Some sand-blast answers

From: Henry (henrya@jps.net)
Date: Mon Feb 28 2000 - 08:41:38 PST


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Hi all,
Here are the answers to some of the questions posed so far. It seems many
are interested, so I'll answer on-list, if no one minds, questions
frequently asked.
Feel free to ask away, I'll answer as best I can.

A good water separator is the holding tank its self. Depending on the
compressor you are using, it will have a tank that holds air at pressure,
kind of like a reserve. The key is to cool
and slow the air so water can condense. A larger tank, maybe made from a
propane tank, can do that. It takes longer to pump up, but holds pressure
better and slows the air flow. If it's winter, the tank will allow cooling
on its own. Sometimes in extreme heat, you can run a little water over the
outside of the tank to cool it extra, thusly cooling the air and causing
condensation. Make sure the tank you use has a separate in and out, ideally
not in line with eachother, and a way to drain the excess water. And also,
make sure it is built to withstand the PSI you are using. This can be very
dangerous!!!!!!! I try to use tanks rated 200 psi or above working
pressure. I use about 1 gal. of reserve capacity for each 1 cfm of air
requirement.
You can buy some commercial separators that look kind of like fuel filters
for diesel big rigs. They work pretty good, but if you are going to use
your compressor for lots of things, that extra reserve tank comes in pretty
handy anyway.
For protective clothing, I use rain gear. It's hot in summer, but the heavy
rubber/vinyl seems to protect pretty well and they don't cost much. Leather
gloves, too.
Make sure to provide yourself with good air. either a good mask, or I use
an air fed helmet. And face protection. If using a mask, get some 100 or so
mesh screen and install it over the face area, it will stop most of the
particles that would bounce back and scratch the lens.
Sand. For what you are doing, cheap is good. Regular river type sand works
ok. make sure to get grain size that matches your nozzle size. 30 mesh is
good for about a 1/8" tip. The larger the grains, the harder they hit for a
given speed. Unfortunately, also the larger the compressor required.
I use 85 CFM @ 100 psi. with a 1/8" ceramic nozzle ( as the nozzle wears,
the opening gets larger, requiring more airflow, or lowering working
pressure) that requires about 15- 20 hp. electric or 40 hp
gas driven compressors, so you will probably have to experiment with how to
compromise using smaller stuff. It will work fine, just take longer.
The exotic sands are fine, but expensive, and unless you are going to
reclaim and re-screen it, just not worth doing. I use Garnet sand, it's
about $20 per sack, so I reclaim it until the grain size is to small and
goes out the dust screen on my re-cycler.
That paint can be hard. Experiment with different angles of attack with
your nozzle. Sometimes you'll find an acute angle allows you to peel the
paint, or a direct angle will break it faster. Rust is rust. I find a
straight shot at it works best.
Sorry for being so long-winded. If you need more info, just ask.
Good luck, and have fun (?????????)
Henry



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