Ask The Expert

Fequently asked questions regarding screw feeders, flexible screw conveyors, FIBC dischargers and auger screws.

What is a metering screw feeder, and what are they used for?

Metering screw feeders use a series of mechanical and electronic components to meter and control the flow rate of dry bulk materials such as grains, powders, and pellets. Consisting of two critical moving parts, the optional agitator and auger screw, screw feeders are relatively low maintenance and easy to clean. The agitator is positioned inside the conditioning section, continuously rotating to prevent bridging, rat-holing and blockages, which can occur when dosing poor-flowing and sticky materials. The auger screw is positioned below the agitator at the bottom of the feeder’s body, rotating at a set speed, moving the material between the screw flights forward from the feeder to the next part of the handling process.

Screw feeders are incredibly versatile, used in thousands of applications, from food to pharmaceutical processing lines, and are easily integrated into almost any bulk material operations. There are three types of screw feeders, volumetric, gravimetric, and micro, which are manufactured from either mild steel or stainless steel 314 or 316, therefore, capable of withstanding harsh and corrosive environments. At Trantec, we manufacture metering screw feeders in various configurations to suit all types of applications, supplying to all industries, from plastics and food to chemical.

What is the difference between volumetric and gravimetric screw feeders?

Both gravimetric and volumetric screw feeders are robust in design and provide high accuracy and reliable dosing. The main difference between the two feeders is that gravimetric feeders incorporate weighing cells and are the preferred choice when dosing difficult-to-handle materials. Gravimetric screw feeders also offer monitoring and reporting options and self-calibrate, dosing the material until it reaches the required target weight. In contrast, volumetric screw feeders require manual calibration to ensure the correct material mass is dosed over a set period. For a full breakdown, head over to our comparison page.

When do you need a screw feeder for positive control?

A screw feeder is a necessary part of any industrial process that requires precise, positive control of dry bulk materials. Positive control is exceptionally beneficial when the material being fed is challenging to handle to ensure that the exact amount of material is dispensed accurately, especially in applications where precise timing is critical.

What is a flexible screw conveyor?

Flexible screw conveyors (also called flexible spiral conveyors, auger conveyors and helix conveyors) offer versatile and efficient performance in conveying bulk materials. They are used across thousands of applications because they offer a  space-efficient, low-cost, effective way of transferring bulk solids and can be easily integrated into most bulk-handling operations.

How does a flexible screw conveyor work?

Flexible screw conveyors consist of a motor and or a gearbox and a stainless-steel helical screw/spiral centralised within the ultra-high molecular weight polyethylene tube. As the screw rotates, this creates a directional force that gently moves the material inside the tube from the inlet end to the discharge point.

What types of material can a flexible screw conveyor move?

Versatile in design, flexible screw conveyors are used across all industries to convey free-flow, poor-flowing and non-free-flowing materials in flake, grain, granular, pellet, and powder forms. However, the material should be assessed to determine the correct conveyor configuration, as some materials can be problematic to handle.

What is a flexible screw conveyor tube made from?

Flexible screw conveyors have a hollow outer ultra-high molecular weight polyethylene tube, also known as UHMWPE or UHMW. Due to its uncompromised quality, UHMWPE is the go-to material for flexible conveyor manufacturers nationwide. The unique structure of UHMWPE makes it impervious to slide friction, chemicals, moisture, and high-impact applications.

How to clean a flexible screw conveyor?

Trantec flexible screw conveyors have a removable cap (also known as an end bung) positioned at the end of the inlet point. Once removed, this permits rapid and problem-free emptying of the conveyor tube. Reversing the rotation of the screw help to evacuate any remaining residue before flushing with water, chemicals or air. The flexible screw itself can be swiftly removed for a thorough cleaning by simply removing the outlet lid and undoing the motor adaptor pins to release the spiral/screw.   

What are FIBC bulk bags?

FIBC stands for flexible intermediate bulk containers. FIBC bulk bags, also known as super sacks, are made from strong, flexible fabric and are intended for industrial use of storing, shipping, and transporting dry bulk materials such as granules, plastics, pellets, and fine powders. They come in various shapes and sizes and hold a range of weight capacities. The most common FIBC bulk bags are conical, spouted, disposable, and single-trip.

How should the FIBC be positioned during the discharging cycle?

Specific steps must be taken to ensure the complete and safe handling of FIBC. FIBC dischargers are supplied with a lifting frame attachment known as a cruciform. The loops of the FIBC should be hooked over the loop carriers on the cruciform and secured correctly. The cruciform is then lifted by a crane, hoist or forklift truck into position. When the FIBC is hung by their loops when lifting onto the discharge frame, it is typical for the FIBC bag to sag to some extent. However, as long as the cruciform is positioned correctly onto the top of the discharger frame, the bulk bag should be sat centrally on the tundish (square dish section that the bag sits on).

What are the features of a bulk bag discharge system?

To list a few, FIBC dischargers are versatile in design. They can be manufactured with an adjustable heightened frame to facilitate various sizes of bags/sacks and are compatible with a wide range of FIBC sack types, from spouted to conical. Split-frame dischargers are also available to accommodate low headroom areas with restricted heights. Bulk bag dischargers are also relatively simple to install, quiet in operation, and offer non-problematic cleaning to keep downtime to a minimum. To promote dust-free unloading of materials that tend to become airborne, air-tight rubber membrane seals are used or features such as a dust containment box or connection to a dust collection system. For more information on Trantec FIBC discharger, please click here. 

What is an auger

An auger is a type of Archimedes screw commonly referred to as a helix or helical screw and is used across all industries, dating back centuries. Auger screws are used for the transferring and depositing of materials and are widely used today in the bulk solids industry, implemented in metering screw feeders and rigid conveyors. The spiral-shaped tool is manufactured in endless configurations, from continuous flighting augers to variable pitch and stepped.

How to make an auger screw?

Auger screws are constructed in various materials depending on the application requirements. Material of construction can include mild steels, stainless steels 303, 304, and 316, and engineering plastics, such as UHMWPE (ultra-high molecular weight polyethene). Depending on the auger’s configuration and the application requirements, augers screws are either welded and fabricated, machined, or a combination of the two. At Trantec, we manufacture our augers using advanced CNC (computerised numerical control) machines. However, if complete machining is not feasible, we manufacture hybrid augers, created using both CNC technology and manual fabrication methods, to produce premium-quality augers.

What is an auger flight?

An auger flight is a spiral blade that rotates and moves loose material from one point to another. Auger flights are manufactured in a wide range of configurations, from notched flighting and tapered to double flighted, depending on the characteristics of the material being handled.

How does an auger screw work?

Auger screws consist of a central core shaft with helical flights surrounding it. As the auger rotates, the flighting turns, which transport the material up the flighting one flight per rotation, to carry the material along the length of the auger to its destination.