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My girlfriend has a sandblasting setup that she bought a couple of years ago to start her own business. She does mostly glass engraving but wanted to also be able to do wood and stone products. The grit that she uses is very expensive and would be ruined if it was used for wood so for her to switch over, she had to completely drain the cabinet and pressure pot, clean everything, then refill and recalibrate for the new medium. This process was very time consuming, so we considered getting a new system just for the wood and stone items. The company wanted about $1,500 to $4,000 for a new system which I thought was completely unreasonable.

This is the arrival of the first system... it is huge!

After looking online at Harbor Freight, we found a nice medium cabinet and a good sized (110lb) pressure pot for a very reasonable price... then they BOTH went on sale. For less than $500 we could purchase both... I just needed to convert the pressure pot to run with a footswitch.

I called the company who would be happy to sell me just the footswitch for $90, the pinch valve for $130, and the bladder for $35. It was time to hit Amazon to see if I could do better... I found an even better footswitch for about $30... 1/3 the price!

I used the Model FV320 Foot-switch, 3 Way, 2 Position

Now I needed to get the pinch valve assembly, the original company wanted $250 for the conversion kit... I thought I could do better. After some research, I found the exact replacement assembly from a company called Airpinch.  (They were very helpful too.)

Step 1: The Pinch Valve - the Key to Using a Footswitch Control

A pinch valve is a housing with a bladder made from rubber, silicone, or other material based on the substance you wish to control. Since this was going to control a very abrasive material, durability was highest on the list. After a quick phone call, I was able to get a part number for exactly what I needed... a 3/4 inch pinch valve, made from glass filled nylon (black), and with a bladder made from BUNA-N. I got the whole assembly with an extra bladder for under $100... much cheaper than what the other company quoted me.

Use these part numbers if you want to duplicate what I have...
AP-6798 Pinch Valve Assembly (AT-06-NF-B60-0606-N)   $62.00
AP-6277 Replacement Bladder (AT-S-06-NF-B60)              $22.50
Total Cost:  $82.00

The original system was set up as shown in the image below. The main tank has 120 PSI that is regulated to 90PSI and distributed to the workshop. This is regulated to 40 to 60 PSI for the pressure pot... more likely 40 PSI. That meant that the bladder assembly was getting the full 90 PSI from the system. After talking to the folks at Airpinch, they said it should only be about 20 to 30 PSI above the pressure of the substance it was controlling, or the life of the bladder would be shortened. They said that a second regulator should be installed to lower the pressure to about 65 PSI if I was running the pressure pot at 40 PSI. The original system did not have this second regulator... it was running between 90 and 100 PSI... so this would be addressed in the new design.

I also did not like that the plumbing stuck out from the pressure pot about 25 inches or so... it seemed to be asking for trouble if something bumped into it. I decided to mount all the regulation and switching valves on the wall to keep them in an area less likely to come into contact with anything. This would also have the added benefit that we would not need to lean over, and we could see the pressure settings as we worked... something we could not do with the current setup.

Step 2: The System Design - Figure Out How It All Works

The first image shows the design layout for a footswitch control system, the second another view without the main compressor. The regulated air comes in at 90 PSI and runs through a water trap to remove any moisture that could have a bad effect on the grit. (It could cause it to clump or jam up in the hoses.) After the water trap it is split into two paths, one to the pressure pot and nozzle assembly, and the other to the footswitch control.

The first path goes through a regulator to get the 40 PSI for the pressure pot, it then goes into a splitter where part keeps the pot under pressure, and the other passes below to a mixing valve where it picks up grit and passes through the pinch valve. From there it heads to the sandblasting nozzle. The Harbor Freight pot has two valves that are normally used to control it when you don't have a footswitch control. I left these in place, but if I were to do it again... I would use them on the manifold and save the $7 each for the ones I got at Lowes. (Because of the footswitch assembly they are no longer needed where they are currently mounted.)

