Flexible Screw Conveyors

Flexible screw conveyors are best used in an economical point A to point B bulk handling application. It is very important to understand the correct use of flexible conveyors, for they are sometimes misapplied. The most favorable use is using the conveyor for one class of product, (see Spiral Configurations below). Different spirals are used for different types of product classes (ie. granular, free flowing, aerate-able, sticky, etc) bulk powders.

Flexible conveyors are used frequently in the food industry because of the ability to clean the relatively few moving parts. Quick disconnect features can be added to make break down and reassembly.

Materials of Construction:
Hoppers, Spirals and Transitions- Painted Carbon Steel, 304 Stainless Steel- Industrial Finish, 304 Stainless Steel- Sanitary Finish.
Conveying Tubes- UHMW Polyethylene, Carbon Steel, 304 Stainless Steel.

How It Works

The spiral auger is free flowing in the internal section of the conveying outer tube. The product being conveyed acts as the bearing for the entire length of the spiral. The motor drive with gear reducer is located at the discharge end of the conveyor. There is typically no bearing on the hopper end of the system. Flexible screw conveyor applications are designed not to run empty and the conveyor will not purge itself out if on an incline.

The auger is flexible due to the large clearance between the turning spiral and the outer tube. The augers are sized by diameter of the tube (3.125" OD, 4.5" OD, 6.625" OD, and 8.625"OD). The total length of the augers range from 40’ for the 3.125" unit and 20’ for the 8.625" unit. The 3.125" and 4.5" auger can be bent in one continuous bend at a factory designed bend radius. The 6.625" and 8.625 augers are straight conveyors only.

Typical Rates

Round Wire Spirals

The cross section of this spiral is round. It is designed for free flowing granular, crystalline and pelletized products. As the image implies, the round spiral allows these types of products to slip past the turning auger. Because the round spiral has the least surface area of all the spirals, the system can start and stop frequently under low torque. The larger particles then respond to the turning auger by interlocking together as they are moving up the spiral.

• Sugar
• Salt
• Plastic Pellet
• Regrind
• Soda Ash
• Sodium Bicarbonate
• Citric Acid
• Maltrin
• PVC

Flat Wire Spirals

The cross section of this spiral is rectangular. It is designed for free flowing aerating fine powder products. As the image implies, the flat spiral has greater surface area and does not allow as much products to slip past the turning auger. Because the flat spiral has greater surface area and is used with fine powders, the system can start and stop frequently under low torque.

• Starch
• Flour
• Talc
• Carbon Black
• Clay
• Diatomaceous Earth
• Spent Brewer’s Yeast

Machined-Edge Wire Spirals

The cross section of this spiral is similar to the flat rectangular spiral, except the underside of the spiral is chamfered. It is designed for non-free flowing sticky powder products. As the image implies, the machined-edge spiral has greater surface area and does not allow the side of the auger to smear the product into the side wall of the outer tube. The machined-edged auger is designed with a larger O.D. than the round and flat spiral to lessen the possibility for products to agglomerate on the inside wall. These systems can start and stop frequently usually under higher torque. Lower RPM’s are incorporated along with soft start technology. These systems are not designed with a bend in the outer tube due to the close proximity of the turning auger and outer tube.

• Cheese Powders
• Titanium Dioxide
• Soup/Cake Mixes
• Ground Rubber
• Hydrated Lime

Applications

This image shows a 45 degree takeoff conveyor that is being used to load wheat flour into 4 side by side mixers. Operators can easily move the portable base, with locking wheel castors. The bag dump station is equipped with a reverse pulse jet dust collector to dump 50 lbs bags in a dust free fashion. The collected dust is returned to the hopper and conveyed into the mixer. The conveyor is 4.5" OD and conveys at a rate of 8,000 # / hour.

This working system is designed to recover sugar fines from a large dust collector bag house. There are multiple bag houses in this system, where 3.125" OD flexible augers turn on and off intermittently to just empty the dust collector hopper, keeping the auger full of product. The augers all dump into a central hopper, and that material is then conveyed to a bulk bag loading frame. The customer then resells the reclaimed product for a profit. There are two augers in this section of the system, each 30’ long and only one continuous smooth, supported bend in each. This conservative design approach creates long reliability for this and other systems.

This working system outlines the typical custom systems that we at Advanced Industrial Design, Inc. successfully design. Granulated Sugar is loaded onto the semi-bulk bag unloading frame via a 2 ton hoist and trolley. The sugar is vacuum conveyed to the mezzanine floor, where forklifts are not practical. The large hopper on the vacuum receiver is on load cells and pulls a batch of sugar until needed. The flexible auger is also part of the loss in weight hopper and is instrumental in lifting the product vertically into a horizontal UTrough conveyor. The sugar batch is precisely elevated out of the scale hopper and dispenses into the horizontal conveyor. The horizontal conveyor charges one of three mixers and is allowed to run longer than the weigh system so that all of the sugar reaches its destination.