Possibly a better alternative to the HF Pressure Pot?

[Ice31]

It would cost more for the tests but it would be interesting to know what the alloys used in the pot and lid are and how close they conform chemically and heat treat wise to the ones made on this continent. Disproving or confirmation of the oft made remarks about Chinese metals.

I could run a PMI on the pot, but I"m not sure the $200 would be that well spent. I'll call the testing lab that I use and see if they will cut me a deal for the sake of personal endeavor and because I spend a lot of money with them already....I'll let you know

Hate to break bubbles or anything and I am not trying to derail what is going on here but I think we both know the burst pressure of these pots and the outcome of the test. Regardless of the number range or even the material type that it is there are a good hefty number of questions which will not be answered by doing these tests. By all means do the test if you want but ask yourself these: Do they conform to a strict standard in which the material type MUST be adhered to and what is the spec on the material composition? We both know they can and will change according to lot numbers so any testing that you perform does not equate to every pot that is sold conforming to the same spec.

The other issue in this is lets say you do arrive at the burst pressure, which is actually easy to find without doing these test what is to stop people here from seeing that data then performing some grossly unsafe practices because of it? Citing this thread as proof of reliability and be in the unsafe region with a false sense of security.


The simple fact remains it's not about what pressure they will explode at or what material they are composed of. Any student of hyperbarics can very quickly spot the weakness in this approach.

You would be correct, except that i never said that I was going to or did I ever intended to take the vessel to burst pressure. Because that doesn't much prove anything except that I wasted my time. I simply stated that I was going to run the same testing that any ASME stamped vessel would be put through to see if the design and the statement of PSI rating is credible. As for the material you are correct, there is no way of knowing lot for lot what they would be using. But it will give me an indication of the type of material they are choosing to use as a whole. I'll be able to see if this specific pot material conforms to any ASME rated material of if they are using some non-tested "home recipe" for material. More testing is never a bad thing.....how people choose to use the information would be up to them.

 

[Smitty37]

Interesting thread.

I found this an interesting thread particularily since I don't intend to use a pressure pot for anything myseld. That being said, I do have to agree with Curtis that there is surely a difference between certified and rated... and if I were looking at an item that has exploding as one of it's failure mechanisms I would go with certified.

Now those who say certified will not tell you at what pressure it will explode are correct but certified will tell you that it has been actually tested to show at what pressure it will not explode.

Rated - well the individual pots might not be tested at all and I'm certain that I want anything that has the potential to cause me serious injury if it fails to actually undergo some serious testing.

 

[ElMostro]

I found this an interesting thread particularily since I don't intend to use a pressure pot for anything myseld. That being said, I do have to agree with Curtis that there is surely a difference between certified and rated... and if I were looking at an item that has exploding as one of it's failure mechanisms I would go with certified.

Now those who say certified will not tell you at what pressure it will explode are correct but certified will tell you that it has been actually tested to show at what pressure it will not explode.

Rated - well the individual pots might not be tested at all and I'm certain that I want anything that has the potential to cause me serious injury if it fails to actually undergo some serious testing.

Smitty, that is the main issue that has not been proven...the whole "exploding" tank thing. There have been plenty of posts over the years about the "elusive exploding HF tank" and I have searched many a place and for the life of me I cannot a single verifiable example of this ever occurring but it comes up again and again not just at IAP but at least one other forum I visit. Why do I care? Well, of my 12 active pressure pots 5 are HF pots that I run at least 2-3 casting cycles a day each at 80 psi and other than an occasional RAR event due to gasket failure they perform just fine. If these things REALLY explode all the time then with as much as I use my HF tanks they would be a prime candidate for an "explosion" and given that I am somewhat of a reasonable individual I would not like that to happen in my shop.

 

[TonyL]

While we are on the subject...has anyone found a better gasket material or a way to ameliorate the one that HF uses?

 

[edstreet]

Now those who say certified will not tell you at what pressure it will explode are correct but certified will tell you that it has been actually tested to show at what pressure it will not explode.

Certified only yields you serious insight into stress fractures with in the materials on expansion due to pressure. It is an indication for life span of the material and when you need to remove it from service. If you really want to look at standards, quality and the like then you need the ultrasound machine.

