Media blasting at home - need help

[Donald H.]

I bought one of the pressurized tank type media blasters from Harbor Freight. It is the tank type that you see on ebay and elsewhere. They all look very much alike. I bought it to blast small metal parts, i.e. remove paint and rust. When it works correctly, it is great at cutting down to the bare metal.

I can't get it to work reliably. Is there anyone out there that has gotten these to work. Here is what is happening:

I am using 70 grit aluminum oxide media and the blaster is set to 90 pounds. When I open all the valves and then the the nozzle valve, I sometimes get a large amount of the media blowing out which doesn't do any cutting. If it does blast correctly, it cuts great, but only blows the media for a second or so then just air, then I have to manually shake the tank, then it will blast with media for a second or so, the I have to shake it again.

Help!!!
Thanks,
Don Harris

[Ronald L.]

Re: Media blasting at home - need help

Do you have a drier on your air line? Or is the media wet or damp in places?

[Tracy C.]

Re: Media blasting at home - need help

Don,

I have the same set-up. It is very important that the valves be opened and shut in the proper sequence or the hose will plug.

To start blasting...
1) open the nozzle valve
2) open the supply air valve (air is now coming from the nozzle)
3) slowly crack the media valve at the bottom of the tank to allow the media to enter the airstream.
4) continue adjusting the media valve until you get the "right mix" at the nozzle.

To stop blasting..

1) shut the media valve at the bottom of the tank
2) after the hose has cleared of media, then shut the supply air valve and let the tank bleed off all pressure
3) shut the nozzle valve.

Also and probably most important...the media must be DRY DRY DRY.

Do not expect to be able to leave media in the tank between uses. The humid air used to pressurize the tank will dampen the media over an extended time. Load about a half of tank at a time, and empty it when finished.

I don't normally need to "shake the tank" untill it's almost empty.

good luck,
tc

[Chuck S.]

Re: Media blasting at home - need help

I bought one of the pressurized tank type media blasters from Harbor Freight...If it does blast correctly, it cuts great, but only blows the media for a second or so then just air, then I have to manually shake the tank, then it will blast with media for a second or so, the I have to shake it again...

I have no experience with pressurized tank blasters, but it seems pretty clear to me: Media is not feeding because (1) the tank is either nearly empty of media or (2) you are using wet air that is causing the media to stick and clump together such that the media is not feeding properly.

The pressure difference should overcome the solidification, but it's probably just making a "tunnel" or hollow close to the feed tube. Instead of forcing the material to feed as intended, air pressure is simply taking the least resistance to the feed tube. Shaking the tank either brings the final remnant of media to the feed tube, or the shaking is breaking up the solidified media.

Here's an idea: When the blaster stops feeding media, and is only blowing air, disconnect the air and slowly depressure the tank without moving the tank. Carefully remove the lid and see what you find.

Personally, I couldn't deal with a tank unit for my primary media blasting needs regardless of price. I have a little cheap, gravity fed, plastic reservoir blaster I use for VERY LARGE PARTS (e.g. a birdcage). It's a huge PITA to keep sweeping up the media for recycling through the blaster. If you're doing much media blasting, a cabinet large enough to contain most parts is the only way to go because the media is constantly being recycled without stopping to sweep. But...these are strictly my editorial thoughts...how you work is your choice.

[Donald H.]

Re: Media blasting at home - need help

Unfortunately, I don't have room for a blasting cabinet, or I would go that way.

As far as wet media, I have two of the water traps, one at the compresser and one on the media tank. Do I need to add a desiccant dryer? I have pored the media out of the tank after use, and it doesn't seem to be wet. But that could very well be my problem.

Thanks,

[Peter J.]

Re: Media blasting at home - need help

Don,
I have had great success with a filter from Tip Tools. It looks like a roll of toilet paper in a metal canister. This is my last line of defense before the air gets to my blast cabinet.

[Chuck S.]

Re: Media blasting at home - need help

Unfortunately, I don't have room for a blasting cabinet, or I would go that way.

