continued sand blaster problems

[MAK]

Boy this thing would be great if I could just work through these problems I keep having. I've got the same Harbor Freight pressurized unit that you can see in the background on some of Keith's pages. I'm using the nozzle with the largest diameter opening and found that it continually clogs at the spray nozzle every few seconds when using the black silica carbide I got at HF. It just seems a little too coarse to maintain a flow even though it's good and dry. I switched to regular play sand from home depot and now it stops flowing every 5 seconds or so right at the base at the sand metering valve. I've tried nearly closed to all the way open and completely open seems to work best but it still won't stay flowing. The only way I can maintain flow is to continually shake the container by rocking it back and forth to jar the sand loose. I did this for about a 1/2 hour today but as you can imagine it's extremely awkward and not working real well...
I've got a pressure regulator set to 125 which has a moisture filter in addition to the moisture filter on the sandblaster. I've tried having the unit 75% full to only 20% full of sand with the same results.
Anyone had this problem before or have any ideas? Is the sand still maybe not dry enough? I've tried leaving it spread out on a tarp in the garage... I've checked all the fittings and valve to be sure there are no obstructions.
thanks for any help.
Mark

[FORDification]

Definitely sounds to me like your sand isn't dry enough. Since you have to shake the blaster to get it to drop down, it's sticking in the tank, and I think you just have to try to let it dry a bit longer. While it's out on the tarp, make sure you have it spread pretty thin and occasionally sift through it to move it around.

The other question is....how CLEAN is the sand? If there are small pebbles or other sandblasting debris in the sand, it'll clog up pretty quickly too. Sometimes the sand you can get for children's sandboxes isn't quite as clean as, say, silica sand....which is what I use.

I've never tried using black silica carbide, so I have no experience as to it's flow characteristics.

[hardtailjohn]

Go get a roaster from the [censored], and fill it with sand, then "bake" it in the oven for a few hours at about 400 degrees (probably best with a "shop" oven... or at least when your wife isn't home!!). I bet you'll find that this helps! If the humidity is anything, you'll be just adding moisture to the sand by laying it all spread out on a tarp.
Just thinkin' out loud...
John H.

[Ford390pwr]

As for the sand you are using, I have been getting the silica sand at home depot. It is described as 030 silica sand. That playground sand has too many pebbles in it! I did use the playground stuff once, but I had to screen it first to get the big stuff out.

The silica sand at HD is about $7 a bag, but well worth the time saved in screening the rocks...

[MAK]

I checked and it is the silica sand I'm using and seems very consistent with no pebbles or large pieces. Must be the moisture still in it. I'll try spreading it out to dry in the house downstairs. I know it's low humidity down there because I can't pet the poor dog without the static sparks flying... If I can get the wife out of the house I'll try the oven. She usually catches me though when I start stealing stuff from the [censored] for use in the garage.
Thanks

[hardtailjohn]

Yah... I was perfectly happy using the dishwasher to clean Harley engine parts one day, when my live-in girlfriend (at the time) came home... she got really "narrow between the eyes" about all tlhe parts in "her" dishwasher.... guess thier priorities just aren't quite the same.
John H.

[MAK]

Do you guys run yours at 120-125 PSI or do you regulate down to a lower number? I've been running mine at about 120 (well, it doesn't stay there long) but thought I would turn it down if a lower psi worked just as well.
Thanks

[hardtailjohn]

It depends on what I'm doing with it... but usually I have it cranked up to at least 120.... although I've run it down to about 60 before when working on some aluminum.
John H.

[FORDification]

Mine always starts off at 120 but drops rapidly, I'm thinking down to the 75-80 range by the time I empty the blaster tank. I don't think turning down the pressure is going to help...if anything, I'd think it would be worse, since there's less pressure pushing down on the sand in the tank towards the outlet at the bottom.

[MAK]

Thanks. I'll leave the settings alone.