Take-up systems
Screw-operated take-up system
The contact pressure of the belt on the drive drum, required to transmit the effective pull, is produced by elongating the belt using a tensioning device.
The end drum can serve as a tensioning drum, if its position can be adjusted by screws (remaining parallel to the drive drum).
Conveyors are often configured like this when Siegling Transilon is used, because Siegling Transilon hardly stretches at all (meaning a short take-up) and is virtually dimensionally stable (requiring no re-tensioning).
An inflexible tensioning device would however not permit any compensation for belts lengthening if they stretch when the conveyor starts up, or due to unequal loads, or the impact of temperature.
Force-dependent take-up systems
On very long, heavily-loaded conveyors, this take-up system should be located directly after the drive drum to compensate immediately for elongations on the top face when the conveyor starts up.
Force-dependent tensioning can for example be achieved with a weight suspended from a rope or cord. Alternatively, pneumatic, hydraulic or spring-loaded take-up systems can be used.
Force-dependent take-up systems are recommended in high and fluctuating temperatures.
Important Technical Limitation: A force-dependent take-up system is not suitable for reversible drives.
Drums
Drum diameter
Particularly in wide conveyors, drums with diameters that are too small are subject to inadmissibly significant deflection, resulting in unwanted belt creasing and mistracking.
Make a counter-check (see page 17).
Drum diameters should always be as large as possible. The minimum diameter permitted is determined by:
- The effective pull to be transmitted (see method for calculating the drive drum diameter).
- The flexural properties of the belt used (see dmin in the product range).
- The flexural properties of the lateral and longitudinal profiles welded on (Technical Information 2, ref.no. 318).
Drive drum
The crown height values, stated in the table below under lines II and III, are maximum values and should in certain exceptional cases be reduced to match those in line I. In particular if lateral forces cause the belt to crease otherwise.
This also applies to centre drives, or wide belts where the distances between the end and drive drum are too small to compensate for the tension in the belt.
The drive drum can be cylindrical, if tracking devices are used.
We recommend the drive has a cylindrical centre section with tapered edges. The length of the cylindrical section of the drum should be b/2 (b = belt width).
For further information, please see page 11.
If the belt width is considerably less than the drum length, the belt width determines the proportions of the drive drum.
| Belt Type | Drum diameter [mm] | ||
|---|---|---|---|
| to 200 | > 200 to 500 | > 500 | |
| I - Single-ply belts | 0.5 | 0.8 | 1.0 |
| II - Double-ply belts NOVO, E10/M, E15/M, E20/M | 0.7 | 1.3 | 1.5 |
| III - 3-ply belts | 1.0 | 1.6 | 2.0 |
As regards 0, UO, A0, E0, V1, U1, UH coatings, drum lagging is often applied to improve friction on the drive drum. The lagging should be made of an abrasion-resistant material, like polyurethane or rubber with a Shore (A) ≥85.
Another method that customers can apply themselves is to wind friction lagging, e.g. Siegling Transilon with U2 coating, in a spiral form around the drum.
To avoid any guidance problems, we recommend, particularly where broad drums are concerned, winding the friction lagging symmetrically for both sides towards the centre of the drum. Any existing patterns or profiled drum laggings (e.g. with rhomboid patterns) must also be symmetrical to the centre of the drum.
The faces of all drums should be smooth. Any pronounced grooves caused by rotation of the drum will have a detrimental effect on tracking.
Roughness RZ ≤ 25 (DIN EN ISO 4287) (Peak to valley height ≤ 25 μm)
Similarly to the wound drum lagging method, we recommend that wide drums with a bare surface should also be lathed symmetrically from either side to the centre.
Any rotational grooves left on the drum will be symmetrical and therefore neutral in terms of tracking.
Lagged surface | Bare surface
