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(This chapter is still being improved. Sorry for inconveniences.)
MODULUS OF ELASTICITY |
| The modulus of elasticity is calculated by dividing the stress by the strain: |
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| where |
M is the modulus of elasticity (ISO 9856) |
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F is the force (N) |
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εelast is the elastic elongation at the end of the specified number of cycles in N/mm |
| In other words: The higher the modulus the lower the elastic elongation per unit stress. See definition here |
TENSION FORCE |
| The modulus of elasticity of a material can be used to calculate the tension force it exerts under a specific extension: |
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| where |
T is the tension force |
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λ is the modulus of elasticity |
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A is the cross-sectional area |
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x is the extension |
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l is the length (m) |
MINIMUM PERIPHERAL FORCE |
| The minimum belt tensions for transmitting the pulley peripheral forces are calculated as follows: |
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| where |
FU |
Minimum peripheral force, |
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C |
Coefficient C, |
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f |
artificial friction coefficient, |
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L |
conveyor length (m), |
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g |
acceleration (m/s²), |
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qRo |
mass of revolving idler parts of top strand (kg/m), |
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qRu |
mass of revolving idler parts of bottom strand (kg/m), |
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qB |
mass of the belt on top strand (kg/m), |
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qG |
mass of the belt in bottom strand (kg/m), |
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H |
lift of the conveyor between discharge and loading area (m), |
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FS1 |
special main resistances, |
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FS2 |
special secondary resistances. |
TAKE-UP LENGTH |
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where
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SSp is take-up length (m) |
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L is centre distance (m) |
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ε is belt elongation, elastic and permanent (%) |
As a rough guideline, use 1,5% elongation for textile belts and 0,25% for steel cord conveyor belts.
Note: For long-distance conveyors, dynamic start-up calculations may be required, because not all elements are set in motion simultaneously, due to the elastic properties of the conveyor belt. |
COEFFICIENT C |
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The coefficient C is a function of the length of the installation.
The total resistances without slope and special resistances are divided by the main resistances. |
ARRHENIUS EQUATION |
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where
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k is the temperature dependence of the rate constant (of a chemical reaction) |
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EA is the activation energy |
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T is the temperature |
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R is the gas constant |
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A is the prefactor (frequency factor) |
| The Arrhenius equation describes the quantitative relation between reaction velocity and temperature (as you know, the speed of chemical reactions increase with rising temperature). |
STRESS IN RUBBER |
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where
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σ is the stress |
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v is the period of strain oscillation |
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δ is the phase lag between stress and strain |
STRAIN IN RUBBER |
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where
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ε is the strain |
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ω is the period of strain oscillation |
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t is time |
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| where |
E' is the storage modulus |
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σ is the stress |
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ε is the strain |
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δ is the phase lag between stress and strain |
INTERNAL FRICTION |
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| where |
tan δ is the internal friction of a rubber |
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E' is the storage modulus (N/mm²) |
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E'' is the loss modulus (N/mm²) |
The tan d is sometimes used to determine the indentation loss of a conveyor belt cover (cf. Energy Saving Belts). E' and E'' should be as low as possible. However, there are a number of misconceptions related to specifiying E' and E''. |
LENGTH RELATED MASS FLOW (m³/h) |
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| where |
v |
is the belt velocity (m/s), |
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lvth |
is the theoretical volume flow (m³/h), |
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ρ |
is the bulk density of the conveyed material (t/m³), |
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φSt |
is the coefficient for determination of the volume flow. |
|
|
| where |
ΡB0 |
is the braking factor related to the rated torque of all drive motors, |
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ηges |
is the overall efficiency of all transmission elements between motor and pulley shaft, |
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PMerf |
is the total capacity of the drive motors required in a steady operating state, |
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PMinst |
is the total installed capacity of the drive motors (N). |
MINIMUM BELT TENSION FOR BELT SAG LIMITATION (top side, loaded) |
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| where |
g is gravity (9,81 m/s²) |
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m'Li is the mass of the conveyed material, uniformly distributed across a section of the conveyor (kg/m) |
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m'G is the length related mass of the conveyor belt (kg/m) |
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IRo is the idler spacing in top run (m) |
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hrel is the maximum belt sag related to the spacing between the carry idlers (%) |
MINIMUM BELT TENSION FOR BELT SAG LIMITATION (bottom side, unloaded) |
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| where |