The footswitch needs to supply the bladder 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. The other fittings were 1/4 inch, but the vent is an 1/8 inch fitting... so after another quick trip to Lowes ($7)... the footswitch was ready to go.

Step 3: Modify the Pressure Pot

The Harbor Freight pressure pot comes with a cast metal fitting that connects with the top valve and acts as a mixing chamber. (Image 1 and 2) If you look at the original sandblasting setup (Image 3) you can see it is completely different. This is what we needed to build into the new system to make the footswitch work properly.

In image 4 you can see how the pinch valve assembly is being put together. We decided that we might need to blast a larger wood item in the big cabinet, so we also installed hose fittings on each of the pressure pots. This way we can simply switch the nozzle assemblies and clean out the cabinet without needing to purge the pots. (Changing out the grit in a pressure pot is a MAJOR chore!)

Image 5 shows one of the disconnects during assembly, and image 6 is after assembly is completed.. The tool on the bottom has been around since World War II... some people say I should not use it... but I feel a tool is meant to be used... and I use this one a lot!  (I've never seen another like it.)

The last two images show the finished pinch valve assembly mounted to the pressure pot, and the original pressure pot (white system) after it has been stripped down and configured the same way. Now we have two interchangeable pressure pots that can be used with either cabinet. Because they just happened to already be painted as they are... we call them the WHITE and the RED systems. The RED system is the newer one for working with stone and wood.

Step 4: Finishing Up

Once the pressure pots were modified, the only step left is to connect them through the regulators so that they can be used. We have two systems with two pressure pots... so in the following images you will see a duplicate set of valves for the pots, and another duplicated set for the foot pedals. In a single system these extra ports would not be needed.

The white system is the original sandblasting setup, the red system is the new Harbor Freight system that has been modified for the foot switch. To use the system it is important to turn the valves on and off in order... if you were to turn off the supply first for example... air could be sucked in from the pressure pot... along with the grit... and pas backward through the pressure regulator. This would damage or destroy the regulator.

Normal activation of the new red system would be like this...
1) Turn on main air supply. This feeds clean 90 PSI into the system to the regulators through the water trap.
2) Set the regulators (top) for 40 PSI, and (bottom) for 65 PSI. This sets the system to the correct pressures.
3) Open the RED pedal valve. This causes the pinch valve to close preventing the system from spraying grit all over.
4) Open the RED pot valve. This causes the grit pot to pressurize.

Of course... be sure the lid is screwed down well... you don't want it to do a grit volcano in the workshop! And before you pressurize the system... ALWAYS WEAR A MASK!!! You really don't want to breathe this stuff... so again... ALWAYS WEAR A MASK!!!

Shutdown is pretty simple...
1) Turn off the pot valve.
2) Turn off the pedal valve.
3) Turn off the main air valve.
4) Step on the pedal to allow the system to bleed down. Some grit will escape.

If you don't want any grit to get out... you could close your grit mix valve at the bottom... but usually it's more trouble than it's worth.

The last image shows the Harbor Freight pressure pot valves. It also has a secondary water trap that automatically vents when the pressure drops below about 15 PSI. It is actually better equipped than the $900 pressure pot that she got with the system.  The image also shows the two valves that are no longer being used... they could be used on your system as the pot and pedal valves. You would just replace them with a standard pipe fitting.

I hope this helps you to set up your own system, we completed the entire project for about $600 including the cabinet, pressure pot, and all the plumbing for the air supplies. It cost us less than what the pressure pot alone would have cost.

