The conveyor belt tensioning system or take-up device is a vital component in ensuring optimium belt performance.
The role of the take-up device is to create and maintain adequate pre-tension to allow the conveyor drive pulley to drive the belt under all running conditions (empty or loaded). Generally there are two main types of take-up. The fixed type (normally refered to as a screw take-up STU) and the automatic or Gravity take-up (GTU). The screw take-up is normally used on short conveyors up to a length of 50m. Over 50m an automatic take-up system should be used to ensure constant pre-tension. The length of the take-up depends on the both the centre distance of the conveyor and the type of belt (see calculation).
Ltu = (L ) X 𝜺 /100
Where:
Ltu = Take up length
L = Center distance
ε = 1.6 – 2.1 for EP fabrics belts depending to the manufacturer
The GTU performs best located close to the drive drum. The GTU bend pulleys will have a minimum diameter based on the belt specification. Movement of the GTU on both the vertical and horizontal axis should be limited to 10mm to avoid excessive movement and associated tracking problems. The GTU should be protected with a return belt plough and must be adequately guarded. The GTU length can store spare belt to facilitate the replacement of a vulcanized splice without the need for additional belting.
GTU Weight and Belt Sag (q/s)
The weight of the GTU should maintain a constant belt sag between the idlers (normally q/s = 1- 2%) hence calculating the correct weight is important. A GTU underweight will lead to excessive belt sag thus increasing belt bend resistance and reducing overall belt and idler life. A GTU overweight will lead to excessive belt tension resulting in belt and joint stretch.
