Many food manufactures will recognize the problem: sticky parts of loose transported goods stay on the belt, so to solve this, you install a belt scraper. When scraping is done correctly, the benefits range from improved operational efficiency to better hygiene and food safety. But when a scraper fails to work well there’s a risk that it can damage the belt surface, leading to bacterial growth and food contamination, as well as tracking problems, harm to belt edges, and a shorter belt life.
I frequently get questions from food industry customers about the use of belt scrapers on their fabric belts or positive drive monolithic belts, so in this blog post, I’ve put together the eight most important things you need to know about conveyor belt scrapers.
1. Why are belt scrapers necessary?
The primary function of a belt scraper is to remove waste and debris from the belt surface during production. This is important because material build-up on a belt can lead to a loss of sprocket engagement, as well as tracking issues from residue build-up on roller drums that can cause belt edge damage and increased motor wear and energy consumption. What’s more, product residue on the belt can result in spillage and material accumulation on the return roller, posing a potential risk of bacterial growth and cross contamination.
2. What types of belt scrapers are available?
There are several types of scraper on the market. Most food processors currently use metal scrapers, or POM or PE scrapers made from hard plastic. Rubber scrapers are also available, although they’re not commonly used in the food industry. The newest solution on the market is a flexible scraper made of TPU (polyurethane).
3. Which are the best scrapers for use in the food industry?
While classic scrapers are usually made of metal or hard plastic, these can damage the belt surface on contact, leading to cracks and scratches that are potential breeding grounds for bacteria and can compromise food safety. Damaged surfaces also reduce belt service life. Furthermore, metal and hard plastic scrapers are prone to uneven cleaning.
The new TPU scraper bars now available for the food industry feature a flexible tip that eliminates the risk of damaging the belt surface. For example, when spillage builds up on the running side of the belt, the roller increases in diameter. This pushes the belt against the primary scraper, which if made of metal or hard plastic, can damage the belt surface. A TPU tip is flexible and adapts easily to belt irregularities.
Even when a classic scraper is mounted on a flexible rig, by allowing belt irregularities to push the scraping bar away from the roller it means that the hard tip cannot accommodate this asymmetry, which results in uneven cleaning. A TPU scraping tip matches the belt surface in all cases, resulting in more efficient cleaning.
4. What are the benefits of a flexible TPU belt scraper bar?
- Easier sanitation and increased cleaning effectiveness and food safety due to minimized accumulation of transported product and a flexible tip that causes no cracks or scratches, so there is no breeding ground for bacteria or cross contamination.
- Extended belt lifetime as the scraper tip does not affect the belt surface and there is no residue build-up on roller drums, which can cause belt edge damage. This leads to lower total costs of ownership and maintenance.
- Reduced downtime as there is no material build-up, which could otherwise lead to a loss of sprocket engagement, tracking issues, or increased motor wear.
- Food certification under EU and FDA regulations: the new TPU scrapers have been designed specifically for food applications (e.g. blue tip color) and meet the highest hygiene standards. Metal detectable and X-ray versions can also be used for extended safety procedures.
5. How do I install a TPU belt scraper bar?
If you are retrofitting a TPU scraper, your engineers will need to prepare a solid metal structure to fix the scraper bar to and keep it perfectly straight. If you are setting up a new conveyor, the OEM will mount this. There are two basic ways to install a scraper bar:
- Using a metal bar to which the TPU scraper is attached. The metal bar installed on the conveyor must have a hinge on the sides that allows the correct positioning of the scraper parallel to the surface of the belt.
- Using a counterweight or spring system that ensures the correct pressure between the scraper and the belt surface. This system helps the scraper to work correctly, keeping the pressure at the level set even if the belt surface becomes distorted. (Note: The same system can be used with hard plastic or metal scrapers, but they do not have the flexibility of TPU scrapers, so the problem of non-homogeneous scraping remains.)
6. Where should the scraper bar be installed?
When the material transported is made of coarse, sticky, or wet particles, a primary scraper can be placed against the drive pulley immediately after the discharge flow. The angle of inclination of the scraper is determined by the type of belt installed and the product transported.
A secondary scraper can be installed along with the primary scraper if more thorough cleaning is required. It can also be installed alone if the transported material is dry and fine. Usually mounted between the drive pulley and the first support roller, in this configuration the scraper pushes directly against the belt to increase cleaning efficiency.
Possible positions for the belt scraper
7. How should I maintain and clean a belt scraper?
This is an important point because if the scraper isn’t cleaned it won’t work correctly. The problem is that scrapers are positioned on the return part of the conveyor and in many cases, they are difficult to reach. Our engineers will be glad to share their experience and help you determine how best to remove all the product accumulated on the scraper. Each situation will have a unique solution.
8. How do I know when I need to replace my belt scraper?
All scrapers lose their effectiveness at some point due to abrasion. If the belt surface remains dirty, you should check the following points:
- Verify if the scraper is clean
- Verify the position of the scraper; it must be perfectly parallel with the belt cover
- Verify the pressure of the scraper against the belt surface
- Check the state of wear of the scraper tip
- After that, if the belt remains dirty, the belt or the scraper have to be replaced
Do you struggle with belt damage caused by scrapers? Habasit has a hygienic alternative for your processing line
Habasit’s new belt scraper bars are available in TPU Polyester and TPU Polyether, with a range of tip hardnesses from 85 to 95 ShA. TPU Polyether scraper bars are particularly suitable for applications involving higher temperatures and humidity, where hydrolysis resistance is required. Habasit TPU scraper bars come in a standard 2.4 m length adjustable to customer requirements. X-ray and metal detectable versions are available for additional food safety. Our TPU scraper bars are food-contact compliant and fulfill both EU and FDA requirements.