As far as wet media, I have two of the water traps, one at the compresser and one on the media tank. Do I need to add a desiccant dryer? I have pored the media out of the tank after use, and it doesn't seem to be wet. But that could very well be my problem...

In humid climates, water comes into the compressor with the ambient air as vapor. The problem with water traps is they only knock out free or liquid water...to get most of the water out of the air, you first have to condense it into liquid. Water vapor remains in the compressed air unless your piping system provides enough cooling to condense the water for the water traps. The closer the trap is to the air user, and further it is from the compressor, the better off you are because of cooling and condensation that happens in the system piping.

Air distribution systems should be designed with a large diameter header (3/4") that slopes back toward the compressor (say 1/4" every 4')...this forces condensate to flow back toward the compressor and a drain leg. The longer and larger the air header, the more likely you will get cooling. Air station "take-offs" should tee off the top of the header and have about 8" or more of upward travel before they turn down to the floor...this reduces the likelihood of condensate being in the air.

A dessicant dryer would probably help as a final polishing dryer, but depending on the design, the dessicant (or a TP type filter) will quickly load up with water, and then the dessicant (or TP roll) has to be regenerated or dried before it will be effective again. In hot damp climates, you may have to resort to a refrigeration dryer for purposes that require really dry air like painting.

[Steven S.]

Re: Media blasting at home - need help

Don,
Take note on the procedure that Tracy laid out, that is absolutely critical with a pressure blaster. Before you go out and spend a bunch of money on additional filters I would give it another try and play with the valves a bit, there is a bit of balancing act there. With my pressure blaster I have to throttle back on the nozzle valve and let more air push through the tank to get ideal flow, just start messing with those valves and you should learn pretty quick what works the best on your blaster.

Good luck!
Steve

[Ken B.]

Re: Media blasting at home - need help

I had 1 just like it..The only media that would go through it consistanly was sand. All other types i used did just what you are experiencing.

[Joe M.]

Re: Media blasting at home - need help

Check out Brrut site for info about pressure blasters. They recommend specific tips to match specific sized air compressors. See their chart. To get the most out of your setup make sure the tip is complimentary to your compressor. Who knew?

Damp media is a show stopper even on the largest blasters. Probably a good idea to filter any media put in the tank to keep out larger pieces and prevent blockage.

[Dan D.]

Re: Media blasting at home - need help

I have similar blaster form Central Tractor. Everything that has been said on this thread is true. It is a big PITA. I struggle with it, but I have learned do deal with it. It plugs up frequently, uses a lot of expensive media, and makes a mess to clean up. I also do not have the space for a cabinet blaster.
I have not had good luck recycling the media either as I have not figured out a way to filter it, and any foreign material gets stuck in the dead mans valve, and you have to shut it down, take the nozzle apart and clean it. The wife does not like the mess in the driveway, and of course you can only use it is good weather ( which is very infrequent in upstate NY. -Dan-

[Gene M.]

Re: Media blasting at home - need help

Donald,
I have both a Tip pressure blaster and a siphon cabinet blasters.
I run three moisture traps at the bottom of plastic pipe drops to collect moisture. The pressure Tip is used in the summer outside for big stuff such as frames.

Important to screen all media and store it dry off cement floor.

I modified the dead shut off to a 3/4" ball valve on the Tip. The original dead shut off started to leak and was too cumbersome to handle. Now I can maintain the other two valves at optimum and operate just the exit ball valve. It has to be open full or off to prevent destruction of valve. I run 150 lbs air and use a big open ceramic tip.

The siphon cabinet I run 90-100 lbs air and use a big open ceramic tip. Every once in a while blow air around to fix sand level. Gotta be careful here to not fill hopper too high.

[Paul J.]

Re: Media blasting at home - need help

Air distribution systems should be designed with a large diameter header (3/4") that slopes back toward the compressor (say 1/4" every 4')...this forces condensate to flow back toward the compressor and a drain leg. The longer and larger the air header, the more likely you will get cooling. Air station "take-offs" should tee off the top of the header and have about 8" or more of upward travel before they turn down to the floor...this reduces the likelihood of condensate being in the air.

