How Much Blast Media Do You Put In a Blast Cabinet?

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Overfilling a siphon or suction style sandblast cabinet is a common mistake. We completely understand why. On most of the economy cabinets, the instructions are poor or nonexistent. To make matters worse, most of these affordable cabinets are sold boasting capacities of 40 pounds or 60 gallons or more.

It’s human nature. If your blast cabinet will hold 25 or 50 pounds of blast media why not just dump it all in? More is better right? There’s more abrasive in there so it won’t wear out as fast and won’t need changed as often. Plus, there won’t be a half empty bag of blasting media sitting around. Win – Win scenario, right? Not so much.

Just because your blast cabinet can hold around 40 or 50 pounds of abrasive, doesn’t mean you should fill it with that much. In fact, your blast cabinet will work better (and your life will be easier) if you don’t use that much. So how much blast media do you fill a blast cabinet with? Before we give you our recommendations, let’s look at why you shouldn’t just “fill ‘er up”.

Why You Shouldn’t Fill Your Blast Cabinet All the Way:

The general idea is to keep the siphon style system supplied with a consistent flow of media without overfilling. Improper media amounts are a common issue we find when troubleshooting poor blast cabinet media flow with customers. Overfilling a blast cabinet can negatively impact flow and blasting performance. This seems counterintuitive. Why would too much abrasive be an issue?

The more abrasive you add, the more weight you add. A metering valve pulls media from the lowest point in the blast cabinet. A siphon tube draws media from a very low point as well. A siphon setup can only use so much media at a time. The rest is excess weight laying in the cabinet pushing down on the abrasive at the bottom. This weight can cause the media to compact together. Tightly packed compacted media is heavy and doesn’t flow as freely into the metering valve or siphon tube. This affects performance.

The extra weight also adds needless stress to the thin walls found on most economical blast cabinets. Furthermore, those extra pounds make moving your cabinet more difficult if you’ve got it on wheels.

Overfilling a blast cabinet offers no real benefit. Many people tend to overfill their sandblaster in an attempt to extend the time between media changes. This is counterproductive. Too much media makes abrasive media changes longer and more difficult than they need to be. You need a much larger container which ends up being very heavy. If you’ve got a blaster filled to capacity, you may need to empty the old media in a few trips which is very inconvenient. Disposing of smaller amounts of spent media is also much simpler than dealing with 25 to 50 pounds at a time.

Instead of over filling your cabinet, put in the right amount and just change media more often. We can tell you from experience, it is much nicer to empty a little media more frequently than it is to dump a lot less often.

We get it. We hate dirty dusty media changes as well. If you’re looking to make those abrasive blasting media changes a lot easier, check out our metering valves with drains. It doesn’t get any easier than our Easy Drain valve! Simply place your container underneath the drain valve, turn the handle a ¼ turn to empty your cabinet. No more struggling with an awkward hinged door. No messing around with a dirty and gritty threaded plug.

One final reason to avoid overfilling your cabinet is contamination. Blasting with contaminated media can cause issues with any paint or coating you intend to apply on the blasted surface. Silicone, oils, grease and other chemicals can find their way into your media from spills, dirty parts and more. If you’ve got all, or most, of your abrasive in your cabinet it all wasted if you need to change it due to contamination.

You now have many reasons to not overfill your cabinet. You’re probably wondering what the proper amount is. So how much sand should you put in your sandblast cabinet?

First of all, don’t use sand in your blast cabinet. It’s not the best choice and blasting with it can cause silicosis and other serious health problems. Use a low free silica abrasive specifically designed for blasting instead. There are many economical choices that don’t cost much more than sand. With that warning out of the way, let’s talk how far to fill your cabinet.

General Rule of Thumb: Fill the Blast Cabinet Hopper About 1/3 of the Way Up. This is Around 6-7″ of Media Depth on Many Cabinets.

Generally, with a simple gravity fed or siphon tube setup you’ll want to fill the bottom of the blast cabinet about 1/3 of the way up. This typically equates to around six or seven inches of media on most floor standing units. This is a good starting point but you can use a little more or less. The perfect amount varies depending on your specific blast cabinet, the type and size of blast media you’re using, how often you’re willing to check and replenish media and more.

