Considering the huge amounts of money spent on conveyors and conveyor belting and the numerous challenges they can present, deciding on exactly what type of edge a conveyor belt should have does not really sound particularly important.
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But strange as it may seem, selecting the right type of belt edge can have an enormous impact, especially in terms of cost. Here, Dunlop Conveyor Belting’s Les Williams throws some surprising light on the subject and provides some useful hints on how to potentially save quite a lot of money.
Living in the past
For many years now there have been continual advances in the technology and the types of materials used to manufacture rubber multi-ply conveyor belts. Gradually, over time, misconceptions and myths are being put to rest. However, there is one persistent technical aspect of rubber conveyor belts where many conveyor technicians and conveyor belt buyers seem to retain outdated beliefs – belt edge types.
There are only three basic types of belt edge. The importance of which type to use is vastly underrated. Choosing the wrong type continues to cost many conveyor operators a great deal of wasted money, both in terms of belt costs and also in repairs, maintenance and lost production.
Full moulded edge.
Moulded edges
Many years ago, moulded edges were the standard because cotton was used as the reinforcing fabric in multi-ply belts. A moulded edge was therefore essential in order to prevent moisture penetrating the cotton fabric and causing it to rot. However, since the inception of synthetic belt carcasses using polyester and polyamide, this problem effectively no longer exists. Although belts without moulded edges are now the most commonly used, moulded edges continue to be needlessly specified within many requests for quotations.
Moulded edges can only be created when a belt is manufactured (assembled and vulcanised) to an exact width. This is a vitally important factor which I will come back to later. During the calendaring of the belt, a small strip of un-reinforced rubber is attached to the side of the carcass. The strip is formed as an integral part of the belt during the actual vulcanising process. This typically creates between 5 mm - 15 mm of unreinforced rubber on the belt edge.
Moulded edges do not provide any structural advantage. In fact they can be susceptible to damage because they can very easily be torn off if the belt wanders off-track for any reason.
Sealed edges
The alternative and most commonly used belt edge type is the ‘cut & sealed edge’ or simply ‘sealed edge’. The majority of fabric multi-ply belting is held in stock in a range of the most commonly used standard widths by the manufacturers, distributors and traders. To maximise efficiency of production and minimise cost, these standard width stock belts are usually made as wide as the manufacturing machinery will allow. These are known as ‘slabs’ which are then cut to narrower widths. For example. 400 m of mm wide belt would be produced that could then be slit (cut) to produce 400 m of mm wide belt and 400 m of mm wide. The belt edges are then sealed.
At Dunlop we automatically create belts with sealed edges in a single process using special cutting knives that rotate at an extremely high speed. The heat created by the friction of the rotating knives melts the carcass fibres and a small amount of the rubber on the edge of the belt, effectively creating a seal. Technically speaking, this is a ‘cut and sealed edge’ but is more commonly referred to simple as being a ‘sealed edge’.
Sealed edge.
Cut edge
Belts with cut edges that are not sealed in any way are produced in the same way but are slit using conventional cutting knives. At Dunlop we do not recommend the use of unsealed (raw) cut belt edges.
Apart from a better visual aspect, having a sealed edge means that moisture is prevented from being drawn into the carcass from the edge by capillary forces. Although the synthetic carcass fibres are hardly affected, moisture can ultimately cause vulcanising problems when making splice joints so it is better to be safe than sorry. Having a sealed edge enables a belt to be safely used in wet conditions and makes it better suited to long term storage outdoors.
Steelcord construction belts
In the case of steelcord and steel reinforced fabric ply belting it is necessary to use moulded edges in order to prevent moisture penetration into the carcass which, over time, would cause the steel to corrode. In Dunlop, all of our steelcord belts are manufactured to a specific set of specifications that fully embed the steel cords so for these reasons they are always supplied with moulded edges.
‘Made to order’
Many conveyor belts are ‘made to order’ for the end-user. These belts are mostly either the more specialised cover grades (such as fire resistant for example), hi-performance carcass constructions (such as steel reinforced fabric ply) or simply a non-standard width requested by the customer. Custom-made belts will naturally have moulded edges.
Avoiding unnecessary cost
If the manufacturer is prevented from making a belt at the widest, most cost-efficient production width then that will have a negative impact on the selling price to the end-user. For example, to produce 600 m of 800 mm wide belt, it is far more efficient to manufacture 300 m in mm width belt and then cut and seal into 2 x 300 m rolls of 800 mm. Demanding a moulded edge rather than a sealed edge prevents this from happening because 600 m of 800 mm wide belt with moulded edges would have to be made to order and take virtually twice the time to produce.
Unnecessarily prolonging the production time has to be reflected in the price. Causing a belt to be made to order rather than being taken from stock also has a major impact on the delivery lead time. Taking a roll of pre-cut belt from the warehouse will invariably be a whole lot faster than scheduling a special production run.
The logical conclusion in all of this is that insisting on having a belt supplied with moulded edges even when there is no practical or technical benefit can be a huge waste of money.
Unsealed (raw) cut belt edge.