<p>I am having a problem with mine, when I push down on the footswitch it takes about 25-30 secounds for the media to start flowing. Any sujestions?</p>
Yes... the pressure settings are too close. the footswitch needs about 20psi more than the pressure pot. It needs to be able to really smash the pinch valve closed quickly... and likewise, it needs to be able to release quickly. When you let go of the footswitch, the air must be able to leave the bladder compartment to the atmosphere unencumbered.
<p>Thanks, I was a little high on the bladder. Forgot that I upped pressures for a different project. Lowered the pot not the foot switch. </p>
Look closely an you will see TWO regulators... the pot is set about 35-40 PSI, and the footswitch is set about 60 PSI... about 20 PSI higher... just don't go over the rated pressure for the bladder... you know... don't run it at 100 PSI for example.
If you look at the setup the way I have it... there is a main valve that supplies air to the entire system, then one for the pressure pot, and one for the footswitch/pinch valve.<br><br>the reason is that you shut off the main air supply... and if you did nothing else... the system would bleed down and equalize... then all the air... and grit would shoot out the hose.<br><br>The way i designed it... you go like this...<br>1) System air<br>2) Pinch Valve<br>3) Pressure pot<br><br>That way the pot isn't pressurized until the pinch valve is ready.<br><br>Shutting down...<br>1) Pressure pot... allow it to bleed down slightly bleed valve open if you have one. (Both pots are connected in my system... so I crack the second open and air bleeds out there.<br>2) Pinch valve<br>3) Main pressure valve<br><br>Hope that helps.
<p>I finally got everything in to do this. </p><p>Did it a little differently. I have both regulators on the pressure tank. I made a small mounting block out of some 3/4&quot; material to support the regulators. I also modified the T fitting at the bottom of the tank. It had a hose nipple on one end of it, so I milled that off and drilled and tapped it for 3/8&quot; NPT. </p><p>Everything works great and I thank you for getting me started on this. I didn't even know what a pinch valve was until I read your writeup.<br></p>
That is awesome! When I had to design and build this... I thought to myself that someday... someone else is gonna want to do it... and that I may as well post the details and try to help them.<br><br>So I'm really glad I was able to help!<br>
<p>I have been using this for a few days now and realized that way I have it plumbed for air the pinch valve had pressure on it all the time, not just when I was using the blast cabinet. So I added a one quarter turn ball valve to shut off all air pressure to it when not in use. Hopefully the pinch valve will last a little longer this way.</p><p>Thanks again for your posting this, you made my job a little easier not having to hold the deadman valve for hours at a time.</p>
<p>I just ran across your write up. Very informative.</p><p>I bead blast a lot of parts and have a 110lb HF pressure blaster hooked up to my cabinet. I have a dead man valve and after a long day of blasting parts my hand got very tired. With your idea it will be a lot easier for me.</p><p>I have already have ordered everything to do this.</p><p>Thank you for posting this. <br></p>
<p>So I came across this your Instructable while trying to find some info on my newly acquired used blasting cabinet and pot and I had to do a double take. I saw the picture and I was like, &quot;What the heck is my shop doing on the internet?&quot; Alright, I guess its not exactly my shop, but pretty darn close. Anyhow, I don't know who made my new used cabinet so I figured I would ask you since I have an exact copy of yours, although mine is not in as good of shape as yours.</p><p>By the way, your right up is what I needed to piece together the box of parts that came with the cabinet. Also, a near replica of your setup. Weird. Thanks very much for your help past, present, and hopefully future. Greatly appreciated!</p><p>Cheers,</p><p>Sean</p>
The white cabinet is one my wife got from an online company... I don't recall which one but i could ask her about it. The red one and the red pressure pot were both from Harbor Freight.<br><br>I'm glad it helped you... I had to go through all the trouble of figuring it out and building it... so I figured that I may as well make an instructable out of it. <br><br>I have a YouTube channel if you want to check it out... http://youtube.com/askjerry<br><br>Jerry
