Positioned alongside the existing silo, the
new silo consists of a 40,000-tonne free
capacity, reinforced, prestressed structure
with a 30m internal diameter and 55m
height. The clinker silo has two reclaiming
tunnels and a precast concrete conical roof.
The silo is founded on a full raft
foundation, 36m in diameter and 1.3m
thick. This raft is in turn founded on an
engineered fill layer, which extends 4m
below the natural ground level.
The silo receives clinker from the kiln at temperatures up to 205°C, via a silo feed Aumund steel pan conveyor. Two DemcoTECH-designed reclaim belts with heat resistant belting extract the clinker to feed the existing plant or rail loading system. The silo discharges at 250tph (tonnes per hour) onto each of the two reclaim conveyor belts.
The new silo was part of an expansion drive by NPC-Cimpor,
which included a new, second cement kiln, requiring an additional
silo for storage of the increased clinker production.
MATERIALS HANDLING EXPERTISE
Johannesburg-based DemcoTECH Engineering is an
acknowledged leader, both locally and internationally, in materials
handling systems for the cement and other industries. The
comprehensive suite includes specialized pneumatic, air-assisted,
troughed AeroConveyorTM and pipe conveyor systems to provide
totally enclosed, environmentally friendly handling.
The DemcoTECH pipe conveyor technology, comprising both
fabric and steel cord belting, and with up to 2,250tph conveying
capacity, can be designed using a triangular tubular gantry fitted
with a mobile maintenance trolley.
“At NOVA Cimangola’s Luanda, Angola plant, for example, we
supplied two maintenance trolleys for the pipe conveyors, which
had to negotiate an incline of up to 15° while carrying four
personnel together with spares and tools.”
The trolleys were manufactured and pre-tested in South Africa
at a 16° inclination, before being containerized for transport to site. The trolleys are self-propelled by an on-board generator
and include hydraulically driven travel mechanisms for a high level
of control. The trolley designs include a number of safety
features such as fully enclosed access facilities, emergency brake
systems and heavy duty traction control.
Working in conjunction with Claudius Peters in Germany,
DemcoTECH also supplied a 150tph pneumatic transport system
to convey cement from a kiln to multiple storage silos at the
Loaded, the pipe conveyors’ open belt is formed into a tubular
shape as it passes through transition idlers, giving it its customary
‘pipe conveyor’ name.
This ‘pipe’ shape is retained along the full length of the
conveyor and enables the conveyor to be curved through vertical
and horizontal curves that are far tighter than is possible with
troughed conveyors, while at the same time retaining the high-
capacity, long-distance conveying capability of troughed
At the terminal point the belt opens up for material to be
discharged in the same way a troughed conveyor is discharged.
On the return-side, the belt is also formed
into a ‘pipe’ shape and can be used to
transport material in the opposite direction,
with significant cost advantages. With the
exception of the specialized belt carcass
design, DemcoTECH’s pipe conveyors, with
diameters of up to 500mm, make use of
readily-available conventional conveyor
“We also engineer two-way pipe
conveyors, multiple curve pipe conveyors and
distributed drive pipe conveyors,” says van de
“Pipe conveyors are ideally suited to the
cement industry, offering opportunities to
reduce the number of conveyor flights,
eliminate transfer points, minimize spillage and
dust generation, reduce the conveying distance
and save total costs, while at the same time
addressing the environmental requirements.”