# My $80 80 psi pressure pot



## More4dan (Mar 7, 2018)

I'm starting down the casting road to oblivion and started gathering tools and supplies.  This should be listed as a hobby unto itself.  My first purchase was a 2 1/2 gallon paint pot I found on Walmart's website.  It was listed for $79.99 with the pot, tubing, regulator, valve, and paint sprayer and free shipping.  It was also advertised as made of Stainless Steel.  What a Deal!!!  Well sort of.  The regulator is broken along with the attached gauge.  The pot is painted making me doubt it is made of stainless.  I emailed the seller who checked with their supplier who "verified" it is made of "Stainless Iron".  They have offered to rebate me $8 or I can send it back.  I countered with a request for a $15 rebate.

Now the good news.  It is marked with a maximum working pressure of 80psi.  I tested it last night to 75 psi w/o popping the pressure relief valve and w/o leaks.  I plan to upgrade the pressure relief valve with a US made ASME coded relief valve, add a better liquid filled gauge, and use the regulator on my compressor to pressurize it.  So for a final cost of $65-$72 I'll have a casting pot to start with good to ~80 psi.  I'll use it to 50-60 psi.

Here is a link to the item.

https://www.walmart.com/ip/10L-Indu...0990&wl11=online&wl12=789033564&wl13=&veh=sem


More to come.

Danny


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## frank123 (Mar 7, 2018)

Replacing that relief valve is a good idea.  

If you're not planning to use that high of a working pressure, it might be good to replace it with one closer the the working pressure  you intend to use.


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## Dehn0045 (Mar 7, 2018)

I wouldn't put too much stock in the "Maximum Pressure", they can basically put whatever they want without much basis in fact or safety margin.  I'd be surprised if the tank is substantially different than the HF tank, which has a "Max" of 60 psi.  I am no expert in pressure vessel code/design/construction, but I know that ASME pressure vessels have strict requirements for design, construction, and testing, which provides a reasonable assurance that they won't explode up to the MAWP (with a substantial safety margin).  These tanks don't offer that.  Basically, what I am saying is, if you wouldn't operate a HF tank (stamped 60 psi) at 75 psi, then you shouldn't operate the one stamped 80 psi there either.  

I'm not saying to throw it away, or that you're involved in some sort of high risk activity like base jumping.  There is a lot of anecdotal these types of tanks operate fine for long periods of time (without modification to the lid retainers) in the 50 to 60 psi range (or higher).  Just don't think there is something magical about the max pressure, it probably won't explode at 81 psi but there is also a relatively unknown probability that it will blow at 79.

All of the above said, I have a HF tank that I have not used but plan to someday, will operate in the 40 to 50 psi range with some additional safety considerations.  Just my 2 cents...


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## More4dan (Mar 7, 2018)

MY plan is to do some reverse Engineering and some testing as well. I did hook up a long hose around a couple corners prior to adding pressure last night to be safe.  I use to review pressure vessel designs earlier in my career as well as safety designs and vent and flare systems up to 20,000 psi.  Even 80 psi of compressed gas in a 2 1/2 gallon pot will kill you if it fails.  ASME requires a test to 1.5 times the maximum operating pressure, (safely with water).  I will reverse that and operate at my Test pressure divided by 1.5.  I was impressed with the weld quality on the tank and hardware.  The fittings and valves were garbage.  Thanks for the advice and concern.

Danny


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## Dehn0045 (Mar 7, 2018)

Sounds like a reasonable approach, I had a sense that you had a background in this sort of thing, but wasn't sure.  I am a Chemical Engineer and have worked in operations at chemical plants for a while, so I don't get too far into the equipment design stuff but probably see more than the average guy.  When I first looked into the paint tanks I was surprised how these inexpensive tanks are sold with essentially no evidence to support their pressure "rating".  Anyway, I hope I can tag along with some of your casting adventures!


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## leehljp (Mar 7, 2018)

I looked on the web site, but they say "50" lbs there.
I think, like HF,  that they are constantly changing items as they (walmart) order similar products from different suppliers on some occasions.

Congratulations though on your purchase. Looking forward to seeing the results of your work here!


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## More4dan (Mar 7, 2018)

I’m a Mechanical Engineer working upstream for Chevron. Use to design and install a lot of pressure vessels.  The optimum operating pressure is listed as 50 psi. The tank is marked at 80 psi. I assumed it would be a 50 psi pot too. 


