Flexible Screw Conveyors

The flexible screw conveyor is an economical & versatile option for a multitude of products & applications.

Spiroflow’s Flexible Screw Conveyors are just that – flexible!  Flexible screw conveyors can convey in any direction – from horizontal to vertical, routed around fixed obstacles and equipment, and from one room to another. Additionally, flexible conveyors are ideal for lifting materials from bag dump stations or storage bins. They can convey products at ceiling height to feed a line of processing or packaging machines – as multiple discharge points can be placed along horizontal sections.

Flexible Screw Conveyors constantly remix material through the action of the rotating spiral – effectively eliminating the risk of product segregation. These conveyors are also an extremely cost effective method of conveying dry bulk solids and ingredients!

Flexible Screw Conveyors are called by many different names, including a flexible auger, flexible screw conveyor, flex conveyor, flexible spiral conveyor, helix or helical conveyor.


  • Design Simplicity
  • Gentle Product Handling
  • Greater Hygiene
  • Dust-free Operation
  • Easy to Clean
  • Constant Remixing
  • Low Cost
  • Low Maintenance
  • Heavy-duty


How It Works

Versatility of installation and the ability to deal with the widest range of material particle sizes, bulk densities, and flow properties puts Spiroflow at the leading edge of flexible screw conveyor technology. Flexible screw conveyors, or auger conveyors, are often the lowest cost means of transferring dry bulk solids from one point to another.

Gentle Product Handling

The rotating flexible screw conveyor spiral, centralized within the conveying tube, gently moves material without degrading it. Its unique action also eliminates the risk of mixed product separation.

Design Simplicity

The simplicity of operation is the key element in the Spiroflow flexible spiral conveying system. The electric motor driven spiral, the only moving part, rotates within a sealed tube, moving the materials along by its Archimedean screw action. This design simplicity eliminates the need for additional operating equipment such as filters or bearings – all adding up to a system that’s hygienic, easy to clean, low on installation and maintenance costs and high on efficiency and performance.

Flexible Screw Conveyor Design

Dust-free Operation

The Spiroflow flexible screw conveyor is totally sealed during operation. Because air isn’t used as a conveying medium, there’s no risk of dust contamination or humidity from the atmosphere, a critical factor when used in food and pharmaceutical applications. Additionally, dust can cause airborne contamination of other products and also pose a threat to the working environment.

Easy to Clean

The simplicity of the Spiroflow flexible screw conveyor system makes cleaning a simple operation. The electric motor may be reversed to empty the conveyor of residual material. It can then be flushed out with water or cleaning solution. If necessary, the spiral can be quickly removed from the tube, and optional quick release connectors enable rapid dismantling and reassembly to minimize downtime.

Flexible Screw Conveyor Cleaning

Low Maintenance

A robust inner spiral is the only moving part of a Spiroflow flexible screw conveyor which ensures trouble-free operation.

Constant Remixing

The action of the Spiroflow flexible screw conveyor ensures the material is being constantly remixed. This is particularly important when feeding premixed product to packaging and tablet machinery.


We offer heavy-duty screw conveyors with Ultra High Molecular Weight Polyethylene (UHMWPE) tubes for abrasive or high bulk density materials.

For the most abrasive metals, aggregates and materials such as glass cullet, we offer our RHINOVEYOR Flexible Screw Conveyor which has an abrasion resistant rubber conveying tube in addition to a heavy-duty spiral. Tests and operational experience have confirmed that our RHINOVEYOR conveying tubes have a significantly longer life than standard UHMWPE plastic tubes in aggressive applications.

Flexible Screw Conveyor Tube


Because of their versatility and ability to handle a wide range of particle sizes, bulk densities, and flow properties, Spiroflow flexible screw conveyors are installed around the world in a multitude of industries.


Hygienic ingredients handling is a fundamental benefit of Spiroflow equipment, designed to satisfy the stringent sanitary demands of the food and allied industries.

Water Treatment

Spiroflow supplies efficient dosing equipment for hydrated lime, activated carbon, and other chemicals used in water treatment.


Spiroflow’s long experience within the chemicals industry ensures the safe handling and accurate metering of these often hazardous materials.

