Have you ever seen a 3:1 ellipsoidal head used on a vessel? 4

[Rubje]

I only seen the standard 2:1 ellipsoidal head used on vessels and I'm curious if anyone seen any other ratio used before.

If so, what was the reason why that particular ratio was used and not 2:1?

 

[Christine74]

I'm curious too. I've reviewed drawings and data reports for hundreds and hundreds of pieces of new and existing equipment and never once have I seen an ellipsoidal head that was anything other than 2:1 (when the corrosion allowance is excluded that ratio changes slightly but I've never seen any ellipsoidal head that wasn't nominally 2:1).


-Christine

 

[david339933]

I have never seen one, but App. 1-4 has K values for many D/2h values.

 

[MJCronin]

You are not talking about an 80:10 head, commonly specified in the PHARMA industry .... are you ?

https://www.paulmueller.com/tank-co...:10 tank heads have,2:1 elliptical tank head.

Please give references to your 3:1 head .... where is your detailed description or are we chasing around a typo ?

MJCronin
Sr. Process Engineer

 

[DriveMeNuts]

2:1 ellipse has a similar thickness to the cylinder. That is convenient.
A 2:1 ellipse is just a Tori head with 90% crown radius and 17% knuckle radius, compared to cylinder diameter.
You can order a Tori head with custom radii.

 

[saplanti]

I guess you can ask anything that can be manufactured, and you need to pay the price. For uncommon dimensions you/manufacturer needs special equipment for the forming process. This will increase the cost a lot.
The common ellipsoidal head is 2:1, and almost all the elliptical head manufacturers have the forming equipment ready.
Your specification may be suitable for torispherical head with a proper crown and knuckle radius selected. However the thickness of if it may be higher than the 2:1 elliptical head.

I suggest talk to the specification provider for the possible typo.

 

[BJI]

As saplanti stated, I have also found that most manufacturers can produce true ellipsoidal profiles, but always 2:1 in my experience.

An interesting discussion on the differences between the 2:1 SE and 90-17 TS in the below paper.

https://doi.org/10.1115/PVP2017-65858

 

[Rubje]

Thanks everyone for the responses!

MJCronin, my reference is ASME VIII Div. 1. They give different k factors for ellipsoidal heads. A 2:1 has a k factor of 1.

Also, why does Pharma use that 80-10 head?

 

[r6155]

It is common in the food industry, in cargo tanks due to its low height.
I have used it a long time ago.

Regards

 

[EngineerEPC]

please refer below snap from theory and design of pressure vessels by John Harvey.

 

[Rubje]

@Ariba01123

Thank you for sharing that reference.

Do you know the difference between sigma 1 and sigma 2 is in the photo?

Interesting that above 1.42 for a/b, the hoop stress becomes compressive near the knuckle and crown region (and above 2 the compressive is greater than the tensile stresses).

 

[EngineerEPC]

Hello Please refer below snap from theory and design of pressure vessels by John Harvey for sigma 1 and sigma 2.