Blaster cabinet media flowing like a wave?

[Kaizen]

Just finished up all the standard mods of hf blast cabinet. Less then satisfied with result so far. I used the below gun with a foot pedal. The pedal does only have a 3/8 inlet but i put a 5/8 id hose up to the gun. Also have a gravity fed set up with 5/8 id up to the gun which has that sized barbs. Tried psi at 60,90,110 and played around with media siphon air inlet control. I'm not getting as consistent as a flow as i expect and as the hose is clear i can see it looks like waves of sand. wondering if anyone has seen this and figured it out? Also the gun has no instructions. Anyone with a similiar gun does the air or media go to the barb that is a straight shot to the tip?

https://www.amazon.com/dp/B07BSJH6SJ/?tag=atomicindus08-20

 

[FredWanaker]

the pickup I have pulls air and sand so the sand flows steadily. he one that came with the box pulled too much sand, which clogged it and made waves. I bought the pickup from a local blast supply.

 

[FredWanaker]

when I wrote pulls air, meaning that the pickup has a breather that is above the abrasive level into the air, and that breather lets the gun draw air too. As that air comes in low in the feed tube, it pulls beads with it. I only blast with quality beads.

 

[Kaizen]

when I wrote pulls air, meaning that the pickup has a breather that is above the abrasive level into the air, and that breather lets the gun draw air too. As that air comes in low in the feed tube, it pulls beads with it. I only blast with quality beads.

Interesting. Does your setup have a vent after the media like mine? or do you use a tube pickup?

 

[BillK]

What blasting media are you using and where are you buying it ? What size nozzle in the gun ? What brand gun ?

 

[Kaizen]

What blasting media are you using and where are you buying it ? What size nozzle in the gun ? What brand gun ?

Presently loaded with hf aluminum oxide 70grit. 8mm nozzle. This gun https://www.amazon.com/dp/B07BSJH6SJ/?tag=atomicindus08-20

 

[BillK]

K,
I cant advise on the nozzle or gun because I use glass bead. I will say that I ran out of beads once a while back and got a bucket of them from Tractor Supply and they sucked. Did not work or act anything like the glass bead I was used to buying from a local blast supply house. I wonder if it might be worth trying a different source of abrasive ?

 

[Kaizen]

K,
I cant advise on the nozzle or gun because I use glass bead. I will say that I ran out of beads once a while back and got a bucket of them from Tractor Supply and they sucked. Did not work or act anything like the glass bead I was used to buying from a local blast supply house. I wonder if it might be worth trying a different source of abrasive ?

I did also get glass so i think i'm going to switch the hoses on the gun and check out the casting to make sure its is drilled as it should be.....i read a few reviews indicating this. Then i'll try the glass and maybe order some on line if i am not getting anywhere.
It flows well so i have not thought moisture or media is the problem. guess i'll keep trying variables.

 

[FredWanaker]

I use quality glass beads because they seem to work best. Just can't over pressurize them or it shatters them. I use a tube pickup, however the idea is the same. Your gun is trying to lift a heavy column of abrasive. By introducing ambient air near the abrasive source, it makes the column flow evenly and the column is lighter. Try putting a piece of the rigid larger hose from about 4 or 5 inches above the abrasive then deep in the well right next to where the abrasives pull from / outflow. See if that helps. If it does you can anchor it with a small P shaped clamps. Also get in the habit of backflowing the abrasive in the hose (purging it) when it seems to slow. That will keep the abrasives looser.

You'll end up with less abrasive per given volume of air, but you will end up with more abrasive and more consistent abrasives being pulled thru the gun, allowing you to do more work.

 

[csp]

You need to adjust your air inlet or possibly get a blast gun with a smaller orifice.

I had a same looking gun as yours and had the same issue. Just for a test I put the HF gun on and was easily able to adjust the air opening on the ball valve to eliminate the surges or waves of media. I'm still using the HF gun with a zip tie on its valve to keep it open since I do have a foot pedal.

 

[Kaizen]

You need to adjust your air inlet or possibly get a blast gun with a smaller orifice.

