Casting Rookie needs help with pressure pot set up

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goirish1127

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Feb 4, 2018
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I want to give casting a go and begrudgingly got a HF pressure pot. I had ordered a different one from Amazon only to get an email the next day saying that they were out of stock and didn’t know if they’d be back in stock for the remainder of time. I have the pot set up after watching multiple videos and tested it today. My issue is the pressure gauge. It never goes above 20 psi but I hear the pot “popping” and then the safety valve goes off. I have tried two different pressure gauges (the one that came with the pot and one from a big box). I suppose that I could have two bad gauges, bu those are pretty slim odds. I have looked in the forums and can’t find an answer to this, although with the vast amount of info on this site I have not looked at every thread, so if someone could point me in the direction of previous thread about this, that would be great as well.

Thanks- Mickey


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Kenny Durrant

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Did both gauges read the same and is there one on the compressor and did it read the same as well? If so then the pop off valve may need adjusting. BUT before you change the pop off valve you need to make sure that the gauges are accurate. I have mine set 5 lbs under the rating of the pot. I also have a regulator on the compressor that's set 5 lbs under the rating of the pot. I use 1 compressor to fill 2 pots so I have a regulator on each pot set to the desired PSI,55lbs, I want in each tank. That way when I fill the second tank, as long as the line pressure doesn't drop below 55lbs, I can maintain pressure in both pots and not affect the blanks.
 

PatrickR

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I take it you have no gauge on your compressor? A regulator?
You’re right about the two gauges chances are they are good since they read the same. It could be the relieve valve is bad.
You say the pot makes a popping sound? It should not make any sounds from being pressurized.
 

goirish1127

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Kenny-

Yes. The gauges read the same. I do have a regulator on the compressor and it’s set at 55 psi. The thing that concerned me is the popping sound coming from the empty pot. Is this normal? It started to get louder right before the relief valve let off. I haven’t done this before and didn’t want the pot blowing on me. I haven’t heard that sound on any of the videos that I have watched, but they are probably edited for sound. I appreciate the quick response.

Is there a way to make sure the gauges are accurate?

Mickey.


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randyrls

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Mickey; I would be very cautious with HF pressure pots, they are NOT pressure tested. The first few times you use them, put the pot somewhere safe like under a workbench and pressurize it from a distance out of line of sight. I believe that Curtis (mesquiteman) uses a shroud around the pressure pots to make sure nothing flies in case of failure. The use of a shroud is common in dive shops where they pressurize scuba tanks.

Cindy Drozda says, "Safety is free, use it to excess"
 
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Rifleman1776

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Mickey; I would be very cautious with HF pressure pots, they are NOT pressure tested. The first few times you use them, put the pot somewhere safe like under a workbench and pressurize it from a distance out of line of sight. I believe that Curtis (mesquiteman) uses a shroud around the pressure pots to make sure nothing flies in case of failure. The use of a shroud is common in dive shops where they pressurize scuba tanks.

Cindy Drozda says, "Safety is free, use it to excess"
"be very cautious with HF pressure pots, they are NOT pressure tested."

You know this how?
 

Kenny Durrant

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If you have 3 different gauges and they're all reading the same I would think they're close if not accurate. I would lower the regulator on the compressor to 40 lbs until you figure out the problem. That way you shouldn't run the risk of over pressurizing the pot. I don't know what the popping sound might be unless there is a problem with the seal. If that's the case I could see that being the problem to the whole issue. I can give you some things to try and look at but remember to think Safety First. If the popping sound Isn't the pop off valve then try to feel around the lid to see if air might be blowing by the O ring under the lid. Maybe turn the pot upside down and put a little water around the seal to see if air is leaking. If that's ok then I would think it has to be the pop off valve because the tank should be empty and the only thing left is hoses and connectors. The pop off valves I've seen on the pots are adjustable. If it's set too low that will make all kinds of noise. Remember I'm no expert I've just been doing a lot of casting. Be careful because when your pressurizing a tank your starting to energize a Bomb.
 

More4dan

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Test with WATER instead of air. A small squirt of water is much less exciting than an exploding pot and shrapnel flying through your shop. It should not be popping. The relief valve will pop when relieving pressure which should be very different than the metal popping. If it’s the relief valve it can be replaced with a better one for under $10 just get one with the correct rating. Remember that whole shrapnel thing. If it’s the pot popping, take it back.


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goirish1127

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Thanks everyone for the input. I don’t believe the popping is the relief valve. It sounds like it’s coming from INSIDE the pot, but it’s empty. I am going to take it back and try a different pot. If it was hissing air I would probably mess around with it, but the way it sounds makes me uneasy.
I am an ER nurse and have seen way too many workshop injuries. I have seen one guy on two different occasions lose fingers on a table saw. Both times it was because the push sticks were out of reach. I told him that if he didn’t start using them he was going to have to borrow toes to give a high five.
I will update when the second pot is here, tested, and (hopefully) used. Thanks again everyone.


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1080Wayne

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The noise might possibly be from the hold down clamps either stretching slightly (not good ) or from them rotating the pot lid ever so slightly . The first should be obvious if the clamps are looser after removing pressure than when you tightened them . The second problem is exacerbated by incorrect clamping procedure . Do not tighten them going clockwise around the pot , one after another . That will pretty much guarantee the lid will rotate in the same direction when pressurized . I find it better to 1 and 3 together by hand , then 2 and 4 , followed by large vice grip individually on 1 , 3 , 2 and 4 , not excessively tight , just a bit more than is easy to apply by hand .
 
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