Minerals & Ceramics

No bulk handling tasks are more arduous than in minerals and ceramics. Spiroflow equipment is robustly built to meet the most exacting demands.

Plastics Rubbers

Spiroflow solids handling equipment is widely chosen to ensure efficient feeding of molding, extrusion and mixing machinery in the volume manufacturing sectors.


Accuracy, hygiene, and consistent feeding are prime requirements in the pharmaceutical field.

Application Suitability
PriceAlmost always less costly than an AMC, rigid screw or pneumatic conveyor
Layout Constraints
(Single Conveyor)
Typically up to 39 ft (12m) but depends on product density & screw speed
Multiple units can span greater distances
One bend only
MaintenanceLow maintenance
Wear only a consideration with abrasive products or if tube is excessively bent
Recommended minimum bend radii should be observed
Installation CostsLow
Energy ConsumptionMedium energy consumption
Dust Control/Air DisplacementConveyor is mechanically dust tight
No systems filters required
Residual MaterialNot 100% self-emptying
Can easily be emptied by running in reverse
DegradationLess than might be expected
Moderate shear stresses produced by screw against tube
Degradation tends not be a problem w/ most granular products like sugar
Fragile ProductsRecommend material test
Maintaining BlendsDepends on densities & material characteristics of materials in blend
Hygroscopic MaterialsRecommend Material Test
Moist MaterialsNot suitable
Cohesive MaterialsRecommend material test
Utilize a proscrew (beveled edge)
Hot MaterialsApplication dependent
With steel tubes handles material temps up to 300°F (149°C)
SludgeNot suitable
SlurriesNot suitable
Fine ParticlesVery fine particles that fluidize readily may require a flat spiral
In some cases, a center core may also be needed
Running EmptyCannot be run empty for extended periods without excessive noise & wear
Starting & StoppingCan be started & stopped under load
ConfigurationsStraight incline, no bends
Incline with 0-90° bend
Incline Feeding a Horizontal Conveyor
Horizontal with Multiple Outlets
Horizontal Inline Twin Screws

Check out our Conveyor Comparison Chart

This document compares our conveyor offerings based on application suitability, configurations, specifications, options & cleanability. Our engineers will assess your application needs & recommend the optimal conveyor system.


Flexible screw conveyors, or auger conveyors, can be utilized in a number of different configurations.  Here is a sampling of configurations we see regularly:

Check out our Conveyor Comparison Chart

This document compares our conveyor offerings based on application suitability, configurations, specifications, options & cleanability. Our engineers will assess your application needs & recommend the optimal conveyor system.


Model N. America
N. America
Typical Capacity up to (approx.)* Minimum RadiusTube O/D
FSC 214Typical Capacity up to lb/hour (approx.)*  1,000 lb/hrMinimum Radius (feet) 6’Tube o/d (inches) 2¼“
FSC 258Typical Capacity up to lb/hour (approx.)*  2,000 lb/hrMinimum Radius (feet) 8’Tube o/d (inches) 2⅝“
FSC 318Typical Capacity up to lb/hour (approx.)*  4,800 lb/hrMinimum Radius (feet) 14’Tube o/d (inches) 3⅛“
FSC 412Typical Capacity up to lb/hour (approx.)*  14,000 lb/hrMinimum Radius (feet) 20'Tube o/d (inches) 4½“
FSC 658Typical Capacity up to lb/hour (approx.)*  26,000 lb/hrMinimum Radius (feet) NATube o/d (inches) 6⅝“
FSC 834Typical Capacity up to lb/hour (approx.)*  58,000 lb/hrMinimum Radius (feet) NATube o/d (inches) 8¾“
Model (UK/Europe)
Model (UK/Europe)Typical Capacity up to (approx.)*Minimum RadiusTube i/d x o/d
Model 37Typical Capacity up to kg/hour (approx.)* 100 kg/hrMinimum Radius (meters) 2.0mTube i/d x o/d (mm) 37 x 43
Model 44Typical Capacity up to kg/hour (approx.)* 400 kg/hrMinimum Radius (meters) 2.5mTube i/d x o/d (mm) 44 x 51
Model 55Typical Capacity up to kg/hour (approx.)* 800 kg/hrMinimum Radius (meters) 3.0mTube i/d x o/d (mm) 55 x 63
Model 67Typical Capacity up to kg/hour (approx.)* 2,000 kg/hrMinimum Radius (meters) 4.0mTube i/d x o/d (mm) 67 x 80
Model 80Typical Capacity up to kg/hour (approx.)* 5,000 kg/hrMinimum Radius (meters) 5.5mTube i/d x o/d (mm) 80 x 90
Model 90Typical Capacity up to kg/hour (approx.)* 7,000 kg/hrMinimum Radius (meters) 7.0mTube i/d x o/d (mm) 90 x 100
Model 120Typical Capacity up to kg/hour (approx.)* 12,000 kg/hrMinimum Radius (meters) RigidTube i/d x o/d (mm) 120 x 136
Model 146Typical Capacity up to kg/hour (approx.)* 22,000 kg/hrMinimum Radius (meters) RigidTube i/d x o/d (mm) 146 x 158
Model 196Typical Capacity up to kg/hour (approx.)* 40,000 kg/hrMinimum Radius (meters) RigidTube i/d x o/d (mm) 196 x 222
* Throughput rates vary depending on bulk density, material flow characteristics and length and elevation of the conveyor.
We recommend material testing to determine the correct model.

