Considerations for creating new manway in Storage tank manufactured in 1958

[Raza Rauf]

Hello Reader,

I am looking for criteria/factors to be considered while creating new manway in a storage tank of acid. The tank is designed on API 650 and manufactured in 1958. The old man way is not safe with respect to size of opening and is at the top of tank. I am thinking to create new manway from the shell bottom of tank.

Please guide in this matter.

Thank you!

 

[IFRs]

Assuming you are not putting a manway in the actual bottom of the tank, use the appropriate sections of section 5.7 for shell manways, review thermal stress relief and toughness of the insert plate / repad / manway components. When in doubt consult with a tank expert or experienced tank contractor.

 

[HTURKAK]

The tank is designed on API 650 and manufactured in 1958. The old man way is not safe with respect to size of opening and is at the top of tank. I am thinking to create new manway from the bottom of tank.

I want to understand shell manhole rather then bottom of tank . The tank constructed in 1958 meaning 62 years old.
Did you check the corrosion? what about the hydrogen grooving ?.

Even at moderate conditions ,( moderate ambient temperature, high acid percentage...) the CS tank could be perforated.

If you provide more info. (tank dimensions, material, internal and external corrosion protection..) ,You may get more valuable comments.

 

[JStephen]

If the tank is a welded tank in good condition, it should be no problem.
Many acid tanks have specific gravity higher than 1, so design needs to allow for that, also for any corrosion allowance.

 

[MJCronin]

1958 ?....... Hmmmmmm ...???!!!!

Is this an all welded or a rivetted tank ?....... You kinda leave out many important details ...

Acid Storage ?.... What kind ?.... Concentrated Sulfuric Acid or lemonaid ???

Can you post pictures ???

MJCronin
Sr. Process Engineer

 

[Dhurjati Sen]

It is replacing a portion of the shell which contains the man-way. Follow the PWHT as mentioned in API 650

DHURJATI SEN
Kolkata, India

 

[Raza Rauf]

Apologies for not sharing complete details in post. Please find the missing details below:

Service: Concentrated Nitric Acid
Shell Material: Stainless Steel
Tank Type: Welded (5 layers of plates, bottom 2 layers 5mm thick, middle one 4mm, and top 2 3mm thick)
Dimensions: 8000mm height and 8920mm diameter of tank
Condition of Tank: Not sure from inside as we'll be inspecting tank after 15 years after giving provision of proper manway at shell.

Pictures of the tank will be shared soon.

 

[JStephen]

API-650 didn't include stainless tanks in 1958, I'm pretty sure, and doesn't include 3 mm plate thicknesses, either. So based on that, I would say it is not an API 650 tank.
I assume "layers" is intended to be "courses", that the lower shell is 5mm thick, second course is 5 mm, third course is 4mm, etc.
That said, I assume a new manway could still be added in the shell if desired. You'd need to confirm appropriate materials, weld procedures, and extent of cleaning, etc.

 

[MJCronin]

Generally speaking, SS is a good choice for a wide range of nitric acids ... 1958 was along time ago ...

What is the concentration of your acid ?

Above 95% concentration there could be some problems ....

https://www.bssa.org.uk/topics.php?article=31

https://www.rolledalloys.com/technical-resources/environments/nitric-acid/

The new "all stainless manway" will be massively expensive and may not be a good investment on a 60 year old tank.

Give some thought to replacement of the entire tank ..... You got 60 years use out of it... Pretty damn good !!!

I would, as a minimum, get a few quotes for a brand-new replacement tank and compare it with the cost of a new manway alone...

Let us know what your final soultion is....

MJCronin
Sr. Process Engineer

 

[Raza Rauf]

MJCronin,concentration is below 95%. Moreover,the party will manufacture manway by its own and new tank is not possible for them in current situation. However, the thickness of tank is satisfactory in comparison to design.

I need guidelines regarding the possibility of new manyway provision in shell and if yes then how to design new manway.