Conveying Systems For Bulk Solid Materials – 21 Questions To Ask

Conveying of bulk solid materials within a factory setting is a complex area. Manufacturers require dust-tight systems that can provide optimum performance, whether equipment is required for food ingredients such as flour, cereals and coffee granules, efficiently transporting waste for the nuclear power industry, or accurately controlling the flow of materials for the chemical and mineral sectors.

Here Spiroflow, one of the world”s leading manufacturers of a full range of equipment for handling dry bulk solids and ingredients, takes you through the conveying options available depending on the customer’s materials, processes and the factory layout.

At Spiroflow’s well-equipped material characterisation laboratory within its UK technology centre in Clitheroe, Lancashire, scientists measure the fundamental physical characteristics of a customer’s material, determining how it will flow into and through conveying equipment to enable the design of the feed hopper and decide which, if any, mechanical flow aids are needed. The type and design of conveyor is matched to the nature of the ingredient. This knowledge enables customisation of machinery exactly to clients’ needs.

Questions to ask when buying a bulk solids materials conveyor

Here is a list of questions that will need to be answered as a minimum before the choice of conveyor system for bulk solids materials can begin:

1. The product(s)?
2. Its/their bulk density(ies)?
3. Its condition (moisture content, average particle size, temperature etc)?
4. Is the product likely to change in anyway in the future?
5. From what is the product being conveyed (silo, big bag, sack tip station)?
6. To what is the product being conveyed (mixer, sifter, mill, reactor)?
7. If it’s a reactor of any type, is there any steam, gas or solvent given off that might enter the conveyor?
8. The horizontal conveying distance?
9. The vertical height to which the product has to be conveyed?.
10. The route of the conveyor (inside, outside, number of bends required etc)?
11. The conveying rate in kg/hour or the batch size over a given time?
12. Is the conveyor to transfer a pre-weighed batch, is it transferring material to a receiver of a given size / on load cells or is it a continuous process?
13. How often / for how long will the conveyor run each day?
14. Is it important to deliver the material to the receiver in a homogenous manner – such as when flakes are added to a liquid to make a lump-free paste?
15. If the product is a mixture, is it essential that the integrity of the mix is maintained?
16. Is the material fragile and how important is it to minimise damage during conveying?
17. What accessories are required (sack tip station, bulk bag discharger, receiver hopper, etc)?
18. Is the conveyor to operate in a dusty or otherwise hazardous area (i.e. do the Atex/Desear regulations apply)?
19. Is the conveyor manufacturer to supply the control panel, level sensors, etc?
20. Will the conveyor be readily accessible for maintenance purposes?
21. For how long is the conveyor expected to run between services

Take account of the material, has it been characterised and understood, how does this guide the solution?

The consistency of component concentrations in a mixture can be a key consideration in their quality. Depending on the differences (size, density, fluidity, shape etc.) the choice of conveyor can be critical to preserving the homogeneity of the ingredients during the handling operation.

The integrity of fragile material, such as dry foods like breakfast cereal and pasta, clearly needs to be preserved, but this can also apply to specialist powders.

For example, spray drying is often chosen as a size increasing mechanism to aid flow or maintain the integrity of a powder blend. For both fragile particles (>2mm) and fragile powders (<2mm) mechanical conveyers offer a more gentle handling solution than a pneumatic system.

For applications that require the product to be contained away from the local environment (which may be to keep foreign materials out or hazardous substances in) the options within the Spiroflow conveying range can be a very good solution. Complete containment can be readily achieved – not true of older technologies like belts or bucket elevator systems.

Conveying rate and route through a factory environment also needs to be addressed to define the type of transit system required. An aeromechanical conveyor is ideal for a high rate, a flexible screw conveyor for a difficult route and a pneumatic conveyor for a really tortuous path.

Which equipment conveys the best solution?

There a wide range of solutions – Flexible Screw, Aeromechanical, Cableflow™,Tubular Drag and Pneumatic conveyors – to meet the most testing conveying challenges. Each technology best suits different sub-sets of classes of material as explained below:

Flexible screw conveyors

Flexible screw conveyors are more than just flexible in the mechanical sense – the range of materials they can convey is very wide and the range of designs can deliver from 25 L to over 40 m3 per hour. It uses the product as the ‘bearing’ for the spiral and as such is both cost effective to purchase/maintain and very easy to clean. Depending on the material and application Spiroflow offers nine sizes and four different spiral designs in a range of materials and finishes.

Aeromechanical conveyors

Aeromechanical conveyors move material in pockets between fast moving discs inside a rigid line. For throughputs between 15–60 m3hr1 this could be the conveyor of choice. For materials with a high densification potential, such as titanium dioxide, aeromechanical conveying is the ideal option.

Additionally, the energy usage per tonne conveyed is less than a fifth of that of a pneumatic system which can be a significant consideration in a high rate 24/7 application. They are perfect for vertical conveying, with no loss of throughput.

Cableflow conveyors

Cableflow™ conveyors are ideal for fragile material such as a coffee granule or breakfast cereal. Compared to a traditional bucket conveyor they offer significantly better containment along with lower downtime and maintenance costs, while conveying up to 21 m3hr1of material.

Tubular Drag conveyors

If you want to move dense, hot or highly abrasive material then none of the equipment detailed above is likely to be suitable. Here is where a Dynaflow™ conveyor is likely to be the best choice.

Dynaflow

A Dynaflow™ drags material with a disc and chain assembly inside a heavy duty transfer line. It can convey via complex routes and at any angle.

These conveying solutions are underpinned by Spiroflow’s 40 years’ process experience and an ability to measure the fundamental characteristics of the materials to be conveyed..