Standard Construction & Components


Food grade UHMWPE (see options for other tubes available)


Carbon/mild steel with option to upgrade to stainless steel

Spiral Profiles

Heavy-duty Round
Proscrew Beveled Edge

Electrical Requirements

2-7.5 hp (1.5-5.6 kW) Motor
Motor sized to application

Pneumatic Requirements

60-80 psi if air agitation is specified

Inlets, Outlets & Feeding

Multiple inlets & outlets
Conveyor designed to be run fully charged & can be run with a full head of material in a hopper
Vibration, air fluidizers or agitators can be fitted to assist with poor flowing products
Inlets can be fitted with baffles, lids, hoppers, agitators, etc. Custom designs available.

Spiral Profiles & Tube Selection

For most applications, the standard round spiral is suitable, combining strength and flexibility. Flat section spirals are recommended for certain light or aerated products.

The Proscrew beveled profile is used for conveying difficult materials such as iron oxide. The semi-rigid construction enables steep conveying angles to be achieved without bends.

The Centre Core is used for very light materials that fluidize readily and for conveyors inclined more than 60°. They are also used to prevent flooding/overfeeding of certain solids in short or horizontal conveyors.

All spirals are heat treated to provide strength and long life. Heavy duty spirals are also available for certain high density or aggressive materials.

Flexible screw conveyor tubes are available in UHMWPE, carbon steel (mild steel), 304 stainless steel or the industry’s only ‘Rhinoveyor’ rubber tubing (used when conveying abrasive material).

Check out our Conveyor Comparison Chart

This document compares our conveyor offerings based on application suitability, configurations, specifications, options & cleanability. Our engineers will assess your application needs & recommend the optimal conveyor system.



