Snagger Posted March 4, 2014 Share Posted March 4, 2014 Hi folks. I am borrowing a friend's brand new Clarke blaster and compressor to clean up some parts for the RRC. I bought Sealey blasting grit from a local tool shop, and it went through the blaster's filler sieve without any trouble. The compressor works perfectly. I am having trouble with the hose between the blaster tank and nozzle clogging up after just a few seconds. I have tried using high air flow and minimum grit, opening the grit valve slowly until I just start getting some, but still the hose clogs up with grit. To clear it each time requires its disconnection from the tank and then a lot of flexing and manipulation to loosen the grit compacted inside. Any ideas what I'm doing wrong, please? Quote Link to comment Share on other sites More sharing options...
David Sparkes Posted March 4, 2014 Share Posted March 4, 2014 Hmmm, Do you have a water trap on the compressor outlet?. I suspect some hoses are better than others, but if the hose you are using is the standard item then it should at least be serviceable, so I'll discount that. I admit I'm not familiar with any Clarke kit, but from your description there is no on/off control at the nozzle itself, and that you switch blasting on and off by switching the airflow into a pressure pot. In terms of 'doing wrong' I can't think of anything else but using wet air. HTH Quote Link to comment Share on other sites More sharing options...
Team Idris Posted March 4, 2014 Share Posted March 4, 2014 Damp air? Usually gets them every time. But I wouldn't rule out something jammed up the hose that is restricting it. But my favourite is still wet air. The other one is the inside of the hose becoming detached from the outside, so it looks fine, but is flat inside under vacuum. If it isn't one of those, I'm stumped Quote Link to comment Share on other sites More sharing options...
Snagger Posted March 4, 2014 Author Share Posted March 4, 2014 There is a water collector on the blaster. It has an inlet valve from the compressor hose into the separator (which is bone dry), with another valve after the separator to control airflow through the nozzle. Another line runs from the separator into the media tank, with a third valve at its base to control media addition to the airflow. The nozzle has a safety "valve" which is just a spring loaded flap which closes over the end of the nozzle, held open by squeezing a trigger on the hand piece. I'm making sure I get full airflow and the nozzle is open before I open the grit valve, but it still clogs very quickly. It could be that the media is damp, though it was a brand new sealed bag and seems dry. The media tank's pressure relief valve spat a couple of snow balls when I opened it to depressurise the tank, so some moisture may have got in there some how. The hose is the standard one and is new (like the whole set up), so while it could be internally damaged, it seems unlikely. Quote Link to comment Share on other sites More sharing options...
yalan Posted March 4, 2014 Share Posted March 4, 2014 You can usually free a clogged tube on these cabinets by putting your finger over the end of the nozzle. Because it is a syphon system, a quick blip on the trigger forces the air backwards down the pickup pipe and clears the tube. I have a clarke cabinet and tried sharp black media first with zero success. Switched to glass beads and things were much much better. But the cabinet isnt great off the shelf. For more ideas.... http://www.mig-welding.co.uk/forum/threads/small-clarke-blast-cabinet-improvement.20261/ Quote Link to comment Share on other sites More sharing options...
Snagger Posted March 4, 2014 Author Share Posted March 4, 2014 This is a bigger unit with pressurised tank, so it doesn't syphon and can't be cleared that way. Interesting about the sharp black media causing you problems - that's what I'm trying to use. It may be a shape that binds together. Quote Link to comment Share on other sites More sharing options...
David Sparkes Posted March 5, 2014 Share Posted March 5, 2014 I suppose we shouldn't miss the obvious question, what is the bore size of the nozzle, and what is the specified size of the grit? I can't say exactly what the relationship 'should' be, because I've not had the problem, but neither have I used 'sharp black media', always reusable aluminium oxide, or rarely, expendable furnace slag, although I can't recall the specified sizes. Thinking about it, I'm not sure I have ever used expendable furnace slag with the current nozzles (spark plugs with the centres removed). Regards. Quote Link to comment Share on other sites More sharing options...
Snagger Posted March 5, 2014 Author Share Posted March 5, 2014 The Clarke instructions state 60-80 grit. The media is measured in microns, so I can't be sure that it matches, but it wet through the sieve easily, which I think would be a reasonable test. The media is apparently the standard stuff sold locally, and is marked as being for industrial and small portable units. The nozzle bore is 3-4mm. Quote Link to comment Share on other sites More sharing options...
David Sparkes Posted March 5, 2014 Share Posted March 5, 2014 I just started thinking about 'where' the tube blocks; is it always mid section, or near the nozzle? Then I extended that thought; is there a dip or U bend in the pipe run, and is that where it blocks? My pressure pot sits on the floor, the media outlet is at the bottom, so the pipe snakes over the floor, but deliberately without any sharp bends. The pipe then rises vertically, curving into the front of the blast cabinet about 4 feet from the floor. Some pressure pots sit on legs, so the media exit is 2 / 3 feet from the floor. If the pipe then drops down before rising to the cabinet, this droop may cause the media to collect in a concentrated area. A possible work round would be to route the pipe from the pressure pot up over your shoulder(s), then downwards 'along' your arm to the cabinet. Regards. Quote Link to comment Share on other sites More sharing options...
Tanuki Posted March 5, 2014 Share Posted March 5, 2014 I'd be checking the desiccator/water-trap on the compressor. Compressing air 'concentrates' the moisture naturally present in ambient air. A proper compressor has a desiccator/dehumidifier on the output - if it doesn't you'll get clotting of abrasives and/or wet-spotting if you're using it for paint spraying. Quote Link to comment Share on other sites More sharing options...
Snagger Posted March 5, 2014 Author Share Posted March 5, 2014 The hose is roughly 6' long and comes out the bottom of the tank. I have been careful to to kink or loop it. I'm blasting in a wheel barrow to catch as much media as possible, so the nozzle is less than 3' off the ground. It must be within the design capability of the unit - it's meant to stand on the floor as it's mounted like a porter's barrow. Quote Link to comment Share on other sites More sharing options...
Snagger Posted March 5, 2014 Author Share Posted March 5, 2014 I'd be checking the desiccator/water-trap on the compressor. Compressing air 'concentrates' the moisture naturally present in ambient air. A proper compressor has a desiccator/dehumidifier on the output - if it doesn't you'll get clotting of abrasives and/or wet-spotting if you're using it for paint spraying. Like I said, the blaster has one. Whether it's effective is another question entirely... Quote Link to comment Share on other sites More sharing options...
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