Chuck:

This is different from the research I did when I designed my system, as well as the diagrams and designs on the compressor web sites such as TP Tools, etc. The air flow forces the condensate to your air stations even if they're sloped backwards. I use a system similar to following link that slopes toward each air station. I have installed drains at the base of each downward leg just before the water traps and filters at each station. Even on the most humid days, I get no condensate into the water traps, and no discernable moisture in the lines. On those hot days the only moisture in my system is a few drops from the tank drain. I believe that you are correct about the lengths of the lines. All of my stations are far away from the compressor.

This is one of several designs on the web:

http://www.tptools.com/StaticText/airline-piping-diagram.pdf

Paul

[Chuck S.]

Re: Media blasting at home - need help

Chuck:

This is different from the research I did when I designed my system, as well as the diagrams and designs on the compressor web sites such as TP Tools, etc. The air flow forces the condensate to your air stations even if they're sloped backwards. I use a system similar to following link that slopes toward each air station. I have installed drains at the base of each downward leg just before the water traps and filters at each station. Even on the most humid days, I get no condensate into the water traps, and no discernable moisture in the lines. On those hot days the only moisture in my system is a few drops from the tank drain. I believe that you are correct about the lengths of the lines. All of my stations are far away from the compressor.

This is one of several designs on the web:

http://www.tptools.com/StaticText/airline-piping-diagram.pdf

Paul

I agree that the TP Tools piping diagram now has the piping sloped toward the end of the header. I was surprised to learn this since my original thinking was based on their diagram. I'm fairly confident that they have changed their design philosphy on piping systems over the years.

I think design philosophy for air piping systems might depend on how much water is in your air...If you are in a very humid climate, such that ALL the water in the air is NEVER condensed, then sloping to the end of the header might make sense. However, if most of the water condensable with header cooling is being condensed before you get to the first station, then sloping to the stations is likely to cause you more problems than sloping toward the compressor.

As for air flow causing the condensate to flow uphill to the end of the header, I'm not sure I'm onboard with that. It seems like it would depend on the velocity in the header, and the amount of slope...if the header is properly sized, the flow velocity should be less than about 5-8 fps to minimize pressure losses and provide slower flow to maximize cooling and condensation. I'm not sure the heavier condensate would be blown uphill at those velocities, but what do I know.

When I lived in El Paso, the relative humity was very low...It seems like the RH varied between 15%-25% most of the year. I could bead blast steel parts to white metal, and leave them closed up in the cabinet for months with no change in appearance. However, there were some months in the year (July, August; the locals called these the "monsoon" months) when I had to drain the tank regularly, and might recover about a quart or more of condensate after each use.

The tank condensate was completely separate from the header condensate because it was upstream of the water trap and pressure regulator. Condensate forms in the tank simply because air use drops pressure in the cool tank causing further adiabatic cooling and condensation. With no more condensation than you are seeing, even at the tank, an argument could be made that sloping your header is pointless except for the times when it's raining outside.

I recently moved near Austin, and had to build myself a new air distribution system. That's when I realized that TP Tools had changed their thinking and their drawing (I'd swear that was the case, but I could be a victim of faulty recall). Anyway, I've only run my compressor sporadically, but my experience has been much like yours...no condensate in the station drains, no condensate in the drain leg, and little condensate in the tank (Whut thuh heck?). We'll see what happens when I crank that baby up for continous operation.

[Peter J.]

Re: Media blasting at home - need help

Chuck,
You know a lot more about condensation than I will ever know, but I built my system from following the Tip catalog diagram flowing toward the end use outlets and am pretty happy with the low level of moisture in my Tip blast cabinet and tool outlets in the main shop. The first run of pipe (six feet) slopes back toward the tank but the rest (fifty feet)is slopped with the flow.
No more than my Quincy runs compared to my old singe stage screaming high rpm Craftsman, I am surprised how much condensation exits the automatic tank drain. My air tools used to drip water when ever I used them and blasting clogs were the norm. With this system I'm a happy camper.
Pete