Converting Pressure Pot To Run With A Footswitch?

[Pollys13]

I'm using a foot pedal to turn the grit supply through the pot on and off using a pinch valve. I'm using a Model FV320 Foot-switch, 3 Way, 2 Position. This is the same as the instructable showing how to do this. http://www.instructables.com/id/Footswitch-Operated-Sandblasting-System/

He says, " The footswitch needs to supply the bladder pinch valve port with a constant pressure, then when you step on it, the bladder needs to be able to vent out."

"Normally the footswitch is used with the IN and OUT ports to control a pneumatic cylinder or similar device, the VENT port would just bleed air into the room. In this application however, the air is fed into what is normally the vent. "

I don't want to run the risk of messing up the pinch valve bladder by connecting the pedal airline connectors the wrong way round. I'd appreciate it if someone could tell me the correct way to connect up the footswitch?

I attach photos of pedal and pinch valve on bottom of pot. The yellow arrow shows the coupler that is connected via airline to the pedal. The T connector above the white arrow will have the hose that goes to the blast cabinet.
The lever on the pot valve, because of the T the lever almost completely opens the valve. I don't know if this will be an issue or not. If it is, besides bending the lever so it avoids the T. Is there another way to do this, another design of lever, type, where available?

The large quick connect at end of pinch valve, is connected to the pot to supply the grit through the pinch valve.

As I say I'm not sure which port on the pedal should be connected to the coupler ( yellow) on the pinch valve? Also the correct in port on the pedal for the main air going in?
Thanks.

 

[rtbcomp]

The worst you can do is supply the bladder with air under pressure, which is what you do anyway so I can't see how you'd damage it.

I don't see why he supplies air to vent port, I would have said connect it up the way it was intended

You seem to be passing grit and air through a PCL coupler, this won't last 5 minutes, even if it works in the first place.

 

[Pollys13]

" I don't see why he supplies air to vent port, I would have said connect it up the way it was intended " Which is?
" You seem to be passing grit and air through a PCL coupler, this won't last 5 minutes, "
Why is that, how should I connect it up?
I fitted hose from pot to pinch valve,see attached, not knowing anything about fittings, airlines and stuff. I used quick connect couplers, in retrospect I should have used elbows, would this be the best way to do it?
The couplers have Loctite 542 thread sealant on them, what would be the best way to undo them?
I tested the system, filter, regulator adjusts to 90 PSI, the other two regulators supply 40 PSI and 65 PSI as they should. I could hear pot being pressurised.

 

[WorkshopChris]

HAve you had this set up working yet? I can't imagine much getting through that little tee fitting.
Some of your air pcl fittings appear to look the opposite way to what I would expect to see.
Air would normally flow from a male fitting towards a female fitting.

 

[Pollys13]

As mentioned above only test run with air no SC 120 grit. Couplers back to front does it actually make a difference? Max pressure would be no more than 50 PSI, other times 5 PSI -15 PSI. So with bigger bore T at these pressures would it make much difference?

 

[rtbcomp]

" I don't see why he supplies air to vent port, I would have said connect it up the way it was intended " Which is?

Assuming the ports are marked , air supply to "inlet", pot to "outlet" and "exhaust" to free air,

" You seem to be passing grit and air through a PCL coupler, this won't last 5 minutes, "
Why is that, how should I connect it up?

The grit will wear it away. The lever ball valves should be regarded as an expendable item too.

I fitted hose from pot to pinch valve,see attached, not knowing anything about fittings, airlines and stuff. I used quick connect couplers, in retrospect I should have used elbows, would this be the best way to do it?

Just use hose tails. The fittings should be 3/8 BSP - I used a malleable iron tee piece at the bottom of my pot.

The couplers have Loctite 542 thread sealant on them, what would be the best way to undo them?

http://m.loctite-repairs.co.uk/en/products/thread-sealants/loctite-542/how-to-apply.html

 

[Pollys13]

OK thanks for input, appreciated, will reply more fully, Saturday, Sunday.

 

[Pollys13]

" I don't see why he supplies air to vent port, I would have said connect it up the way it was intended. "

I contacted him and he replied,

" If you did that, the pedal would supply air when you pressed it... since supplying air smashes the valve SHUT... the sand would flow all the time EXCEPT when you stepped on the pedal. They way I did it, the flow is REVERSED... the valve is snapped SHUT until you step on the pedal and allow the air to bleed OUT of the valve allowing it to open. A pinch valve has basically a balloon that inflates squishing the sand and stopping the flow... you need it to be ACTIVE UNTIL you step on the pedal... exactly opposite normal design. "

In view of what he says, looking at photos of pedal I posted before.Which port has airline in from the 65 PSI regulator and which port would be airline out to the quick connect on the pinch valve? One of ports at front has letter P on it.

