Screw conveyors are used in a wide verity of industries and applications and are the most versatile conveyor for bulk materials. While the majority of screw conveyors are shafted with a spiral wrapped around a center pipe and bushed and drilled at each end for shafts, shaftless screw are a unique product where the center pipe is eliminated and only the spiral is used to convey the bulk material. With this unique design shaftless conveyor are ideal for sticky and sluggish bulk materials like sludge and dewatered wastewater.
Shaftless Conveyor Advantages
Shaftless screw conveyors offer a verity of advantages to shafted conveyors for conveying bulk materials including for following.
- Ideal for sticky and moist bulk materials.
- Can easily be designed to run up to 100% full.
- Can run vertically in many applications.
- Eliminates the need for intermediate hangers to coney long distances.
- Lower power consumption due to less system friction.
Shaftless Conveyor Disadvantages
With the many advantages of shaftless screw conveyor there are disadvantages too and include the following.
- Requires some moisture in the bulk material.
- The torque capacity of the spiral is much less than a shafted conveyor.
- Limited on length and rates because of the reduced torque capacity.
- The spiral runs on liners that must be replaced at regular intervals.
- Typical costs are 2x-3x of a shafted conveyor.
Shaftless Conveyor Design
Shaftless conveyors are a unique conveyor and designing them does not fall into any set standards. Although CEMA has standards for spiral diameters and bar size the design of the capacity, drive attachment, liner system and drive system all require specialized experience. One of the most important design elements is the drive system, drive shaft and especially the design of the spiral and material selected for it. Because there is no center pipe to carry the torque of the drive the spiral must have the strength to do so. The spiral is like a large spring and because of that wants to unwind when torque is applied. Using a variety of high strength and hardened materials the spiral is designed to handle the available torque while staying in the stress and deflection limits of the design. Some of the common materials used for shaftless spirals include the following.
- A36 Carbon Steel
- T1/A254 High Strength Steel
- 8620 Carbon Steel
- AR 400 Carbon Steel
Still have questions about shaftless conveyors? Then send us an email at [email protected] or give us a call at (682) 231-1228