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## chartle (Mar 8, 2018)

I love the pic of the box it comes in. Is that what sealed the deal?


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## MRDucks2 (Mar 8, 2018)

I bought a California Air Tools labeled pressure pot online through the Home Depot website. It came in a CAT labeled box but the pot has no specific markings. Has a big curved sticker on the lid that says “Max operating pressure 90 psi”. 

Pressured it up, pop-off let loose at 40 psi. Began to adjust pop-off so it tripped at 85 psi and took it up to 80 psi and let it set overnight. Did great... the first time. Began to plumb for casting and was having issues holding pressure. Sealed up every possible plumbing leak and still not good. 

Check lid seal and it was leaking, no damage to the seal but deformity to the outer ring of the lid. Hmmm. Went online to CAT website and downloaded manual (none included with my unit). Manual said not to pressurize above 60 psi. Called them asking about a new lid and they called back indicating they do not sell lids by themselves, never recommend their pots above 60 psi and should return to Home Depot. 

At this point I reformed the outer ring and pot holds well at 55 psi with pop-off at 60. Obviously something is askew I n the labeling and such, but decided not to chase it. 


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## leehljp (Mar 8, 2018)

Thanks Dan and Mike for clarifying the data. It bugs me when something is written one way and then actually made much more durable, or vice versa! I understand that there are those that will, without common sense, way overload things and end up with a Darwin award - and therefore the company overbuilds and understates for pure safety purposes.

I am not an engineer, but I do tend to overbuild things, and they do last. I grew up on a farm, and with broken machines such as plows, disks, trailers, axles, my dad discovered I had a knack (at 10, 11 and 12 years of age) for correctly diagnosing the real underlying problem that caused a break at a different place; then he discovered I could arc weld better than he could. He took me off the tractor and put me to shop maintenance. What I fixed didn't break again. The high school Shop teacher came and talked my dad into making me join the FFA so that I could go to school district FFA welding contests! 

I don't doubt your ability knowing your backgrounds. Thanks for clarifying the data.


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## Curly (Mar 8, 2018)

I would suggest to you, not because you don't get it, and people without any engineering or trade related backgrounds, to fill the pot with as much water as you can before applying test air pressures. That way if it does have a Myth Busters moment the air in the pot will be minimal and have less destructive energy.

Personally because my compressor may be used for other things at the same time and have the pressure set to 90 or 100 psi, I have a regulator on a short hose to the pot. That way there can't be any dangerous mistakes made if the air compressor regulator setting is forgotten.

You got a good deal on it.


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## More4dan (Mar 8, 2018)

chartle said:


> I love the pic of the box it comes in. Is that what sealed the deal?





And the box it came in looked as bad as the picture. LOL. $12 refund supposed to be on its way for the busted regulator and gauge I’m sure due to the poor packing and sorry box. 


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## More4dan (Mar 8, 2018)

Curly said:


> I would suggest to you, not because you don't get it, and people without any engineering or trade related backgrounds, to fill the pot with as much water as you can before applying test air pressures. That way if it does have a Myth Busters moment the air in the pot will be minimal and have less destructive energy.
> 
> Personally because my compressor may be used for other things at the same time and have the pressure set to 90 or 100 psi, I have a regulator on a short hose to the pot. That way there can't be any dangerous mistakes made if the air compressor regulator setting is forgotten.
> 
> You got a good deal on it.





A big Amen on testing with water! And good advice on a dedicated regulator, I’ll also add an air drier too. I was really concerned after reading bad reviews of the company that sells the pot through Walmart. So far so good. 


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## chartle (Mar 8, 2018)

More4dan said:


> A big Amen on testing with water! And good advice on a dedicated regulator, I’ll also add an air drier too. I was really concerned after reading bad reviews of the company that sells the pot through Walmart. So far so good.
> 
> 
> Sent from my iPhone using Penturners.org mobile app



I plan on making a drier using one of these and descant beads from Amazon.


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## More4dan (Mar 8, 2018)

chartle said:


> More4dan said:
> 
> 
> > A big Amen on testing with water! And good advice on a dedicated regulator, I’ll also add an air drier too. I was really concerned after reading bad reviews of the company that sells the pot through Walmart. So far so good.
> ...





Where did you find this?  Looks like the oxygen filter I’ve seen in the hospital. 


