hydrocyclone harmony
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Hydrocyclone Harmony
is of the same quality no matter whichsupplier it comes from, but this is not the
case. There are many polyurethane screen-media suppliers in the market and the
products they offer are all different.
Ensuring maximum efficiency from your sand washing plant
By Ben Winter, design engineer, CDE Global
When considering hydrocyclone-basedsand washing plants there are
several factors which should be
considered to ensure minimum plant wear.
The benefits of replacing inefficientbucket-wheel systems with hydrocyclone
washing plants have been well documented.
However, these operational efficiencies can
be further enhanced by considering anumber of key factors that can help reduce
operating costs.
Vertical vs inclined
cyclonesPlants which include an inclined
hydrocyclone configuration generate excesswear on one side of the cyclone resulting in
increased costs for spare parts and
unnecessary plant downtime. This can beavoided by employing a plant with a vertical
hydrocyclone arrangement.
Consideration should also be given to
the extent of the rubber lining within thehydrocyclone, as this is key to ensuring
maximum wear resistance. CDE’s experience
of sand washing around the world has led to
the conclusion that a cyclone lined with10mm of rubber offers the best solution.
Cyclone discharge and
feedboxA large rubber-lined feed box positioned to
ensure the cyclone underflow is discharged
across the full width of the dewateringscreen will maximize the screening area and
ensure high-efficiency dewatering of the
sand. It is also helpful if this feed box can be
opened in order to monitor the cyclonedischarge on to the dewatering screen.
If the feed box is too small it will result in
excess wear in the feed box itself as well as
on the dewatering screen. This will occurbecause all of the discharge impacts on the
centre of the screen rather than being
spread across its full width.Also, discharging the cyclone underflow on
to the centre of the screen means that the full
screening area is not being utilized, which
results in the sand product having a highermoisture content than should be the case.
Dewatering screenWhile polyurethane screen media is generally
accepted as the only sensible choice for sandwashing plants, it is important to consider thetype of polyurethane selected as well as the
set-up of the screening panels.
Often, it is assumed that all polyurethane
Consider, too, how the dewatering screenpanels will be secured in place. When using
panels that have to be bolted into position itis important to take into account the
reduction in screening area that this ‰
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Sand Processing
causes, as well as the increase inmaintenance downtime when the panels
need to be replaced. By selecting modular,
non-bolted panels, maintenance time can be
significantly reduced.Another factor to consider is the wear
protection offered to the screen. For example,
are polyurethane side panels included tooffer this additional protection? Given its
wear-resistance properties, polyurethane
is, once again, the best option here.
Finally, as with any dewatering operation,the longer the material can be held on the
screen the more efficient the dewatering
process will be. It is important that design ofthe sand washing plant ensures this objectiveis being met. The introduction of a dam bar
at the end of the dewatering screen can help
allow this to happen. Sand washing plants
that do not have a means of retaining thesand on the screen for the longest possible
time will deliver washed sand with a
higher moisture content than should be thecase.
Rubber springsIt is important to consider the means by
which the vibration from the screen is
transferred to the material, to ensure it isdewatered most effectively. Typically, rubber
springs transfer 10–15% more energy to the
screen than systems which employ steel
springs. This results in better dewatering ofthe material and also helps protect the
screen frame from vibration that is likely tolead to plant failure.
Systems that employ steel springs tend to
transfer a lot of vibration to the screen
frame compared with rubber springs. InCDE’s experience, more often than not this
results in damage to the frame, which
means increased costs and downtime.
Slurry pump protectionProtecting the slurry pump in the sump areareduces the risk of damage to the pump and,
ultimately, plant failure due to the ingress of
rogue aggregates from the sand washing
phase. Although only a small measure, it canoffer significant advantages for operators.
Plants that include an integrated pump
ensure that the pump is protected fromdamage by rogue aggregates by means of a
polyurethane pump protection mat with a
20mm aperture.
Matching cyclone anddewatering screen specsMatching the capacity of the cyclone to the
dewatering screen specifications ensuresoptimum performance of the sand washing
plant. If the screen is too small to manage
the volume of material coming from the
cyclone, the result is excess wear on thescreen. This, in turn, can lead to cracking of
the screen due to overloading. It also means
the sand is not being dewatered as effectivelyas it should be.
Float systemThe purpose of the float is to maintain therequired level within the sump even if there
are variations in the slurry feed rate. This
also ensures the sump never overflowsleading to the loss of fine sand to ponds.
Vertical float systems are much more robust
than other types.
SummaryImportant considerations when using ahydrocyclone system include:
• Maximizing the rubber lining within
the hydrocyclone; this is a key factor in
ensuring maximum wear resistance.• Positioning a feed box to ensure the
cyclone underflow is discharged across
the full width of the dewatering screen;
this maximizes the screening area.• The longer the material can be held on
the screen, the more efficient the
dewatering process will be; consider adam bar at the end of the screen to aid
this.
• It is important to consider the type of
polyurethane that is selected as well asthe set-up of the screening panels.
• Matching the capacity of the cyclone to
the dewatering screen will ensure
optimum performance of the sandwashing plant.
For further information visit:
www.cdeglobal.com
A typical Evowash sand plant from CDE