Standard Components
TubesDiameter: Size based on application requirements
Material: UHMWPE, Carbon steel (mild steel), 304 stainless steel
SpiralType: Round, Heavy Duty Round, Flat, Proscrew or Center Core
Material: Carbon steel (mild steel) or 304 stainless steel
Drive MotorMotor: Selected based on application requirements. Typically 2-7.5 hp/ 1.5-5.6 kW.
Screw: Up to 1,150 rpm depending on the size of the conveyor
Controls: Motor starter, controls by customer or see options.
InletMaterial: Carbon steel (mild steel) or 304 stainless steel
OutletMaterial: Carbon steel (mild steel) or 304 stainless steel
Offered at various angles: 0º, 30º, 45º, 60º, 90º or custom angle
Diameter: 6” or 8” / 150mm or 200mm
Feed HopperMaterial: Carbon steel (mild steel) or 304 stainless steel
Models: Horizontal, 30º or 45º
Capacity: Up to 29 ft3/min or 0.82 m3/min
Accessories: Heavy-duty Top Grid
Hopper Bag Slitting ShelfThis work shelf is mounted to the side of our feed hoppers.
Hopper CoverThis is designed to fit the feed hopper and is supplied complete with a dust vent and sock.
Dust HoodThis Carbon steel (mild steel) or 304 stainless steel hood is designed to fit our range of feed hoppers and is supplied with a plastic access curtain and vent connection.
Solimar Air PadsIncludes air pads, all necessary plumbing, an air regulator and a timer board.
Inlet VibrationInlet vibration is used to aid the flow of materials that can bridge in the hopper.
Electric or pneumatic.
AgitationUsed to promote the flow of materials and break up any soft agglomerates before entering the conveyor.
Motor starter, controls by customer or upon request.
Drop Out BoxA drop out box (also called a ‘drop trap’) enables easy access for cleaning.  Hand knobs are supplied and eliminate the need for tools. A safety switch ensures that the system cannot be operated with the cover removed.
Reversing TrapA removable end cap on the inlet of the flexible screw conveyor allows for the maximum recovery of un-used product. An operator can run the spiral in reverse prior to product changeover to emptying the system.  A safety switch ensures that the system cannot be operated with the cover removed.
Quick Release Tube ConnectionsQuick release tube connections facilitate rapid access for dry and wet cleaning of the inside of the convey tube. Hand knobs eliminate the need for tools.
Quick Release Outlet CoverA quick release outlet cover facilitates rapid access for cleaning the inside of the outlet housing. We will utilize a proximity switch.
Level SensorA capacitance sensor is mounted through the side of the chute/discharge for indication of low and/or high solids level.
Intrinsically Safe Level SensorA capacitance sensor, suitable for an explosion-proof classified area, is mounted through the side of the chute/discharge for indication of low and/or high solids level.
Polished SpiralAll product contact weld seams and surfaces to be ground and polished to #4 finish with a 1/32” to ⅛” radius. No weld undercuts are allowed.
Side Mount DriveTiming belt drive with motor mount beside the outlet
Pusher ConveyorThe drive can be mounted at the inlet instead of the standard discharge location.
Sanitary SealThe sanitary seal is comprised of a lip seal and stand-off between the drive and the outlet.
Mobile FrameA carbon steel (mild steel) or 304 stainless steel mobile frame support is provided with casters and support for the discharge housing.
Right Angle Gear ReducerThe motor is positioned at a 90º angle from the discharge.
Center CoreThe center core is a UHMW polyethylene rod that fits inside the length of the spiral.
Flexible Discharge HoseOur flexible discharge hose is supplied with a stainless steel hose clamp and is offered in PVC, white neoprene or urethane.
ControlsFlexible screw conveyors can be supplied with any of the following control systems:

Motor Starter Control Panel
VFD Control Panel
Loss-in-weight Control Panel
Gain-in-weight Control Panel

Hopper Discharge Equipment for Assisting Product Flow

Paddle/Finger Type Agitator

For certain sugars & other soft, sticky materials

Scroll Type Agitator

For flour, baking flour, cement

Lump Agitator

For friable plastic waste, hygroscopic product (salt/sugar), chocolate or cracker lumps.

Auxiliary Equipment

Static Bag Dump Stations

Here is an example of a basic bag dump station.  This particular bag dump station has a bag support shelf, dust hood, vibration & level probe.

Mobile Bag Dump Stations

Mobile bag dump stations are typically configured with a dust hood and an integral flexible screw conveyor.

Multi-way Feeders

Multi-way flexible screw conveyors allow up to three conveyors to be fed from a single feed point. The system features swiveling inlet assemblies that allow the conveyors to be quickly installed and positioned as required, giving users valuable operational flexibility.

Dry, free-flowing products (sugar, salt, rusk, plastic granules) are fed smoothly and consistently – without the pulsing that occurs with pneumatic systems – allowing ingredients and additives to be metered to processing and packaging machines.

Low-cost Solutions

Often, companies needing to improve their production processes, reduce dust or eliminate manual handling just do not have the capital expenditure budget to upgrade the feed systems to a multiplicity of individual machines. At Spiroflow, we can supply mobile flexible screw conveyors for dry ingredients with or without an integral dust hood as a cost-effective answer to feeding several machines.

