Rectangular pressure storage tanks
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![[Hearth.com] Rectangular pressure storage tanks](/talk/data/attachments/190/190913-d8914c60e0ea2821fa46938014a9dc65.jpg?hash=rDBLLH8Rwi)
NateB
Feeling the Heat
I don't, but I used American Solar's tank, and it is doing a great job. http://www.americansolartechnics.com/products/. I looked at that tank when I was starting my install, and it was to expensive for me.
I am somewhat concerned that there is no reference to pressure rating in the link or any reference to an ASME stamp. Any tank can withstand pressure as atmospheric pressure is 14.7 PSIA. A pressurized tank for a boiler needs to be rated for the boiler safety relief rating. Some states are code states and any pressurized than needs an ASME stamp which raises the cost as the tank comes with a "pedigree".
I looked at these options several years ago and went with my no pressurized tank. I hauled it and installed it myself.
I looked at these options several years ago and went with my no pressurized tank. I hauled it and installed it myself.
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Bad LP
Minister of Fire
The price is attractive and the size is very good but it does not have a ASME rating. That could or could not be a problem IF something were to go wrong with the system that involved the insurance company. That is just not something I'm willing to gamble with.
For non pressurized storage there is a very nice gentleman selling his Solartechnics tank here on the site. I bought his Tarm boiler and saw the tank un-assembled and neatly stored. He was in New York and it looked like it would easily fit in a pickup truck with a few straps.
For non pressurized storage there is a very nice gentleman selling his Solartechnics tank here on the site. I bought his Tarm boiler and saw the tank un-assembled and neatly stored. He was in New York and it looked like it would easily fit in a pickup truck with a few straps.
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Perg,
I have that exact tank that I bought from new horizons. I'm on my 5th heating season now and haven't had any problems. I don't believe it is ASME certifified but I think it's rated to 35 PSi.
I have that exact tank that I bought from new horizons. I'm on my 5th heating season now and haven't had any problems. I don't believe it is ASME certifified but I think it's rated to 35 PSi.
Thanks for the feedback. I want to have pressure storage but was tinkering with the idea of 2 psi on storage side using a plate heat exchanger.
per my drawing attached.
per my drawing attached.
maple1
Minister of Fire
If I could afford it, I wouldn't hesitate to get the New Horizons tank. Most on here (me included) who have pressurized storage, do it with used LP tanks - and I doubt very much any of them are ASME tagged, or at least not tagged for what they are now being used for.
500 gallons is not really much storage for what looks like you have going on in that diagram, particularly with a HX in between - I have 660 and would like to have 2x that. If I wasn't going full pressurized with no HX, I would check out American Solartechnics tanks as suggested above - AKA forum member Tom in Maine.
500 gallons is not really much storage for what looks like you have going on in that diagram, particularly with a HX in between - I have 660 and would like to have 2x that. If I wasn't going full pressurized with no HX, I would check out American Solartechnics tanks as suggested above - AKA forum member Tom in Maine.
ASME tags mean that the tank has been built to a long term established code. When a shop attaches an ASME tag, they are taking responsibility if it fails. All the materials and methods of fabrication used are traceable back to the suppliers and the code. When a non stamped vessel gets sold the original seller still has liability if it fails, the tank may still be quite beefy and designed by someone but its higher risk. Unlike an air vessel or a steam vessel, water is non compressible, this means that there isn't much potential energy stored up an pressurized tank. If a weld fails, it sprays out water and make a mess. If its 190 degree water anyone in the immediate area may get serious burns. When a pressure vessel for steam fails or a compressed air tank fails it can cause destruction as there is lot of stored energy in the tank that can released quickly.
Most but not all states ultimately use the ASME boiler code to govern pressure vessels. Any tank operated above 15 psi is a pressure vessel in a state that has adopted ASME boiler code as law. (unless the state has specifically made exclusions to exempt specific classes of tanks from the rules) the code is the law. A storage tank operated over 15 psi would have to be ASME stamped or equipped with a safety device or adequate size and capacity that it relieves at or below 15 psi so it cant exceed 15 psi. Some states aggressively enforce this across the line (like the Commonwealth of Massachusetts) and many do not. The rules are most likely still in place (unless excepted) so there is a large "gray market" for non code vessels. Technically if a non code vessel fails in state with ASME code, the insurance company does not have to pay out for damage caused by a tank failure as it was an illegal installation. Many folks don't realize this risk or assume it wont happen to them and elect to use non code vessel to save bucks up front.
