Engineering tools
Quick calculations, plant-side.
Six calculators maintenance and project engineers reach for every week. Change a number and the drawing and the answer follow. Results are close working figures. For a binding selection, send us the conveyor and we check it free.
Belt selection
Pull, power and rating
400 t/h · 26% fullLoading point
Material lands on the belt at the tail, through a chute or hopper.
12.0 m · 4.6°Incline and lift
Every metre of lift is weight the drive must raise, all day.
150 mCentres
Long runs add idler drag. Short runs feel the loading point more.
Drive endHead and discharge
The drive pulley at the head pulls the loaded belt and throws it off.
Belt pull at drive
10.6 kN
Power at drive
29.4 kW
Tight side tension
15.0 kN
Capacity used
26 %
Belt strength needed
150 kN/m
At 1000 mm wide, at least 3 plies to trough and carry the load
Start from
Why we suggest EP 250
Where the pull goes · 10.6 kN
- 1
How much material sits on the belt
44 kg/m400 tonnes an hour at 2.5 m/s means every metre of belt carries about 44 kg. A faster belt carries less per metre for the same tonnage.
- 2
What resists the belt
10.6 kNIdlers turning, the belt flexing over them and the material rocking add up to running drag. The loading point, scrapers and skirts add more, which matters most on short conveyors (factor C 1.59). Lifting 12.0 m adds the weight of the load itself.
- 3
Why the tight side is higher
T1 15.0 kNA pulley can only pull a belt by grip. Rubber lagging grips with friction about 0.35, over 200° of wrap. The capstan rule says the tight side must then be 1.42 times the pull, so the slack side never drops to zero and the belt does not slip.
- 4
From tension to belt strength
150 kN/mSpread over 1000 mm of width, the running belt carries 15.0 N per mm. We multiply by 10: a splice is weaker than the belt, starting surges overshoot, and the carcass ages. That gives 150 kN/m.
- 5
Enough plies for the width
≥ 3 pliesTension alone would allow 200 kN/m, but a 1000 mm belt needs at least 3 plies to sit in the trough and carry the load between idlers without sagging. That lifts the choice to 250 kN/m.
- 6
The belt to start from
EP 250The smallest standard rating that clears both is 250 kN/m, built as 250/3. More plies make a stiffer belt that takes impact and holds fasteners better. Fewer plies flex more easily round small pulleys.
Estimate in the manner of DIN 22101: secondary resistance factor C 1.59, friction f 0.025, drive wrap 200°, idler and belt masses assumed. Splices, starting, curves and take-up are not checked. Use it to shortlist, then send us the conveyor.
Plain words
The terms behind the numbers
What each engineering word means, and something everyday that behaves the same way.
Effective tension
FuThe total pull the drive must give to keep the loaded belt moving.
Like the force to keep a loaded cart rolling up a slope.
Tight and slack side
T1 · T2The belt is pulled hardest just before the drive (T1) and least just after it (T2).
Like a tug of war: the stretch of rope being pulled is the taut one.
Capstan rule
e^μθHow much tighter one side can be than the other before the belt slips, set by grip and wrap.
Why a rope turned round a post can hold a boat.
Lagging
μA rubber or ceramic skin on the drive pulley that raises grip from about 0.25 to 0.35 or more.
Like tyres gripping better than steel wheels.
Wrap angle
θHow far the belt goes round the drive pulley. More wrap, more grip. A snub pulley adds wrap.
Two turns of rope hold better than one.
Safety factor
SHow many times stronger the belt is than its running tension, to cover splices, starts and ageing.
A lift rated for 8 people that could hold far more.
Secondary resistance
CExtra drag at the loading point, scrapers and skirts. Short conveyors feel it most.
The extra shove to get a cart going, beyond keeping it going.
Troughing angle
The tilt of the side idlers. A deeper trough carries more and spills less.
A bowl holds more soup than a plate.
Surcharge angle
The slope the material settles to on top of a moving belt, usually about 20°.
The little heap a spoon of sugar makes.
Bulk density
t/m³How heavy a cubic metre of the loose material is: coal about 0.9, stone 1.6, iron ore 2.4.
A bucket of stones outweighs a bucket of coal.
Belt rating
kN/mThe breaking strength of one metre of belt width. 630 kN/m is 630 N for each millimetre of width.
Strength per width, so belts of any width compare fairly.
Plies
The layers of woven fabric inside. They share the pull and give the belt its body.
Like the layers in plywood.
Want the conveyor checked properly?
Send the conveyor details, a tender clause or your current belt. The engineering check is free and comes back with a datasheet.