Can someone identify this 1930s-vintage pressure vessel? 2

[mb3928]

Visiting family in Bellingham WA and found this 1930s-vintage, riveted, spherical pressure vessel repurposed as art in a new park. Apparently the site used to be a paper mill, and the sign says this unit was a relief vessel for the taller digesters to the right in this photo:

https://cob.org/wp-content/uploads/554A3950-news.jpg

Any idea why this would have been constructed as a sphere? I've seen spherical pressure vessels for LNG storage but never heard of them being used in a pulp mill, though I'm certainly no expert.

 

[JStephen]

They still make spheres now, likely for the same reasons, economics, etc.
The local sewage plant has a little sphere in it, I think chlorine storage:

https://goo.gl/maps/Tr7sfJejxpi6TMC38

 

[Christine74]

According to thin-walled pressure vessel theory, a sphere is the optimal shape for a pressure vessel in that it offers the highest ratio of contained volume to volume of steel required for the vessel construction.


-Christine

 

[dig1]

Spherical rotary pulp digesters were made and some are still in use.

 

I think transport limitations and vessel capacity are straightforward reasons we don't see more spherical vessels. One of our local refineries has a set of four dating from probably the 1970s; IIRC about 12 foot Ø.

I'm guessing spherical is trickier to fabricate relative to cylindrical, although it could have been the other way round in the 1930s. Forming tools were different back in the day, and almost certainly you could not purchase heads off the shelf like you can nowadays. As a WE I would rather fabricate a cylinder than a sphere.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[mb3928]

ironic metallurgist, that's why I was surprised & curious... the sign on site said it was a relief vessel for the large, cylindrical digesters next to it. So why fabricate it as a sphere if it's operating at the same pressure as other, larger, cylindrical vessels? I figured if anyone could answer it would be someone on this forum.

 

[chicopee]

If you can get the National Board/ASME pressure vessel numbers from nameplates affixed to these vessels, you can then get copies of the Manufacturers Data Sheets for a fee from the National Board. The sheets will list the manufacturer(s).

 

[DriveMeNuts]

Perhaps the process is under cyclic pressure service and therefore fatigue is the governing failure mode.
If the spherical vessel experiences a different rate of cycles then it will be designed differently.

Today labour makes up rouphly 50% of the cost of a large vessel made from standard carbon plate. In the 1930's labour was cheap (i.e. compensated with food tokens). When the material makes up 80% of the cost of the vessel, a lot of emphasis will be placed on optimising the design to minmise material usage.

 

[dig1]

The cylindrical batch digesters are definitely under cyclic service, typically they cycle 5-6 times a day from 150 psig to atmospheric (about 350 degrees F to whatever they cool to before the next batch) and the pressure change from operating to atmospheric is relatively rapid. If the spherical tank were actually a liquor accumulator tank it would also be under cyclic loading, but not as severe, and Christine's comment regarding volume/steel would fall in line.

 

Fatigue is in the details, not the overall shape of the vessel.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[DriveMeNuts]

When conducting the detailed design, the calculations guide the engineer into deciding if a cylindrical vessel is best with an end consisting of either Flat, Tori, Ellips or Hemispherical head. The Engineer doesn't decide this by throwing dice.
The same detailed design also influences the overall shape of the vessel (i.e. Sphere, cylinder, cube).
Process or transport requirements may also influence geometry.
A culture of "because this is how we have always done it" also influences a vessels geometry.
As well as Volume/Steel optimisation.

If the spherical vessel has more cycles than the cylindrical vessels, then if it was a cylindrical vessel (like the others) it would need to have a thicker shell. If going thicker is not possible then options are to make it a smaller diameter cylindrical vessel, or make it a sphere.

I wonder if Volume/Steel optimisation was the primary driver for design and the cylindrical vessels were just too voluminous to fabricate as spheres.

 

If the spherical vessel has more cycles than the cylindrical vessels, then if it was a cylindrical vessel (like the others) it would need to have a thicker shell.

That would be the most costly way to design against fatigue.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[DriveMeNuts]

Agreed, and that could be why it is spherical.
It's all speculation without additional information.

 

[Christine74]

https://www.mcdermott.com/getmedia/...82fde83149/hortonsphere-2020-digital.pdf.aspx

"The most common use for the Hortonsphere vessel is ambient temperature liquid storage. This method uses high stress advantages of the spherical shape to minimize wall thickness."

https://www.transtechenergy.com/lpg...tanks-vs.-lpg-storage-spheres-/-hortonspheres

"Because Hortonspheres generally hold more volume per vessel than cylindrical storage bullets, less overall piping will be needed for the interconnection of vessels on site, which can reduce overall project costs.

Additionally, mathematically speaking, the spherical shape delivers the smallest possible surface area per unit of volume than any other shape. Because of this, the overall coating/painting cost per unit of volume is also lower for spherical vessels than for cylindrical tanks.

Finally, the spherical shape also offers the most uniform stress resistance, which allows for a thinner wall. Thus materials cost per unit of volume is also lower for spherical vessels."


-Christine

 

Materials are rarely the most significant cost factor in purchasing a pressure vessel today.

I see the obvious advantages, but there is also:

- EPC overhead & overcharging (by far the single biggest cost)
- Fabrication difficulty (spherical cannot be easier, and few shops are equipped to make them)
- Transport

How pipework is significantly reduced is unclear; perhaps that was marketing in action?

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[JStephen]

I will point out that in the days when this was made, every little town across the country had one of those tin-woodsman type water tanks, and the bottoms of those tanks are half-spheres. So there weren't many people set up t0 make spheres, but the ones that were, made a bunch of spherical shapes along the way.

 

JStephen,

What I was saying earlier ... different times, different tools.

For starters this tank is riveted. Whereas mechanizing the welding (or even manual welding) would be relatively difficult, riveting doesn't care about position.

Second, the vessel being perfectly symmetrical, all panels would be formed with a single tool, to the same profile. Forming and every other operation would have been done in one shop, quite unlike today where plate profiles are cut by one party, plates rolled by another, heads sourced from another, and finally assembled by the final fabricator. Supply chain has gotten a lot more complicated!

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[Ericapi]

Where in Bellingham are these pressure vessels? Next time I am on the west coast I would like to see these in person.

Eric
API 510 & 653

 

[mb3928]

Waypoint Park in Bellingham. There are a number of interesting remnants of the old paper mill that are on display there. (And a nice beer garden!)

 

google satellite view (2021) shows only the sphere, with a lot of the land being vacant dirt.
Street view (2013) shows all the tanks, but they are not located together.
Looks as planners wanted to keep the sphere, for which they should be applauded. Industrial history is history too.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."