Abrasion loss

DIN53516/10N

- Lower is better

- Check 10N or 5N

- Alternative = ISO 4649  

Hardness Shore A

Extend to Shore D

For elastomer only

- Higher or lower is not better, just different

Elastomere temperature

Apart from being a danger of degration is too high, temperature also infue on the elasticty of eslatomere.

Higher = softer  /  Lower = harder

Therefore, sometimes it's necessary to adjust the use of elastomere or to use a different hardness

Natural Rubber

Positive

Good Price

Good Friction

Good abrasion resistance (100mm³)

High impact and vibration absorption

Good elasticity

35° to 90° Shore A

150 to 90 mm³ ISO4649

Negative

Oil degradation

80°C max

Costly molding tools

Best uses

Shock absorber

Drum coating

Sealing skirt

Centering system

​

Poor uses

Belt cleaner blades

​Rubber oil absorption

​Natural rubber can absorb oil, grease and hydrocarbon.
It inflates, becomes sticky, slack and lose its grip with vulcanized other parts.

Synthetic rubber can offeer more or less oil resistance : Nitrile, butyle, Neoprene...

Polyurethane is insensitive

Synthetic Rubbers

Similar to Natural Rubber but…

​

Positive

Slightly higher temperature limit

Better chemical resistance

Negative

Higher price

​

Examples: Nitrile, Butyl, Neoprene ...

Rubber ozonolysis

On sea level, ozone (O3)  is mainly found in industrialized and high density zones. It can react with some parts in rubbers (Natural, Nitrile, Butyle) creating acids on surface and creates cracks. Thoses cracks can be infiltraded by dust material and interfers with belt cleaners

​

​

Polyurethane Esther (MDI PUR)

Positive

High abrasion resistance (20mm³)

Average impact absorption

Cheap molding tools

55° to 95° Shore A

30 to 20 mm³ ISO4649

​

Negative

Medium friction

High Price

80°C max

Bad vibration absorption

Bad elasticity

Hydrolysis weakness

Best uses

Scraper blade

Sealing skirt

​

Poor uses

Shock absorber

Motor pulley lagging

Polyurethane hydrolysis

Hydrolysis is a chemical reaction where a polymere molecula is broken by water molecula.

For polyurethane, hydrolisys reaction start at 60°C.

First step the PUR becomes sticky plasticine.

Final result is a friable hard PUR.

Polyurethane Ether (TDI PUR)

Similar to Polyurethane Esther but…

​

Positive

Slightly higher temperature limit

Better hydrolysis resistance

Negative

Higher price and minimum quantity

Other polyurethane : HDI,  IPDI...

Other applications

Polyethylene UHMW

Positive

Average price

Low friction

Average abrasion resistance

Food grade

Average impact resistance

Can be partially recycled

Negative

Poor abrasion resistance

Bad UV resistance (virgin/white)

60°C max

Bad elasticity

Best uses

Hopper coating

Impact bar top

Scraper deflector

Security bar

Poor uses

Scraper blade

Polyamid 66

Similar to Polyethylene but…

​

Positive

Slightly lower friction

Slightly higher temperatutre resistance

Cheaper price

​

Negative

Lower abrasion resistance

Lower chemical resistance

Hydrolysis weakness

Ozonolysis weakness

Hardness Vickers (Hv)

Alternative : Hardness Rockwell (HRA), Mohs scale

For hard material only

- Higher is better against abrasion

- Gives a proportional indication of the wearing resistance

​

​

Be careful :

Harder   =   Weaker against   impact

Sintered Alumina

Positive

Very high abrasion resistance

1100-1300 Hv

Food grade

400°C max

Low friction

Average compression resistance

​

Negative

High price

Poor impact resistance

Difficult to shape

Best uses

Drum lagging (profile wear issue)

Hopper coating

Low impact bar top

Rubber coating top

Security bar

Poor uses

Scraper blade (blunt issue)

Impact protection

Agglomerated Alumina Grains

Positive

High abrasion resistance

900-1100 Hv + epoxy

100°C max

High friction

Negative

High price

Poor impact resistance

Low compression resistance

Best uses

Drum lagging

Brake pad

​

Poor uses

Impact protection

Wear Resistant Steel (Mn, Ni, Cr, Ti)

(ex: Creusabro, Hardox...)

Positive

Good abrasion resistance

High impact resistance

450°C max

450-500 Hv

​

Negative

High price

Best uses

Chute

Conveyor Head Box

​

Poor uses

Belt cleaner blades

Cast Basalt

Positive

Good abrasion resistance

700-800 Hv

Average impact resistance

400°C max

​

Negative

Difficult to shape

Outdated material against sintered aluminate

Best uses

Chute

Pipe

​

Poor uses

Applications where sintered aluminate is possible

Wear resistant Cemented

Tungsten Carbide

(10%Co+Cr+V.C)

Positive

Ultra high abrasion resistance

1600-1800 Hv

700°C max

Low friction

Negative

Very high price

Very poor impact resistance

Low compression resistance

Best uses

Belt cleaner blades

​

Impact resistant Cemented

Tungsten Carbide

(20%Co)

Positive

High abrasion resistance

800-1000 Hv

700°C max

Low friction

Good impact resistance

Average compression resistance

​

Negative

Very high price

±30% lower lifetime

Best uses

Belt cleaner blades with impact

Mining bucket

​

PUR vs Tungsten

Polyurethane is soft enough to let some material pass in between it and belt

​Tungsten is hard and offers a cutting edge able to stop smallest particles

Sintered alumina vs Tungsten

May experience rounded edge wearing

Nearly no any material can corrode it

Always offers sharp cutting edge

Some uncommon acids can corrode it

PUR vs Rubber

More friction (> more centering effect)

