grit valves for cheap pots

[Dcal]

I'm not so pessimistic or certain and I'm always prepared to accept when I'm wrong but I can't see why it wouldn't work.
In fact I still think it's a better way to do it.

I don't see any reason why it would clog up because the grit stays out of the valve until it goes through the metering flap then it's straight through and out the blast pipe.
The way yours and I assume Clemco's works (if I've picked it up right) seems more likely to clog.

I can't try it out now as I've drilled a 4 inch hole in the bottom of the pot!

We will see and just think, if we didn't try we would never know.

 

[brightspark]

the way you have it its no better than a ball valve . any inconsistency in the media and it will need re regulating. no need to reinvent the wheel .I just feel as though you have spoilt a nice job

 

[DAPPH]

Just a thought , from one in their dotage .

Beside having a de watering & oil removal filter set on the incoming airline to prevent clogs happening , could it be arranged so that inside the grit reservoir there is a fine jet of air being just above the outlet , pointing into the metering vale intake so it disturbs / fluffs up whatever is going into the supply valve .
This air jet could be intermittent ie. Happens when you hit a press to supply air button .
There shouldn't be any abrasive wear to speak of inside the tank nor on the valve .

Alternatively have a simple air jet & on off lever valve to blow into the grit in the tank from near the bottom to fling it about and break up any clogging/caking so it falls down broken up to the metering control inlet .

 

[brightspark]

the weight of the grit or sand sits in top of the outlet which is half inch bsp in to the metering valve there is never a problem. the problem lies if any water gets down to the tee piece under the reg valve and builds up with grit then fills the chamber back up .I don't have that problem or any other. its a tried and tested design and I have used them for over 35 years doing hundreds of wheels and motorcycle parts along with sandblasting 2 houses

 

[brightspark]

im half way through making another pot for someone. all the parts are made and machined he is just going to weld it all up and assemble it . no need to test to see if it works .it will il put a piccy up when its done . here is the bought one note the lever underneath and the flat top screws under the pot https://www.centurywise.co.uk/shot-...metering-valves-/junior-flat-sand-valve-miser the black one shows underneath which is upside down and the silver one the correct way up

 

[Dcal]

Managed to get a few hours in the workshop to finish and install the media valve.

I also made and installed longer legs and a big bung to let me easily empty the grit.

Change the fittings on the blast hose to the claw type.
The blast pipe is a bit of high pressure hydraulic hose.

Just need to try it out and if it doesn't work as I hope (or as badly as brightspark says it will) I can turn the valve upside down (or right side up) and try again.

My guess now is the metering valve acts as a buffer and needs to be full of grit to work properly.
Then it doesn't matter if the pot is full or almost empty of grit, the metering valve should be full and so will deliver the same amount of grit to the blast pipe.

If that is the case the cone I machined in the valve is exactly the wrong thing to do as the cross sectional area of the valve can change (and so the area of grit the air pressure is action on.)
If so I can weld a floor in it or machine it to a cylinder.

be interesting to see how this goes and I should more about metering valves before I'm finished.

 

[Dcal]

Got everything together and blasted for an hour or two and even with the valve upside down it has worked perfectly.

I half filled the pot with new supafine jblast and then topped it up with jblast that had been through the pot a few times (so very fine and dusty) to see if the different grades affected the feed.
It took about 30 seconds to adjust the flow and then I didn't change anything until the pot was empty.

I don't have anywhere enough air so need to keep stopping to let the compressors catch up (3HP belt drive and a 2HP direct) and even stopping and never turning the grit feed off didn't cause a blockage.
I use a 3mm nozzle so any issues normally shows up straight away.
i also didn't need to divert any air into the pot to get the grit moving like I had to with the ball valve type.

These are the bits I blasted.
The air-box and motor cover took a lot of work the rest just needed a quick flash.

Maybe early days but I am really pleased with the results from my diy metering valve.
I don't really know how to improve its functionality, seem to do what it's supposed to, other than putting an adjustable stop on the feed lever.
I'm just sorry I persevered for so long with the useless ball valves which caused no end of frustration.

 

[scottmk1]

Good work, looks like it's well worth doing.

 

[Dcal]

Good work, looks like it's well worth doing.

Definitely.
Really excellent tool now not just the most frustrating pile of junk, but it took a lot of mods to get there and not just the metering valve.

 

[scottmk1]

What else have you done? I've got a new elcheapo pressure pot that I want to start using soon and was going to make a metering valve then use as is, apart from the gun, I've replaced that with a tungsten nozzle and my cabinet has a foot pedal/deadman to operate.

