When does a tank need to meet AWWA standards?

[leeboy4130]

I am working on some drawings to replace our rusted out 6000 gallon rectangular cold well tank that sits below our cooling tower. Looking at the original drawings for the tank, it states to be constructed in accordance with AWWA. I am curious as to when a tank needs to be to this standard? Is it only tanks that are used at a business? Is it a liability thing? The drawings for our current tank do not show any structural support, yet the actual tank has 2x6 tubing welded all around it (appears to be way over engineered). I am wondering if the 2x6 tubing was added because of the AWWA standard, and how I would go about designing the new tank to be structurally sound.

 

[JStephen]

AWWA standards are normally used for storage tanks for municipal water systems, and your state health department may require privately-owned water systems to comply with them as well. For non-potable tanks, there usually isn't any requirement to comply with AWWA standards, although it may be convenient to do so.

There aren't any common tank standards that address rectangular tanks and AWWA was probably used for lack of something better. You could use the minimum thicknesses and the allowable stresses from the standards, and comply with requirements for accessories to the extent they are applicable.

 

[stanier]

Any standards apply if enshrined in legislation or contract. This may be netween the parties, government, insurer or even public expectation. Otherwise they are of a voluntary nature. The standards system has a great deal of overlap and contradiction in requirements. That is why you cannot cheery pick sections from one set of standards and apply to another.

Standards do offer a measure of protection for the engineering professional but they are no substitute for first principles and engineering expertise.

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King

http://waterhammer.hopout.com.au/

 

[racookpe1978]

In this case, I'd recommend going back to your insurer ... You're in a refit case, on your own property/company (not a new contract building for somebody else and not a municipal water group) and - if you cite a specific clause and specification (just because that's what was done in the past in the last contract and spec) - you might be causing a lot of new inconvenience and extra expense that really not justified and not relevant to the tank you are actually going to make..

 

[Guest102023]

stanier,

Well I can't build a pressure vessel to B31.x no matter what my customer thinks.

 

[stanier]

brimstoner,

Where did I suggest you build a pressure vessel to B31x? However I have designed and built underground slug catchers to ASME B31.3 with the agreement of the owner and authority. These could arguably be pressure vessels however because of their length and diameter all parties agreed that ASME B31.3 was apprpriate.

You on the other hand are talking about a 'tank' which is an atmospheric unit NOT a pressure vessel.LOL

The point I was making was that standards should be used in their enirety. Too often inept engineers like to design to one standard and then attempt to fabricate, test or commission to another.

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King

http://waterhammer.hopout.com.au/