Is fiber board at bottom tank better thermal than grout? 2

[thien2002]

Is Cathodic Protection required for 6000 Ton-Hour Thermal Energy Storage Tank (54'x36' CRT), A36? Would Corrosion Allowance required for Roof Plate, Shell Plate, Bottom Plate, and Framing?
Can we use 2 layers of 1/2" asphalt impregnated fiber board at the bottom plate to foundation interface? Is this going to provide a better thermal break than grout? True or False?

 

[unclesyd]

I see no need for the CP.
I would add a corrosion allowance 1/8" over all.
I don' have the proper code books, so if A36 is still allowed it would be ok. We have some tanks built from A36.

We use asphalt impregnated felt(single layer) under some tanks, mainly heated as in you case. We have some large floating roof storage storage tanks also with felt. I would use it as it is a good thermal brake though some of the newer grouts are good insulators but a lot more trouble.

What temperature are you going to operate the tank?

What type foundation is your tank going to sit on?

 

[JoeTank]

If you are asking about CP of the interior, I'd say that it all depends on your water characteristics. We write plans and specs for water tanks for many uses and find that the answer is not obvious.

I believe that the quality of the internal lining is far more important than the CP system. If the internal lining is installed properly, a CP system probably isn't needed. Also, if the lining is not installed under the observation of a third party you can pretty much count a lining with a short service life. The coatings inspector should be NACE certificated or similarly trained. If the lining system is installed without the oversight I would suggest CP be provided in order to minimize the damage due to corrosion. Also, keep in mind that the higher the temperature, the higher the corrosion rates.

Steve Braune
Tank Industry Consultants

http://www.tankindustry.com

 

[thien2002]

Here is my Tank spec's:
between 40-60F, 630K Gal, 54x36', Above Ground, storage of thermally stratified chilled water based on 650T of Peak Cooling Load, 40F Chilled Water supply to 56F.

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unclesyd (Materials) Jan 14, 2004
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We use asphalt impregnated felt(single layer) under some tanks, mainly heated as in you case. We have some large floating roof storage storage tanks also with felt. I would use it as it is a good thermal brake though some of the newer grouts are good insulators but a lot more trouble.
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What temperature are you going to operate the tank?
40-60F
What type foundation is your tank going to sit on?
We required concrete ringwall foundation meeting the requirements of AWWAD100, AWWA D-10387, and ACI 318. Contractor provide submittals for 4000psi concrete, 2.5ft depth, 2225 PSF Press at base.
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My question: Do you know thermal property of Impregnated-Asphalt Felt so I can compare between Grout & Asphalt Felt?
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SteveBraune (Structural) Jan 14, 2004
If you are asking about CP of the interior, I'd say that it all depends on your water characteristics. We write plans and specs for water tanks for many uses and find that the answer is not obvious.
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My Question: What would considered a good lining system, can we test the interior lining? Can you explain the relationship between lining & cathodic protection?
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Your helps are greatly appreciated and your knowledge will pass along to others. Thank you!

 

[JoeTank]

Last year I had to figure out how to determine the soil temperatures below an asphalt storage tank operating near 400 degrees F. It took a lot of research, but in end I came away with the understanding that, among other things, the asphalt impregnated fiberboard under the tank bottom was of precious little value insulation-wise.

Steve Braune
Tank Industry Consultants

http://www.tankindustry.com

 

[JoeTank]

Further to your questions...

The internal linings of most water tanks would consist of a three-coat expoxy lining system. The lining acts as a barrier between the water and steel and must be holiday (pinhole) free. The customary test is called a holiday test. This type of test uses a wet spong and a low voltage electrical circuit. The device is passed over the entire surface and if a pinhole in the lining is located the electrical circuit is completed and a light goes on. The area is then repaired and retested.

With regards to CP and internal linings... The lining is required, but the CP is optional. In the event of a lining failure, the CP would provide an added measure of corrosion protection. Unfortunately, most CP systems are designed for protection based on a coating failure of only a few percent of the lining surface. I think of CP as a secondary line of defense that will minimize the shell damage in the event of a minor coating failure.

As previously posted, the application of the lining is extremely important and is your best way of protecting the steel. It will require a detailed detailed specification, a competent contarctor and third party inpection to acheive the service life you desire.

Steve Braune
Tank Industry Consultants

http://www.tankindustry.com

 

[thien2002]

First, thank you Steve, maybe I should consider your firm as our tank consultant on our next project. With all the helps are very accurate and professional, yours are the best.

Steve, what do you think about the cost of impregnated asphalt fiber board versus grout? How about their thermal properties?

Thank you!

 

[JoeTank]

Regarding costs, I really don't know as I have not ever compared them.

If you are considering covering the entire area under tank, the fiberboard would likely be cheaper as it can be easily layed down before the bottom is placed. Grounting an entire bottom would be a real technical challenge and therefore probably very costly.

I don't believe that either will make much difference in the heat leak into the chilled water tank. The grout thermal properties would similar to concrete. The thermal properties of the fiberboard made no significant differences in the heat transfer for a heated asphalt problem I worked on last year.

Low temperature tanks such as annhydrous ammonia and propane are typically founded on a ring of wooden or pearlite concrete blocks. The interior pad is often foamglass insulation blocks. But, this would be ahuge overkill for a chilled water tank.

Steve Braune
Tank Industry Consultants

http://www.tankindustry.com

 

[thien2002]

Steve, that is great to know someone already researched on the fiber board myth which was assumed to give thermal breaks on chilled water tanks. I believe our contractor has experience with the grout technical difficulties when laying down the grout so they would give us advice to replace grout with fiber board. I think I would recommend lining and surface preparation to be SSPC-SP10 and 3 coat epoxy lining system, if you have the time, can you recommend the manufacturers and basic system or equivalent. Thank you.