CONVEYOR STRUCTURE DESIGNED FOR CONVEYING RUN OF MINE MATERIAL

While many people might have thought that all the possibilities for development in the area of conveyor technology had been exhausted, a totally new system of transporting bulk material has now been created, known as RopeCon.

The need to transport large volumes of bulk material over long distances is very quickly confronted with ecological and economic barriers.

The best-known means of transporting large volumes of bulk material over long distances include:

Rail:
Only economic in the case of very large distances, only low gradients possible, unsuitable for difficult terrain. Loading and unloading terminals required

Truck:
Personnel-intensive, high dust and noise emissions, extremely high energy consumption, unsuitable for difficult terrain.

Ropeway:
Discontinuous material feed, intermittent conveying, only suitable for transporting bulk material up to approx. 500 t/h.

Conventionalconveyor:
High energy consumption due to flexing of the conveyor belt, in mountainous terrain only possible with bridges, cuttings or tunnels.

Particularly where there is a need to transport material over ecologically sensitive terrain, this therefore often leads to conflicts between economic necessity and environmental desirability.

The search for the ideal long-distance conveyor for bulk material led to an amazingly simple solution It is based on a patented idea from Doppelmayr and combines the advantages of ropeway technology with the benefits of belt conveyors - the RopeCon long-distance conveyor was created.

This latest development in the area of continuous conveying will be developed for manufacture in the shortest possible time thanks to Doppelmayr's experience in ropeway construction, Doubrava's experience in handling bulk materials and ContiTechs conveyor belt know-how.

RopeCon, the latest continuous conveying system for transporting all kinds of bulk materials over medium to long distances, essentially consists of a special conveyor belt with vulcanized corrugated side walls which runs on two track ropes in the upper and lower belts via running wheels attached to the belt. The belt performs a haulage and support function and, just like a conventional belt conveyor, is driven by a drive pulley in the head or tail station.

With this conveyor system it is possible to cover extremely long transport distances (up to 20 km), whereby the track ropes are carried by a suitable number of support towers, similar to those used on aerial ropeways, and rigged at either end.

After passing the drive station the belt is turned over, then turned back again before it reaches the return station so that the soiled side of both the top and bottom belt always faces upwards.

Commercial grade, torque-balanced, galvanized, fully locked coil ropes are used as track ropes. Track rope support frames every 6 m to 12 m maintain the position of the track ropes in the rope spans and retain the spacing between the upper and lower belt. These frames also ensure that the material transported remains in place in the case of high wind velocities, thus preventing lift-off or deropement. In addition, a belt cover can be fitted to the frames if required. The four track ropes in combination with the steel support frames replace the bridge construction of a conventional conveyor.

The conveyor belt consists of a flat belt with multi-layer polyester-colyamide fabric or with steel cord reinforcement. It is fitted with corrugated side walls which keep the bulk material in position Cross members are mounted at certain distances (to suit the loads; along the length of the conveyor to hold the wheel sets (rope sheaves). These wheel sets are supported by the track ropes which run along the sides of the conveyor belt. The high side plates on the wheels ensure the precise tracking of the belt even in the case of side winds. The wheels are made of high-grade polyamide which has optimal rolling resistance and is UV resistant.

The wheels are inspected in the loading station, so that no maintenance is required along the track and thus no complex catwalks are necessary.

-	Conveying distances	up to 20,000 m
-	Theoretical mass flow rate	over 5,000 t/h
-	Lump size	up to 300 mm
-	Belt speed	up to 6.0 m/sec
-	Belt type	EP or steel cord
-	Towers spacing	over 500 m possible

Fig.3. Return/tension station with belt turning devices

2.3 THE BENEFITS

Conveying distances of up to 20 km

Conveying capacities over 5,000 t/h possible

Easy means of crossing obstacles such as rivers, gorges, buildings, roads trees etc.

Extremely long rope spans of over 500 m possible

No maintenance parts along the track, therefore no catwalks required

Significantly lower kinetic resistances than with conventional conveyor belts

Minimal noise emission

No preparation of the track necessary, i.e. no tree clearing, no bridges, no cuttings, no tunnels

Minimum time and effort required for removal

No belt skewing is possible

No belt guiding devices required and therefore no damage to belt edges (increased service life of conveyor belt)

Sturdy and extremely low-maintenance construction

Corrosion protection work reduced to a minimum

3. ROPECON at STRENGEN/AUSTRIA

3.1 GENERAL INFORMATION

In order to develop a new conveyor system for series production it was essential to subject RopeCon to the harshest test conditions possible.

The final section of the S16 Arlberg expressway between Tyrol and Vorarlberg is currently being completed with the "Strengen Bypass" construction project. The key feature of this final leg is the twin-section Strengen Tunnel which is approx 6.8 km in length.

it had originally been planned that the excavation waste from the tunnel would be transported by truck from both the eastern and western ends of the tunnel and taken to a dump site.

