The problem of choosing a trommel can obviously differ depending on whether it is mobile or fixed equipment. For mobile equipment, the road gauge imposes certain dimensional constraints, which we do not necessarily have in the case of fixed screens.
Diameter and length determine the screening surface and therefore the throughput, all other things being equal.
The length determines the residence time of the product in the trommel, and therefore influences the quality of separation.
The diameter is generally for mobile equipment fixed at the maximum possible with regard to the road gauge. For fixed trommel screens it is sometimes determined according to the size of the largest incident objects, the space available if this is limited, the mode of feeding etc.
The drive system must permanently ensure the perennial rotation of the ferrule, even for dense products such as earth, rubble, or sticky products such as sludge compost for example. The latter, because they tend to obstruct the mesh, tend to increase the weight of the product in the shell and therefore can cause an overload of the drive system.
It is therefore necessary to provide a good margin of safety in terms of torque, traction of the motor system also: for example the dimensioning of the rollers if the drive is done by the carrier rollers. If it is done by chain, here too precautions are required, in particular for the dimensions of the chain and the motor pinion (duplex chains also in certain cases).
The speed of rotation of the trommel is also an important parameter: it must be continuously adjustable, and the smaller the diameter, the more the speed is generally slightly increased.