I had a same looking gun as yours and had the same issue. Just for a test I put the HF gun on and was easily able to adjust the air opening on the ball valve to eliminate the surges or waves of media. I'm still using the HF gun with a zip tie on its valve to keep it open since I do have a foot pedal.

Thanks. These damn fittings are gonna put me in the poor house lol. I do have the hf gun so i can switch them out and test that as well. I figured with enough air all problems should be fixable.

 

[Kaizen]

I use quality glass beads because they seem to work best. Just can't over pressurize them or it shatters them. I use a tube pickup, however the idea is the same. Your gun is trying to lift a heavy column of abrasive. By introducing ambient air near the abrasive source, it makes the column flow evenly and the column is lighter. Try putting a piece of the rigid larger hose from about 4 or 5 inches above the abrasive then deep in the well right next to where the abrasives pull from / outflow. See if that helps. If it does you can anchor it with a small P shaped clamps. Also get in the habit of backflowing the abrasive in the hose (purging it) when it seems to slow. That will keep the abrasives looser.

You'll end up with less abrasive per given volume of air, but you will end up with more abrasive and more consistent abrasives being pulled thru the gun, allowing you to do more work.

Thanks i can try that easy. How do you purge on a set up like this? On my pressure blaster i just take the tip off and open her up but this has 2 feeds so not sure?

 

[FredWanaker]

cover the tip for a second with the other hand then step on the pedal while it is covered. That forces the air backwards and cleans out the supply hose.

 

[csp]

I did also get glass so i think i'm going to switch the hoses on the gun

How is it set up now? The hose that's inline with the outlet should be your air supply, the other the media.

 

[Kaizen]

How is it set up now? The hose that's inline with the outlet should be your air supply, the other the media.

right. tried switching it and did not work at all so ruled that out pretty quickly

 

[Kaizen]

I got it working well enough. Still have some wave action but no where like what i was seeing before. My report.
-Gun looked fine. Will order another nozzle that is smaller to try out.
-put a tube down into the pipe at the bottom of my pickup and tried with orignal media. No improvement.
-Changed media to 70/40 crushed glass and it worked well. Still have tube down there and 100psi.
I have some other things that ya'll sugested that i will try. Still need to finish electrical and vacuum system.
Thanks for your experienced advice

 

[FredWanaker]

this is essentially the same as how mine is built. This image is from secondchancegar. You can see how the air is introduced close to where the gun pulls the media in. Mine came from Temple Associates aka TheGritGuy.com which is a NorCal abrasive / blasting supply. The side with the tee sits at the bottom of the pickup.

 

[csp]

this is essentially the same as how mine is built.

The OP isn't using an internal siphon tube from the bottom of the cabinet. His media is dropping out the bottom of the cabinet and is being siphoned through a hose external to the cabinet. His second photo shows this arrangement. The partially open ball valve is where air is introduced that provides the supply air in the venturi effect to **** media to the gun.

 

[Kaizen]

The OP isn't using an internal siphon tube from the bottom of the cabinet. His media is dropping out the bottom of the cabinet and is being siphoned through a hose external to the cabinet. His second photo shows this arrangement. The partially open ball valve is where air is introduced that provides the supply air in the venturi effect to **** media to the gun.

Correct. The air tube getting air before where i have my air inlet is interesting enough to play with. I think because my vacuum setup is causing a negative air situation in the cabinet, it would not **** any air in. I think the media and gun orifice was my current problem.

 

[FredWanaker]

"negative air situation in the cabinet"

The back usually has some vents in it. If you look at the image I posted, when that tube draws media, it draws air too which makes the column of media lighter and easier for the gun to lift. The gun acts like a carburetor, meaning the compressed air flow siphons the media into the air stream. The media is PULLED, not pushed. When the column is heavy, or compacted it is too hard for the media to be lifted so you are getting waves. With that tube, the air is pulling media from the bottom so there is no solid column to lift. It also spaces out the media so there is less friction lifting it to the gun. My original tube system that came with it also made the waves you describe and it was a PITA using it. This upgrade just made it work so well. Good Luck.

