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-   -   H.F. Portable sand blaster not blasting (http://www.hotrodders.com/forum/h-f-portable-sand-blaster-not-blasting-210328.html)

Riot Racing 12-14-2011 05:30 PM

H.F. Portable sand blaster not blasting
 
Hello all,
I had purchased a harbor freight (HF) sand blaster with vacuum cleaner attachment. I thought it was the greatest invention in the world. Unfortunately it was not a very agressive blasting unit so i returned it and got my money back.

Details
I found a 20lbs portable sand blaster on Craigslist for $20 so I went and bought that as a replacement. I thought this pressure vessel type blaster would work better than a venturi type blaster. Pictured:http://www.harborfreight.com/media/c...mage_18026.jpg

The guy I bought it from said it worked. I have had this thing sitting in the garage for months. I can't get it to blast. I removed the valve on the bottom of the tank and replaced it with a piece of straight pipe. This valve was used to let the sand flow from the tank into the "Y' fitting that then brings the sane to the gun. I decided that I would never need to reduce the amount of sand flowing from the tank.

I use to have a filter at the top of the tank between the tank and my air line going into the tank. I got rid of this because it broke.

Direct Question for the lazy reader
When I try and blast air is flowing from the nozzle. Very little IF ANY media flows out of the nozzle. I completely opened all the valves at the top and the bottom, but that didn't change a thing.

Why wont thins work? Any suggestions on what to fix?

I will post some pictures later to demonstrate the valve setup on the blaster.

lanier ledford 12-14-2011 07:09 PM

sand blaster
 
You have to have pressure on the sand in the pot top (to push sand down), you have to have a valve ( at the bottom) to regulate the amount of sand coming out to nozzle. there should be a little less pressure pushing the sand down and an more on the nozzle to help suck the sand into the hose. Remember, more pressure the harder it cuts and , more sand, less cutting and heat it will create on the part. Your air supply has to be dry or it'll cause the sand to ball up. You really need a receiver tank to give the air time to let the moisture steal out. intake from air supply on top, discharge on top a drain **** on the bottom open just a little to help keep the moisture running out. It take a lot of air flow and pressure (80 psi or better) to sand blast.

oldcpecdr 12-15-2011 05:56 AM

Another Question
 
Not to hi-jack this thread but am looking at a similar unit for a small job...does using glass bead help eliminate the moisture issues ?

Thanks...

Mike B

OneMoreTime 12-15-2011 06:21 AM

Glass bead will not relieve moisture issues..you need dry air..regular sand will clog one of those units probably the clog is in the nozzle for the OP..

Sam

Riot Racing 12-15-2011 09:23 AM

Quote:

Originally Posted by OneMoreTime
Glass bead will not relieve moisture issues..you need dry air..regular sand will clog one of those units probably the clog is in the nozzle for the OP..

Sam

I call it SAND but I am actually using a product called "Black beauty". "Black Beauty" is one fo the most common abrasive blasting medias there is. Its efficent, reusable and fairly inexpensive.

I wonder if this was the problem. Would this be the issue? I had try glass bead once, that didn't work either.

Quote:

You have to have pressure on the sand in the pot top (to push sand down), you have to have a valve ( at the bottom) to regulate the amount of sand coming out to nozzle. there should be a little less pressure pushing the sand down and an more on the nozzle to help suck the sand into the hose. Remember, more pressure the harder it cuts and , more sand, less cutting and heat it will create on the part. Your air supply has to be dry or it'll cause the sand to ball up. You really need a receiver tank to give the air time to let the moisture steal out. intake from air supply on top, discharge on top a drain **** on the bottom open just a little to help keep the moisture running out. It take a lot of air flow and pressure (80 psi or better) to sand blast.
I understand your point completely about the pressures at the different points of this blaster. But, the valves used to adjust these pressures are just a simple ball valve. These are not veyr precise valves where the pressure can be fined tuned.

Look at the picture I have attached. There are two valves at the top of the tank. One controls air pressure going into the tank. The other goes downward to where the sand gets pushed out from the tank to push the air/sand to the exiting nozzle. I thought both of these should be completely open to get the maximum blasting efficency. Although, I have tried adjusting one valve at a time to see if I can get sand blasting, your comment make sense to not have the same pressure at both locations.

I am really starting to wonder if I need a filter or some sort of additional reservoir in between the tank and the airline??? The filter I had previously run was this:
http://www.harborfreight.com/media/c...mage_13986.jpg

Maybe I should run something like this?
http://www.harborfreight.com/media/c...mage_13991.jpg

I wish there was a one way valve that would not let debris back into the airline...

gow589 12-15-2011 11:22 AM

The valve absolutely has to be there. Changes in pressure or volume of sand can require it to be tweaked making it dump sand one minute or not flow any the next. It is a required member for operation.

Dry air is an absolute must. I have used the small filters which help but nothing replaces a good drier. An air drier is a must if much blasting is done.The volume of air just works the air compressor heating it up and is the only way you can adequately overcome the moisture from the heated air compressor.

