CONVEYOR KNOWLEDGE & INFORMATION TECHNOLOGY (Pty) Ltd
Registration Number 2000/009433107
Dear Sir,
Thank you for your interest in the ConveyorKit Pipe Conveyor ! In response to your Client’s queries regarding the suitability, cost and design of a pipe conveyor for this application, we are have provided said details below.
Our pipe conveyor has been retrofitted on two plants where pneumatic conveying systems had been used for many years to convey cement or potash. Both installations are in India and a major justification for the retrofit was the reduced total operating cost and flexibility in increasing the throughput of the plant.
On the Potash Plant, a 45 kW drive unit on the pipe conveyor has replaced approximately 300 kW in compressor, pump and filter unit drives and the absorbed power on the pipe conveyor is approximately 25 kW. On the cement plant the capital cost had a payback period of less than 2 years, based purely on the saving on power. In both instances the on-going maintenance costs for bend replacement and level of maintenance skills needed on compressors, etc. provided further justification for the pipe conveyor.
The pipe conveyor, like troughed conveyors, is generally far more flexible in its conveying capacity than are pneumatic conveying systems. With the incorporation of variable speed controllers, the belt speed ( and hence throughput) and be regulated on the pipe conveyor to suit the operational conditions, within the design range of the conveyor.
To this end we believe that your Clients’ requirements to convey up to 600 tph of cement could be accommodated better using a pipe conveyor than a pneumatic conveying system. In addition, if there is any doubt about the future requirements in excess of 600 tph, the pipe conveyor could be upgraded relatively easily.
Regarding the capacity and conveying distance requirements, there would be no problem satisfying either the 600 tph or the 1.3 km distance. Our reference installations extend from approximately 200 m in length conveying at 250 tph, through to 3.2 km in length at 1800 tph. We have an installation in Richards Bay South Africa where we convey heavy minerals (Zircon, Rutile, Illmenite, etc.) over a distance of 1 km at 2500 tph to feed a ship loading facility. We therefore believe it would be more cost-effective to use a pipe conveyor than to erect silo(s) at the jetty and upgrade the pneumatics.
Our pipe conveyor designs include features which are beneficial to our Customers in terms of capital cost and on-going operational cost / complexity.
To a large extent our success has been in the ‘de-mystifying’ of the pipe conveyor concept and we have published numerous articles to this effect over the last 5 years. As a result we have found greater enthusiasm from Clients worldwide in their consideration of the pipe conveyor as an alternative technology to troughed conveyors and pneumatic systems and we are recognised as having the greatest number of pipe conveyor installations per year for 3 years running.
For longer distance conveying applications (i.e. greater than 500 m) our experience is that conveyors must often be elevated to clear existing structures, roadways, railways and the like. In these applications we recommend that our triangular conveyor gantry be used and that a traveling maintenance trolley be incorporated onto the gantry (seen adjacent – Richards Bay RSA, 1000 m long, 2500 tph, 4.2 m/s belt speed, 360 mm nominal diameter).
There is a substantial capital cost saving in using this design due mainly to the fact that the structure is light-weight, there are no permanent access platforms and the on-going maintenance of sheeting (i.e. box gantries or similar) and flooring, etc. is reduced substantially which, at coastal applications can be costly.
Where the pipe conveyor is to be shorter a number of options are available and, in discussion with the Client, we generally select the most appropriate design.
For ground-line applications the pipe conveyor can be incorporated into a stringer-type module which is secured to individual plinths (Fig. 1 – L & T Tadipatri, India), or mini-gantries are used (Fig. 2 - Indo Gulf, India).
Figure 1
Tadipatri ‘Downhill’ Pipe Conveyor, 600 m long, 1000 tph clinker, 120 degree C material temperature, 100 m drop to discharge point, 3.4 m/s belt speed, 340 mm nominal pipe diameter. Gantries used at a low ground clearance to cover rough mountainous terrain, 12 m long with panels at 2.0 m pitch, 600 mm wide access walkways both sides.
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Figure 2
Indo Gulf Pipe Conveyor, 3.2 km long, 1800 tph coal, rock phosphate & ore. Nominal pipe diameter 450 mm, 3.5 m/s belt speed.
