Fragile materials are prone to damage such as crushing, breakage, and pulverization. It is important to choose a conveying system that will minimize those damages as much as possible while also maximizing the output rate of your process line.
What are the best conveyors for conveying fragile materials? Which ones minimize material loss, degradation, and breakage? Which conveyors can be configured to work in a variety of environments?
In this blog post, we will explore these questions and more. We’ll also look at how conveying systems impact process efficiency and throughput when it comes to fragile materials like coffee beans, breakfast cereal, nuts, and more.
Main Causes of Material Damage
To better explain the ideal conveyor system for fragile materials, we first need to take a closer look at the two primary causes of material damage during conveying:
- Relative motion
Freefall, or, more specifically, the landing after a free fall, typically occurs when product is transferred between conveyors and when the material is fed into the conveyor or discharged from it.
Relative motion refers to the relative motion between particles and between particles and a stationary conveyor component. This can be observed in vertical bucket elevators where materials are scooped out from a boot by the buckets.
To preserve product integrity, it is crucial to minimize the effects of free fall and relative motion during material transport. There are several conveyor types that would be suitable for this.
Tubular Drag Cable Conveyors
For fragile materials in the food processing industry, tubular drag cable conveyors are hands down the best choice, especially for transporting nuts (pecans, almonds, walnuts, peanuts, pistachios), coffee (ground coffee, roasted coffee beans, green coffee beans), tea, dried peas, dried beans, seeds, rice, grains, frozen fruits and vegetables, and breakfast cereals.
The main principle of tubular cable systems lies in an enclosed tube with a coated stainless steel cable running through it. This cable pulls evenly spaced discs inside the tube, which gently pushes the material forward.
With tubular cable conveyors, there are no rollers or drums. The inner tube prevents abrasion and damage to the material.
The benefits of tubular drag cable conveyors include:
- Gentle on delicate products
- No food contamination or dust
- No noise pollution
- Efficiently transports material from one end to the other
- Low maintenance and cleaning costs
- Low energy expenditure
- Modular design (can fit any floor plan and layout)
- Systems can be customized for specific needs
A wrap/tube conveyor starts as an open belt conveyor and then “wraps” itself into a tube, enclosing the product as it travels between the inlet and outlet.
This conveyor type can accommodate multiple inlets and outlets, as well as different inclines or even curvatures. It is relatively easy to clean and an incredibly gentle commercial solution for transporting fragile materials.
Wrap conveying is an excellent choice for the following products:
- Fish and shellfish
- Animal and pet food
- Fish food
- Corn, and more
The downside to wrap conveyors is a reduced transport capacity per unit length of belt compared to open belt conveyors.
Vibratory or vibrating conveyors function based on vibrational energy that causes materials to move up or down a pathway. The conveying surface is usually a trough with vibratory components attached to it, making it shake lengthwise. These vibrations cause the material to “hop” with the same frequency of the vibrations towards one end of the smooth trough.
These conveying systems can operate at high temperatures and lead to very low material degradation. Even though the relative motion in these conveyors can be high, they don’t significantly impact material integrity.
Because of their vibrating feature, they are better suited for larger particles than fine powders, such as ground coffee. Cohesive materials might stick to the conveyor and could be discharged in the form of agglomerated lumps.
Other downsides to vibratory conveyors are that they can operate only over short distances and are not suitable for high inclines.
An industrial and mining classic, the belt conveyor is not a bad option for moving fragile materials. The conveyed product or material remains stationary on the belt during transport, drastically reducing any chance of damage. This kind of system can be installed in any space with enough available floor area.
When it comes to belt conveyors, there are two types: open type and closed type. Which one you use depends on what material will travel along the belt; if fragile materials are your key focus, then the closed type is best.
Belt conveyors have a limited conveying angle, though this can be increased with a textured belt.
Open belt types have no means of protecting the moving material from outside contamination, preventing material loss due to windage, or preventing dust from spreading inside the facility. Closed belt systems, on the other hand, are not that easy to clean. If they are not properly maintained, you could face potential contamination issues inside the enclosure.
How to Choose the Right Conveyor
Weighing the pros and cons of each conveyor system is a good place to start your selection process. However, you should consider more than just the benefits and drawbacks of each. Which machine is most appropriate for your needs? Which material will you be conveying, which production process are you using, what weight capacity do you need to meet demand, etc.?
The answer may not always seem clear at first glance, but with some research and evaluation, the right conveyor for your application can be found.
Consider the following characteristics of your material:
- Moisture content
- Bulk density
- Particle shape
- Sensitivity to humidity and temperature
- Drop testing data
- Units or volume to be conveyed
- Particle distribution data
- Optimal temperature of the operating environment
Ideally, the conveyor manufacturer will enable a test run of the material on the conveyor before purchasing. During the test run, make sure you observe all of the following:
- The distribution of particles along the conveyor’s length and width ensure uniformity.
- If your material is sensitive to humidity or temperature, make sure that these conditions are measured as well.
- Make note if any segregation occurs in relation to particle size.
- Check for any undesirable properties such as static charges or corrosiveness that may show up during the test.
When a material is fragile, it may not survive being dropped from higher heights or while traveling through choppy air currents in conveying systems. For delicate products such as cereal and coffee beans, drop testing data (a controlled fall) can help confirm that your product will make the trip without breaking.
Another consideration is the product’s bulk density and its flowability (or lack thereof). If you need to pack a lot of cereal into a small volume, your material may not be ideal for conveying systems that require compacted loading or high throughput rates. The same goes if it does not readily stick together in clumps during transportation.
Finally, aside from material characteristics, don’t neglect your own requirements:
- Budget – Going over your budget is not a good idea, but it is also not advisable to go for a cheaper option solely because of its price.
- Power requirements – The power bill for your conveying system is a significant portion of the total cost.
- Facility floor size – If space is limited or ceilings are low, tubular drag conveyors could make more sense than any other conveyor type.
- Conveyor layout and routing
- Ease of cleaning and sanitary requirements – You want to be able to clean your system as easily and quickly as possible.
- Desired conveying rate – Your desired conveying rate may not be sustainable given the power requirements and floor size constraints.
- Safety – The last thing you want is a conveyor system causing injury to your employees or damaging other equipment.
When it comes to fragile products and materials in the food processing industry, there are four primary types of conveyors you should consider: tubular drag conveyors, vibratory conveyors, wrap/tube conveyors, and belt conveyors. Each one of these types has its pros and cons depending on your specific needs.
Before you make the final decision on the new system for your facilities, take a moment to consider the material and business requirements, such as material type, particle shape and size, moisture content, bulk density, as well as site constraints, budget and power requirements, and more.
If you are looking for a system that is gentle on the products and minimizes production loss or degradation of fragile materials like breakfast cereal, coffee beans, nuts, then an appropriate conveyor to check out would be tubular drag conveyors.
Contact Cablevey Conveyors for more information on tubular drag conveyors and how they can help expand your business.