Page 62 - HUB-4 Issue 98

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Skirt around the subject
Along the length of the loading zone, the entire enclosure
needs to be well-sealed with belt skirting.
• Single skirting should be cut to match the belt’s trough
angle for a tighter seal. The best designs can be mounted
externally for easy and safe adjustment.
• Dual skirting is an engineered design that incorporates a
primary and secondary seal, providing an additional layer
of protection against spillage and fugitive dust. Dual
skirting is available in urethane and rubber.
• Self-adjusting skirting systems use gravity to apply light
downward pressure, minimizing maintenance needs and
making them the right solution in some situations. [Fig.5]
Figure 5 - Skirting is the only solution to ensure a well-sealed
loading zone, whilst a series of dust curtains act as a brake to
slow air speed.
Curtain call
Turbulent air can be stabilized by extending the transfer chute
enclosure along a specified length of the conveyor, providing
more space for larger particulates to drop back onto the belt.
While some airflow will still be present, the key is to slow it to
under 1 meter/second (m/s) (approximately 200 feet per
minute), slow enough for particulates to settle.
Strategic curtain placement gives dust particles more time to
agglomerate and settle onto the belt. Chutes that are
properly sealed and retrofitted with three curtain zones
recirculate the airflow and allow dust to settle. Field tests
show a drastic reduction in emissions of both nuisance and
respirable dust with the correct curtain set-up.
Discharge Debris
Fugitive material at the discharge zone can also be
problematic. Carryback from inadequate belt cleaning can
lead to spillage and cause airborne material along the entire
length of the belt return.
To prevent carryback, manufacturers of belt cleaners have
devised durable solutions capable of cleaning belts from the
most abrasive, corrosive, acidic, or liquid substances without
damaging the belt. [Fig.6]
Figure 6 - Keeping conveyors clean is vital to prevent fugitive
material from being carried back along the return side of the
belt.
CASE STUDY: Energy-from-waste processing –
Germany
A major energy-from-waste plant in the Hamburg region of
Germany, processes around 300,000 tonnes of waste annually.
The facility handles a variety of materials and generates
energy in the form of electricity and heat, while also recovery
residual materials for reuse. A key part of the operation are
its 40 conveyor belts – from 800mm to 1200mm in width and
typically running at 1.3 m/s – used to transport abrasive
materials through the process. Persistent carryback on most
conveyors led to excessive cleaning demands, undermining
productivity and creating potential safety risks.
Martin Engineering’s experts visited the site and
recommended an innovative belt-cleaning solution, the highly
effective CleanScrape® Primary Cleaner and SQC2™
Secondary Cleaner. Both cleaners are perfectly suited for
tough conditions where space is limited. They have long
service life and deliver effective belt cleaning without risk to
the belt or splice. CleanScrape® Primary Cleaner is especially
durable and has a unique design. It is installed diagonally
across the discharge pulley, forming a three-dimensional
curve, and incorporates a matrix of tungsten carbide tips.
Applying minimal pressure, it removes hardened material
without damaging the belt or splice.
A total of 30 CleanScrape® Primary Cleaners and 5 SQC2™
Secondary Cleaners were installed on the affected conveyors.
Thanks to the optimised belt cleaning performance, the plant
achieved a higher level of productivity with much less
maintenance. The installation significantly reduced the
amount of cleaning and unscheduled downtime, which
lowered the cost of operation.
Conclusion
While conveyor transfer points are not the only source of
dust, they are among the most prevalent generators of
particulate emissions. Beyond health and safety, eliminating
airborne dust delivers numerous benefits, including better
housekeeping, improved environmental management, less
maintenance, process efficiency, greater productivity and
whole-life cost reduction.
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www.hub-4.com May/June - Issue 98