+ Lower abrasion resitance

= shorter lifetime

​

Less friction (> less centering effect, may be sometimes poor)

+ higher abrasion resitance

= higher lifetime

Pulley force transmission

Friction : Euler-Eytelwein formula

(Note diameter has no importance)

Micro gear

Micro gear is not friction, it's a mechanical link only possible with one spiked hard part grab into one tender other

Like friction, micro gear can have some slipping issue

​

Porous Aluminate vs spiked Aluminate

Regardless of the level of wear, the friction stay the same

As the spikes reduce due to wearing, the transmission created by micro gearing decreases and disappear

Spikes are never higher than 2,5mm

Positions

Constant pressure

Wearing of the blade, irregularity on the belt thickness, belt cleaners needs to have a dynamic and adaptative pressure system to be adaptatives, ex: steel springs, elastomeres, air pressure...

Some of them can't works on 2 ways belts

It's also the solution to "stock" pressure and reduce interventions

Importance of tension pulley for pressure

The tension pulley, apart from keeping enought winding on the head drum (cf. EULER formula) also prevents the belt to move up and down where secondary belt cleaner is installed. Ex: belt way reversion, start of long conveyor without adaptative tension...

Waring: when moving down, the belt can have a huge force and movement distance above the cleaner elasticity therefore it can damage it.

Always keep an eye on its cleanliness to avoid belt deformation or lift up.

Irregular wearing

Conveyor belts carry material in mound shape, leavind more material to clean in the center than the sides

Therefore, all belt cleaners will have an irregular wear

If nothing is made to correct this, the cleaner will only have pressure on the sides and won't clean proper the belt anymore whatever the remaining size of the blade

No compensation

With compensation

Sealing skirt wear

Material dust and sealing skirts can create lateral gaps on the belt very difficult to clean. Sometimes it's just impossible.

Contact angles

Obtuse angle

Clean with reduced pressure

Needs nearly perfect surface, can be dangerous if no secure pressure system (sometimes not enought like hole in belt) 

Can increase belt cracks

Perpendicular angle

Needs more pressure to clean

Requires precise adjustement

Can clean any kind of surface, nearly never any danger

Angle adujstement

90° angle

Optimum cleaning

95° angle

Strong vibrations

Bad cleaning

85° angle

Bad cleaning

Can be used when huge surface bumps and damages

Specific angle modification

Some belt cleaners uses elasticity that chnage the angle

Need to check angle when belt is running/ adjust a different angle when stopped

Tangent angle

On primary position, the force pushes against the belt cleaner

On 85° angle, there is a specific danger to damage (swallowing) the belt cleaner and so the belt

1 or 2 ways belt

Mechanical ability

Material evacuation

Mono blade vs multi blades

Mono-Blade

Slightly better cleaning

Perfect for recycling

Multi-Blade

Materials can pass inbetween blades

Not compatible with paper, wire or fabrics

Holes or patch on the belt

Damage on sides or side movements of the belt

Adjustments on blade(s) replacement

Adaptation to irregular shape

Cost regarding wear and accident

Side movements

Belt side movement can be due to :

- Perpendicular transfer

- Conveyor geometry failure (accident)

- Idlers brackets alignement failure

- Drum alignement failure

- Belt shape (banana)

- Belt junction alignement failure

- Wind

- Season change (temperature dilatation> conveyor deformation)

- Heat source (conveyor deformation)

Note 2 ways belts are more capricious

Differential speed

Small diameter

= High rotation speed

Big diameter

= Slow rotation speed

__________________________

Belt move to smaller diameter

= Increasing roller speed

Belt move to bigger diameter

= Decreasing roller speed

__________________________

​

Difference of speed rotation

= Difference of friction

= Generated pivoting force

Minimum side movements

Some tracker keeps belt centrered continuously

Most tracker react only after a minimum side movement 

Edges damage

Belt side movement are typically the problem that created belt sides damages

​Belt centrers are generally installed only when there is a problem

Paradoxally, many belt trackers use contact with belt edges to detect its position and so can be a source of damage for the edges

Fluid state

Loading point generaly mixes toghether the material and air and create a temporary kind of fluid.

Because of the material flux, this fluid can have more pressure than atmosphere on some points.

Therefore, the sealing has to be much more efficient and resistant on tloading point.

Please also note a good sealing only exist when both parts match each other and regulary adjsuted. That's why we had to consider the sealing depends on what is under and above the belt.

Ponctual support

Because idlers are ponctuals support, the belt can have a sinusoidal shape. If the skirt doesn't follow this shape, material can easely go out of the conveyor or even destroy the skirt on closing angle.

Impact bar are a good and easy solution to make the belt flat and easier to seal.

Its also a continuous belt support without any punching hole risk.

Transition zone

When the belt quit the tail pulley with a flat shape and comes to the idlers with U shape, it needs a minimum distance to tranform called "transition zone".

There is different method to evaluate the transition zone length depending the charateristics of the belt but we can generally consider the following formula :

TDmm= [ width of the belt m] x [x Angle) ] x 45

ex: Belt 800 angle 30°

  = 0,8 x 30 x 50

  = 1200mm

Because the conveyor is a machine to transport from a point to another, the loading point is, most of the time, close to the tail pulley and can be on the transition zone.

Installing impact bar in this transistion zone is difficult enought to be declined by most impact bed manufacturers, but not impossible.