 

[Dcal]

Pretty much what you have done.
I worked with exactly your mods for a couple of years and it worked OK but was hard work.
The metering valve was the thing I should have done long ago but I didn't have a lathe or know how to go about making the valve.
You should probably go with the @brightspark version as it's tried and tested I might have just got lucky with mine, but for now I'll keep using it until it gives problems.

In fairness there seems to be little information on the net on these valves. (Maybe I'm just searching for the wrong thing.)
Without having a valve to copy it's hard to know what to make.
The discussions on this thread certainly brought out some of the issues for me and I would probably make something different if starting again, However as I have what I have now and it seem to work very well, I might as well give it a good trial.

Best mod was probably replacing the hopeless nozzle and dead-man with a straight through tungsten nozzle.
I have this on plumbing fittings (as you can see in one of the photos) and it is loose so I can remove it to clear blockages inside the cabinet without tools (hopefully not a regular occurrence now)
I also fitted a foot pedal which I use with the cabinet or when blasting outside, with just just the pot.
I changed the blast pipe for a bit of twin wire hydraulic hose I had laying about when the one that came with it wore through. I would like something more flexible for inside the blast cabinet but haven't done anything about that yet.

Does anyone know of a hose that would be suitable and would last? I have a bit of silicone that might work but would it contaminate what I'm blasting and cause problems with painting? (fish eyes?)

The legs to increase the height is a nice to have.
I did it because I was always adjusting the ball valve.
If my new metering valve continues to works as well as it does now it is less of a issue and probably not worth doing.
I will put an adjustable stop on the valve so I can set it and then move it to the off position when I'm not blasting.
It's very confusing to know what ways off at the moment so will do that soon and put up a photo of what I end up with.


As you can see I also installed a big bung to empty the pot and to give access to blockages but I'm not sure that was necessary as I rarely have had to fully empty it (only once really, when a bit of wire got through the sieve and stuck in the outlet) but emptying through the filling point is a pain.

Another tip is I ran a bunch of A3 laminate covers through the laminator and use them as covers for the screen.
Cost next to nothing compared to the proper covers. I just cut them to size and stick them on with duct tape.
I have good dry air (not enough but what I have is dry) as I run it through a desiccant dryer (proper one I got from a member on here)) but I also pass all the air through one of the clemco breathing filters and I have never had a drop of water in the system.

https://www.hodgeclemco.co.uk/wp-co.../PPE Accessories - Breathing Air Filters.html

Next mods are to sort the blast cabinet.
On the to do list are -

1. Fit a claw fitting for the blast pipe where it enters the cabinet. At the moment it just goes through a hole but it's too big because it has to take the fittings and clip.
2. Change the light to 2 number 20 watt leds flood lights that are mounted at the top of the cabinet.
3. Properly sort out the extraction with a 4 inch pipe from the machine, through a cyclone dust extractor and on to a 4 inch wood chip workshop extractor. My cabinet has the built in vacuum which works OK but it quickly gets overloaded with dust.
4. Install a roll of clear plastic on the inside of the screen that I can wind on from the outside instead of changing the covers. (Will need a few brush seals and the extraction working properly first)
5. Install a couple of bars so I can lift and move the cabinet about with my pallet truck - This one is easy but on the very long finger.

I have all the bits I just don't have the time yet.

 

[brightspark]

I use steam hose to the blast nozzle .quite flexible its thickish rubber with braided string through it . if your using a foot pedal make sure ittakes agood volume of air without restriction I use minimum 10mm bore hoses and claw couplings so not to reduce the flow . it makes a big difference . most people wouldn't notice the loss but having being blasting with small pots and larger ones for years I can tell the difference using restricted pipes and fittings

 

[brightspark]

another pot nearly finished for a friend heres the valve

 

[captain-destructo]

another pot nearly finished for a friend heres the valve

why make one when you could have made two
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.
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if you decide to make any more valves keep me in mind

 

[martin62]

Hi brightspark I am going to make my own Blast Pot with a grit valve like yours. Do you have any drawings if not is there any dimensions critical for it to work. Aidan

 

[brightspark]

Hi brightspark I am going to make my own Blast Pot with a grit valve like yours. Do you have any drawings if not is there any dimensions critical for it to work. Aidan

can send u some pictures of them in pm

 

[martin62]

 

[Brad93]

Need to make something like this

 

[brightspark]

a lathe and a welder is all that is needed to make the pots and some metal a bottle .time and enthusiasm

 

[Brad93]

What size diameter round bar do I need?