Reinforcing Pad: flat pattern

The pad welded round a nozzle on a shell or a pipe: rolled to the shell, with the hole for the nozzle and a tell-tale hole, whole or in two halves. The pad welded round a nozzle on a shell or a pipe to reinforce the opening: the plate rolled to the shell, with the hole for the nozzle and a tell-tale hole, whole or in two halves.

Configurations

• Round a radial nozzle. The pad is rolled to the shell round a nozzle square to it, on the axis of the shell. Under Pattern it is one plate, slid over the nozzle before it is welded in, or two halves, fitted round a nozzle already welded in.

A worked example

The round a radial nozzle configuration with the sizes SheetMorph opens with, in mm. One plate, the pad, with the hole for the nozzle: 1 part, 0 seams.

How it is developed

Development of a rolled plate (unrolled cylinder). This is a triangulated approximation: the curved surface is divided into small flat triangles, each laid out at its true size. The finer the division, the closer the pattern is to the surface; SheetMorph states the deviation it found.

• The pad is part of a cylinder, so it unrolls flat. Laid flat it is as long along the shell as its diameter and wider round the shell, by the arc it spans; its hole is the same, so neither is a circle on the plate.
• The hole is cut before rolling, and the pad slid over the nozzle before the nozzle is welded to the shell.
• Roll the plate to the shell with the long way of the plate round the shell.
• A tell-tale hole of 6 is in each piece, to test the welds with air and to vent the space under the pad.

Checked before it can be exported

Every pattern SheetMorph draws is checked against the 3D part it comes from. For this example:

• Surface connectivity (passed): 62 facets form one plate, the hole marked on it: every edge inside a part joins exactly two facets, every open edge one (V - E + F = 1).
• Developed edges equal true 3D lengths (passed): 186 facet edges compared between the 3D surface and the flat pattern (max deviation 1.88e-12).
• Shared edges and seam closure (passed): 61 internal edges are shared vertex-for-vertex between adjacent facets; 0 seam(s) have mating edges of equal true length (max deviation 0).
• Developed facets consistently oriented (passed): All developed facets are counter-clockwise (outside face up); none is mirrored or degenerate.
• Developed area equals surface area (passed): Facet area in 3D and in the flat pattern agree (difference 4.66e-10).
• Cut outlines closed and non-overlapping (passed): 1 closed outline(s); no outline crosses itself or another outline.
• HOLE-N lies within its plate (passed): 48 points of the hole compared with the edges of the plate; its developed area is 70681.4761.
• HOLE-T1 lies within its plate (passed): 16 points of the hole compared with the edges of the plate; its developed area is 28.2774.

Assumptions

• The pattern is developed on the mid-thickness surface; inside or outside sizes are converted to it by the thickness.
• Curves are chains of chords between division points.
• No seam, lap, weld-preparation or pressing allowance is added.

Limits of this module

• The nozzle is radial and on the axis of the shell; a pad round an offset (hillside) or inclined nozzle is not modelled.
• The pad is round seen along the nozzle and no wider than nine tenths of the shell; a pad wrapped further round, or a full sleeve, is not modelled.
• The tell-tale hole is drawn plain: tapping it is left to the drawing.
• Each half of a split pad is laid out in one strip from the hole to the edge, its lines across being chords of the shell: laid flat it is within a few tenths of a millimetre of the shell unrolled on usual sizes, a little short round the shell. A whole pad is closer.
• The weld is not modelled: the hole is the size of the nozzle and the pad meets the shell on its inside.
• Curves are chains of straight chords between division points.
• No seam, lap, weld-preparation or pressing allowance is added, and plates are not nested onto stock sheets.

Conventions

Coordinate system. The part stands on the Z axis with End A at Z = 0. Angles round the axis are measured from +X toward +Y, counter-clockwise seen from +Z.

Divisions and thickness. A circle is divided into 4N equal chords. Sizes are inside, mid-thickness or outside sizes; the pattern is developed on the mid-thickness surface and the views show the sizes as entered.

Shell. The shell stands on the Z axis and is shown, not developed. Its diameter is the one the pad sits on, the outside of the shell, which is the inside of the pad: give the sizes as inside sizes, and the pad is rolled on its mid-thickness.

Nozzle and pad. The nozzle is radial, its axis along +X, square to the shell axis and crossing it. The hole in the pad is the outside diameter of the nozzle, and the pad is round, both seen along the nozzle; the pad is centred on the nozzle, its lowest point at Z = 0.

Lying flat. Laid flat, the pad and its hole are as long along the shell as their diameters and wider round it: each takes up the arc of the angle it spans round the shell. A whole pad is laid with the shell axis upright; a half lies on its straight edge, the line along the shell where it meets the other half.

Halves and tell-tale holes. In two halves the pad is cut on the line along the shell through the axis of the nozzle, above and below the hole. Seen from outside, looking along the nozzle at the shell, +Y is on the right: the right half, on that side, comes first. A tell-tale hole is drilled in each piece midway between the nozzle and the edge of the pad, on the line round the shell through the nozzle, to test the weld and let gas out.

Change the sizes to your own in SheetMorph, check the drawing, add seam and flange allowances, and export DXF, PDF, SVG, CSV or G-code. Check every pattern against your own standards before cutting.

Other vessels

• Shell with Nozzles: A cylindrical shell unrolled to a rectangle, with the holes for up to four radial nozzles marked in their developed shape.
• Tank Shell: The shell of a storage tank or silo in courses and plates from stock, the vertical seams staggered, with a nozzle or manway marked on its plate.
• Silo: A silo, bin or hopper as one job: the body, the cone bottom from its wall angle, the spout, a support skirt and a cone roof, with what it holds.
• Sphere: A sphere made of plates: gores from pole to pole, or zones round it, with a round cap at each pole.
• Dished Head: A vessel head in petals round a crown plate: torispherical, hemispherical, semi-elliptical (2:1), or a cone with a knuckle.