Why can't I use the round-hole shell with the collar diameter?

Because the cone does not reach the shell at the collar diameter — it reaches it flared. On a nozzle with a 200 collar and a 400 fictitious base in a 600 shell, the hole comes out 298 by 274, against the 206 of a 200 cylindrical branch. Marking it by the collar makes a hole too small for the cone to pass.

The same four figures as the conical tap — collar, fictitious base, length and angle — plus the pipe and the shell length. Enter the same in both parts and you have both patterns for the job, and they match because the intersection is worked out once, in one place in the code.

Where does the shell seam go?

Diametrically opposite the hole. A longitudinal weld does not run through a cut-out.

Why must the shell be much longer than the hole?

Because the hole measures the cone's diameter AT THE SHELL'S SURFACE divided by the sine of the angle, and on a tilted nozzle that grows quickly. The guard uses the fictitious base, which is deliberately generous — the cone is narrower where it meets the pipe.

Cylinder with Conical Branch Hole flat pattern

What it is

The shell with the CONICAL nozzle's hole already marked — the mate of the conical tap, and the part that closes the job. The round-hole shell will not do: a conical nozzle reaches the shell already flared, which is the whole point of it, and opens a larger hole of a different shape.

Where it is used

Vessel shells with reinforced nozzles, headers with flared take-offs, cyclone bodies, any shell that is going to receive a flared-base nozzle.

Measurements the calculation needs

D2 Diameter 2
H Height
D Diameter
D1 Diameter 1
C Branch length
ANG Angle
DV Divisions
THK Thickness

Worked example

The values the form comes pre-filled with, run through the tool itself:

Diameter 2	600 mm
Height	900 mm
Diameter	200 mm
Diameter 1	400 mm
Branch length	500 mm
Angle	90°
Divisions	32
Thickness	6 mm
The flat pattern fits a plate of	1866 × 900 mm

Frequently asked questions

Why can't I use the round-hole shell with the collar diameter?: Because the cone does not reach the shell at the collar diameter — it reaches it flared. On a nozzle with a 200 collar and a 400 fictitious base in a 600 shell, the hole comes out 298 by 274, against the 206 of a 200 cylindrical branch. Marking it by the collar makes a hole too small for the cone to pass.
What do I enter?: The same four figures as the conical tap — collar, fictitious base, length and angle — plus the pipe and the shell length. Enter the same in both parts and you have both patterns for the job, and they match because the intersection is worked out once, in one place in the code.
Where does the shell seam go?: Diametrically opposite the hole. A longitudinal weld does not run through a cut-out.
Why must the shell be much longer than the hole?: Because the hole measures the cone's diameter AT THE SHELL'S SURFACE divided by the sine of the angle, and on a tilted nozzle that grows quickly. The guard uses the fictitious base, which is deliberately generous — the cone is narrower where it meets the pipe.

Measurements the calculation needs — Cylinder with Conical Branch Hole

Calculate a Cylinder with Conical Branch Hole

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