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## chartle (Mar 8, 2018)

More4dan said:


> chartle said:
> 
> 
> > Where did you find this?  Looks like the oxygen filter I’ve seen in the hospital.
> ...


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## Oldfolks (Mar 21, 2018)

You got a great deal Dan. I just looked at the link and the price is now $102.69.


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## More4dan (Mar 21, 2018)

Oldfolks said:


> You got a great deal Dan. I just looked at the link and the price is now $102.69.





Thanks Jerry, I’m tracing down a slow leak.  I may have to change the seal, about $20. Doesn’t mean the $102 on wouldn’t have the same issue.   Or I can just leave the air hose attached and the regulator can keep the pressure constant. 

Danny


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## Dehn0045 (Mar 21, 2018)

Soapy water (dish soap, a little higher concentration than you would use to do your dishes) is good for finding slow leaks.  Just put in a spray bottle and cover all the possible leak points.


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## More4dan (Mar 21, 2018)

Dehn0045 said:


> Soapy water (dish soap, a little higher concentration than you would use to do your dishes) is good for finding slow leaks.  Just put in a spray bottle and cover all the possible leak points.



Good advice, I'll have to give that a try.

Danny


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## More4dan (Mar 21, 2018)

chartle said:


> More4dan said:
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> > chartle said:
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## chartle (Mar 21, 2018)

More4dan said:


> chartle said:
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## More4dan (Mar 21, 2018)

I’m thinking if you reversed the flow direction the 40 micron filter would keep the silica out of your tools. Not sure why you would filter the inlet of the dryer. 


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## randyrls (Mar 22, 2018)

I had never heard of using water and minimal air to test pressure rating.  I learned something new today!

Thanks!!


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## More4dan (Mar 22, 2018)

randyrls said:


> I had never heard of using water and minimal air to test pressure rating.  I learned something new today!





When something fails during testing with water it makes a small splash. The water doesn’t compress so it can’t expand rapidly if the vessels burst. Gas will compress and rapidly expand resembling an explosion if the vessel fails sending shrapnel in all directions. 


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## chartle (Mar 22, 2018)

More4dan said:


> I’m thinking if you reversed the flow direction the 40 micron filter would keep the silica out of your tools. Not sure why you would filter the inlet of the dryer.
> 
> 
> Sent from my iPhone using Penturners.org mobile app



Well my plan is to have sort of a filling station above where I cast, on  my table saw. 

The air would first come into a small filter water trap to I'm hoping catch  most of the water and then into the beads through the outlet, down a 1/2" PCV pipe and out holes drilled in the sides of the pipe. I will probably shove something like a plastic scrubby into the pipe to keep the beads out. The air then goes up the filter through the beads and out the inlet with something shoved in there to keep the beads from shooting out, then into one of those cheap 1/4" plastic coiled hoses into the pot.


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## More4dan (Mar 22, 2018)

chartle said:


> More4dan said:
> 
> 
> > I’m thinking if you reversed the flow direction the 40 micron filter would keep the silica out of your tools. Not sure why you would filter the inlet of the dryer.
> ...



I was thinking of cutting thin slits near the bottom the down pipe and flowing down through the desiccant and into the pipe.  That way the air flow will force the desiccant beads into the chamber.  If done like the video and if the bit of brillo pad comes loose, the beads are headed down the air line. The air direction from the video also puts constant strain on the down tube especially if the filter plugs.  It would challenge the glued joint.  Pressure and flow from the outside of the tube instead of the inside would push the downtube upward into the cap.

I do like the idea of a water knockout before the desiccant dryer.  If I plan to use the dryer for painting I will have to have some kind of filter downstream of the desiccant dryer too.  Thanks again for the great ideas.

Danny


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## PatrickR (Mar 22, 2018)

Have you all been having moisture problems with casting? In a year or so casting with epoxy I have not. I’m not doing anything special. Just compressed air through a standard moisture trap/filter. (I’m in the Midwest so high humidity at times) I understand it being a problem in a production shop with a compressor that runs a lot (I’ve spent some time in a spray booth) but you may be fixing a problem that does not exist.


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## More4dan (Mar 22, 2018)

PatrickR said:


> Have you all been having moisture problems with casting? In a year or so casting with epoxy I have not. I’m not doing anything special. Just compressed air through a standard moisture trap/filter. (I’m in the Midwest so high humidity at times) I understand it being a problem in a production shop with a compressor that runs a lot (I’ve spent some time in a spray booth) but you may be fixing a problem that does not exist.





