When handling sulphur, operators must consider risks such as
explosions, fires and environmental protection, and bulk-handling
equipment needs to be able to prevent or contain these hazards
Sulphur is considered to be a hazardous commodity in many
places, not only because it is prone to explode and cause fires,
but also because of the negative impact on the environment in
the event of dust emissions and spillage through careless
handling. As a hazardous commodity, sulphur handling comes
with ever stricter requirements for minimizing pollution and calls
for operators to secure shiploading and unloading operations by
eliminating spillage and minimizing dust emissions. To meet these
requirements, state-of-the-art environmentally-friendly
equipment is required.
“Everyone in the business knows that there are three mai
issues when unloading sulphur: the high explosion risk, extreme
corrosion, and stringent requirements for environmental
protection,” says Anders Svensson, Cargotec Sales Manager.
“These difficulties were the trigger for Cargotec looking at
different solutions and developing a full range of Siwertell
unloaders that can offer economical, clean and safe sulphurunloading
“Siwertell loaders and unloaders are among the highestperforming
environment-friendly systems available for sulphur
handling that the market can offer. Their conveying line is based
on totally-enclosed screw conveyors configured in such a way
that negative pressure is created in the conveying line and all
connection and transfer points are totally enclosed and sealed.”
For unloading operations, cargo pick-up is carried out below
the cargo surface in the ship’s holds. With a unique inlet feeder
mechanically guiding the cargo into the screw conveyor, Siwertell
unloaders are designed for a layer-by-layer unloading method,
which minimizes dust creation from cargo ‘avalanches’ inside the
hold. They are also equipped with loading chutes that reduce
dust creation at the loading point.
A Siwertell unloader can be configured to discharge sulphur
either to a jetty conveyor, for further transportation to storage
areas, or directly into trucks or rail cars. “The most common
and efficient way, especially for travelling rail gantry-based
unloaders, is to integrate the unloader in a complete conveying
and storage system,” explains Jonas Fack, Sales Director for Bulk
Terminals at Cargotec. “In such cases, the transfer point from
the Siwertell unloader to the jetty conveyor is rendered dustproof
through a specially-designed transfer trolley with
integrated dust suppression system.”
Direct discharge from the Siwertell unit to trucks — which is
the most common application for the road-mobile unloader
range — or rail cars is carried out through specially-designed
loading bellows also fitted with an integrated dust suppression
“There are often restrictions where sulphur can be unloaded
because of the environmental risks associated with it, however,
because our Siwertell unloaders have totally-enclosed systems,
operators can continue to unload sulphur even in areas where
the strictest environmental regulations apply. There are many
examples of Siwertell unloaders operating in environmentallysensitive
areas or close to populated areas.”
Handling sulphur involves many risks. Apart from environmental
ones, the largest hazard, also involving the most serious
consequences, is the risk of explosions and fires. To handle this,
Cargotec has developed a safety system, known as the ‘4S’
(Siwertell Sulphur Safety System), which is designed to minimize
the risk of explosions and detect fires.
To prevent explosions and fires, the Siwertell unit is equipped
with nozzles that spray water at the inlet feeder and in the
conveyor transfer points. An automatic lubrication system is
installed to lubricate and cool down end bearings and
intermediate bearings.
“Even with preventive technology in place, there are rare
occasions on which an explosion occurs anyway or a fire starts,
so we have designed a system that reacts immediately upon
detection and extinguishes any fire,” Fack says. There are fire
detectors along the conveying line, and when activated these
automatically start the fire extinguishing system spraying water
and stop the conveyors. This is vital to prevent fires entering the
storage building.
To manage any explosion, the conveyor’s steel casings are
reinforced with extra-thick steel, and explosion-venting valves
are fitted along the conveyors and dust collectors to relieve
To achieve an economical unloading operation, all cost factors
have to be minimized. The most important factor is governed by
the real through-ship capacity. This not only depends on the
rated capacity, but equally — or even more importantly — on
the efficiency of the unit during clean-up, where an arm system
plays a significant role in providing adequate reach to all corners
of the ship’s holds. “The Siwertell unloader has a flexible and
strong unloading arm, which means that a high through-ship
capacity with minimal unloading time can be achieved. This
substantially reduces shipping and crew costs,” says Fack.
As energy prices continue to rise, minimal consumption is
important. “We design unloaders to consume the minimal
amount of energy, for example, only 0.2 litres fuel/tonne is
required with a Siwertell 5 000S unloading prilled sulphur —
which is granular and therefore free flowing — or about
0.7kWh/tonne with a larger 1,600tph [tonnes per hour]
Svensson adds that: “Operating a Siwertell unit on a dedicated
sulphur mission is extremely cost efficient. The speciallydesigned
conveying line with stainless steel components is
practically maintenance-free. There are few moving parts in a
screw conveyor and with its well-proven unique design, wear is
considered minimal, therefore running costs of a Siwertell
sulphur unloader are limited to consumables.
“Also, clean, dust-free unloading operation is an advantage
from an environmental perspective, as well as from an economic
one. With an uncontaminated operation, there is no need to
spend time and money on cleaning the jetty, ship or
neighbourhood. Loss of material, and its value, is consigned to
“Although dedicated systems are the most cost efficient,
Siwertell unloaders can handle virtually any dry bulk material.
This offers the operator a valuable sense of flexibility, as they can
combine the unloading of sulphur with other bulk cargoes, such
as fertilizer, phosphate, cement, grain or biomass.”
Depending on the size of unloader and the port’s power grid,
Siwertell unloaders can be powered from a diesel-driven engine
or directly from the grid. To comply with the latest exhaust and
noise emission regulations, the diesel engines are continuously
upgraded to fulfil the latest emissions regulations.
Road mobile units are normally powered from a diesel-driven
engine onboard the trailer, while the larger gantry rail-based
units are powered via a mains high-voltage cable on a reel
attached to the gantry.
Road-mobile unloaders can be used to discharge barges and
smaller ships, up to about 15,000dwt. They are mounted on a
semi-trailer, and are all fully road mobile for transportation
between different ports or between berths in the same port.
“The transition from transport mode to unloading mode is easily
carried out by only one person and takes about 30–45 minutes.
This unique design offers customers enormous flexibility to use
their unloader in more than one port and on different berths”.
For larger ships, Siwertell unloaders are normally installed on
travelling rail gantries. “This type of installation is the most
efficient set-up from an operational perspective and also
provides the best opportunity to adopt a truly environmentallyfriendly
sulphur-handling system.”
In ports where there are no rails, or where the unloader
needs to be moved away from the jetty, installation on a rubbertyred
gantry is possible. Also, as an alternative solution, Siwertell
unloaders can be mounted in fixed positions.
Cargotec improves the efficiency of cargo flows on land and at
sea — wherever cargo is on the move. Cargotec’s subsidiary
brands, Hiab, Kalmar and MacGregor along with its tactical
brands, such as Siwertell, are recognized leaders in cargo and
load handling solutions around the world. For dry bulk handling,
Cargotec supplies ship unloaders, shiploaders, conveying systems,
terminal solutions and reclaiming systems. Cargotec’s sales
totalled €2.6 billion in 2009 and it employs more than 9,500
people. Cargotec’s class B shares are quoted on the NASDAQ
OMX Helsinki.