API 650 Tank Rebuild - Type and quantity of weld inspections 2

[Lorenzo Loreto]

I'm working on the decommissioning and rebuild of a sulphuric acid tank based on API 650.

I have some questions about the weld inspecions as we've had some problems with it in the past.

How much (percentage) of the welds that is needed to be ispected by method?

We'll apply:

- Liquid Penetration
- Ultrasound
- Vacuum box (bottom)

 

[Geoff13]

API 650 is for the construction of new tanks and thus is not applicable

API 653 Section 10 addresses dismantling and reconstruction of an existing tank. Section 12 addresses the required NDE.

 

[JStephen]

Note that an owner can specify more stringent requirements for materials, welding, or inspection if required by the particular services; you're not limited to the standard requirements.

 

[MJCronin]

Lets make sure that we have a shared understanding of the english language, shall we ?

I have worked on several industrial acid tank projects and have specific questions

1) Was the old tank containing "Concentrated Sulfuric acid" ? - Because these are typically 100% replaced
What are the details of the tank/contents ? - tank age,material size, roof type, venting, anchor bolts and coatings

2) If the tank was intended to carry DILUTED H2SO4 - It might be rebuilt - Commonly, such tanks might have a thinned
shell section in mid span of the shell

3) What is your desired code of construction/repair? What is the Corrosion Allowance you desire ..
(or are you lost and just shopping around for an answer that you like)

4) I said this in 1978 and will say it again "THE AiCHE should grow some testicles and develop tank codes for
the common acids sold in the marketplace (e.g. H2SO4, HCL etc etc)

5) Many many eng-tips threads available on concentrated H2SO4 tanks, pumps, piping and corrosion available to you

Why won't you tell us more ?

Is this the first acid tank replacement/renovation you have worked on ?

MJCronin
Sr. Process Engineer

 

[JStephen]

There is this standard. I'm not familiar with the current issue, so can't comment on the usefulness:

https://webstore.ansi.org/standards/nace/nacestandardsp02942006

 

[Lorenzo Loreto]

Lets make sure that we have a shared understanding of the english language, shall we ?

I have worked on several industrial acid tank projects and have specific questions

1) Was the old tank containing "Concentrated Sulfuric acid" ? - Because these are typically 100% replaced
What are the details of the tank/contents ? - tank age,material size, roof type, venting, anchor bolts and coatings

2) If the tank was intended to carry DILUTED H2SO4 - It might be rebuilt - Commonly, such tanks might have a thinned
shell section in mid span of the shell

3) What is your desired code of construction/repair? What is the Corrosion Allowance you desire ..
(or are you lost and just shopping around for an answer that you like)

4) I said this in 1978 and will say it again "THE AiCHE should grow some testicles and develop tank codes for
the common acids sold in the marketplace (e.g. H2SO4, HCL etc etc)

5) Many many eng-tips threads available on concentrated H2SO4 tanks, pumps, piping and corrosion available to you

Why won't you tell us more ?

Is this the first acid tank replacement/renovation you have worked on ?

MJCronin
Sr. Process Engineer

I misspoke; English is not my first language. The tank will be fully replaced.

It has always operated, and will continue to operate after replacement, with 98% sulfuric acid.

We have no requirements regarding corrosion issues or other technical demands. We do not have an project engineering departament. The tank will be replaced by an identical model to the previous one.

 

[LittleInch]

Section 8 of API 650 gives you the minimum weld test requirements together with figure 8.1.

These are minimum though. For such a tank contents I think you should consider an increase in amount or percent compared to this minimum.

Who exactly is going to write your tank construction specification and advise on things like this? I strongly suggest you get some local engineering consultants involved who have good experience of such tanks.