I have seen a number of 'certified' tanks explode due to double plugging and other abusive practices. I should also send my dive buddy a link to this thread so he can get a good laugh, he use to work at the US Navy Experimental Dive Center (NEDU) in Panama City, Florida doing testing, both destructive and non. He is also a saturation diver. Some of the horror stories he has is just down right sickening.

We also know that most failures and the like will be from seals, gaskets, couples and fittings.

 

[ElMostro]

Now those who say certified will not tell you at what pressure it will explode are correct but certified will tell you that it has been actually tested to show at what pressure it will not explode.

Certified only yields you serious insight into stress fractures with in the materials on expansion due to pressure. It is an indication for life span of the material and when you need to remove it from service. If you really want to look at standards, quality and the like then you need the ultrasound machine.

I have seen a number of 'certified' tanks explode due to double plugging and other abusive practices. I should also send my dive buddy a link to this thread so he can get a good laugh, he use to work at the US Navy Experimental Dive Center (NEDU) in Panama City, Florida doing testing, both destructive and non. He is also a saturation diver. Some of the horror stories he has is just down right sickening.

We also know that most failures and the like will be from seals, gaskets, couples and fittings.

Ed, I re-read the whole thread and missed the funny part...where is the humor?

 

[Smitty37]

Now those who say certified will not tell you at what pressure it will explode are correct but certified will tell you that it has been actually tested to show at what pressure it will not explode.

Certified only yields you serious insight into stress fractures with in the materials on expansion due to pressure. It is an indication for life span of the material and when you need to remove it from service. If you really want to look at standards, quality and the like then you need the ultrasound machine.

I have seen a number of 'certified' tanks explode due to double plugging and other abusive practices. I should also send my dive buddy a link to this thread so he can get a good laugh, he use to work at the US Navy Experimental Dive Center (NEDU) in Panama City, Florida doing testing, both destructive and non. He is also a saturation diver. Some of the horror stories he has is just down right sickening.

We also know that most failures and the like will be from seals, gaskets, couples and fittings.

I have admittedly not looked into the specific certification standards involved...

I presume any certified tanks you saw explode were subjected to pressure beyond what they were certified to withstand.

I agree completely that you will see a lot more seal failures, etc than exploding tanks - at least I hope like heck you would.

That being said and not being completely unversed in certification in general - particularily to US Government MIL-Specs - I will stand by what I said earlier.

 

[BSea]

We also know that most failures and the like will be from seals, gaskets, couples and fittings.

This is actually a good thing. A failed seal isn't catastrophic. It might make some noise, but it isn't dangerous. Ask you dive buddy about blown tank valve o-rings. Other than having it happen at depth (which I've never heard of), it's no big deal. Just some loud pop, and a lot of hissing till the valve is turned off.

And as far as double plugging, what do you mean by that regarding pressure pots? I understand what you mean for a scuba tank.

I'm really interested in Ice31's hydro test. At 1.5 X max rated pressure, that should be a pretty good indicator. So if a HF pot will hold at 120 PSI (80 x 1.5), it should make us feel a little better at running the pressure up to 60.

 

[Ice31]

Now those who say certified will not tell you at what pressure it will explode are correct but certified will tell you that it has been actually tested to show at what pressure it will not explode.

Certified only yields you serious insight into stress fractures with in the materials on expansion due to pressure. It is an indication for life span of the material and when you need to remove it from service. If you really want to look at standards, quality and the like then you need the ultrasound machine.

I have seen a number of 'certified' tanks explode due to double plugging and other abusive practices. I should also send my dive buddy a link to this thread so he can get a good laugh, he use to work at the US Navy Experimental Dive Center (NEDU) in Panama City, Florida doing testing, both destructive and non. He is also a saturation diver. Some of the horror stories he has is just down right sickening.

We also know that most failures and the like will be from seals, gaskets, couples and fittings.

Your friend has a very cool job...that being said the tanks he is involved with, i assume, are formed or extruded tanks not welded vessels. Diving tanks are made in much the same fashion at welding gas tanks and operate at a much higher PSI than a casting pressure pot. Hydro testing a pot this size at such a low pressure is virtually harmless so we'll move forward as planned. I do appreciate EDSTREET's concern over this process and he brings up some very good points.

We deal with pressure vessels of all types....from 6 gal "bottle tanks", 1,000 gal ammonia "wagons", 30,000 ammonia tanks and all the way up to 160,000 gal butane, propane, NG storage tanks. We have to follow a strict code of testing to re-certify a vessel after we have repaired, altered, or re-rated it...following the same practices on my HF tank will give me the same piece of mind as any other tank we work on.