At short notice ARGE Tunnel Strengen awarded Doubrava and Doppelmayr a contract to install the continuous conveyor system "RopeCon" at the western end of the tunnel. The authonties and local residents were immediately convinced of the advantages (emissions reduced to a minimum), which meant that the project planning and installation could be completed within a very short space of time. The transport costs have been reduced, the 115,000 truck journeys no longer required mean a major reduction in environmental impact as far as noise and pollution are concerned since over 100,000 litres of fuel have been saved. The Situation on site is predestined for the construction of RopeCon. The installation crosses the B316 Arlberg national highway, the Rosanna River and Arlberg West railway line.

3.2 BRIEF DESCRIPTION OF THE INSTALLATION

The waste material produced from the blasting work in the tunnel is transported from the twin tunnels to the loading station by dumper truck and tipped into the loading bin. From there it is metered and fed into the single-Jaw crusher with the aid of a reciprocating feeder. The crushed material is then transferred to the RopeCon via a vibrating feed chute.

Longitudinal Profile - RopeCon - Strengen

3.3 CONTRACT REQUIREMENTS

Fully automatic operation of the system

Availability: 365 days/year and 24 hours/day

Warranty covering the total period of use: 30 months or 1.1 million m

Warranty covering maintenance costs and energy consumption

No damage to the installation though unsorted broken drilling bars or anchor plates

3.4 TECHNICAL DATA

-	Location	Strengen - Flirsch (Tyrol/Austria)
-	Altitude	1,097 m above sea level
-	Temperature	-30 C to 25 C
-	Material conveyed	Landeck quartz phyllite
-	Bulk density	1,660 kg/m
-	Lump size	0 - 1,000 mm
-	Size of crushed material	0 - 250 mm
-	Total volume conveyed	1.1 million m
-	Running period	30 months
-	Feed	discontinuous
Fig.4. Detail view of the loaded belt
-	Distance between drum centres	248.9m
-	Vertical rise	17.2m
-	Rope span 1	115.1 m
-	Rope span 2	124,9m
-	Belt width	800 mm
-	Useful width	630 mm
-	Corrugated side wall height	200 mm
-	Belt type	EP 1250/4-7T/3T
-	Track rope	4 x 42 mm
-	Rope type	WS 1670 N/mm
-	Basic tension	4x475kN
-	Moving mass	39.0 kg/m
-	Weight of support structure	56.0 kg/m
-	Mass flow rate	600 t/h
-	Volumetric flow	360 m/h
-	Belt speed	2.62 m/sec
-	Idling power	5.5kW
-	Calculated motor power	45.3 kW
-	Installed motor power	75.0 kW
-	Filling factor	30%

4. ROPECON at LENZING/AUSTRIA

4.1 BRIEF DESCRIPTION OF THE INSTALLATION

Wood chips are fed onto the RopeCon by a 21 m long feeding conveyor.

The track for the RopeCon has been chosen by drawing a straight line from the loading to the unloading point, thereby crossing existing infrastructure. The unloading point is located on an existing building where the wood chips are unloaded into a surge bin. The rope tension forces are diverted into a concrete block anchored in the hill nearby.

A cover of coated aluminium ensures that the wood chips remain in place in the event of high wind velocities.

Longitudinal Profile - RopeCon Lenzing

4.2 TECHNICAL SPECIFICATIONS

-	Material conveyed	wood chips
-	Lump size	20-40 mm
-	Temperature	-25 C to 40C
-	Horizontal length	662 m
-	Vertical rise	38 m
-	Theoretical mass flow	350 t/h
-	Theoretical volume flow	930 m/h
-	Motor power in operation	56 kW
-	Belt speed	2.62 m/s
-	Belt width	800 mm
-	Side wall height	200 mm
-	Track ropes	2 x 52 mm, 2 x 42 mm

Fig.5. Proposed track of RopeCon Lenzing

5. COMPARISON OF CROSS SECTION AND MASSES CONVENTIONAL BELT CONVEYOR VERSUS ROPECON

Fig.6. Conventional Conveyor bridge vs. RopeCon-System

In Fig 6 it can be seen, that the cross sectional area occupied by the RopeCon is only 30% of a conventional belt conveyor.

An example of a 3,000 m long conveyor is shown in Fig.7. At the same belt speed and mass flow, RopeCon has only 90 % of moving masses and 30 % of total weight of support structures.

