Does anyone use a non-pressurized, open carbon steel storage tank?? The Garn is basically that. I'm considering an open tank treated with chemicals for storage.
non-pressurized carbon steel storage tank??
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The tanks you see on farms that store diesel are an option. Most you see are up on stand and gravity feed the oil. They are less $$ than pressurized tanks.
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ewdudley
Minister of Fire
Der Fiur Meister said:
If your situation lends itself to it, you could consider a "feed and expansion cistern" (a.k.a. "European open system" here on hearth.com). The expansion tank is situated a couple feet higher than anything else in the system and it is open to atmospheric pressure. This helps minimize the surface area exposed to the air and you can float some mineral oil on the surface to help some more. Best of all it allows the boiler, storage, and the system to be interconnected without heat exchangers.
But the trick is to get some dozens of gallons of expansion tank up above the system, plus there needs to be a one inch or greater pipe going directly from the boiler that can discharge into the top of the tank in the case of steam blow-off.
Here's a thread that touches on the topic:
https://www.hearth.com/econtent/index.php/forums/viewthread/39312/
--ewd
woodsmaster
Minister of Fire
The fuel tanks won't work in the area I have. I need to get the most out of the space. I have an area of 5'x9'. A rectangular tank with usable space of 4'x8'x4.7 (5' high less 3" air above water for expansion) and 6" wall / insulation is the largest possible. I need more than 500 gal.
The Boiler side is a closed loop with water run through a plate HX. There's another pump on the tank side of the HX pumping to the tank. Elevation won't impact this. The tank would have an open top, much like some of the EPDM tanks discussed here. There are three system loads drawing heat from the tank. All are separated by either another HX or just pump to another closed tank (at a much lower elevation in the shop).
Pre-fab'ed SS tanks are expensive. SS sheet welded in place runs $1200 for this size tank. Polypropylene has the temp rating (200* or more), but is also high in cost and maybe not available in a size that usable. HDPE works, but only to 150-180* depending on manufacturer. EPDM liners only lasts 5-6 years at 180* max (I want the option of higher temps), concrete works in some water applications, but makes no sense in this area because of lost space and other reasons. Propane / fuel tanks won't fit.
I can buy the carbon steel sheet and weld it together in a couple hours with a mig welder for less than $400. Add plywood and framing for structural walls, and insulate to R24 sides / R32 top. This ~1135 gallon tank is under $800. I'd go with SS, but that's over $2000. In the end I'm hoping for the same 20+ year useful life.
I spoke with a lab that Garn recommends for testing their boiler water. The lab said we could add chemicals to protect this tank much like the open Garn. The thought is that if chemicals can raise the PH / regulate the conductivity etc. on a Garn so they can last 20-30 years, I should be able to expect the same with this tank.
One difference between a Garn and a fabricated carbon steel tank would be that Garn adds a sacrificial anode. That could be installed on this tank as well. Same for the separate ground rod / wire. Short of any other answers from this site I've also thought of speaking with an engineer that I know who specializes in cathodic protection systems for steel structures. However that adds cost for the unit and electricity use.
Thanks for your ideas. I was hoping someone else had first hand experience with a carbon steel open tank.
The Boiler side is a closed loop with water run through a plate HX. There's another pump on the tank side of the HX pumping to the tank. Elevation won't impact this. The tank would have an open top, much like some of the EPDM tanks discussed here. There are three system loads drawing heat from the tank. All are separated by either another HX or just pump to another closed tank (at a much lower elevation in the shop).
Pre-fab'ed SS tanks are expensive. SS sheet welded in place runs $1200 for this size tank. Polypropylene has the temp rating (200* or more), but is also high in cost and maybe not available in a size that usable. HDPE works, but only to 150-180* depending on manufacturer. EPDM liners only lasts 5-6 years at 180* max (I want the option of higher temps), concrete works in some water applications, but makes no sense in this area because of lost space and other reasons. Propane / fuel tanks won't fit.
I can buy the carbon steel sheet and weld it together in a couple hours with a mig welder for less than $400. Add plywood and framing for structural walls, and insulate to R24 sides / R32 top. This ~1135 gallon tank is under $800. I'd go with SS, but that's over $2000. In the end I'm hoping for the same 20+ year useful life.
I spoke with a lab that Garn recommends for testing their boiler water. The lab said we could add chemicals to protect this tank much like the open Garn. The thought is that if chemicals can raise the PH / regulate the conductivity etc. on a Garn so they can last 20-30 years, I should be able to expect the same with this tank.
One difference between a Garn and a fabricated carbon steel tank would be that Garn adds a sacrificial anode. That could be installed on this tank as well. Same for the separate ground rod / wire. Short of any other answers from this site I've also thought of speaking with an engineer that I know who specializes in cathodic protection systems for steel structures. However that adds cost for the unit and electricity use.
Thanks for your ideas. I was hoping someone else had first hand experience with a carbon steel open tank.
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