All "certified" means is that it's been engineered, the process has been proved and destructively tested, material is traceable, and it has been manufactured and tested to a code of standards, mostly ASME, that are recognized industry wide.....so in essence if I can swing the material PMI and find out that it matches a standard ASME recognized material recipe out of ASME Sec. II, part D, and then get the calcs back and prove the design can handle the 60psi MAWP, add on PT of the welds, UT of the shell and head, and finalize it all with a hydro test...I'm not sure what else would be present in a "certified" tank...

And at the end of the day we will still be left with...

1) the weakest point is the open joint and that is were the failure would occur
2) it's made in China...which for some people is a deal breaker
3) It's still a $80 HF pot that some wouldn't use if you paid them to
4) I had some fun doing the testing, and never intended the results to "change the world" of HF pressure pots


PS......all asme certified tanks post 1999 are made to a 3.5:1 safety factor....meaning if the MAWP is 60 then the Max BURST is more than likley 210psi....before '99 the safety factor was 4:1...I believe it changed back in 1968 to the 4:1 and before that was 5:1.....all changed because of the uniformity of the manufacturing process of the material. As the process has been more refined over the decades so has the quality of the steel produced. thus the safety factor dropping.

 

[edstreet]

Now those who say certified will not tell you at what pressure it will explode are correct but certified will tell you that it has been actually tested to show at what pressure it will not explode.

Certified only yields you serious insight into stress fractures with in the materials on expansion due to pressure. It is an indication for life span of the material and when you need to remove it from service. If you really want to look at standards, quality and the like then you need the ultrasound machine.

I have seen a number of 'certified' tanks explode due to double plugging and other abusive practices. I should also send my dive buddy a link to this thread so he can get a good laugh, he use to work at the US Navy Experimental Dive Center (NEDU) in Panama City, Florida doing testing, both destructive and non. He is also a saturation diver. Some of the horror stories he has is just down right sickening.

We also know that most failures and the like will be from seals, gaskets, couples and fittings.

Your friend has a very cool job...that being said the tanks he is involved with, i assume, are formed or extruded tanks not welded vessels. Diving tanks are made in much the same fashion at welding gas tanks and operate at a much higher PSI than a casting pressure pot. Hydro testing a pot this size at such a low pressure is virtually harmless so we'll move forward as planned. I do appreciate EDSTREET's concern over this process and he brings up some very good points.

We deal with pressure vessels of all types....from 6 gal "bottle tanks", 1,000 gal ammonia "wagons", 30,000 ammonia tanks and all the way up to 160,000 gal butane, propane, NG storage tanks. We have to follow a strict code of testing to re-certify a vessel after we have repaired, altered, or re-rated it...following the same practices on my HF tank will give me the same piece of mind as any other tank we work on.

All "certified" means is that it's been engineered, the process has been proved and destructively tested, material is traceable, and it has been manufactured and tested to a code of standards, mostly ASME, that are recognized industry wide.....so in essence if I can swing the material PMI and find out that it matches a standard ASME recognized material recipe out of ASME Sec. II, part D, and then get the calcs back and prove the design can handle the 60psi MAWP, add on PT of the welds, UT of the shell and head, and finalize it all with a hydro test...I'm not sure what else would be present in a "certified" tank...

And at the end of the day we will still be left with...

1) the weakest point is the open joint and that is were the failure would occur
2) it's made in China...which for some people is a deal breaker
3) It's still a $80 HF pot that some wouldn't use if you paid them to
4) I had some fun doing the testing, and never intended the results to "change the world" of HF pressure pots


PS......all asme certified tanks post 1999 are made to a 3.5:1 safety factor....meaning if the MAWP is 60 then the Max BURST is more than likley 210psi....before '99 the safety factor was 4:1...I believe it changed back in 1968 to the 4:1 and before that was 5:1.....all changed because of the uniformity of the manufacturing process of the material. As the process has been more refined over the decades so has the quality of the steel produced. thus the safety factor dropping.

In the manual they state 200psi I was going to originally post that but I was reminded of many of the issues I posted earlier about and wanted to clear the air first.

We also know that most failures and the like will be from seals, gaskets, couples and fittings.