I’m just setting up for the first time. I’ve read where moisture may have caused some issues. No experience yet.  We do have high humidity almost every day in South Texas. I also don’t have a moisture trap /filter on my air system. 

Danny


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## chartle (Mar 22, 2018)

I put an inline desiccant filter on my pot and only after 2 or 3 used it started to turn pink. I can only imagine it getting worse as summer hits and I cast in my 1890 sandstone foundation basement.

To me its sort of like a best practises kind of thing.


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## PatrickR (Mar 22, 2018)

Danny, no matter what you use the compressor for you need a separator/filter. The tank will eventually corrode and expel rust etc and it will also stop any liquid. About $30 at HF. Desiccant seems like overkill and an unnecessary maintenance item.


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## More4dan (Mar 22, 2018)

PatrickR said:


> Danny, no matter what you use the compressor for you need a separator/filter. The tank will eventually corrode and expel rust etc and it will also stop any liquid. About $30 at HF. Desiccant seems like overkill and an unnecessary maintenance item.





I use to have one installed but it leaked too badly. I’ll replace it.  The desiccant materials are purchased and on their way, so I’ll give it a go. When it becomes too much trouble I may try to do without or just repurpose for painting only.  Thanks for the advice. 

Danny



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## Curly (Mar 22, 2018)

In the olden days  when I was an aircraft mechanic on firebombers we used air systems to open and close the bomb tank doors until they switched over to hydraulics. The screaming  little air air compressors feed into a dryer reservoir that was about the size of the water filters you are considering but they were filled with marbles. The expanding air chilled and the water condensed around the marbles and ran to the bottom of the dryer reservoir. We would drain them via a petcock in the bottom. Try the marbles and see it that works and if it doesn't switch to the desiccant. 

I have a standard water trap regulator assembly and have never had water in the line but the 80 gallon tank gets most of the water unless I'm running it hard with the air sander. I'd only consider a dryer if I was spray painting and had water main it to the gun.


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## More4dan (Mar 23, 2018)

I like the idea of the marbles. I’ll have to careful not to lose them. 


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## Curly (Mar 23, 2018)

Maybe you can find mine. Lost them ages ago.


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## chartle (Mar 30, 2018)

More4dan said:


> I use to have one installed but it leaked too badly. I’ll replace it.  The desiccant materials are purchased and on their way, so I’ll give it a go. When it becomes too much trouble I may try to do without or just repurpose for painting only.  Thanks for the advice.
> 
> Danny
> 
> ...



Did they come in yet I just ordered and received some and as I looked at the amount I bought, one quart, I was worried it would fill the canister. I put a 1/2" PVC pipe down the middle and filled it up. I recall when I put the beads in my wish list I did some sort of calculation to see how much I would need and I guess I got it right since one quart fills it to the top.

Now I just have to either find or get a new O ring. I thought I got one with the canister but its nowhere to be found.


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## More4dan (Mar 30, 2018)

chartle said:


> More4dan said:
> 
> 
> > I use to have one installed but it leaked too badly. I’ll replace it.  The desiccant materials are purchased and on their way, so I’ll give it a go. When it becomes too much trouble I may try to do without or just repurpose for painting only.  Thanks for the advice.
> ...





I had the same thought when I saw the qt container. Glad it will be enough. I’ve been a little sidetracked lately gathering old broken watches off eBay. Bummer about the o ring. Mine has one, thankfully. 

Danny


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## chartle (Mar 30, 2018)

More4dan said:


> I had the same thought when I saw the qt container. Glad it will be enough. I’ve been a little sidetracked lately gathering old broken watches off eBay. Bummer about the o ring. Mine has one, thankfully.
> 
> Danny
> 
> ...



I'm pretty sure it had one. I've had this filter for a few months now and have opened and closed it it many times think how I was going to add the pipe. I think it got misplaced. I even think I had it my hand once thinking now what is this big O ring used for. 

I'm sure I can find one at Home Depot Loews or even Walmart because they sell these filters.


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## chartle (Apr 21, 2018)

More4dan said:


> I had the same thought when I saw the qt container. Glad it will be enough. I’ve been a little sidetracked lately gathering old broken watches off eBay. Bummer about the o ring. Mine has one, thankfully.
> 
> Danny



Found it in the shavings on the floor of my shop. :biggrin:


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