Get a tailored quotation for pressure vessel heads, stainless spheres, or firepit bowls. Our engineers review your drawings, materials, standards, and quantities to provide accurate pricing and delivery options.
Get a tailored quotation for pressure vessel heads, stainless spheres, or firepit bowls. Our engineers review your drawings, materials, standards, and quantities to provide accurate pricing and delivery options.
A few years ago, a buyer emailed me a drawing and one line of panic:
“Can you quote this head cheaper if I switch the shape?”
I stared at the sketch, sipped my coffee, and thought, Yep. This is the question. Because “elliptical” and “torispherical” heads look kind of similar to normal humans… until you start paying for steel, press time, weld prep, and code thickness.
So let’s talk like real people. No textbook voice. No fluff. Just what changes, what it costs you, and how I decide which one I’d pick.
When people say elliptical head in pressure vessels, they usually mean a 2:1 ellipsoidal head.
That “2:1” matters. It means the ellipse shape follows a standard proportion that codes and shops understand. It’s a smooth, continuous curve from the crown down to the weld line.
A torispherical head (often called ASME flanged & dished, or “F&D”) uses two radii:
Two families. Two personalities.
One flows like a smooth hill. The other looks like a dinner plate with a rolled lip.
Smooth curve the whole way. No sudden “corner-ish” area near the edge.
If you run your finger along the profile, it just… keeps going.
Big gentle dish in the middle, then it tightens up near the edge in the knuckle area.
That knuckle behaves like the “problem child” when pressure ramps up.
And yes, engineers obsess over that knuckle. For good reason.
Pressure doesn’t push evenly in the way your gut assumes.
With an elliptical head, the stress spreads out more smoothly over the surface. That usually lets you hit a given pressure rating with less thickness compared to a torispherical head of the same diameter and material.
With a torispherical head, stress concentrates more near the knuckle and the transition area. So to satisfy code rules, you often need more thickness (or more careful design details).
Does that always happen? Not always. But it happens enough that I treat it like the default until proven otherwise.
And steel thickness changes everything. Weight. cost. forming difficulty. shipping. even how annoyed your rigging crew feels on install day.
Elliptical heads usually come deeper (taller) than torispherical heads for the same diameter.
That sounds boring until you try to fit the vessel into a tight plant space.
Got a skid? A container limit? A platform with pipes in the way? Suddenly head depth turns into a real-life problem, not a drawing detail.
If you need a shallower overall vessel, torispherical often wins the layout argument.
If you need better pressure efficiency, elliptical often wins the thickness argument.
See the trade? Always a trade.
Let me be blunt.
If you tell a shop: “Give me the most economical standard head,” you’ll hear torispherical a lot.
Why?
But here’s the twist.
If your torispherical design forces a much thicker plate to meet code, you can burn those savings fast. Real fast.
So torispherical can cost less. It doesn’t automatically cost less.
I’ve watched people “save money” by switching shapes… and then lose it again on thickness, weight, and handling.
Ouch.
Both head types weld to the shell. No shock there.
But torispherical heads sometimes bring more fuss around the edge geometry and knuckle transition, especially if someone asks for tight tolerances, odd materials, or thicker plate.
Elliptical heads, with their smooth profile, can feel more predictable during fit-up in many standard builds.
Not always. Shops vary. Tooling varies. Operator skill varies.
Still, if I had to bet my weekend on “which one gives fewer surprises,” I often lean elliptical when pressure and thickness climb.
Here’s a “coffee talk” rule that rarely steers me wrong:
If your vessel lives in a high-pressure world, you and I both know what happens. Every extra millimeter of thickness becomes a tax on your budget.
And your crane.
And your schedule.
| What you care about | Elliptical (2:1) | Torispherical (F&D) |
|---|---|---|
| Stress distribution | Smoother | More concentrated near knuckle |
| Typical required thickness (same dia/pressure) | Often thinner | Often thicker |
| Head depth (height) | Deeper | Shallower |
| Common availability | Very common | Extremely common |
| Cost at low/moderate pressure | Can cost a bit more | Often cheaper |
| Cost at higher pressure | Can save money via thinner plate | Can get expensive via thickness |
| Layout constraints | Needs more length | Saves length |
No magic. Just trade-offs.
If a friend asked me over coffee, “Which one should I pick?” I’d ask one question first:
How much pressure are you really dealing with?
Because I pick elliptical when:
Elliptical feels like the “I don’t want surprises later” option in a lot of serious service conditions.
I pick torispherical when:
Sometimes the best engineering choice looks boring.
Boring can be beautiful when the schedule looks ugly.
Want to get a fast, accurate quote and not play email ping-pong for three days? Send these up front:
And please—please—attach the drawing. Even a rough one.
I can’t “guess” your nozzle loads from vibes.
Neither. That’s the honest answer.
Elliptical wins when pressure efficiency and smoother stress flow matter. Torispherical wins when space, standard tooling, and cost pressure matter.
The only bad choice? Picking the shape because someone told you “it’s always cheaper” without checking thickness and layout.
If you want, paste your diameter + design pressure + material, and I’ll tell you which one I’d lean toward—and why. No salesman talk. Just shop-floor logic.