This section (adjacent) comprises panels supported on individual plinths along the jetty. Panels are tied together to form a cost-effective modular stringer. At the head-end (see left), the conveyor elevates to 30 m above ground level and is supported in an open-type gantry with trestles at 20 m pitch.
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In terms of the route selection for the pipe conveyor at the GBC Facility, the pipe conveyor can negotiate radii which often assist the designers in guiding the belt around / over existing obstacles. I have included a few pictures below which illustrate some of our installations and which demonstrate the flexibility of the conveyor.
Vikram Ispat - India, 250m long, 350mm diameter, 400 tph HBI briquettes, compound vertical & horizontal curves. |
Rock Phosphate, Richards Bay, South Africa. |
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The pipe conveyor is often preferred over the troughed conveyor due to the fact that the product is enclosed within the belt, thus preventing moisture contaminating the material as well as the fact that product cannot leak out, or be blown off of the belt. The return-side belt also encloses the dirty side and prevents spillage along the structure.
Transfer points are usually eliminated by the pipe conveyor. The fact that the pipe conveyor can be routed around relatively tight radii offers the flexibility in the layout to negotiate vertical and horizontal curves, thereby eliminating the need for transfer points. Transfer stations in themselves are usually sources of spillage and pollution and are a large contribution to the operational budget for the life of the facility.
The visual impact of a conveyor on the environment is more prevalent in decision-making process today. Our experience has been that in Richards Bay in particular, the environmental case required the conveyors (now 3 pipe conveyors) to have the smallest possible footprint and the lowest visual impact. Both the boxed gantry and triangular gantry (seen below) with maintenance trolleys were considered and as can be seen from the pictures below, the triangular gantry is far less imposing than the conventional sheeted gantry (not our installation) seen adjacent.
Notwithstanding the absence of sheeting, the pipe conveyor overlap is selected to ensure that no water ingress occurs into the transported material. In the case of the Richards Bay projects for example, ConveyorKit had to guarantee that the sealing in the overlap. In this application therefore we can assure the Client that there would be no moisture ingress into the product en-route to the ship.
Depending on the layout of the pipe conveyor envisaged for GBC, the terrain over which the conveyor must be routed, the environmental impact assessment requirements and the complexity of the route, we would be able to prepare a pipe conveyor design which is best suited for the application and your Client’s needs.
For this application, the length of 1300 m and conveying rate of 600 tph of cement is certainly feasible.
We would use either a steel cord belt or fabric belt, depending on the Client’s preference. Our Indo Gulf conveyor used twin drives (one tail, one head) and a steel cord belt. At Richards Bay we have used fabric belt on all three conveyors, one of which has a 450 kW head drive unit.
Usually fabric belting is preferred wherever possible, from a cost and maintenance point of view. Typically an 800 N/mm 3 or 4 ply belt would suffice in this case.
For a bulk density of 700 kg/m3 we would use a belt speed of between 3.0 and 3,5 m/s. The pipe diameter would be a nominal 375 mm and in the absence of sheeting, we would use a 1500 mm wide belt to secure an improved overlap.
For the structure we recommend the triangular gantry with maintenance trolley. Gantry lengths at Richards Bay range from 20 m in length up to 48 m where the conveyor crosses the river. The positioning of the trestles would determine the gantry lengths along the route, and we suggest that the maximum span be kept within 50 m, to ensure an economic design. Longer gantries are feasible is essential, but are more costly per meter.
In terms of budget costing for a 1.3km long pipe conveyor, we assume the conveyor would be elevated over its’ entire length and that the trestles would be steel, not concrete. The indicative cost for this conveyor ex-works South Africa would be AU$ 3.75 million. Added to this would be the freight, shipping and transport to site, the erection and commissioning of the conveyor. We assume that all of the latter would be sourced / supplied by yourselves.
The above mentioned price would include the rollers, belting, gantries, trestles, pulleys, drives, on-board field instruments, maintenance trolley, head and tail-end chutes and skirts, take-up station. All civil works, erection, tie-ins at each end, power and control systems would be by others.
I trust that the above is sufficiently comprehensive for your evaluation and that of your Client. Should you have any further queries in this regard we would be pleased to assist as we are able.
Yours faithfully,
A. Woollon - Operations Director
ConveyorKit
