How to Support very long Pressure Vessel (Bullets) on two saddles? 6

[BZ29]

Hi.
I have come across design of some horizontal pressure vessels (ASME Sec VIII Div.1/2) that are extremely long.
Eg
The longest among them is:
Diameter: 8m
Length T-T: 62m
Internal pressure: 38 bar
External: Full Vacuum
Specific Gravity: 0.51

I am unable to handle the saddle stresses. Can anyone guide how to manage this on two saddles?

Also there are others with same problem even with length in range of 37m.

 

[0707]

Ask a specialist to make a stress analysis.

 

[KevinNZ]

Assuming the gross bending mid span is OK. You should be able to get the local stresses at the saddles under control with pads and/or a thicker vessel wall at the supports. A ring beam saddle might work.

This can be analyzed with FEA tools (and knowledge of the code rules for FEA design)

 

[BZ29]

Yes, First i balanced the midspan stresses with the shear stresses on sides of saddles, by adjusting the saddle locations. Then i added saddle stiffener rings to reduce some stresses, and finally had to increase the shell thickness to some extent to get them under allowable values

 

[Krausen]

Did you consider a third saddle? May be the cheapest & simplest solution

 

[r6155]

This is a very heavy storage tank.
Two supports are fine and there is not need to increase the thickness of the shell on the saddles. I did a quick check.
You must take into account the stresses during PWHT, lifting and transportation.

Regards

 

[MJCronin]

This will be a record setting, monster horizontal pressure vessel on two supports.... !!!!

Do you really want to do this, Najeeb ?

Explain why this volume must be contained a single tank and why multiple tanks cannot be considered ...

... and NO I will not accept "because my boss told me so" ... or "because the client wants it"

For my calculation of your horizontal monster, I am getting about 3133 cubic meters of capacity (~828,000 gallons ?) when most ASME bullets currently in LNG use have about 120,00-150,000 gallon capacities.

Can anyone fabricate, test and transport your goliath to your part of the world ?

At 8m diameter, (26 ft) your monster pressure vessel CANNOT be transported in most of the uSA and all of EUROPE..

Have you even bothered to talk with a fabricator yet ?

... or are we all just wasting time and you are designing a make-believe vessel that cannot possibly be built !!

Explain !!!

MJCronin
Sr. Process Engineer

 

[MJCronin]

Your proposed monster would be CONSIDERABLY BIGGER than this FOUR SADDLE Record setter ...

https://www.thefabricator.com/thefa...nd-how-a-175-ft-long-pressure-vessel-was-made

MJCronin
Sr. Process Engineer

 

[r6155]

See

https://www.foremost.ca/foremost-energy-equipment/pressure-vessel-manufacturers/

Pressure Vessels – Foremost

Our experienced designers, engineers, and fabricators have designed and manufactured some of the largest and most complex heavy wall vessels in the industry. Our capabilities include up to 40’ diameter, 300’ length, 8” thick, and up to 800,000 lbs. We can custom design and manufacture vessels for any process.  Options include Heavy Wall Vessel design, Surge Vessels, Slug Catcher Vessels, and Misc. Storage Bullet configuration.

Regards

 

[dik]

Supports at about 1/5 points for minimal stress. For safety and cost reasons, you should consider a third support.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[r6155]

Look at this.

 

[MJCronin]

Well,.... it certainly looks like BZ29 (Najeeb) has no more interest in this topic and has probably gone back to his old job

I imagine that, between times, he will keep on playing around with his purloined copy of COMPRESS.

Rumor is that he will be soon modelling an ASME VIII distillation column taller than the Burj Khalifa

He will probably be coming back to eng-tips to ask questions about the large number (3000+) anchor bolts required and how he can possibly install them all onto a 60 m diameter skirt he has selected...

Hopefully, BZ29 won't be wasting anymore of our time in the future

MJCronin
Sr. Process Engineer

 

[ilovechickens]

I do not have much experience with vessels but I thought once you put a third saddle in it became statically indeterminant and was not recommended?

 

[r6155]

@ ilovechickens
Yes.
It is very difficult to ensure the stresses in each saddle during service.

Regards

 

[BZ29]

Hi. Thank you everyone for guidance. and specially "MJCronin".

For anyone suggesting third saddle, what i have read and understood, that is not recommended. And in my case also, client sketch had only two saddles.

Yes MJCronin, we are fabricator ourselves and it was at cost inquiry stage yet, and not for detailed engineering.

You are right, this was may be among some of the worlds largest pressure vessels. Location is KSA & it was from ARAMCO having tons of experienced engineers from all of the world. so we cannot just say that the sizing was totally irrational. Hopefully transport is manageable, or otherwise can be split for final assembly at site.

 

[DriveMeNuts]

I wouldn't recommend a 3rd saddle on a vessel as stiff as this. Temporary transport cradles for hydrotest and transport, yes.
Air separation units 75 metres long and 6 metres in diameter are transported from China to KSA in two halves. You have much difficulty transporting across land anywhere with heights more than 6 meters.

 

[MJCronin]

DriveMeNuts,

BZ29 states:

"Yes MJCronin, we are fabricator ourselves and it was at cost inquiry stage yet, and not for detailed engineering"

Translation: ... We are playing around here and have NO INTENTION of building a vessel this big

Yes sir, it would be moronic to build a vessel this big....

Therefore, BZ29 and his ilk are building castles in the sky and your statement on a third saddle support does not apply

MJCronin
Sr. Process Engineer

 

[RVAmeche]

No need to be so abrasive all the time MJC...

 

[r6155]

Think in inspection and testing.
PWHT in one piece in the manufacturer.
Transportation is not a problem.

Regards

 

[MJCronin]

Sorry Ameche, .. I place no limits or restrictions on your tone, speech or use of words...

... and you shall place none on mine ...

I use no vulgarities, racial slurs or other things specifically prohibited on these fora

IMHO, we are being gamed here and wasting our time on someone who, by concealment or other subterfuge is having fun ..

I understand that you feel differently... perhaps as some kind of a speech traffic cop.

Do you truly believe that such an absurd vessel was actually going to be built ?

MJCronin
Sr. Process Engineer