Blast hose Clogging Up.

[Pollys13]

New system put together, original 3/8 fitting in bottom of pot,dropping grit into 3/8 ball valve, into 3/8 T connected to 3/8 bore of pinch valve sleeve. New 3/8 regulators and 3/8 piping on wall board. Air is supplied to pot with 3/8 hose, compressor to wallboard has 3/8 hose. Yesterday system working fine more or less as should. Today started having problems, eventually found the 3/8 hose on end of pinch valve, carrying grit to cabinet was completely blocked up, as was the hose in cabinet. We disconnected both hoses and unblocked, cleared them. completely. Not tried system again.

What we are wondering is?, If the pinch valve itself is working as it should and all things being..... equal???. The pinch valve housing, we have put a 3/4 npt x 3/8 bsp adapter on it, to fit the 3/8 hose. What about if we get a 3/4 npt x 1/2 bsp and a 1/2 bore hose. Replacing the 3/8 hose that got clogged up with a larger bore hose to and inside the cabinet, would this prevent the hoses clogging up?
Can also get a 3/4 npt x 3/4 bsp adapter so could fit a 3/4 bore hose if bigger would reduce liklyhood of clogging. That said what kind of adapter do I need to fit a 10 mm od tungstun tip into a larger bore hose?
I had though moisture but grit feels. spinkles through fingers fine, unless I have this wrong and only requires...... tiny amount of damp in grit to cause clogging problems?
The ball valve at start only opened about 1/4-1/3 to start but bit more as time went by.
Cheers.

 

[hotponyshoes]

If it was working fine yesterday them I would say moisture.

It might not be in the grit, could be coming through the air line.

 

[Pollys13]

If it was working fine yesterday them I would say moisture.

It might not be in the grit, could be coming through the air line.

This is wall board set up, in photo, middle regulator connects to actuator port on pinch valve. Only using low pressures for etching glass around 25 psi for pot. On wall board where air comes in from regulator top left, as you can see has water trap as does pot. Am using 5M long hoses from compressor to wallboard as well as one feeding air from board regulator to pot, the pinch valve hose just as long. ?As I say is only a tiny amount of moisture enough to clog up a blast hose?

 

[hotponyshoes]

I dont have a pot so not sure but I have a recirculating blast cabinet and the feed pipe for that will clog up if I leave the media sat in there for long unused. I have a dryer on the airline but it's a damp workshop and even though it is supposed to be a sealed system it still seems to absorb enough moisture to cause issues.
The finer the grit the worse it clogs and I am running a fair bit more pressure than 25psi.
It will normally clog around a coupling or restriction but I have had it bunging up in the middle of the hose before.

 

[Pollys13]

I'm using 120 mesh size grit so is a very, very fine, the pinch valve hose to hose inside cabinet is connected with an NPT/bsp nipple adapter.

 

[brightspark]

heres mine. if your using a 3mm jet on the end a 10mm blast hose will work fine putting a larger blast hose and larger fittings on n will not be the answer my 90cfm pot has a 6mm jet and only uses a 15mm blast hose . chances are if the blast hose is clogging up its either getting flooded with 2 much media or the media you are using has the odd few particles of media that block the jet and then fill the hose .I presume your using an open 3mm jet on the end of hose . take some pictures of your set up and post them. what pressure are you running mine run at over 90 psi

 

[Pollys13]

The nozzle oriface is 2.5 mm, measured it with clear plastic ruler, could be 3 mm.

 

[brightspark]

how long can you use before it blocks up and have you a water separator on the pot

 

[Pollys13]

heres mine. if your using a 3mm jet on the end a 10mm blast hose will work fine putting a larger blast hose and larger fittings on n will not be the answer my 90cfm pot has a 6mm jet and only uses a 15mm blast hose . chances are if the blast hose is clogging up its either getting flooded with 2 much media or the media you are using has the odd few particles of media that block the jet and then fill the hose .I presume your using an open 3mm jet on the end of hose . take some pictures of your set up and post them. what pressure are you running mine run at over 90 psi

Running the pot around 15-25 psi, pinch valve around 45-65 bring air into wall board about 75-80 psi.
Photo of top of pot air comes in from pot regulator on board into a hosetail to right of watertrap, splitter pipe takes air into top of pot, part otherside of water trap takes same air pressure down to one end of pinch valve, where ball valve, T etc are, grit/air mix comes out other end going to cabinet, the quick connect on actuator port on valve have replaced with hosetail.
Yeah as I say, started to play about, air not coming through, or air coming through continually, then only grit, then sort of grit frothing out of the nozzlle but under no pressure. Took hosetail out of actuator port in case inpinging on pinch valve sleeve, wasn't inpinging so put back on. Took end of pinch valve housing off, all seemed in order so put back on.

 

[brightspark]

I just shut mine off and open it with a ball valve next to the water separator all at 90 psi I use a secondary tank on the end of the air hose next to the pot which aids cooling and less water getting to the separator on pot

 

[Pollys13]

I just shut mine off and open it with a ball valve next to the water separator all at 90 psi I use a secondary tank on the end of the air hose next to the pot which aids cooling and less water getting to the separator on pot

OK thank you So you are pretty sure problem is due to letting too much grit drop down, that could contain larger bits of grit, that the other grit gathers around eventually causing a blockage? Don't think moisture gathering in lines might be part of problem?
Cheers.

 

[jordhandson]

H Polly just my four peneth, if it was working yesterday this is just a thought, what where you blasting was it heavily rusted, Ie has any ****e gone into the blast hose blocking it, what size grit you using, as 3/8 wont take a lot to get it block. I use in the cabinet 1inch ID hose down to 6mm nozle and it can still block and I have 180 CFM air if needed, regulated down depending on whats being blasted.

Another thing I have in the bottom of the cabinet which does help with stopping the ****e is sieve I used the metal from a household kitchen strainer, this type cheap as chips, dont go to mesh supplier, much money



you need the holes to be a bit bigger than the grit your using.

 

[Pollys13]

OK thanks, etching glass, using 120 mesh sized grit. I did buy a sieve from ASDA, holes thought were small enough but no, will need to contact grit supplier to find grit partical size. Yes, have seen prices of metal mesh prices on Ebay...... extortionate
When emptied cabinet after using yesterday, discovered small bit of painters masking tape about inch square, used to stick the resist to glass, removed the tape. Didn't see any other tape in grit in cabinet, or when emptied through funnel back into pot.

 

[brightspark]

have you a decent extracta on your cabinet . have you tried kiln dried sand . I run it in my pot mainily in cabinet or outside with an air fed helmet as its not good for health without . give it a try and see how you get on it shouldn't give any problems unless your getting water in the air line

 

[Pollys13]

I'm using the extractor that was supplied with cabinet, seems to do the job. No not used kiln dried sand, it might be fine enough but don't know if would be hard enough, not really reusable like SC as break up into dust quickly. Have Googled but not found anyone using sand for glass etching.
Thanks for trying to help
Will start system again and introduce grit very slowly to avoid flooding system and avoid blasting any masking tape holding resist on glass, that might have blown off and ended in grit, didn't see. Will let forum know how got on.
Cheers

 

[CompoSimmonite]

Is the blasting medium damp ?

 

[Pollys13]

Is the blasting medium damp ?

From what I can tell no, aren't any water droplets in either of the traps, again from what I can tell the grit seems dry to me.