g |
is the gravity (9,81 m/s²) |
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m'G |
is the length related mass of the conveyor belt (kg/m) |
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IRu |
is the idler spacing in bottom run (m) |
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hrel |
is the maximum belt sag related to the spcing between the carry idlers (%) |
PRIMARY RESISTANCES IN AN EVENLY TILTED CONVEYOR |
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| where |
f is the friction factor in top and bottom run |
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L is the conveyor length (m) |
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g is the gravity acceleration (m/s²) |
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m'R is the mass of the idlers (kg/m) |
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m'L is the mass of the conveyor belt with an evenly distributed load (kg/m) |
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δ is the even inclination of the conveyor (°) |
| MAXWELL MODEL |
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| where |
ε is strain |
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σ is stress |
| VOIGT MODEL |
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| where |
η is dynamic viscosity |
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τ is total stress |
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γ is total deformation |
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D is shear rate |
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G is shear modulus |
| Used to express the relaxation behavior of polymers. |
| ROLLING RESISTANCE |
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| where |
F is resistance force |
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Crr is the dimensionless rolling resistance coefficient |
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Nf is the normal force |
| or |
|
 |
| where |
E' is the storage modulus (N/mm²) |
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tanδ is the internal friction |
| MINIMUM TRANSITION LENGTH (m) |
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| where |
B is belt width (mm) |
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λ is troughing angle (°) |
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S is the safety factor |
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KG is the belt parameter |
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Kf1 is the troughing parameter |
| PERIPHERAL FORCE (N) |
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| where |
FH is the main resistance |
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FN is the secondary resistance |
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FS1 are the special main resistances |
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FS2 are the special secondary resistances |
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FSt are the resistances due to slope |
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| where |
PTr is the drive power (pulley) |
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v is speed (m/s) |
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| where |
C is the coefficient (main resistance factor) |
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f is the resistance coefficient |
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L is belt length (m) |
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g is acceleration (m/s²) |
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qRO is the mass of the idlers on top side (kg/m) |
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qRU is the mass of the idlers on bottom side (kg/m) |
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qB is the belt mass (kg/m) |
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qG is the mass of the conveyed material (kg/m) |
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H is the lift (m) |
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FS1 are the special main resistances |
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FS2 are the special secondary resistances |
|
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| where |
qG is the conveying mass (kg/m) |
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H is the lift (m) |
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g is acceleration (m/s²) |
|
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| where |
m'G is the length related mass of the conveyor belt (kg/m) |
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g is acceleration (m/s²) |
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b is width (mm) |
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δ is troughing angle |
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l is idler length (mm) |
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B is belt width (mm) |
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Tx is drive traction |
ELASTIC ELONGATION (ISO 9856) |
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| where |
Δle is the elastic elongation (mm), |
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Io is the initial length of the test piece(mm). |
PERMANENT (PLASTIC) ELONGATION (ISO 9856) |
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|
 |
| where |
Δ lp is the permanent elongation (mm), |
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Io is the initial length of the test piece (mm). |
| For the drawing: |
FU is 10% force of the belt breaking strength multiplied by the test piece width (N), |
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FL is 2% force of the belt breaking strength multiplied by the test piece width (N), |
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ΔF is the test force range. |
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| where |
ΔL is the amount by which the length changes (mm) |
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F is the force |
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Ao is the original cross-sectional area |
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Lo is the original length (mm) |
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| where |
F are the resistances to motion |
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v is belt speed |
| RESISTANCES TO MOTION |
- |
| where |
FH are the primary resistances (idlers, belt indentation, etc.) |
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FN are the secondary resistances (feeding, scrapers etc.) |
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FS are extraordinary resistances |
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FSt are gradient resistances |
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| where |
FGH is the downhill force |
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FG is the weight force |
Gravity acts straight down (= the weight of the conveyor belt) and the support force acts away from the conveyor. Since the conveyor is sloped, there is a net force acting down the slope.
See also Clamping Force |
| ROOT MEAN SQUARE |
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| Please see here for reference! |
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