Tube Holes in Tubesheet : Point to ne noted while designing heat exchanger

Tube hole finish affects the mechanical strength and leak tightness of an expanded tube-to-tubesheet joint. In general:
(1) A rough tube hole provides more mechanical strength than a smooth tube hole. This is influenced by a complex relationship of modulus of elasticity, yield strength and hardness of the materials being used.
(2) A smooth tube hole does not provide the mechanical strength that a rough tube hole does, but it can provide a pressure tight joint at a lower level of wall reduction.

(3) Very light wall tubes require a smoother tube hole finish than heavier wall tubes.

(4) Significant longitudinal scratches can provide leak paths through an expanded tube-to-tubesheet joint and should therefore be removed.

Hence its important to show roughness during design, and ensure it durign fabrication.

Good day!