If you use a blast cabinet for finishing applications, you can recycle your abrasives by sending them through the blast cabinets several times, literally “re-cycling” them through.
What benefits can you gain from recycling abrasives, and what factors and best practices should you consider when you do? We’ve developed this short guide to help you navigate the process.
Why You Should Recycle Abrasives
Recycling abrasives is advantageous because it helps you reduce costs. New abrasives are expensive, often costing hundreds of dollars per ton. Recycling your old abrasives enables you to lower your blast cabinet media costs significantly.
Recycling abrasives is also important because it helps you reduce waste and lower your environmental impact. Some organic abrasives, such as walnut shells, degrade easily in the landfill. Others like glass and metals take much longer to break down.
Some blasting materials contain plastics, which, in addition to biodegrading poorly, can contain chemicals that leach into the soil, posing environmental and health hazards. Recycling blast cabinet media helps you reduce your waste output and do your part for the environment.
What to Consider When Recycling Abrasives
Before you start recycling abrasives, consider the various factors that affect recycling, as well as some general best practices. That way, you’ll know you’re getting the best value as you recycle abrasives in your blast cabinet.
Variables That Affect Recycling
Below are several variables that determine how extensively you can recycle your abrasives:
- Abrasive hardness: The hardness of your blast media often determines its suitability for recycling. Media with higher ratings on the Mohs Hardness Scale are generally better candidates.
- Abrasive size: Smaller abrasives wear down more quickly. You will typically get less recycling out of them and will need to use new abrasives more frequently.
- Abrasive shape: Shape sometimes affects the longevity of your blasting media. For example, glass is significantly softer than many other blasting materials. However, because materials like glass beads and steel shot have a durable, round shape, they last longer than other media of comparable hardness.
- Abrasive volume: The volume of your abrasives is important because a higher rate of pounds per minute will generate more heat. Excessive heat can wear down the abrasive and reduce recycle rates.
- Part hardness: Harder parts wear down abrasives more quickly and usually lead to shorter recycle rates.
- Abrasive delivery method: Some blast cabinets use a pressure pot for direct pressure, whereas others use a two-hose injector gun for siphon delivery. These two methods deliver very different abrasive speeds, even at the same blast pressure, and they affect the recycle rates you get from your blast media.
- Part-to-nozzle distance: The distance from the blasting nozzle to the part affects maximum impact velocity. A shorter distance results in higher maximum impact velocity and can reduce recycle rates.
Factors to Consider Before Recycling
Before you start recycling abrasives, consider a few critical factors like these:
- Whether your abrasive is designed for single or multiple uses: If you plan to recycle, be sure to choose an abrasive hard enough to withstand repeated blasting cycles. Usually, these abrasives have a “multiple-use media” label, whereas softer materials are designated as single-pass media.
- How long your blasting media typically lasts: Multiple-use blasting abrasives’ life spans primarily depend on their hardness and size, though we’ve seen how other factors can play a role. If you choose a softer abrasive like slag or garnet, you will likely get only a few uses out of it. If you select a more durable material like steel shot or silicon carbide, you might achieve dozens of or even a hundred recycles. Be sure to choose the right abrasive to get your intended results.
- External variables that might affect your abrasive’s life span: Remember that various other factors can affect the number of times you recycle your blasting media. If you know you will have particularly hard parts in your blast cabinets or use high blasting pressure, extensive recycling may not be a feasible option.
- How well your blast cabinet’s features work for recycling: Some blast cabinets are more suitable for recycling than others, and some have a specific design optimized for this purpose. If your blast cabinet uses direct pressure, or if you use a short nozzle-to-part distance, you will wear out your abrasives more quickly. Siphon blasting and longer distances will give you a higher recycle rate. A separator reclaimer also makes recycling much cleaner and more efficient.
Rules for Reusing Abrasives
Below are a few rules you should consider when you plan to recycle abrasives:
- Avoid recycling soft abrasives: The abrasive cabinets designed for recycling generally struggle to handle softer abrasives like sand, slag and sodium bicarbonate. These abrasives turn into dust during abrasion and can easily clog the dust collector. You will need to use harder abrasives to avoid accumulating potentially hundreds of pounds of dust per hour.
- Know your abrasives’ maximum impact velocity: Different abrasives have different maximum impact velocities — that is, different speeds at which they hit the abraded object. Softer abrasives, for instance, tend to have lower maximum impact velocities. Knowing the maximum impact velocities for your abrasives helps you avoid wearing your blasting media down too quickly and reducing your recycling rates.
- Learn to estimate the number of recycles: As we’ve seen, several variables affect how long your abrasives will last, so recycling rates will vary with different projects and equipment. Still, calculating approximately how many recycles have already occurred can help you make an educated guess about how many more you can complete. You will need to know the hours of blasting that have occurred, the pounds-per-minute rate of abrasives through the nozzle and how many pounds of abrasive are in the blast cabinet.
- Use a high-quality separator reclaimer: A good separator reclaimer is essential for helping you maximize your recycling rate. If your blast cabinet has an ineffective separator reclaimer — or none at all — the abrasive will collect dirt and dust. It will blast inefficiently and could contaminate the part in the cabinet. Using a blast cabinet with a quality separator reclaimer helps you get the most value from recycling your abrasive.
- Know when to change out your abrasives: Using the same abrasives too long impedes the efficiency of your blasting — the same way trying to sand wood with worn-out sandpaper would take much more time and effort than using a new piece. Be sure to remove your old abrasives once they get too worn down, and start fresh with new blasting media.
Dependable Finishing Solutions From Finishing Systems
When you’re ready to get started with recycling your blast cabinet media, partner with Finishing Systems. We carry an extensive selection of abrasives, so you can choose one that meets your finishing needs and is suitable for multiple blasting cycles. We also provide a wide range of blast cabinets for use with various media.