Choosing the right conveyor belt is crucial for optimizing efficiency and ensuring the longevity of your equipment. Whether used in manufacturing, logistics, or food processing, conveyor belts play a vital role in moving materials smoothly and reliably. This guide will walk you through the essential factors to consider when selecting a conveyor belt for your specific needs, helping you make a well-informed decision.
Understanding Conveyor Belt Types
Before diving into selection criteria, it’s essential to know the types of conveyor belts available. Each type is designed for specific applications and operational environments:
1. Flat Belts
Flat belts are one of the most common types used for transporting items in packaging, manufacturing, and assembly lines. They’re ideal for applications where items need to be moved in a straight line.
2. Modular Belts
Modular belts are made of interlocking plastic segments, making them versatile and easy to clean. They’re often used in food processing and industries that require frequent cleaning or sanitation.
3. Cleated Belts
Cleated belts have raised sections (cleats) that help in moving materials at an incline. These are commonly used in industries where items must be transported uphill, such as food or agriculture.
4. Timing Belts
Timing belts feature teeth on the inner side that match with pulleys, ensuring precise and synchronous movement. These belts are ideal for applications that require accurate positioning and are often used in automated systems.
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Key Factors for Choosing a Conveyor Belt
Several factors influence the selection of the right conveyor belt. By considering each factor carefully, you can select a belt that aligns with your operational requirements.
1. Load Capacity
Understand the weight of materials your conveyor will be carrying. Heavier loads require a more robust and durable belt to prevent wear and tear. Always check the weight limits provided by the manufacturer and ensure your chosen belt meets these requirements.
2. Material of the Belt
The material of the conveyor belt should be compatible with your working environment. Common materials include:
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- PVC: Affordable and suitable for light to moderate use in dry environments.
- Rubber: Durable and ideal for heavy-duty applications and industrial environments.
- Polyurethane (PU): Often used in food processing due to its resistance to oils and fats.
- Silicone: Used in applications where high heat resistance is required.
3. Speed Requirements
The speed at which the belt moves depends on the specific application. High-speed conveyors may need belts with special coatings or materials to withstand friction and prevent damage. Additionally, timing belts may be preferred for precision operations where speed control is essential.
4. Environmental Conditions
Consider the environment where the conveyor will operate. Factors like temperature, humidity, exposure to chemicals, and potential for dust accumulation will affect the longevity and performance of the belt.
- For high-temperature environments, choose heat-resistant materials like silicone.
- In wet or food-processing environments, choose materials that resist water and bacteria, like PU or modular plastic belts.
5. Surface Requirements
Depending on the product or material being transported, you may require a specific surface texture on the belt. For example:
- Smooth surfaces are ideal for products that need to slide easily.
- Rough or grip-friendly surfaces are better for items that could slip, especially on inclined belts.
- Anti-static surfaces prevent static electricity buildup, useful in electronics and sensitive manufacturing environments.
Special Features and Customizations
Some applications may require conveyor belts with unique features or customizations:
1. Cleats and Sidewalls
For applications where materials need to stay securely on the belt, consider belts with cleats and sidewalls. These additions prevent items from slipping off, especially on inclined conveyors.
2. Food-Grade Standards
If you’re in the food industry, ensure that the belt material is food-grade and meets necessary sanitary standards. Food-grade belts are typically made from non-toxic, easy-to-clean materials that resist bacteria.
3. Oil and Chemical Resistance
In industries where belts are exposed to oils, fats, or chemicals, it’s crucial to choose a material that can withstand exposure without deteriorating. Materials like PU or specially treated rubber offer better resistance to these substances.
Cost and Maintenance Considerations
While selecting the right conveyor belt, it’s essential to balance upfront costs with long-term maintenance expenses. Here are a few points to consider:
- Initial Investment: Quality conveyor belts may cost more initially but will save money in the long run by reducing the frequency of replacements and repairs.
- Maintenance Requirements: Some materials, like modular belts, are easy to clean and replace, making them cost-effective for applications that require frequent maintenance.
- Lifespan: Durable materials like rubber and polyurethane offer a longer lifespan, especially in heavy-duty applications.
FAQs About Choosing Conveyor Belts
Q: How do I know if a conveyor belt material is food-safe?
A: Food-safe belts are typically labeled as FDA or food-grade certified. These belts are made from non-toxic materials, often polyurethane or silicone, which resist bacteria and can be cleaned easily.
Q: Can I use one type of belt for multiple applications?
A: While some belts can be versatile, it’s generally best to choose a belt specific to each application for optimal performance. Factors like load, speed, and environment vary widely between applications, impacting a belt's performance and lifespan.
Q: What is the best conveyor belt for outdoor use?
A: For outdoor use, choose belts made of rubber or polyurethane, which are durable and can withstand varying temperatures, UV exposure, and other environmental factors.
Q: How often should I replace my conveyor belt?
A: Replacement frequency depends on the belt’s material, usage, and environment. Regular inspection for wear and tear is essential to gauge when replacement is necessary to prevent unexpected downtime.
Choosing the right conveyor belt involves considering various factors, from material and load capacity to environmental conditions and maintenance needs. By carefully evaluating each of these aspects, you can select a conveyor belt that meets your specific requirements and maximizes productivity.
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