<p>That would be great if I could find out where that white cabinet came from. The little red one runs ok, but I've made a number of modifications to it. I'm looking forward to getting the big one up and running. It's going to be a lot of fun! I did watch the video of your wife getting the cabinet. That is always a fun day. Thanks again!</p>
Write to Eve directly as she is the one who purchased it and researched the company. <br>Evetaitcreations@gmail.com<br>
<p>Thank you for the tutorial. It is very helpful for a newbie to sandblasting. I didn't see the length or size of air hoses you used for the foot pedal...I assume they are 3/8&quot;? What length did you use &amp; did you also buy them at Lowe's or similar DIY store? Thanks!</p>
Thanks Jerry. Just one more question- what is the minimum size air compressor needed for this system? Do you recommend any particular compressor?
Yes, just standard 3/8 for the foot pedal and I think it was 1/2 inch for the nozzle... we just reused the same hose for the nozzle. As for length... we cut as needed.
<p>I should have mentioned that Airpinch is our brand name for our pinch valves, but our company is Richway Industries. ..... </p>
<p>Hi. I am Rich from Richway and we always like to hear how our valves are being used. You don't have to order a spare bladder (we call them sleeves) because they last a long time, but they do wear out and never when you want them to. But buna-N does age harden over time (even on the shelf) so trying to keep a spare for too long may not be a good idea. I would probably wait a year or two before ordering a spare. call us or email with any questions you may have. just use info@richway and start out with &quot;attention Rich&quot; at the beginning. </p><p> We are pretty much a DIY company, because we do plastic rotational molding, plastic injection molding, rubber molding, metal fabrication, powder coating, CNC machining (mold making and production), plus assembly --- and we have a maker bot. We like the challenges and fun of new things! We are a family owned and operated company with ab 35 total employees.</p><p>We started making pinch valves in 1985. </p>
<p>Thanks, Jerry- love this. Just what I've been looking for. The guy at Airway (Pinchvalve) says that you're the best marketing they have for these parts. </p><p>Two questions- I went ahead and ordered the spare bladder, but I'm wondering if she has had to put it in.</p><p>Second, what compressor does Eve use? I need to upgrade my old oil-less noise maker. Thanks!</p>
<p>Has anyone found a replacement for the pinch valve, I tried finding it online but I believe the company AirPinch has changed names and I don't see this model anymore.</p><p>Thanks Again,</p><p>Devin</p>
<p>I just ordered the parts. New price on the valve is $66.60, on the replacement bladder is $24 and change. </p>
I just called and verified... <strong>Richway</strong> is correct... if you go to their web page you can call and ask for sales.<br> <br> Toll Free: <strong>(800) 553-2404&nbsp;</strong>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br> Voice:<strong> (319) 987-2976</strong>
Hey jerry, <br><br>Awesome tutorial. For some reason I am having trouble with my set up. I have everything plumbed right to my knowledge. I took a video of my set up if you are interested. I have 100 psi going to a tee. one reg set at 65 going to vent port on the pedal. Another reg set at 40 going to pressure pot. It worked for a few minutes then stopped. Now barely any air at all comes out of the nozzle when the pedal is pressed down. Let me know if you can think of anything. Thanks!! <br><br>
Verify that when you step on the pedal two things happen...<br>1) The pressure is stopped to the bladder.<br>2) The bladder is free to vent to the outside.<br><br>If the bladder cannot vent, it remains inflated. If this is functioning, then I suspect your grit to air ratio may have been too high, and the hose filled up with grit and became blocked.<br><br>Jerry
<p>thanks for the response. I will check next time im at the shop. How can i tell if pressure is stopped to the bladder? I am unsure how to check that honestly. </p>
<p><strong><em>Before I installed mine</em></strong>... I put my lips where the bladder would connect... if I blew when the footswitch was not connected, the air would go through easy. When I pushed the footswitch and blew, the air went to the connector that I would attach the compressor to. That is how I knew that I had it configured right. When pressed, the bladder is connected to the high pressure, when not pressed, it <em>SHOULD</em> be connected to the external atmosphere.</p>
