sandblasting unit self build?

[Harry44]

Thinking about going bigger than my 20 gallon blaster next year, not happy with the build quality and think i can do better myself.

I have a shed that i do my blasting in which is 16ft so my idea is to buy a 150 or 200 litre receiver tank and sit it in the corner of the room, and have a long blast hose coming off it.

I am wanting to cut the top of the cylinder and flip it over so it works as a good way of the media to drop into the tank once sieved, so my first question is, is it safe pressure wise to flip it and run a good mig weld around the outside?

My second question is, is there a place i can buy a 4" threaded insert and cap, like these but in mild steel? if not i could blast the galvanising off these and finish them?

http://www.pipefittingsdirect.co.uk/contents/en-uk/d7.html

Also i have a lot of this type hose around, will it last a while if used on the outlet side of the blaster or should i buy some rubber?

http://www.ebay.co.uk/itm/271254732...49&var=570176672195&ssPageName=STRK:MEBIDX:IT

 

[WorkshopChris]

My second question is, is there a place i can buy a 4" threaded insert and cap, like these but in mild steel? if not i could blast the galvanising off these and finish them?

Something like this?
http://www.lsengineers.co.uk/catalog/product/view/id/5946

 

[Harry44]

this is similar like what i want to do

http://www.dodgecharger.com/forum/index.php?topic=53871.0

 

[Harry44]

thats perfect workshopchris, thanks

 

[brightspark]

[QUOTE="Harry44, post: 919892, member
Also i have a lot of this type hose around, will it last a while if used on the outlet side of the blaster or should i buy some rubber?

http://www.ebay.co.uk/itm/271254732480?_trksid=p2057872.m2749.l2649&var=570176672195&ssPageName=STRK:MEBIDX:IT[/QUOTE]that hose wouldn't last 5 minutes using it for blasting u need a decent rubber blast hose if your only using a 3mm blast jet u can get the hose from ace engineering sandblasting supplies

 

[rtbcomp]

I used rubber car heater hose because I had some and it lasted surprisingly well. I found that 3/4 bore lasted longer than 1/2 inch, although I had to adapt the nozzle to fit the larger bore.

 

[henry Kadzielski]

Good morning gents.
The internal diameter of the blast hose should be about 4 times of the diameter of the nozzel being used. Blasting performance is related to the pressure at the nozzel. Every psi above 100psi you get 1.5% increase in blasting speed. However for every psi under 100psi the reverse is true. Now from the above pictures I couldn't see what metering valve was being used to control the flow of grit (abrasive) and the use of the ball valve to control the blast has it's problems. The grit passing through the ball valve will very quickly erode the valves internals and make it non functional. Now the type of nozzel being used is also very important. There are straight and ventury nozzels. The ventury have a better spread of the abrasive in the blasting zone and give a more uniform blast pattern.
Some of us know this as we have all gone through the pros and cons, and also have done this for some time. One last thing to remember and probably the most important is moisture in the blast air. This will condense down the hoses and cause abrasive feed issues. This is by far the most common problem with blasting

 

[brightspark]

Good morning gents.
The internal diameter of the blast hose should be about 4 times of the diameter of the nozzel being used. Blasting performance is related to the pressure at the nozzel. Every psi above 100psi you get 1.5% increase in blasting speed. However for every psi under 100psi the reverse is true. Now from the above pictures I couldn't see what metering valve was being used to control the flow of grit (abrasive) and the use of the ball valve to control the blast has it's problems. The grit passing through the ball valve will very quickly erode the valves internals and make it non functional. Now the type of nozzel being used is also very important. There are straight and ventury nozzels. The ventury have a better spread of the abrasive in the blasting zone and give a more uniform blast pattern.
Some of us know this as we have all gone through the pros and cons, and also have done this for some time. One last thing to remember and probably the most important is moisture in the blast air. This will condense down the hoses and cause abrasive feed issues. This is by far the most common problem with blasting

I don't use a ball valve on mine there crap[ and hard to regulate. I make my own. I use a 6mm jet and 15mm bore blast hose correct for the size. it runs at 90 psi and 90cfm

 

