school board.png

TG Basics

Confidential - For internal use only

Thoses informations are only a small simplified part of existing knowledge around conveyor belt

Contact me for more

Arnaud WARTELLE

Materials : Elastomeres and plastics

Abrasion loss

DIN53516/10N

- Lower is better

- Check 10N or 5N

- Alternative = ISO 4649  

Image1.jpg

Hardness Shore A

Extend to Shore D

For elastomer only

 

- Higher or lower is not better, just different

Image3.png
Image1222.png

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

Image6.jpg
Image21.png
Image8.jpg
Image10.png
Image11.jpg
Image9.jpg

​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

Image1kkj.png

Synthetic Rubbers

Similar to Natural Rubber but…

Positive

Slightly higher temperature limit

Better chemical resistance

 

Negative

Higher price

Examples: Nitrile, Butyl, Neoprene ...

Image14.jpg

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 MDI Ester

Positive

High abrasion resistance (25mm³ to 12mm³)

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

molecule PUR r12.png
Image16.jpg
SealBloc r2.png

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.

Ikkljjkllkjjkmage1.png
Image1.png

Polyurethane MDI Ether

Out of

range

Similar to Polyurethane Esther but…

Positive

Slightly higher temperature limit

Better elasticity

Better hydrolysis resistance

 

Negative

Higher price and minimum quantity

Slightly lower abrasion resitance

Methylene-diphenyl-diisocyanate-3D-vdW.p

Other polyurethane

Out of

range

NDI: Rollers (Vulkollan®), silentbloc...

TDI : Foam, adhesives...

HDI, IPDI : paint, coating...

tdi.jpg

Rubber or polyurethane additives

Electrical conductivity
Increased abrsion resistance
Bactericidal

...

barium-sulphate-500x500.jpg

Polyethylene UHMW 1000 - 6000 - 7000

(Hostalen, Lactène, Lupolen, Stamylan, Supralen, Eltex)

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

Image19.jpg
Image20.jpg

Best uses

Hopper coating

Impact bar top

Scraper deflector

Security bar

 

 

Poor uses

Scraper blade

Image21.png
Image22.png
Image24.jpg
Image23.png

Polyethylene HD

250 - 500

Similar to UHMW but lower price and quality

Polyamid 66

(Nylon, Ertalon, Tecamid, Tecast,  Sustamid, Traidamid, Nylatron)

Out of

range

Similar to Polyethylene but…

Positive

Higher temperatutre resistance 100°C

Slightly higher mechanical resistance

Cheaper price

Negative

Lower abrasion resistance

Lower chemical resistance

Hydrolysis weakness

Ozonolysis weakness

Image25.jpg
Image26.jpg

Materials : Metals and ceramics

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

Image4.jpg

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

Image27.png
Image28.jpg

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

Image32.jpg

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

Image34.png
Image35.jpg
Image36.png
Image37.png

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

(ex: Creusabro, Hardox...)

Out of

range

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

Image38.png
Image41.jpg
Image40.png

Cast Basalt

Out of

range

Positive

Good abrasion resistance

700-800 Hv

Average impact resistance

400°C max

Negative

Difficult to shape

Outdated material against sintered aluminate

Image42.jpg
Image43.jpg

Best uses

Chute

Pipe

Poor uses

Applications where sintered aluminate is possible

Image44.png

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

Image45.png
Image46.jpg

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

Imagejjgghg1.png

Other special

Cemented Tungsten Carbide

- Food grade

- High chemical resistance

...

Pulley Basics

Pulley force transmission

Friction : Euler-Eytelwein formula

(Note diameter has no importance)

Micro gear

Image1000.png

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

Belt cleaners Basics

Positions

Image1 (3).png

Primary/ tangeant

Secondary / underlying

Internal

Design

Mono-blade

One unique blade supported by eslastic tension system

Multi-blade

Several independant blades supported by elastic tension system

racloflex N 800 multilame2.png
RacloFlex Sw r100.png

Irregular wearing

Image67.png

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

Therefore, all belt cleaners will have more wear in the center

Manual compenstation

Image4.png

To compensate the irregular wear, belt cleaner needs to be able to chnage its shape

Segmented /

adjustable mono-blade

Image100.png

Adjustable Multi-blade

Quickening wearing effect

If the belt cleaner maintenance is forgotten for a long period, it can start to let material pass trought it. In reality, material start to pass over the blade(s) and its wear speed increases a lot.

qw0.png

Very slow wear due to the belt

qw1.png

Slow wear due to some dust

qw2.png

Quick wear due to grains and dust

Automatic compenstation

To prevent forgetting of maintenance (quick wear) and/or to reduce it, some belt cleaners have partial automatic compensation

Image72.jpg

Automatic Mono-blade

Image14.png

Automatic Multi-blade

Constant pressure

Image10.png
P-TZ r3 B.JPG
Image8.jpg

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

Image78.jpg
Image2thytyh.png

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.