Hi, love the set up! Was wondering with your knowledge if you know whether this setup could be used to make a machine that works using 50micron aluminium oxide powder? Want to build one for cleaning fossils
<p>It should work the same way... just adjust the pressure to work with the medium you are using. I don't know the micron size of the grit Eve is using... just that she uses 120 and/or 80 grit.</p>
<p>Hi,</p><p>I wanted to make a similar setup, but for only one pressure pot, I don't need to swiitch between blasting media.</p><p>I was just curious why such an elaborate setup? I have seen this done with a pinch clamp (that actually pinches the hose) foot pedal and no separate pinch clamp and bladder.</p><p>Is your set up more precise, better control, etc.?</p><p>Thanks.</p>
<p>Eve purchased a system with the cabinet, abrasive pot, and a vacuum. When she discussed getting a separate system for doing rock and wood, she wanted to clone the system she already had. Rather than spending $900 on a pressure pot system, I decided to build my own... so I examined the one she purchased and duplicated it.</p><p>I could be wrong, but pinching the hose repeatably may eventually erode through it. This system has been running flawlessly since I first constructed it a few years ago.</p><p>The flow control can be fine tuned by adjusting the pot pressure, but likely that would be the case no matter how you stopped the flow.</p>
<p>what size and where did you get the tubes and fittings to supply the foot pedal?</p>
I got them at Lowes... just standard plumbing fixtures. I took the pedal with me and kinda Macgyvered it as I went.
<p>Hi! Great article, really helpful! One question regarding the valve/pedal hook up; I see you supply air to the valve via the vent port on the pedal. When operating pedal, does the air from the valve vent out via the &quot;in&quot; port?</p><p>Thank you!</p><p>Eivind, Norway</p>
When you step on the pedal, the air from the compressor is stopped. The air pressure trapped in the pinch valve is released via the unused port. It then relaxes and allows the air-grit mixture to pass through.
<p>I need to do a similar setup, I use both a Soda Blaster, which has no deadman nozzle, and a pressure pot for glass carving. One thing I would recommend here, is to use an exhausting valve between the supply and the regulators, or at least at the compressor to decompress the air in the lines. You could also use these same valves to safely decompress the air in the pressure pots as well. Thanks for sharing, and much cheaper than what I've been seeing available. Love the new cabinet too! That is now on my wish list :)</p>
I've thought about that actually.. what I can do... is close the valve to the main air compressor, then gradually open the valve for the second pressure pot. The air bleeds out that way.<br><br>It is tempting to install a TEE and valve next to the over-pressure safety valve however... then I could just turn to vent.<br><br>Thanks!<br>Jerry
This is the one that I use. I have them coming off each compressor, and after each hose real, and other hose/tool connection points.. http://www.northerntool.com/shop/tools/product_200478515_200478515
<p>I was asked what the stuff I used to mount my pipes was. Here in the USA, you can get pipe strapping which is thin perforated strips that you nail up to the floor joists. Apparently in the UK... finding these is not quite so easy. I did a bit of searching... and other than pipe clips... you should be able to use this.</p><p><a href="http://www.toolstation.com/shop/p77295" rel="nofollow">http://www.toolstation.com/shop/p77295</a></p><p>Go to <a href="http://www.toolstation.com" rel="nofollow">www.toolstation.com</a> and search for <strong>FLAT STRAP</strong>.</p>
<p>Coolio tutorial, I am getting into sandblasting too! Mostly planning on using it to sand down glass bottle lips and light engraving.<br><br>Based on your tutorial I am thinking of getting the <br><br>FV320</p><p>MTL1/4-N02 and MTC1/4-N01 for the air in/vent hook up. I see you used a combination of brass fittings and plastic to hook up your foot pedal but I think I'll go with the direct plastic push in, less connections less leaks right?</p><p>Maybe some 1/4&quot; OD polyurethane tubing as well, since they're under $20 for 98ft. Think I'm going with clear. Think their part number is PU1/4-30C</p><p><br>After a quick search with the part number I found them on Amazon and eBay, but I think I am planning of buying my parts from MettleAir.com seems like the prices are better there.</p>