Operators can either load the conveyor direct from small sacks or wheel the mobile unit with a suitably sized collection hopper under a silo, mixer or process vessel. Alternatively, as the photo shows, our mobile conveyors can be furnished with an integral bulk bag unloader. Mobile, easy to clean flexible screw conveyors can help solve ingredients handling problems within a short pay-back period.

Check out our Conveyor Comparison Chart

This document compares our conveyor offerings based on application suitability, configurations, specifications, options & cleanability. Our engineers will assess your application needs & recommend the optimal conveyor system.


Continuous Mixing & Blending with Flexible Screw Conveyors

Thorough mixing is achieved over a short length of material flow with Spiroflow’s Inline Twin Screw (ITS) continuous proportional blender. It is steplessly adjustable for any blend ratio and is designed for use with any free free-flowing, granular, flake or pelleted materials. Accuracy of the Spiroflow ITS is to 2%, depending on material and application, making it suitable for a wide range of uses in the food, chemical, building products and other process industries specifications.

Continuous Mixing & Blending


The Spiroflow ITS incorporates a novel principle in that the feed of the secondary ingredient is introduced directly into the center of the flow of the primary ingredient. The unit has two rotating spiral type conveyors of different diameters. The steel tube of the smaller conveyor is located within the spiral of the other. As the diagram shows, the tube of the smaller conveyor extends beyond the inlet hopper of the larger conveyor. This ensures that the flow of the minor ingredient is introduced into the primary one at the optimum point for thorough mixing. Stratification of different ingredients, which occurs with other types of mixer, is avoided by the unique design of the Spiroflow ITS due to its mechanical action.

Output Rates

Spiroflow ITS blenders are made up of standard sized Spiroflow rotating spiral conveyors and can be designed for any required throughput up to a maximum of 10 tph.

Food & Pharmaceutical Applications

Hygienic versions of the Spiroflow ITS with quick release connectors for ease of disassembly and cleaning are available for use in the food, chemical and pharmaceutical industries.

Flexible Screw Conveyors Mixing


  • Mix quality can equal that of more expensive batch equipment.
  • Little or no particle breakdown during mixing even on friable materials.
  • Short process length minimizes the size of the unit, saving floor space or simplifying overhead installation.
  • The mixture is conveyed and continuously mixed for approximately 3 feet (.9m) by the larger spiral to the discharge outlet.
  • Can be used effectively with two or more components of similar or greatly differing particulate size and density.


Flexible screw conveyors can transport a multitude of materials.  Here is a list of materials generally considered for this type of conveyor.  Our engineers will carefully assess the properties of your material and likely perform a material test to ensure your conveyor performs exactly to your expectations.


  • Bakery Additive Blends
  • Barley
  • Bran
  • Bread Crumbs & Premix
  • Brown Rice
  • Cake Mix
  • Calcium Carbonate
  • Cheese, Powder Blends
  • Cinnamon
  • Cocoa Beans
  • Coffee Beans, Green
  • Coffee Beans, Whole
  • Coffee, Ground
  • Corn
  • Corn Fiber
  • Corn Flour
  • Corn Meal
  • Corn Starch
  • Cracker Crumbs
  • Dehydrated Vegetable Meal
  • Dextrose
  • Donut Mix
  • Drink Mix
  • Dry Beans, Ground
  • Flour
  • Flour Blends & Mixes
  • Food Ingredients
  • Food Stabilizer
  • Soybean Hulls
  • Spices
  • Spices, Powdered
  • Split Peas
  • Starch
  • Starch & Dextrose Blend
  • Starch Derivative
  • Sugar & Skim Milk Powder Blend
  • Sugar, Brown
  • Sugar, Granular
  • Sugar, Unrefined Granulated
  • Various Ground Fruits
  • Vegetable Shortening, Powdered
  • Vitamin Powder
  • Wheat
  • Whey
  • Whey Protein
  • Xanthan Gum
  • Freekeh Cracked Wheat
  • Garbanzos
  • Gelatin
  • Guar Beans & Guar Powders
  • Guar Gum, Whey, Non-fat Dried Milk & Salt Blend
  • Krill
  • Lentils
  • Malt
  • Maltodextrin
  • Milk Powder
  • Non-Sodium Leavening Acid
  • Nutritional Supplement Powder
  • Pancake Inclusions
  • Pasta
  • Peanuts, Raw & Peanut Skins, Shelled
  • Peanuts, Roasted
  • Potassium Chloride
  • Potato Skins
  • Potato Starch
  • Processed Pork
  • Pulp, ground wet seed, wet skins
  • Quinoa
  • Rice Hulls
  • Rye
  • Salt
  • Salt Based Food Products
  • Soy Flour
  • Soy Nuggets


