Dead load on storage tank roof 1

[mjpetrag]

I am trying to find guidance on roof access for above ground storage tanks. Some of our tanks have instrumentation/hatches that need to be accessed for routine inspections, and no platform/grating on the top of the tank roof that is supported externally. There is a safety concern around the storage tank roof not being able to hold the weight of a person and their equipment, so we have adopted taking thickness readings and applying test weights prior to accessing the roof. Are there any API RPs or other standards that address this specific issue?

-Mike

 

[IRstuff]

Shouldn't you find out what the designer designed it for?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[r13]

Is this a floating roof? There should be record drawing around. If nothing, I'll try access using man-lift, or crane, with proper PPE, lifeline and tiedown as required by OSHA. A crew of two persons should be worked together, while one walk on the roof to take reading.

 

[mjpetrag]

The issue is even though we would know what the roof was originally rated for, the concern is uneven thickness over time as corrosion removes metal. Some of these tanks have been in service for 50+ years.

These tanks are a mix of Internal Floating Roof and fixed roof storage tanks.

-Mike

 

[JStephen]

Practices vary.
If you are periodically inspecting tanks per API-653, you should have a handle on the condition of those tank roofs.
You can add walkways, fall-protection points, etc. You can relocate hatches or instrumentation at the edge of the roof and access them from platforms mounted on the shell.

 

[HTURKAK]

You did not define the fixed roof whether supported or self supporting cone roof. The applicable code is API 653 which Mr.JSTEPHEN pointed out.

The new proposed platform/grating on the top of the tank roof may be supported to roof rafters or alternatively platforms may be mounted on the shell .

If you provide roof plan(s) and corrosion survey assessment, together with proposed platforms , you may get better responds..

 

[LittleInch]

Detect where the supporting beams are and paint them on the roof then only walk on those bits.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[mjpetrag]

The tanks are a mix of self-supported domed roofs and supporting beams. The supporting beam walkway painting is a pretty elegant solution without capital cost, which we could implement on the roofs that have those supports.

-Mike

 

[MJCronin]

IMHO....

A Modest Proposal...

There comes a time, after 40 or 50 or even 60 years.... when a storage tank has served it's useful life, the owners have made all their money, and it must be dismantled and replaced.

...despite what the MBAs/accountants will say...

Wouldn't it be great if petroleum storage tanks were treated as if they were as important to public safety as ..... say, highway bridges ???

Then. like our nation's bridges, we could develop an independent inspection criteria, give the tank a score and know how much useful life is left !!!

The scoring of the tank, would of course include an evaluation of the roof !!!

.... and the public who live near these storage tanks would have access to their evaluation scores..

What do you think ??

MJC

MJCronin
Sr. Process Engineer

 

[LittleInch]

MJC

Far too sensible a suggestion. Wash your mouth out with soap and flagellate yourself for such a suggestion about how to waste money on something which still has a value $$$

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[MJCronin]

LittleInch, et al ......

It is comforting to note that, as the tanks around the world will approach 100. 125 and 150 years old, that Our grandchildren will be attempting new ways to evaluate the ultimate strength of the last 1 mm of Ferrous Oxide !!!

https://www.eng-tips.com/viewthread.cfm?qid=473593

MJCronin
Sr. Process Engineer

 

[IFRs]

API 653 has some guidance on roof condition and inspection

 

[LittleInch]

Well we all travel from time to time on railway / railroad systems built 150 or more years ago.

So far most of them are still standing.

Though a major bridge in london at 140 years old has been closed to everyone whilst they argue about who is going to pay to replace / repair it.

https://www.bridgeweb.com/Growing-cracks-force-full-closure-of-Hammersmith-Bridge/7352

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.