Are you using the same hose that came with the pot? And what nozzle/valve are you using? (HF seems to be selling the pots with a ball valve + nozzle now instead of with their Deadman.)
In the instructable I spelled out exactly which valve I am using...<br> <br> <em>Use these part numbers if you want to duplicate what I have... </em><br> <strong>AP-6798</strong> Pinch Valve Assembly (AT-06-NF-B60-0606-N)&nbsp;&nbsp;&nbsp; <strong>$62.00 </strong><br> <strong>AP-6277</strong> Replacement Bladder (AT-S-06-NF-B60)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <strong>$22.50 </strong><br> <br> Take a closer look and read the article... all the information is in there. I unscrewed their hose and installed the pinch valve assembly where the old unit was. There are close-up images in the article as well.<br> <br> Eve has not used the sandblaster as much as I had hoped... she is doing a lot of CNC stuff right now... but should be getting back to it soon.<br>
How does the pinch valve attach to the blasting hose? I really want to get this set up in my cabinet soon because siphon feed takes to long on larger parts. Also I blast to prep metal for powder coating and use 70 grit aluminum oxide, how do you feel the pinch valve would hold up with this abrasive at around 60-70psi? Thanks in advance.
Look at the design images again and this should be a bit more clear.<br> On one side is the TEE connector where the grit and air mix, on the other is a reducer which goes to a barb fitting. If you look at the unmodified pot you will see the original...<br> <br> View image <a href="https://www.instructables.com/file/FD9BUMVH58PK8GS" rel="nofollow">https://www.instructables.com/file/FD9BUMVH58PK8GS</a> and you will see the reducer on the right... what screws into this is shown on the next image <a href="https://www.instructables.com/file/FI6LJ0JH58PK8H8" rel="nofollow">https://www.instructables.com/file/FI6LJ0JH58PK8H8</a> The hose connects to this barb fitting and is held in place with a clamp.<br> <br> Reference this: <a href="https://www.instructables.com/file/FJ4OQXOH4VQL3QX" rel="nofollow">https://www.instructables.com/file/FJ4OQXOH4VQL3QX</a><br> <br> Aluminum oxide is exactly what she is using on this (red) system... it holds up quite well. The white system is for glass, the red system is for metal, rock, and wood.
Hey Jerry, <br> <br>I have one more question for you if you don't mind, I want to order all the parts tomorrow to do this project but I was curious to see how happy you were with your outcome, how responsive the valve is, and how the rubber on the pinch valve is holding up for you ? <br> <br>Thanks for your time. <br>Lenny
I have not had any problems at all. It has been working well... every bit as good as the $900 version.
Thanks Jerry, I found the locations after I posted the comment I guess i was a little excited, I have wanted to add a foot pedal to my blaster for a while. thanks again. <br> <br> <br>Lenny
Hi Jerry, <br> <br>I really enjoyed your tutorial, I am wondering if you could tell me where you found your pinch valve and foot pedal? <br> <br>Thanks again for the tutorial! <br> <br>Lenny
Lenny -<br> <br> I gave the locations in the Instructable... I got the pinch valve from <strong>AIRPINCH</strong>, there is a link in the instructable. <a href="http://airpinch.com" rel="nofollow">http://airpinch.com</a> <strong>AP-6798</strong> Pinch Valve Assembly (AT-06-NF-B60-0606-N)<br> <br> The footswitch came from <a href="http://amazon.com" rel="nofollow">http://amazon.com</a> search for the one I specified in the instructable <strong>Model FV320</strong>.<br> <br> Jerry
Hi jerry, <br> <br>i am a self-taught sandblaster and i even created a couple of pressure pots. regarding the t-connector, i would suggest to insert a rubber inside the connector, that way, it prolongs the wear &amp; tear. an inner tubing of an old bicyle or motorcycle will do :)
That is probably a good idea... the falling abrasive probably does cause wear at that point. I'll do install that when we are going to change the grit... it would be a good time then. <br> <br>Thanks, <br>Jerry

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