The quick connects I put on by mistake,I put a load of Loctite 542 on just to make sure so if can't disconnect by hand, releasing the thread sealant I have a flame gun that fits on small disposable butane gas cannisters, says can reach 1300 C.Your Loctite link says about 250 C. So intend to use this and stillson wrench to act as a heat sink.In other areas cut a slot in aluminium sheet and hang over nut whatever. Assuming there will be sealant residue, would I clean that off with a small brass/steel brush?

The malleable iron T you use does it matter if black would a galvanised T do just as well?

I'm going to need to orientate the new T in such a way so doesn't block full movement of pot valve handle. Uum..... part of the difficulty is the other end of pinch valve goes into wheel when rotated, any ideas?

Don't want hose permanently connected trailing around from end of T, as can't use quick connects, will use tail barb and jubilee clip, so can put on and take off as needed.

" The lever ball valves should be regarded as an expendable item too. " Yes I read that somewhere, also I seem to recollect, inserting a sleeve into valve? To prolong its life?
Cheers mate, appreciated

 

[rtbcomp]

" ..

" If you did that, the pedal would supply air when you pressed it... since supplying air smashes the valve SHUT... the sand would flow all the time EXCEPT when you stepped on the pedal. They way I did it, the flow is REVERSED... the valve is snapped SHUT until you step on the pedal and allow the air to bleed OUT of the valve allowing it to open. A pinch valve has basically a balloon that inflates squishing the sand and stopping the flow... you need it to be ACTIVE UNTIL you step on the pedal... exactly opposite normal design. "

Yes of course - that makes sense.

In view of what he says, looking at photos of pedal I posted before.Which port has airline in from the 65 PSI regulator and which port would be airline out to the quick connect on the pinch valve? One of ports at front has letter P on it.

Experiment

.. Assuming there will be sealant residue, would I clean that off with a small brass/steel brush?

An ordinary wire brush would be fine

The malleable iron T you use does it matter if black would a galvanised T do just as well?

Go for the cheapest

I'm going to need to orientate the new T in such a way so doesn't block full movement of pot valve handle. Uum..... part of the difficulty is the other end of pinch valve goes into wheel when rotated, any ideas?

Fit a short length of rubber hose between the T and the pinch valve.

Don't want hose permanently connected trailing around from end of T, as can't use quick connects, will use tail barb and jubilee clip, so can put on and take off as needed.

Just wrap the hose round the top of the pot, or use a pair of claw connectors. IIRC I have the smallest size on my pot, you may need an adaptor to cahnge from 3/8 to 1/2 inch BSP.

https://www.hodgeclemco.co.uk/products/consumables-spares/couplings/

" The lever ball valves should be regarded as an expendable item too. " Yes I read that somewhere, also I seem to recollect, inserting a sleeve into valve? To prolong its life?
Cheers mate, appreciated

Some metering valves have a rubber sleeve in them, not feasible in a ball valve because the sleeve would need to pass through the ball.

 

[brightspark]

there a gate valve with a rubber choke sleeve in them

 

[rtbcomp]

^^ That's right - I remember seeing that now.

 

[Pollys13]

Just tried to manually undo one the quick connects. I applied quite a significant degree of force, as I say put a load of thread seal on to make sure,won't budge.
Couplers are quite close to plastic of pinch valve and pot valve housing.
Pinch valve is almost 200 a pop, couldn't find anything in UK, so came from America.

I'd prefer to not to use the butane torch if possible. I saw a YouTube about loosening thread seal without heat, he used brake cleaner.
I've Googled but can't find any more info, do you know about using brake fluid?
Do I need to replace the T that's already in place?
Ordered the hose tails a few minutes ago
Cheers.

 

[graffian]

I had a Guyson pot and cabinet, It just had a pedal and a Norgren air valve to control it.
I have a spare air valve from it.

 

[Pollys13]

I had a Guyson pot and cabinet, It just had a pedal and a Norgren air valve to control it.
I have a spare air valve from it.

When I was looking into getting a suitable cabinet. I seem to remember coming across those Guyson cabinets at auction. Googled Norgren but can't get an angle on how one would work?

 

[Pollys13]

I have a pass through cabinet has slots in side and top so can pass large sheets of glass through surface etching and carving into glass, like shower doors and such like. It has roller arms on side you can fit to support the glass.
Can't buy this sort of cabinet in UK or Europe so had to import from America. The slots are covered with brushes. I'm going to be using the dust extraction unit that was supplied with the cabinet. Also I have a 3M half face mask and bought suitable filters to handle glass dust.