  • Acrylamide
  • Alumina
  • Ammonium Tetrafluoroborate
  • Anionic Powder
  • Austin Black
  • Bisphenol-A
  • Calcium Carbonate
  • Calcium Carbonate, Precipitated
  • Calcium Chloride
  • Carbon
  • Carbon Black
  • Carbon Pellets
  • Cerium Oxide
  • Fumaric Acid
  • Fumed Silica
  • Fumed Silica Flour
  • Harborlite Perlite
  • HDPE PP Flakes
  • Lithium Sulfate
  • Magnesium Oxide
  • Wax & Salicylic Acid
  • Mold Flux
  • Oxalic Acid
  • Pentaerythritol (PE) Dust
  • Pentaerythritol (PE) Powder
  • Polyaluminum Chloride
  • Polyvinyl Alcohol
  • Potassium Chloride
  • Sil-Cell
  • Soda Ash
  • Sodium Aluminosilicate
  • Sodium Bicarbonate
  • Sodium Carbonate
  • Sodium Gluconate
  • Sodium Hydroxide Spheres
  • Sodium Tripolyphosphate (STPP) & Powdered Citric
  • Acid
  • Starch, Vermiculite
  • Stray Dust Pellets
  • Sulfur Powder
  • UHMWPE, Fine Powder
  • Urea

Plastics & Rubber

  • Compounded Plastics
  • Epoxy Resin Flake
  • Hot Melt Pellets
  • PET Flake (Regrind)
  • PET Pellets
  • Plastic Flakes
  • Plastic Regrind
  • Polyethylene Beads
  • Polymers
  • Polyphenylene Oxide
  • Polypropylene, Shredded
  • PPO (Polyphenylene Ether) Powder
  • Prills
  • PVA Plastic Chips
  • PVC Flour Dust
  • PVC Regrind
  • PVC Resin with Carbon Black
  • PVC & Wood Shavings
  • PVC, Recycled
  • Recyclable Plastic
  • Resin
  • Rubber Crumb
  • SEBS Crumb Rubber

Minerals & Mining

  • Amps (Similar to Talc)
  • Bentonite
  • Bentonite Clay Blend
  • Clay, Dry
  • Coal Dust
  • Coal, Powdered
  • Copper Chips, Recycled Ground
  • Diatomaceous Earth
  • Epsom Salt
  • Foundry Sand
  • Friction Grind Dust
  • Limestone
  • Mullite & Zircon Sand
  • Nickel, Chrome & Aluminum Oxide Powder
  • Rock Salt
  • Sand
  • Sand Dust
  • Silica & Clay
  • Silica Gel
  • Silica Sand
  • Silica, Flour-like
  • Soil, Low Plasticity Clay

Paints, Pigments & Coatings

  • Acrylic Powder
  • ATH (Aluminum Trihydrate) Powder
  • Black Powder Coatings
  • Cellosize Polymers
  • Corfree M1 Flakes (Nitrite-free dibasic acid mixture)
  • DDDA (Dodecanedioic Acid) Powder
  • Paint Chips
  • Pigment, Blue Dye
  • Pigment Chips
  • Powder Chips

Building Materials

  • Cement
  • Carbon Cement Based Blend
  • Cement Powder
  • Cement/Sand Mix
  • GGBFS Cement
  • Paper, Compacted
  • Sand
  • Wood Dust
  • Wood Fines
  • Wood Flour blend


  • Biochar
  • Diatomaceous Earth
  • Dolomite, Calcium Carbonate
  • Humic Powder
  • Lignin
  • Lime
  • Nutrifen
  • Peat & Biochar Blend
  • Quick Lime


  • Brake Lining Material, Uncured
  • Dried Sewage Sludge