and easier and quicker to install. Most of our overland ,as said before, do not require ANY post alignment If it is done, it is not at the idler transom.
Beyond our website information, we are willing and available to discuss these advancements.
Conveyor Dynamics, Inc.
1111 W. Holly St.
Bellingham, Wa. 98225
I've worked in structural and reinforced concrete construction for 35 years. The difficulty of using concrete as a structural frame might have more to do with the necessity to keep at a minimum the steel reinforcing rods 1.5 diameters at a minimum beneath the concrete face.
The expansion of the reinforcing steel due to differentials in the coefficients of thermo expansion can lead to exfoliation of the concrete covering the reinforcing steel.
In addition the reinforcing steel does not take compressive force alone (as the concrete does and must handle tension forces also.
This might create design problems that determine even greater depth of reinforcing steel relative to the concrete face and create members to bulkly and thus impractical.
The tollerance for structural steel is generally +/- 1/4 inch. This tollerance does not take in consideration the expansion/copntraction coefficients per temperature changes, and thus I think that the slotted holes are much more a function of consideration for the assembler than related to the qualities of steel as a suitable structural component.
I would suggest that regardless of the ergonomics - that structural steel is the easiest and most cost effective method with which to construct over land conveying systems.
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