Flat-Bottom Heads

Profile and terminology

The FHA flat-bottom head has a flat central area, a rounded edge and a straight flange. This formed profile is different from a plain flat plate used as a closure.

GB/T 25198-2023 models: FHA

Specify the inside diameter, corner radius and straight flange so the formed shape can be identified. For the illustrated FHA profile, inside depth is the sum of the knuckle radius and straight flange length. Suitability and thickness must be checked for the actual vessel design.

What to include in your inquiry

Inside diameter; nominal thickness; minimum formed thickness; knuckle radius; straight flange length; inside depth; material grade; quantity.

Use millimetres for dimensions. Identify the exact material grade rather than only writing “steel” or “stainless steel”. You can also include edge preparation, inspection requirements, delivery needs and a drawing reference in the notes.

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Drawing and design review

These descriptions identify geometry and information needed for an inquiry. They do not establish allowable pressure, certify compliance or replace a vessel design calculation. Confirm the applicable standard, drawing and final dimensions before ordering.