 

[tester19]

The best thing I did and I have a suction type setup. Is to measure how much vacuum I was pulling at the air inlet to the gun. It then was very easy to adjust things to maximize the vacuum reading. I am currently pulling 15" of vacuum at the gun. With this much vacuum I have zero problems pulling any type of media up and thru the gun.
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[gregs]

Just to be clear. The siphon tube you pictured is oriented with the tee in the bottom of the cabinet in the media? Then the "gun" hose is attached to the other end of the steel tube and the hose that is taped to it just remains open? I am guessing you attached in the same location as the original HF tube? What size is the metal tube?

 

[Kaizen]

Just to be clear. The siphon tube you pictured is oriented with the tee in the bottom of the cabinet in the media? Then the "gun" hose is attached to the other end of the steel tube and the hose that is taped to it just remains open? I am guessing you attached in the same location as the original HF tube? What size is the metal tube?

Quote who you are asking as this thread has fractured a little

 

[gregs]

this is essentially the same as how mine is built. This image is from secondchancegar. You can see how the air is introduced close to where the gun pulls the media in. Mine came from Temple Associates aka TheGritGuy.com which is a NorCal abrasive / blasting supply. The side with the tee sits at the bottom of the pickup.

Just to be clear. The siphon tube you pictured is oriented with the tee in the bottom of the cabinet in the media? Then the "gun" hose is attached to the other end of the steel tube and the hose that is taped to it just remains open? I am guessing you attached in the same location as the original HF tube? What size is the metal tube?

 

[FredWanaker]

that is correct. The media is pulled in from the tee end, which sits deep in the media cabinet. The hose to the gun clamps to the steel rod. Then the plastic hose sits above the media level. When the gun is triggered, it pulls in air which lifts media with it. Since the column is media and air, it goes thru the steel tube much easier than trying to lift a solid column of media. The one I bought, which looks like this came from a blasting supply - Temple Associates, AKA http://gritguy.com/ . I went to their shop with the same problem you have, this was the inexpensive fix they proposed, and suddenly my media blaster worked like it should have in the first place. I THINK it is 1/2" but I don't want to go take everything apart to go measure it. It could be 7/16.

 

[gregs]

I think I remember a mod like that using the original siphon tube. You drill thru the pickup tube into the air tube to create the "tee", then weld up the outside hole in the pickup tube. Then crimp the bottom end of the air tube shut. The only thing is it seems like the original metal tube is kinda on the small side.

 

[FredWanaker]

you must introduce air into the media low down so that the air pulls the media back with it. Let's say your pickup tube is 18" long. If it is full of solid media, the siphon action of the gun has to lift that whole 18" column of media. If the column is mostly air being pulled up, then the siphoning of the media is at the bottom of the tube. The siphon pickup is 18" closer to the media than before. One interesting thing I noticed is that before when I stopped pulling the trigger, media stopped. Now when I stop pulling the trigger, there is still a tiny blast of media that comes out at that moment from the momentum it already has moving towards the gun. If I could only do one mod to a HF booth it would be to replace the pickup completely with one like this.

 

[Jswain]

If you replace the pedal with a higher flowing unit you may have better results. Unless that one is drastically different then the cheap ones on Amazon/eBay while the threads are 1/4npt inside the orifice is only 1/8" or smaller.

Pretty easy to build with a 3/8" whistle valve or buy a premade unit from tptools etc.

 

[Kaizen]

If you replace the pedal with a higher flowing unit you may have better results. Unless that one is drastically different then the cheap ones on Amazon/eBay while the threads are 1/4npt inside the orifice is only 1/8" or smaller.

Pretty easy to build with a 3/8" whistle valve or buy a premade unit from tptools etc.

Yea.......my supply is 3/4 inch and i spent the money on big air so i will be doing that at some point. Not even sure if i need anything more then a ball valve. I am sure i'm getting plenty of air now but at 120psi. I think i can run it at lower psi if i have more flow.

 

[FredWanaker]

the foot pedal only controls the amount of air going to the gun. I don't know the pressure ratings on that clear hose.

Here is what the setup should look like. You already have an air metering valve but if you purge the line I think maybe it might blow out it unless there is a ball and spring in it. Maybe run a line from that to the inside of the cabinet so any line purging won't blow on the floor. I found the photo online.