This is actually a good thing. A failed seal isn't catastrophic. It might make some noise, but it isn't dangerous. Ask you dive buddy about blown tank valve o-rings. Other than having it happen at depth (which I've never heard of), it's no big deal. Just some loud pop, and a lot of hissing till the valve is turned off.

And as far as double plugging, what do you mean by that regarding pressure pots? I understand what you mean for a scuba tank.

I'm really interested in Ice31's hydro test. At 1.5 X max rated pressure, that should be a pretty good indicator. So if a HF pot will hold at 120 PSI (80 x 1.5), it should make us feel a little better at running the pressure up to 60.

Double plugged references over pressure valves and similar devices. The burst disc that fails at a certain pressure range. Designed to fail to save the system from something nasty. There have been many that would add 2+ disc to increase the pressure needed so they could over fill the tanks. The 'plug' references electrical junction boxes with the break out circle plugs. i.e. defeating safety systems so you can do unsafe practices. In our case a seal that ruptures at 60 psi gets replaced with a seal that ruptures at 200 psi so someone could use a higher pressure.

Even still a failed seal can spew materials all over the area and you will be finding things weeks to come. If it's a gauge that blows you can have plexiglass and all the other internal mechanisms acting as a grenade and while it may not be fatal it would be major suckage.

 

[Smitty37]

Aquick check of ASME yielded this general statement:

Certification

A certificate will be granted by ASME only after the applicant successfully demonstrates the implementation of their quality program to the ASME review/survey team. After ASME reviews the report submitted by the review/survey team, the Society will either authorize the issuance of the certificate or request additional action by the applicant. Certificate Holders may request changes to their certificates after issuance. (MY emphasis)

It seems to be saying that in order to get certification an appropriate quality control system must be in place. Which would imply to me that at least some actual testing of certified pots is taking place - I have seen few quality control systems that do no require at least some physical testing.

 

[MesquiteMan]

Smitty,

According to the tech support person I spoke with at Binks, each of their pots are individually tested before certification. Thus the unique serial number and date of certification on each pot.

Aquick check of ASME yielded this general statement:

Certification

A certificate will be granted by ASME only after the applicant successfully demonstrates the implementation of their quality program to the ASME review/survey team. After ASME reviews the report submitted by the review/survey team, the Society will either authorize the issuance of the certificate or request additional action by the applicant. Certificate Holders may request changes to their certificates after issuance. (MY emphasis)

It seems to be saying that in order to get certification an appropriate quality control system must be in place. Which would imply to me that at least some actual testing of certified pots is taking place - I have seen few quality control systems that do no require at least some physical testing.

 

[Smitty37]

Smitty,

According to the tech support person I spoke with at Binks, each of their pots are individually tested before certification. Thus the unique serial number and date of certification on each pot.

Aquick check of ASME yielded this general statement:

Certification

A certificate will be granted by ASME only after the applicant successfully demonstrates the implementation of their quality program to the ASME review/survey team. After ASME reviews the report submitted by the review/survey team, the Society will either authorize the issuance of the certificate or request additional action by the applicant. Certificate Holders may request changes to their certificates after issuance. (MY emphasis)

It seems to be saying that in order to get certification an appropriate quality control system must be in place. Which would imply to me that at least some actual testing of certified pots is taking place - I have seen few quality control systems that do no require at least some physical testing.

That's kind of what my contention was. I seriously doubt any manufacturer can get certified without physical testing.

 

[Ice31]

So sorry that it has taken me so long to get back to this....after running the hydro test and have the engineering calculations performed it does boil down to the material used. Assuming that a standard gaged sheet metal was used the calculations show that the pot can easily take pressure up to 120psi. The weak point as we all know is the gasket sealing surface and bolts. Remember the MAWP is 60psi for these pots...and the max pressure is 80psi. That means that the pot is meant to work at 60 psi and can handle spikes to 80psi. I am not going to spend the money at this time to have the PMI done to see what material is used in the pot. If and when I do I'll have a conclusive report as to what the pot is engineered to handle.

This information does't really change anything in my opinion except that I have a little more confidence in the pot that I use. I have still installed a safety chain to the lid in case of a clamp failure. So if the lid were to give way the lid wouldn't go anywhere. Can't be too safe.

 

[TonyL]

Thank you for performing and sharing the "report".