A question for rtbcomp

[Shox Dr]

After looking high and low for a blast pot, I decided I was been lazy and 100+quid was better spent on other stuff I have started to build one.

I found a picture you had posted a while back, and have a question for you.

Why do you need so many control valves in the line.

 

[malcolm]

The one to the top left shuts off the air supply so you can release pressure in the pot for refilling. The one at the bottom controls the amount of grit you get in the air. Not sure the one to the right is necessary.

Sorry - I'm not rtbcomp. I'll try harder next time.

 

[Shox Dr]

That's how I thought it was, but in another post he says open the lot and play with the pressure to get the flow right

 

[malcolm]

There's no flow into the pressure pot, so if the valve to the top left is open at all the pot will be suitably pressurised.

I took the comment as regulating pressure into the whole system. In the cheapo eBay blaster the gun has a valve, but as it's after the medium has been mixed in it needs to be completely open or completely closed. Otherwise it will get blasted. So pressure needs controlling elsewhere. I do it on a regulator before the blast pot system.

 

[Omniata]

The one on the right will regulate the draught "blowing the grit through/out" in my opinion

There'll have to be some pressure in the pot to force the grit out and the amount of grit, as Malcolm said, is set my the bottom valve...

Not sure otherwise...
Sorry if I'm wrong

 

[rtbcomp]

The main air stream goes through the bypass valve (the one on the side), this will mix with the grit dripping through the bottom valve, the mixture then goes along the hose to the nozzle.

It's necessary to pressurise the pot because there will be air pressure at the bottom which has to be overcome to allow grit to flow.

When the pot is nearly empty air may pass through the pot, give it a kick to dislodge sticking media.

Ignore the gate valves, that diagram was for an experimental setup.

Yes, adjust the pressure supply to the pot via a regulator.

 

[Shox Dr]

Just as I thought. Thanks

Next question; Do the fittings at the bottom ever need replacing, because of media wear.

 

[rtbcomp]

....Next question; Do the fittings at the bottom ever need replacing, because of media wear.

Yes. The original pot had quite a nice mixer but the hose tail on it wore away and it wasn't replaceable so I've used a 3/8 BSP female malleable iron T-piece whch doesn't seem to wear.

I've used 3/8 BSP to 14mm hosetail for the blast pipe, this does wear but I've lined it with steel tube whch prolongs its life dramatically.

 

[Shox Dr]

Cool, I'm going to be using 1/2" Black Iron fittings. 1/4" Air line tail fitting to 1/2" stab into a ball valve, then the Reg next a tee in to the top of the pot, down to another ball valve then tee to the outlet, short stab and then hose.

I'll cut the top guard, and lower ring off the bottle tonight. I'll start to pipe it up tomorrow, where is the best place to get flexible pipe from, that will withstand the grit

 

[rtbcomp]

These people sell blast hose, but I'm using car heater hose at the moment - doesn't last as long but much cheaper and I got given a roll!

http://www.arco.co.uk/products/3923500/148837/Arco_12_bar_Shotblast_Hose

http://www.acegrit.co.uk/

Lets have some pics when it's done!

 

[Shox Dr]

OK, I've got a mate who has a good supply of Hydraulic hose, I'll give him a call

 

[Jaeger_S2k]

]

Lets have some pics when it's done!

NO!
Let's have some pictures as you build it as I have that in mind for later, much later.

 

[rtbcomp]

NO!
Let's have some pictures as you build it as I have that in mind for later, much later.

Probably better to start a new new thread, the title of this one doesn't really reflect "how to build a gritblaster."

 

[Shox Dr]

Now now, boys

I'll be sure to start a new thread when I get stuck into it. The boss has ordered the black iron fittings I need, so it won't be long

 

[stormin]

These people sell proper blast hose by the metre.

http://www.centurywise.co.uk/category.asp?cid=8

Not that expensive, hard wearing and a lot, lot more flexible than heater or hydraulic hose.

 

[rtbcomp]

Thanks for that, looks like reels of 10m?

I think I'll get a roll to try when my current stock is used up.

The Arco hose is slightly cheaper