	RopeCon		Conventional Conveyor
Distance between drum centres Gradient Rope span / bridge Belt width Corrugated side wall height Belt type Mass flow rate Volumetric flow Density Belt speed Filling factor	3,000 0 200 650 140 St11206/3 1,000 625 1 600 335 74	m 0 m mm mm m t/h m/h kg/m m/sec %	3,000 0 40 800 St1600 6/4 1,000 625 1,600 3,35 73
Moving Masses:
q-material q-belt q-top idlers q-bottom idlers	829 17.7 3.8 3.8	kg/m kg/m kg/m kg/m	82.9 19.9 10.4 4.8
Total moving masses	377,700	kg	413,700
Steel structure weights incl. tower (15 m)
Rope (20 0m) / bridge (40 m) Platform Track rope frame 12m / idler frame 1.5m	136 7,5	kg/m kg/m kg/m	442 25.4 8.5
Weight in rope span/bridge construction	143.5	kg/m	475.9
Total weight of support structures	430,500	kg	1,427,700

Fig.7. Comparison of moving masses and weight of support structure

6. EXPERIMENTAL TESTS AND COMPARISON WITH CONVENTIONAL CONVEYOR

The Department of Conveying Technology of the University of Leoben carried out experimental tests at the RopeCon system in Strengen. Sound emission and power consumption were measured depending on belt speed and load conditions. Both results were compared with conventional belt conveyors.

6.1. MEASUREMENT OF THE SOUND PRESSURE LEVEL

The sound pressure level of the RopeCon system and two conventional belt conveyors was measured along the transport track at a belt speed of 2.62 m/s.

Fig. 8. Measurement of the sound pressure level

The RopeCon showed a maximum value between 55 and 60 dB(A) in a distance of 1 m. The two conventional belt conveyors had between 70 and 77 dB(A) in the same distance.

This can be explained by the bigger distance between the rollers and the lower number of bearings of the RopeCon compared to conventional belt conveyors. Additional, noise which results out of the movement of the rollers on the ropes is much lower than the noise of a belt running over idlers. The sound emission of the RopeCon system has no impact on the environment in medium distances. According to Austrian law the installation of a RopeCon is allowed in 10 m minimum distance to living areas. (This is not valid for feeding and discharge stations.)

A comparison between the RopeCon and conventional belt conveyors with similar conveying capacities shows a 3-times higher sound emission of the conventional belt conveyor.

Fig.9. Example of a sound pressure level chart

6.2 COMPARISON OF THE REQUIRED DRIVE POWER ROPECON VERSUS CONVENTIONAL BELT CONVEYOR

The required mechanical power, resistance forces and belt tensile forces were measured at the RopeCon in Strengen.

Fig. 10. Measurement of motor acting power

Based on the experimental results a computer program was designed, which allows a calculation of the required drive power of RopeCon at different belt speeds and transport length. A comparison between RopeCon and conventional belt conveyors was carried out for different conveying distances, at belt speeds of 3.35 m/s and a transport capacity of 1,000 t/h. The results are shown in Fig. 11.

	RopeCon		Conventional
Distance [m]	empty	loaded	empty	loaded
1,000	25.1	57.8	35.5	104.0
2,000	44.5	100.2	69.1	202.3
3,000	64.0	142.5	102.7	300.5
6,000	122.3	269.5	203.5	595.0

Fig. 11. Comparison of required drive power - RopeCon versus conventional belt conveyor

In both operating modes, empty and loaded, RopeCon shows lower values for the required drive power. This advantage increases with bigger transport capacities and conveying distances.

7. SUMMARY

With RopeCon a long-distance conveyor has been developed which combines the advantages of ropeway technology with the benefits of belt conveying technology.

Total moving masses, weight of the support structure and required drive power of the RopeCon are significantly lower compared to conventional belt conveyors. The sound emission of RopeCon is 3-times lower than the emission of a conventional belt conveyor.

The RopeCon in Strengen has now been running for approx 25 montns. Operating fully automatically and trouble-free under extremely harsh conditions. With this new long-distance conveyor Doubrava, Doppelmayr and ContiTech have taken a great step towards a new mechanical conveying technology for the continuous feed of bulk material. This development has already attracted a great deal of international attention which points to a highly successful future.

AUTHORS:

Hermann FRUEHSTUECK

Doppelmayr Seilbahnen GmbH, Rickenbacherstr. 8-10, A-6961 Wolfurt. Austria

Hermann FRUEHSTUECK holds a diploma in mechanical engineering he has been employed by Doppelmayr since 1984 as project and sales manager and holds the position of area manager for material ropeway systems. Doppelmayr Seilbahnen GmbH is the worlds leading lift and ropeway manufacturer with branch offices, plants and agencies all over the globe and has so far built and erected more than 8,400 installations in 71 countries on 5 continents.

Tel.: +43-5574-604-374: Fax: +43-5574-75590

E-mail: hermann.fruehstueck@doppelmayr.com

Franz KESSLER

Department of Conveying Technology and Design Methods, University of Leoben, Franz-Josef-Straβe 18, A-8700 Leoben, Austria

Professor Dipl.-Ing.Dr.mont. Franz KESSLER studied Mechanical Engineering at the University of Leoben and is since 2000 the head of the Department. In his career he has been involved with continuous mechanical handling equipment, especially belt conveyors as well as oil drilling and production technologies. On top of that KESSLER works as a consultant for various companies worldwide.

Tel.: +43-3842-402-250; Fax: +43-3842-402-254;

E-mail: kessler@unileoben.ac.at