For a gravity fed setup like a metering valve, around 6 inches of blast media is a great starting point. It provides enough media to get a consistent flow of abrasive without over filling. For a siphon tube, filling the cabinet so the sand rises up to around 6 or 7 inches up the siphon tube (typically about hallway up the tube) is a good starting point. Of course, not all cabinets are the same so contact your equipment manufacturer if you need clarification.

What do we mean by 1/3 full?

The bottom of most cabinets is angled and has a funnel shape, much like an upside-down pyramid or triangle. This funnel shaped hopper helps media slide down to the bottom where it can enter the siphon system. Fill this area about 1/3 of the way up.

You don’t need to do any weighing, volume determinations or calculations here. Just visualize how far up a 1/3 of the way is. Stand in front of your blast cabinet. Essentially you want to visually divide the lower area that holds the abrasive into 3 sections of approximately equal height. Visualize a line going straight across this area about 1/3 of the way up. Fill abrasive inside the cabinet to this level.

The diagram below should help demonstrate:

How exact do I need to be?

This isn’t rocket science. You can generally eyeball around a 1/3 full and that will be close enough to the proper amount. Keep it simple. Six inches or so is a great happy medium to help ensure you’re not putting in way too much or way too little. Things just tend to work “out of the box” this way. Will your cabinet malfunction if you dump in 9 inches instead of 6? Is filling to 3/8 instead of 1/3 going to ruin blasting performance? Probably not.

Can you get by with 3 or 4 inches? Yes, especially with something like our metering valve setups that allow you to blast with much less media in the cabinet. We routinely blast with about 3” of media in the bottom of the cabinet on cabinets with metering valve upgrades.

Generally we use as little media as possible so we’ll typically fill the hopper funnel up about 1/3 of the way up or less. This works for most cabinets. Approaching half way up the media hopper is getting to the point of overfilled. If you’re filling your blast cabinet to capacity it is definitely overfilled.

The main points:

  • You need less media than you probably think
  • Too much abrasive can cause issues
  • Full is overfilled
  • 1/2 way full is probably overfilled and can cause issues.
  • In our cabinets we fill the hopper 1/3 of the way up or less.
  • Don’t fill over the top of an siphon tubes. Halfway up straight tubes is typically far enough.
  • Don’t bury any air inlet tubes or air openings with media

What if I’m having a hard time visualizing 1/3 or 6-7″?

Not everyone can easily visualize six inches. Visualizing a fraction of something doesn’t come easy to all of us. There’s nothing wrong with measuring using a ruler or yardstick. You can always mark the proper level once you’ve established it. We’ve got a couple more tips that might help as well.

Tip: Fill to the Shelf on the Harbor Freight Style Cabinets

On the Harbor Freight floor standing, 40lb capacity Central Pneumatic cabinet you can use the level of the shelf on the outside of the cabinet as a reference. The shelf reinforcement area is around 1/3 of the way up the hopper. Fill the blast cabinet with media up to around the level of the shelf. If someone has removed this shelf, you can usually locate the bolt holes in the legs where the shelf used to mount and use those as your visual reference point.

The photo below demonstrates what the inside of these cabinets look like when filled to the recommended level.

Another Tip: Use can also use the siphon tube as a visual aid. Many of the economical siphon tubes have a length in the neighborhood of 12 to 15 inches. Filling up about halfway up the blast tube or so should be close enough in these cases.

What about benchtop and smaller blast cabinets?

You can use the same basic concept of filling up to about 1/3 of the height of the hopper area. This may not be 6 or 7” deep in smaller cabinets. The The concept is the same. Fill the hopper up partially, avoid overfilling and avoid covering the top of siphon tubes or any air inlet.

How Much Blast Media Do I Need in my Cabinet? Quick Summary:

  • Fill the bottom of your cabinet about 1/3 up the hopper
  • This is often in the neighborhood of 6 to 7 inches on many cabinets. That may not be true on very small bench top cabinets
  • To avoid overfilling, fill about halfway up the blast siphon tube. Avoid covering any air inlet tubes or air holes
  • Handy Visual Reference: Fill to around the level of the shelf support on the Harbor Freight style 40 lb floor standing blaster.

There you have it! Hopefully this post helped demonstrate just how much blast media you should add to your cabinet. Keep in mind this article pertains to simple siphon tube or gravity fed blasting setups. If you’ve got a media reclaimer you typically add media there. Around 7 inches or so is probably the correct amount. Contact the manufacturer for their specific recommendations if you’re unsure. As always, feel free to contact us with any questions you might have. We’re here to help!

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