A propane tank was at one point must likely a stamped pressure vessel. As the vessels age they need to be inspected and tested on a routine basis. They are usually designed for a specific design life and most commercial tank owners inspect their tanks and abandon them when they no longer pass inspection or they just decide they are old enough to scrap them. Frequently the physical stamp plate may still be on vessel but without inspection and possible pressure testing by an authorized party, they are no longer a valid code vessel and subject to the same risks as any non code vessel. There are many folks who buy these old tanks and alter them for storage, they really don't know what condition the tank is in or how much abuse it may or may not have gone thru. If they repair or alter the tank by installing new nozzles or larger nozzles they are altering the tank and that requires a ASME repair stamp (R Stamp). If the work is done by someone covered by a R stamp and the vessel is inspected and witness tested in front of an authorized person (usually a state boiler inspector) then the tank can be recertified. This is generally quite expensive and would offset the cost savings for an unknown tank. There are a lot of folks who claim to be certified welders and may work for R stamp shops but unless the repair is done under the control of the R stamp shop, its most likely not a code repair. It may make the tank owner feel good but it means nothing legally except that there may be another plantiff (the welder) sitting in court with the tank owner if it fails and hurts someone. There are reportedly shops that do code alterations and recertify tanks that have proper code stamps, I haven't looked into them but they will need to charge a premium as the paperwork and insurance required to keep a R stamp is extensive and expensive.
Ultimately everyone accepts risk into their life, that everyone's right to accept that risk as long as they know what the risks are. Unfortunately a lot of folks don't realize the risk they are accepting into their home when they go with a pressurized non code tank built from a scrap tank. Even if a typical homeowner is willing to take a risk, the bank that holds the mortgage is not going to and in the case of uninsured loss things could get messy. For those who own their home outright they have the right to do what they want and if the tank fails they have the right to pay for the repairs if the insurance elects not to pay.
I elected to go with non pressurized storage. It takes up less room and was a lot easier to haul home, carry down into my basement. and install. Since the storage water never gets changed and the heating water never gets changed corrosion isn't an issue. The life of the PVC liners appear to be quite long, there were some experiments with other materials, like EPDM that have been less successful.
Most but not all states ultimately use the ASME boiler code to govern pressure vessels. Any tank operated above 15 psi is a pressure vessel in a state that has adopted ASME boiler code as law. (unless the state has specifically made exclusions to exempt specific classes of tanks from the rules) the code is the law. A storage tank operated over 15 psi would have to be ASME stamped or equipped with a safety device or adequate size and capacity that it relieves at or below 15 psi so it cant exceed 15 psi. Some states aggressively enforce this across the line (like the Commonwealth of Massachusetts) and many do not. The rules are most likely still in place (unless excepted) so there is a large "gray market" for non code vessels. Technically if a non code vessel fails in state with ASME code, the insurance company does not have to pay out for damage caused by a tank failure as it was an illegal installation. Many folks don't realize this risk or assume it wont happen to them and elect to use non code vessel to save bucks up front.
A propane tank was at one point must likely a stamped pressure vessel. As the vessels age they need to be inspected and tested on a routine basis. They are usually designed for a specific design life and most commercial tank owners inspect their tanks and abandon them when they no longer pass inspection or they just decide they are old enough to scrap them. Frequently the physical stamp plate may still be on vessel but without inspection and possible pressure testing by an authorized party, they are no longer a valid code vessel and subject to the same risks as any non code vessel. There are many folks who buy these old tanks and alter them for storage, they really don't know what condition the tank is in or how much abuse it may or may not have gone thru. If they repair or alter the tank by installing new nozzles or larger nozzles they are altering the tank and that requires a ASME repair stamp (R Stamp). If the work is done by someone covered by a R stamp and the vessel is inspected and witness tested in front of an authorized person (usually a state boiler inspector) then the tank can be recertified. This is generally quite expensive and would offset the cost savings for an unknown tank. There are a lot of folks who claim to be certified welders and may work for R stamp shops but unless the repair is done under the control of the R stamp shop, its most likely not a code repair. It may make the tank owner feel good but it means nothing legally except that there may be another plantiff (the welder) sitting in court with the tank owner if it fails and hurts someone. There are reportedly shops that do code alterations and recertify tanks that have proper code stamps, I haven't looked into them but they will need to charge a premium as the paperwork and insurance required to keep a R stamp is extensive and expensive.
