Screw blades spacing is the gap between two neighbouring blades. It is an important parameter for the structure of the screw, because it directly determines the ability to convey solids out of the fluids.

When screw diameter is fixed, the bigger the screw blades spacing, the larger the helix angle and the more chances of suspensions blocking in the screw blades. Big screw blades spacing will also reduce the number of screw blades cycles. The suspensions can not be distributed evenly and it will cause the machine vibrating unsteady.

Conclusion:
1) For suspensions difficult to separate and transfer, the screw spacing should be less, in general 1/5-1/6 of the decanter drum diameter, so that the solids can be transported successfully.
2) For suspensions easy to separate and transfer, the screw spacing should be larger, generally 1/2-1/5 of the decanter centrifuge drum, in order to increase the solids transferring capability.