Pressurised sandblaster - anyone

[jcbadger]

Hi all

does anyone own one of these 10 gallon pressurised sandblasters you can buy on ebay? They all look the same - orange or red in colour - cost around £100.

I have one and it tends to clog very frequently to the point it's inefficient to use. Seems likes its a common problem and not always down to the size of the grit or compressor. Problems seem to surround the issue of moisture - and it doesn't need to be much moisture to upset it's operation. Some advise fitting a 2nd water trap and others say fitting long coiled copper tubing to the airline; inserted into a bucket of ice water to keep the air cooler and thus preventing condensation forming inside the air line.

My question is therefore twofold:

Is a water/moisture trap the same thing as a 'water separator' or 'air dryer' as I've seen on some american forums? Made of glass or plastic with a small nipple at the bottom to let water drip out.

Where do you fit it? There is already a water trap on the sandblaster - this would be a second one to improve water removal from the compressed air.

By the way the blaster works fine for blasting away rust so I do have a big compressor to run it but its just so inefficient when it clogs up after less than a minute. I find that I have to shake the tank to get the grit to fall to the bottom of the tank and into the bottom outlet hose

Any other advise would also be most welcomed. Thanks.

 

[rtbcomp]

Welcome to the forum. I run one of these all day everyday with very few problems.

I have an extra filter/regulator (thing with a glass bowl) on near the pot and I run the pipe upto it at tank pressure. I don't think there's any need for ice buckets. Does this problem occur after an hour or so of use? If so, it sounds like a moisture-in-the-air problem.

When the flow of grit stops I assume the air is still coming out of the nozzle. If so try closing the bypass valve. If air continues then there is a path through the pot to the nozzle. What's happening here is that a hole is being "drilled" through the grit, which is failing to fall down as the grit is used. Shaking the pot dislodges the grit and away you go.

This can be caused by moisture or excessive dust in the grit.

If the flow of air stops when you close the bypass valve then the most likely problem is a foreign body blocking the bottom valve. Remove it and see if a lump of something drops out!

Tip - when you re-fit the bottom valve, fit the air pipe the other way round so the swivel union screws into the mixer, this makes it mush easier to remove in future.

 

[jcbadger]

Hi

Thanks for your reply. It literally happens as soon as I start - I only get a few seconds blast then I have to shake the tank - and then a few more seconds and then shake again - totally impractical. I'm running at 100psi with all valves fully opened.

Which valve do you mean by the bypass valve?

Yes, grit stops coming through but air still does. It sounds exactly as you describe. You can hear the air inside the tank as if there is a hole drilling through the grit. Once you give it a good shake the tone changes and the air sound in the tank lowers in tone as if the grit is plugging up the 'hole' and filling up the delivery hose. It then works for a few seconds and then stops again. Am I also operating at too high a PSI and and opening the valves too wide? I read elsewhere that some people runs at 70psi and partially crack open the valves - not fully opened. thanks

 

[rtbcomp]

I run mine at about 90 psi.

The bypass valve (my name for it!) is the one down the side of the pot.

The top valve & bypass should be fully open and the bottom valve adjusted to get a just visible stream of grit. With an unworn valve this will be about half-open. The adjustment is VERY sensitive and takes about 10 secs to settle down between adjustments.

If you have a valve on the nozzle this should be fully open too.

 

[jcbadger]

hi

Thanks. Your second water trap - did you screw it onto the thread directly next to the water trap that is already part of the pipework on the blaster. So literally are they next to each other?

 

[rtbcomp]

No - it's on the end of the copper pipe in my blastroom, then there is a short length (about 1m) of hose to the pot.

I installed a ball valve on the inlet side of the regulator so I could de-pressurise it overnight.

The regulator bowl fills up quite quickly, but the one on the pot doesn't seem to catch musch water. I'm not sure if this is because it's not all that good or because the reg. has removed all the water first.

I suspect the copper pipe run from my compressor (about 4 metres) allows quite a bit of moisture to condense out.

 

[rtbcomp]

Another thing occurs to me - are you filling the pot to the top?

As it becomes nearly empty it's more difficult for the media to drop down into the mixer. I usually end up shaking my pot when it's nearly empty.