Ultimately everyone accepts risk into their life, that everyone's right to accept that risk as long as they know what the risks are. Unfortunately a lot of folks don't realize the risk they are accepting into their home when they go with a pressurized non code tank built from a scrap tank. Even if a typical homeowner is willing to take a risk, the bank that holds the mortgage is not going to and in the case of uninsured loss things could get messy. For those who own their home outright they have the right to do what they want and if the tank fails they have the right to pay for the repairs if the insurance elects not to pay.
I elected to go with non pressurized storage. It takes up less room and was a lot easier to haul home, carry down into my basement. and install. Since the storage water never gets changed and the heating water never gets changed corrosion isn't an issue. The life of the PVC liners appear to be quite long, there were some experiments with other materials, like EPDM that have been less successful.
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Mike Fromme
Burning Hunk
A stupid question: Your storage is unpressurized, is the boiler pressurized and giving up its heat through a heat exchanger in the tank? Does the water in the tank flow directly through the distribution piping with no heat exchanger? I'm just curious.
We use a single heat exchanger to input and remove heat from our tanks.
All our heat exchangers are now stainless steel.
I have done systems without heat exchangers, but the systems should be non-ferrous. Dick Hill and I had done systems that were without hx and were ferrous but we dosed them with some heavy duty corrosion inhibitors. Garn does this but it does warrant ongoing testing.
All our heat exchangers are now stainless steel.
I have done systems without heat exchangers, but the systems should be non-ferrous. Dick Hill and I had done systems that were without hx and were ferrous but we dosed them with some heavy duty corrosion inhibitors. Garn does this but it does warrant ongoing testing.
So, the boiler and distribution could be closed and under pressure this way? What does this exchanger look like? They used to be big coils of copper, no?
I have one of Tom's copper heat exchangers that I use to charge the tank as well as pull the heat out. I don't heat DHW as I have separate system for that.
I did need to remove the cover and coil at one time and the water in the tank was perfectly clear. There was some chalking on the coil. The coil is a handful to deal with and it comes with tywraps to keep it easy to move, the tywraps all failed due to prolonged immersion. Once the coil is in place they are not needed but pulling the coil out of the tank without them was like lifting a bundle of snakes. I have a couple of valves and two big unions right at the edge of the tank so pulling the coil doesn't require draining the system, but getting the coil empty requires low pressure compressed air to blow it out.
For the heck of it I had some type K thermocouples that I installed in the inner wall behind the liner. I never hooked them up to a chart recorder but with my handheld I can definitely see the impact of stratification. The tank top is not a structural piece and Tom supplies warning labels to that effect. I built a large shelf that hangs from my rafters with removable boards on the bottom so I have access to the tank if I need it in the space above my tank. I store plastic totes of kindling and a few unimog parts on that shelf.
One minor modification I did on mine is the bottom of the tank insulation sits up off the floor on Dricore panels, that keeps any moisture buildup that may come up under the basement floor in check as it has a place to escape on the edges.
I did need to remove the cover and coil at one time and the water in the tank was perfectly clear. There was some chalking on the coil. The coil is a handful to deal with and it comes with tywraps to keep it easy to move, the tywraps all failed due to prolonged immersion. Once the coil is in place they are not needed but pulling the coil out of the tank without them was like lifting a bundle of snakes. I have a couple of valves and two big unions right at the edge of the tank so pulling the coil doesn't require draining the system, but getting the coil empty requires low pressure compressed air to blow it out.
For the heck of it I had some type K thermocouples that I installed in the inner wall behind the liner. I never hooked them up to a chart recorder but with my handheld I can definitely see the impact of stratification. The tank top is not a structural piece and Tom supplies warning labels to that effect. I built a large shelf that hangs from my rafters with removable boards on the bottom so I have access to the tank if I need it in the space above my tank. I store plastic totes of kindling and a few unimog parts on that shelf.
