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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