Minus Side of a Formed Head

[Fizza453]

Why, in ASME Code like UHT-33(Section VIII-1), convex side of a formed head is called minus side?
One possible answer, I think, since convex side is weaker in bearing pressure as compared to concave side so convex side is called as minus side and concave side is called as positive side.
Thanks in advance for feedback.



Nasir
Welding Engineer
DESCON ENGINEERING LIMITED
PAKISTAN

 

[bernoullies123]

or the 'plus side' / concave in the code.

I would assume that:
(+) signifies tension i.e. positive internal pressure on the concave
(-) signifies compression i.e. negative internal pressure (positive external pressure) on the convex side

Anyway since it is in brackets (intermittently), I think it is an adder for clarification and not quite constitutes an issue in the code per this forum.