One minor modification I did on mine is the bottom of the tank insulation sits up off the floor on Dricore panels, that keeps any moisture buildup that may come up under the basement floor in check as it has a place to escape on the edges.
I have a 500 gallon de-commissioned stainless chemical tank and heat the water with a 30 plate heat exchanger. I have double copper coils bathing in the tank. Having an unpressurized system makes it easy to heat your domestic hot water by just running the supply through a coil and not having to mess around with side arms on your domestic water tank.
A tank that can easily be moved into the basement has a big attraction factor.
Not that I'm thinking of adding a wood boiler.....no, that's not it......no, that's not it......no....
Not that I'm thinking of adding a wood boiler.....no, that's not it......no, that's not it......no....
We changed over to stainless because the coils are easier to handle and are less expensive.
The Chalking that Peakbagger mentions on copper coils is a tarnish layer which is what protects the copper from corrosion.
Our coils used cable ties for shipping and installation. The deterioration is less of an issue after they are in place.
We still use them but use non-degradable ties where needed.
The coils look like, well, coils.
Happy Solstice Day.
The Chalking that Peakbagger mentions on copper coils is a tarnish layer which is what protects the copper from corrosion.
Our coils used cable ties for shipping and installation. The deterioration is less of an issue after they are in place.
We still use them but use non-degradable ties where needed.
The coils look like, well, coils.
Happy Solstice Day.
With my tank being 6 feet high, I had to lay it on it's side to slide the coils in then it was so heavy I had to use a come along attached to the ceiling to get it upright. I used a few cans of automobile cooling system anti corrosion treatment when I first installed it 9 years ago and haven't had it open since. Thought it would give some protection to the copper. I have a steam boiler sight glass and the water in there looks clear but that doesn't tell me what it looks like on the bottom nor does it tell me what the copper looks like.
Celebrate the shortest day of the year, folks but for me I'm looking forward to the longest night.
Celebrate the shortest day of the year, folks but for me I'm looking forward to the longest night.
On a similar but different note, my 120 gal. buffer tank is pressurized, and has a 1.5" corrugated stainless steel coil in it for domestic hot water. Very happy with the dhw production.
On stratification, with heat exchangers being the mode of heat transfer in the non-pressurized tank design, I can see good stratification being the rule since the storage water in the tank is never disturbed, as it is with a pressurized tank. True?
On stratification, with heat exchangers being the mode of heat transfer in the non-pressurized tank design, I can see good stratification being the rule since the storage water in the tank is never disturbed, as it is with a pressurized tank. True?
Well,maybe. I only have one sensor well half way up, half way down, MIDDLE
and only light one 3 to 4 hour fire per day. I always check the temperature just before lighting the daily fire. The circulator launch temperature is 187 degrees but shortly after launch the tank temperature will drop about 2 or 3 degrees.
I;m drawing from about 6 inches from the bottom and distributing on the top with a 2 foot long perforated 3/4 inch tube just above the high water line so I would say it is mixing a little. I'm only moving as much water as needed to keep the boiler from reaching high limit and going to idle mode.
and only light one 3 to 4 hour fire per day. I always check the temperature just before lighting the daily fire. The circulator launch temperature is 187 degrees but shortly after launch the tank temperature will drop about 2 or 3 degrees.I;m drawing from about 6 inches from the bottom and distributing on the top with a 2 foot long perforated 3/4 inch tube just above the high water line so I would say it is mixing a little. I'm only moving as much water as needed to keep the boiler from reaching high limit and going to idle mode.
Fred, I thought you were circulating the boiler water and the dhw through heat exchangers and the tank water was isolated from that?
No way is that tank rated to 35 psi and it definitely isn't up to ASME standards. Knowing the source I doubt it has any legal rating at all. Not saying it's not a decent tank, but pressurizing it beyond 5 psi would be a risk I wouldn't take.
Mike Fromme
Burning Hunk
When installing the system this seemed like the simplest way to go for someone with limited brain power. I also only distribute heat from the tank so the actual "heat making" portion is about as simple as you can get. It has served me well for the past nine years
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