I also got rid of the deadman. After hours of using the blaster I found that a quick coupler screwed in the end is easier to use. I buy them by the handful. When they wear through I throw on another. The hole is slightly larger which means more volume, surface area and less air speed meaning slightly weaker. It has worked well for things I have used it for.


http://www.rc-tech.net/pantera1/strip/strip22.jpg

http://www.rc-tech.net/pantera1/strip/strip14.jpg

oldred 12-15-2011 02:20 PM

Quote:

Originally Posted by lanier ledford
Remember, more pressure the harder it cuts and , more sand, less cutting and heat it will create on the part.

Just a note about blasting sheetmetal since this has come up a bunch of times,

It's a misconception that sandblasting heats a part and warps it, the warpage is caused by the peening effect not from heat. I mention this because many parts have been ruined from warpage because steps were taken to prevent heating when heat is not the problem, high pressure does however contribute to warpage but blasting at direct angles is the biggest culprit. About two years ago this subject came up and a couple of us decided to prove or disprove this heat myth so using an IR thermometer we monitored the temperature on an old truck hood while sandblasting the opposite side. Starting with a temperature of 68 to 70 degrees before blasting we expected to see little change as the blasting started but surprisingly it actually dropped about 4 to 6 degrees! I would guess the cooling effect would be from the air flow but whatever the reason the temperature on the backside of the metal being blasted actually cooled slightly even with the metal warping. The real reason fro the warpage is the sand acting as millions of tiny peening hammers that displace metal causing the surface to "grow" and thus to distort, this effect is cumulative and attempting to keep the part cool by whatever means will not prevent it from warping.

1ownerT 12-16-2011 07:21 PM

Quote:

Originally Posted by oldred
Just a note about blasting sheetmetal since this has come up a bunch of times,

It's a misconception that sandblasting heats a part and warps it, the warpage is caused by the peening effect not from heat. I mention this because many parts have been ruined from warpage because steps were taken to prevent heating when heat is not the problem, high pressure does however contribute to warpage but blasting at direct angles is the biggest culprit. About two years ago this subject came up and a couple of us decided to prove or disprove this heat myth so using an IR thermometer we monitored the temperature on an old truck hood while sandblasting the opposite side. Starting with a temperature of 68 to 70 degrees before blasting we expected to see little change as the blasting started but surprisingly it actually dropped about 4 to 6 degrees! I would guess the cooling effect would be from the air flow but whatever the reason the temperature on the backside of the metal being blasted actually cooled slightly even with the metal warping. The real reason fro the warpage is the sand acting as millions of tiny peening hammers that displace metal causing the surface to "grow" and thus to distort, this effect is cumulative and attempting to keep the part cool by whatever means will not prevent it from warping.

Great info! :thumbup:

oldred 12-16-2011 07:45 PM

Here's a little more on the heat myth that's caused so many problems in the past. Lot of good info here and for anyone even considering sandblasting sheetmetal this is a good read that just might save someone a lot of headaches. :)

http://www.hotrodders.com/forum/sand...yth-76938.html


Sandblasting causing heat warpage is a very common misconception and one that can lead to a heck of a lot of grief!

deadbodyman 12-17-2011 05:05 AM

I have one of those after you get the water traps on it and the valves replaced it'll work just fine but when mine gets plugged up all I do is put my finger (gloved) over the nozze; it'll unplug it quick....The only problem I have with mine is the sand valves wear out fast and need to be replace often...That abrasive wears a hole in the brass valve body especially the nozzel valve

Kevin45 12-19-2011 06:03 AM

With quite a few of that type of sandblaster, "Black Beauty" does not seem to work too well. The white sand is finer and works way better. BUT, you need everything dry. Both the air and the sand.

matts37chev 12-19-2011 06:49 AM

Quote:

Originally Posted by oldcpecdr
Not to hi-jack this thread but am looking at a similar unit for a small job...does using glass bead help eliminate the moisture issues ?

Thanks...

Mike B

if you are only doing small jobs
I have had pretty good luck with very inexpensive siphon type blaster :thumbup:
I actually just use real sand from work that I clean and sift into five gallon buckets
I would think with some store bought blasting media it would be even better
same rules apply dry air and sand

Riot Racing 12-20-2011 09:04 AM

I appreciate all the good info. I need to buy some new filters to try and dry things up. I don't think my current problem is a clog though... But I don't know for sure.

I can dry the sand I am using pretty easily. At work we have a fairly large oven than I can put the sand into. I have done this before and it works fairly well.

DEADBODYMAN
What type of valves are you using? The same type that came on the blaster? Maybe the issue is the valves that are on the blasting unit?

Finger over the blasting tip works great! I use that trick in my siphon type blasting cabinet.

deadbodyman 12-22-2011 05:35 AM

The sand wears right through the brass body of the ball valve.

Riot Racing 12-23-2011 08:45 AM

[QUOTE=gow589]
I also got rid of the deadman. After hours of using the blaster I found that a quick coupler screwed in the end is easier to use. I buy them by the handful. When they wear through I throw on another. The hole is slightly larger which means more volume, surface area and less air speed meaning slightly weaker. It has worked well for things I have used it for.

http://www.rc-tech.net/pantera1/strip/strip22.jpg

I was thinking about my situation a little more and just realized what you were trying to demonstrate with this picture and post.

You eliminated the valve with cone shaped nozzle attached to it. So you have lost the control to turn the blaster "on" or "off". But who cares about that right? Because you control the amount of air entering into the pressure vessel, you can turn it "off" from there.

Is that correct?


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