Converting a suction blast cabinet to pressure blast

[rtbcomp]

^^ I had the 10 and 20 gallon versions of that, they're all over Ebay.

They're OK, the first thing I did was to remove the valve at the nozzle and replace it with a straight tungsten carbide nozzle, much better in a confined space and lasts considerably longer.

 

[scottmk1]

I'll check out the ones on ebay then. Just ordered a couple of nozzles from Ace Engineering, looks like they no longer make the pots though.

 

[Dcal]

That's the one I have
It will work out of the box but the ceramic nozzles and dead-man aren't worth installing.
I think they all come from the same factory.
The funnel and sieve are well worth having.
The PPE is not.

 

[rtbcomp]

I'll check out the ones on ebay then. Just ordered a couple of nozzles from Ace Engineering, looks like they no longer make the pots though.

I had one of those ACE blasters, it was way overpriced, needed filling every 10 minutes, the mixer T-piece at the bottom lasted a day if you were lucky, the eyebolts holding the lid down jammed with grit and stripped. Otherwise they were a good little pot.

 

[scottmk1]

Sounds like I'd be better off with the el cheapo one then.

 

[julianf]

If a small group of people want the valve cast, and I'm supplied with a pattern, I don't mind casting some.

I won't be able to do the finishing, as my lathe is miles away, so someone else would have to volunteer that.

I would cast them without charge, but I would only want to do them for people who are actually doing builds right now - not those that might think about doing so in 3 years time when they get around to it. (Otherwise the list will be too long for me to want to do)

Again, would need the pattern, and someone else would need to do the finishing. Just me for the casting.

Offer to be retracted at any time for no reason at all, but it's certainly valid now! : )

 

[armalites]

This may be of use with regards to valves. My Vixen has a Saunders weir valve at the bottom of the pressure pot. They are not anywhere near as expensive as you'd think.

The Saunders part number on mine is IA015S1ZXA2H01 which translates to a Industrial type A(weir) valve in SG iron with rubber diaphragm and 1/2 BSPP female ends

Googling the part number finds nothing but I've just spoken to a lady at www.heaps.co.uk who knew what it was immediately.
The valves are £39.60 +vat but unfortunately they are waiting on stock which will be a few weeks.
The 3/4 BSP version is £46.60 in stock
The 3/8 BSP version is £39.90 waiting on stock
All the individual parts are available too so you can replace the diaphragm is if it wears
Only issue is the shipping which is £12.50
I may be tempted to fit one to one to the ebay 20 gallon that I have.

Given that Vixen fit them to professional cabinets I can't see that's it viable to start casting/machining parts.

Vixen want £160 + vat for a valve

I've just spoken to these people and they have similar prices
http://www.valvestock.co.uk/contact.php

£41.25 for same valve, again they are waiting on stock but they do have the same valve with a butyl(not as good as rubber in this application) diaphragm for £46 in stock.
Spare rubber diaphragms are £8 so you just replace the diaphragm with a rubber one when it wears

 

[Dcal]

I'm in.

If @brightspark or anyone else can give me the dimensions I'll have a go at making a set of patterns.
I also happy to try machining the cast blanks but I'm no machinist.

This is defiantly something I want to do.

 

[armalites]

I'm in.

If @brightspark or anyone else can give me the dimensions I'll have a go at making a set of patterns.
I also happy to try machining the cast blanks but I'm no machinist.

This is defiantly something I want to do.

Surely it makes no sense when you can buy a fully functioning valve for £40?

 

[Dcal]

@armalites Sorry I posted before I saw you reply.
I would be very interested in trying one of the Heaps valves.
What are they like?

If I'm sure of getting the right thing (need your help here) I'm happy to order one and report back.

Anything will be a big improvement on what comes with the pots.

 

[armalites]

I only know about them because my Vixen VM36 has one fitted as standard. They are quite a simple thing commonly used in industry.

Basically in the centre of the tube there is a raised section like a weir, the handle operates a diaphragm which regulates the flow over the weir.

Mine doesn't get a huge amount of use but I've never changed a diaphragm and the unit was second hand when I bought it.

This is a flange mount but the part number I listed is for a 1/2 BSPP female which is what my unit uses. Easy to take apart if you get a blockage, 4 bolts and no media ever gets near the moving parts. They are more design for fluids but obviously work fine with blast media and you can replace the diaphragm for £8.

 

[scottmk1]

Very useful info there, thanks.

 

[Dcal]

Thanks @armalites
Will that valve work on these cheap pressure pots?
Reason I'm asking is it not just a much higher quality version of a ball valve. (Or really a gate valve)
I changed my ball valve and it's probablynow even less controllable than the completely stuffed one I had on it.
I have tried every combination of grit regulating valve position, air control to the blast delivery pipe and to pressurise the blast pot itself by throttling back the air to the blast pipe and I can get no consistency of results.
I've seen it discussed on other threads that a venturi effect is used to suck the grit into the air stream and was wondering if that design of valve would accommodate this.
I've had a few proper big Chemco blast pots apart and they seem to fully pressurise the grit pot.
I've no experience of any of the smaller blast pots.

 

[armalites]

The problem with a ball valve or a gate valve is the grit affects their operation, that can't happen with one of these diaphragm valves because all it's doing is the equivalent of squeezing the tube the grit comes through. The valves on the cheap pots are just ball valves as you say and they do not cope will with grit in them. When I first got my ebay one I had the grit grind a hole through the side of the ball valve.

The pressure pot on my cabinet has a poppet valve like the big Clemco pots so it means when the air is released the poppet valve drops and all the grit returns to the pot.

All these valves do is regulate the flow of media and air from the bottom on the pot into the air stream

 

[scottmk1]

https://www.sandblasters.co.uk/pressurised-blasting-pots-32-c.asp

Any comments on those 2 on that page as a starting point? I would be intending on fitting a Saunders valve as shown above, and a tungsten nozzle straight into the end of the hose. My cabinet has a foot operated valve so I'd look at using that too, to deliver the air supply.

 

[armalites]

If you are happy to spend the extra £25 I think the easy fill one would be the way to go.

 

[brightspark]

I only know about them because my Vixen VM36 has one fitted as standard. They are quite a simple thing commonly used in industry.

Basically in the centre of the tube there is a raised section like a weir, the handle operates a diaphragm which regulates the flow over the weir.

Mine doesn't get a huge amount of use but I've never changed a diaphragm and the unit was second hand when I bought it.

This is a flange mount but the part number I listed is for a 1/2 BSPP female which is what my unit uses. Easy to take apart if you get a blockage, 4 bolts and no media ever gets near the moving parts. They are more design for fluids but obviously work fine with blast media and you can replace the diaphragm for £8.

View attachment 174886

that valve is totaly useless. its just a choke valve. squeezes up the silicone tube inside .ok on large pots but that's about it no use on pots less than 90 cfm using a 6mm jet the type I make are on the Clemco mini pot not a choke valve there not any better than a ball valve small scale

 

[brightspark]

What about this one? https://www.machinemart.co.uk/p/clarke-cpsb100b-32l-pressurised-sandblaster/

Suggestions for alternatives welcome too!

there ok apart from the media metering valve if you don't want to make a complete pot

 

[scottmk1]

I think making a pot would be too time consuming, as I've plenty projects on the go already. In saying that I do have a vertical air receiver hanging about doing nowt.........

 

[brightspark]

just knocking another pot up for someone I won't be doing any more this is the 6th im not welding this one though guys doing it himself. il post it up when finished it will be the same as the one in the picture near the saw I just blasted the rust off