[henry Kadzielski]

good morning brightspark.
From what I have experienced before, the 15mm blast hose is on the small side. For 6mm jet I would be using a min of 3/4"hose. The performance of you system probably would increase with the increase in blast hose. You would find that if you had a hyperdermic pressure gauge and pushed it into the blast hose just before the jet you would not be getting 90psi. Rated air consumption for a 1/4" jet is 103cfm, so I can see how you are running at 90. That 10 psi does make a significant differance. Your air supply hose to the pot should be at least 25mm. In blasting it is a accumilation of losses that results in lower than expected performance. However if you are satisfied with the results just ignore what I have said. What abrasive are you using and do you have any steps in place to reduce the moisture that gets moved down the line. Your grit control valve is crude however effective, do you realise that you could adapt a basic micro control valve inplace of your lever operated type. Most grit control valves are rotary, which makes them easier to fine tune the abrasive volume. Just a thought

 

[Harry44]

would a 3mm tip be good? doing car shells and parts

 

[rtbcomp]

^^ It would be slow, probably OK for a one-off restoration but not for a commercial setup. Be careful with flat areas like doors, roof, wings, boot lid & bonnet, there's quite a lot of heat generated, add that to the constant pounding panels will easily distort.

As Henry says, a ball valve at the nozzle will soon wear out, don't use it to regulate the flow - it must be either fully open or fully closed. I got rid of mine altogether.

 

[brightspark]

good morning brightspark.
From what I have experienced before, the 15mm blast hose is on the small side. For 6mm jet I would be using a min of 3/4"hose. The performance of you system probably would increase with the increase in blast hose. You would find that if you had a hyperdermic pressure gauge and pushed it into the blast hose just before the jet you would not be getting 90psi. Rated air consumption for a 1/4" jet is 103cfm, so I can see how you are running at 90. That 10 psi does make a significant differance. Your air supply hose to the pot should be at least 25mm. In blasting it is a accumilation of losses that results in lower than expected performance. However if you are satisfied with the results just ignore what I have said. What abrasive are you using and do you have any steps in place to reduce the moisture that gets moved down the line. Your grit control valve is crude however effective, do you realise that you could adapt a basic micro control valve inplace of your lever operated type. Most grit control valves are rotary, which makes them easier to fine tune the abrasive volume. Just a thought

thanks for the advice the set up of pipes jets and grit valve have been copied of a hodge clemco mini pot 40 years ago i never have a problem with water in the lines. I use a water separator on the pot which I leave the drain off slightly open to start with start the mobile comp up run it full belt not running grit through within 5 minutes the hoses and pot get warm and the condensation disappears. warm dry air . then start blasting. once regulated it will run all day none stop without a problem using either copper slag expendable or kiln dried sand . did a couple of houses with the kiln dried and use it on aluminium parts and have done hundreds of wheels and a lot of motorbike frames

 

[henry Kadzielski]

Good morning gents.
Warm dry air, you are lucky that, that is working for you. I have two larger compressors 1 electric 80cfm with a refrigerated dryer and a diesel 300cfm with a separate refrigerated air dryer. Both on startup don't give trouble with moisture, however run for any longer than 10 minutes and things start to happen. The first thing you see is a light mist (vapour) out from the jet. However if it is working for you don't change. One thing to note here sand, any type of, is illegal to use here due to silicoses. I use garnet of varying grades depending on the material to be blasted. Both sand and copper slag are dusty and people complain. Soon as they complain we get a visit from the environmental people with paper work for a donation. Some sites that I have visited have a stipulation of crushed glass so go figure. This is also dusty and quite harsh on the throut if you breath it in.

Harry44.
The 3mm nozzel as has been stated before will be slow. However as rtbcomp has stated be very careful as the heat generated by the blasting process on the thin panel will make it warp. One of the tricks that panel beaters use to remove small dents and or hail damage is to blast the affected area. This causes the area to expand and pops out the dent. There is quite a bit more to it than what it seams but it works. I have blasted the brow of my truck (area above the windscreen) damaged due to stones, got too close and the areas bulged out a little. Not evident at first, but when painted with the top coat and shiny, the evidence was there.
Unfortunately there is no substitute for horsepower when it combs to blasting. The slower you go the more fatigued you get and then you give up doing it right. You also have to consider the coating time of you base material.

 

[rtbcomp]

A point I should have mentioned about flat panels is use a DA sander instead of blasting them. I used to do some work for a body repair shop and on bonnets &c they just wanted me to blast the edges, creases and the bracing. They did the rest themselves with a sander.

Sand is illegal in the UK too, Copper slag (J-Blast) and crushed glass (I made my own) are my favourites for general blasting of steel.

Another point the home user might consider is that perhaps it's not such a good idea to have a big pot. If you're using 1 or 2 3hp compressors they will be running continuously, so stopping to fill the pot frequently would give them a bit of rest.