1-ATM Flat Disc Viewport Thru-hull Calculator   

Illustrative Design - Not for Fabrication
This calculator is provided for informational and illustrative purposes only.   It does not constitute an engineered design or approval for fabrication or operation.   Final designs must be evaluated by a qualified professional engineer and comply with applicable ABS and/or ASME PVHO requirements.


This calculator sizes the STEEL thru-hull (flange and rim/weld) that a flat disc acrylic viewport bears against -- this does not provide a rating for the acrylic window itself, which comes from the ASME PVHO-1 empirical thickness-to-diameter chart and is outside the scope of this tool.

Additionally, it does not calculate or consider any additional reinforcement required for the hull opening.   See ABS "Part 4 - Chapter 4; ABS Rules for Building and Classing Steel Vessels" for details pertaining to openings and reinforcement.


Design Depth:   feet
Pressure per Foot:   psi/ft
Window Outside Diameter (Do):   inches
Unsupported / Seat ID Diameter (Di):   inches
Seat Material Yield Strength:   psi
Allowable Stress Factor:   (fraction of yield)
Weld Allowable Shear Stress:   psi

Design Pressure:   psi
Total Load on Seat:   lb
Bearing Width:   inches
Bearing Area:   in²
Bearing (Contact) Stress:   psi
Required Flange Thickness (distributed load):   inches
Required Flange Thickness (conservative, edge-load):   inches
Required Weld Leg Size (strength only):   inches

Notes:

• Use the distributed flange thickness if you're comfortable modeling the bearing load as spread across the full seat width; use the conservative value if you want the fully cautious case (load assumed concentrated at the inner/free edge).

• The calculated weld leg size is almost always far smaller than code-minimum fillet size for the base metal thickness involved (per AWS D1.1 or similar) -- code minimum will govern, not this number.

• The rim (vertical leg) thickness is not calculated by pressure load the way the flange is -- it should generally match or exceed hull plate thickness so it can actually take a proper weld and behave as a rigid anchor for the flange, per fabrication practice rather than a stress formula.