Its cleanliness has to be monitored to avoid belt deformation or lift up.

It's also important to clean it before installing a belt cleaner (wrong belt shape)

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

Image64.png

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

Image65.png
Image66.png

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 also the belt

1 or 2 ways belt

Mechanical ability

Imagenhgnh2.png

Material evacuation

Sealing skirt wear

usurebavette1.png
usurebavette2.png

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

Scratch wear

belt scratches.png

When the belt has scracth wear, some dust can pass throught the cleaner without any solving solution. Scrathes can occur more in specific industry like recycling.

Material hardening

sw colmatée.png

​Some material harden when stuck on cleaner blade (ex: glass composition). This creates a different front shape that allows material to built up and push aside cleaner and belt, severly reducing cleaning efficiency. There is no other solution than clean regularly the cleaner but unfortunately this is nearly never made.

Belt centrers Basics

Side movements

- Convevor geometry

ex: heat source, weather & seasons, accident

- Component geometry

ex: worn pulley lagging, clogged pulley, blocked idlers, pulley or idlers alignement

- Belt geometry

ex: shape (banana), side storage, junction alignement failure

- External force

ex: perpendicular transfer, heterogenous loading, non centered loading, wind

Note : 2 ways belts are more capricious

Image2hyhy.jpg

Belt stop

Specific idlerrs can be used to try to stop the belt to a maximum outgoing position.

This solution is limited to low force.

On high force, the idler can be broken or cut, or the belt can fall back on itself.

Belt movement slow-down

​Inverted idlers bracket doesn't center the belt (except for specific "auto-stable" belt) It only slow down the belt movement but it makes the centrer efficiency less reactive and shorter

Oblic rolling effect

When a idler is oblic, its rolling movement create a pushing force on the belt perpendiculary to the rotation axle

Therefore, you can apply a force on the belt by adjusting idlers and pulley angles

oblique.png

3 idlers supports often present 2 oblic external idler to try to always push the belt to the center 

oblique3.png

Active centerers uses this principle with a central pivot to rotates and push the belt to the required direction

centerer principe.png

Detecting belt outgoing

​There are many different principle or mechanisms to detect belt position and  manage rotation on pivots

Thoses different systems have different advantage

trackerc3.png
trackerc1.png
trackerc4.png

Rotation speed

rotatiion.png

When the belt runs:

- Big diameter idlers turn slowly

- Small diameter idlers turn quickly

Conical rollers

Conical rollers have many diameter

The diameter giving rotation speed is the average diameter of all diameters in contact with the belt

Friction is null on average diameter but increases as we move away

rotatiion cone 3.png
rotatiion cone 4.png
rotatiion cone 1.png

If the belt leave small diameter

- average diameter increases

- rotation speed decreases

- friction decreases

= less friction at lower speed

If the belt reach smaller diameter

- average diameter decreases

- rotation speed increases

- friction increases

= more friction on higher speed

Pair of opposite conical rollers

On pair of opposite identical conical rollers...

 

if the belt has the same contact on both rollers, they will have same friction at same speed

bicon 1.png

if the belt has different contact on both rollers, they will have different  friction at different speed

Ex: going to external right, friction and speed :

- decrease on left

- increase on right

bicon 2.png

Pair of opposite conical rollers + central pivot

1. Pair of opposite conical rollers on central pivot makes the whole assembly turn when belt move

2. The oblic result pushes the belt to the center

3. When the belt reach center position, there is no more difference between conical rollers friction and speed, the system returns to perpendicular position

Vario principle2.jpg

Biconical pulley

Be carefull to not make confusion : Bi-conical pulley shape tends to pull the belt to the center due to tension differential in the belt.

No question of rotation speed (only one piece)

Tambour.png

Transfer and sealing Basics

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.

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= [ belt width (m)] x [ Angle (°) ] x 50

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.

Rolling resistance

resiste roul.png

A loaded belt carryed on idlers has a wave shaepe amplified by loaded material. This shape has to defrom to "climb" each idler giving a rolling resiance.

Gliding surface

resiste fri.png

A gliding surface works with friction so it's crucial to choose the appropriate material. 

With PE-UHMW, the friction is low (0,21) and because there is no rolling resistance, the power consomption is only ±15% more than idlers

​Since 1964

Get the job done !

Protected ©

Visitors :