I asked someone about air tightness of cabinet, he said,

" You should not have a problem with the dust extraction system. The idea of a dust extractor is to create a "Negative" air pressure inside the cabinet, so outside air flows in, not inside air flowing out. No sand cabinet is sealed tight. Neither of the ones I had have been. I had a dust extractor at one time, but did not like the idea of it still exhausting cleaned air inside the shop. Its the particles you can't see that worry me more than visible dust. I also still wore a respirator. Then I finally exhausted my cabinet to a vent in the wall so all the dust went outside. If your system extracts small enough particles like glass dust, you should be fine. Also make sure it does create a "Negative" pressure inside the cabinet.
Here is how I would check it. Turn on your system. Light a cigarette or a small piece off oiled rope that smolders and gives off smoke. Hold it close to the brush gaps and see if the smoke is drawn inside the cabinet. If it is, you have Negative pressure inside and your good to go. Remember. The idea is not having a perfectly sealed cabinet. The idea is making sure you have Negative pressure inside the cabinet, so any air flow is from the outside of the shop to inside the cabinet. That's what protects you, not a completely sealed cabinet. "

I noticed the foot pedal plan guy, he has same cabinet as mine, he taped up the sides of the cabinet.
In view of what the other guy said I asked him earlier why taped up cabinet.

He came back with, " In theory that is fine... but when you have 2 milling machines at $10,000 for one, and $5,000 for the other plus a lathe that get grit on them... and that grit will DESTROY the machines... you want MORE of a negative pressure. So either buy a 400 CFM, or make the 100 or so CFM 4X as effective. I went with plan-B. "

I saw these 3/8" claw connectors just need to look around for the best price. Ordered the 3/8" hose tails.
That Loctite freeze spray and other brands, havn't seen it mentioned so don't think can use on sealed threads.
Thanks again for the helpful advice.

 

[merryman]

Am I missing something, or will that foot valve have no chance of working, as they work pressure on when pressed down, pressure off and exhaust open when up. You can get valves that work the opposite way, rear brakes on trucks are pressure on, brakes off. So put your foot on brake pedal and the pressure is released to fetch the brakes on. Also the PCL valves will have rubber seals in them so heat them and you will destroy the seals. Never heard of using brake cleaner, it smells a lot like Loctite cleaner and that is used to make high strength Loctite cure. You can usually get Loctite to let go without resorting to heat, though I do use heat on the giant ultra fine thread nuts, holding Honda Quad axles in place. 542 is only medium strength, so not all that much more difficult to shift than a nylock nut.

 

[Pollys13]

Also the PCL valves will have rubber seals in them so heat them and you will destroy the seals.
Ok thanks, point taken

 

[vx490]

Hi all, this seems like a complicated solution, although of course you may be trying to solve a slightly different problem. I wanted to operate my pressure pot with a foot switch but I didn’t even think about switching the grit on and off! Just the air. So I had one of these compressor auto drains lying around ,https://www.ebay.co.uk/itm/Automati...745346?hash=item3f99d3f842:g:YzYAAOSw9gRaJOYr. It’s very easy to just take off the timer mechanism leaving you with an electrically operated air valve. Then I plumbed it into the air supply to my pressure pot and plugged it in via an extension lead with a foot switch https://www.ebay.co.uk/itm/Foot-Swi...Lead-Elderly/232775807375?hash=item363284f18f. Voila, works perfectly. Hope that helps someone.

 

[armalites]

I have a Vixen Jetair industrial cabinet, it has a pressure put and the foot switch simply supplies air. The pressure pot does have a poppet valve but there is no control for the grit. The air provides pressure to the pot and the flow downstream of the pot for blasting

 

[Pollys13]

Hi all, this seems like a complicated solution, although of course you may be trying to solve a slightly different problem. I wanted to operate my pressure pot with a foot switch but I didn’t even think about switching the grit on and off! Just the air. So I had one of these compressor auto drains lying around ,https://www.ebay.co.uk/itm/Automati...745346?hash=item3f99d3f842:g:YzYAAOSw9gRaJOYr. It’s very easy to just take off the timer mechanism leaving you with an electrically operated air valve. Then I plumbed it into the air supply to my pressure pot and plugged it in via an extension lead with a foot switch https://www.ebay.co.uk/itm/Foot-Swi...Lead-Elderly/232775807375?hash=item363284f18f. Voila, works perfectly. Hope that helps someone.

OK thanks for input, would work for you but not for what I want.