I think Figure F-2 ( Permissible Details of Compression Rings ) is self explanatory ..

the width of roof area participating the compression area ( except detail i )

wh = maximum width of participating roof
= 0.3(R2 * th)**0.5 or 300 mm (12 in.) whichever is less.

If the tank subject to external pressure ( vacuum ) then look app. V

Dear HTURKAK;

Figure F.2 (shaded area) is used to calculate the Participating Compression Area.
I am looking for calculating the Cross-section Area (my resulted detail is detail i)?
Specifically, can elaborate how to calculate this Cross-section Area as referred to 5.10.5 & 5.10.6 (API 650 edition 13th).

Mohd Yaseen

The equation in 5.10.5 is the minimum required area at the roof-shell junction. The shaded area in Figure F.2 is the available area, and must be greater than the minimum required area.

It may be that 5.10.5 and F.2 are not consistent in their naming, but this is the meaning.

Geoff

Dear Geoff13;

You replied that the shaded area in Figure F.2 is the available area (Participating Compression Area as stated in F.2.2) must be greater than (or equal) the minimum required area (Cross-sectional Area as stated in F.2.2).

Ok, let us come to statement in 5.10.5.2 that given equation (P D^2/8 Fa tan θ) about the Nominal Material Thickness – Any Corrosion Allowance ONLY & Nothing mentioned about the Cross-sectional Area. Here is the question?

I guess some wording or typing mistake in my edition as its very clear in the pervious editions (see attachment).


API 650 13th;
F.2.2 Required Compression Area @ Junction shall be calculated as in F.5.1
Participating Compression Area @ Junction shall be determined by Figure F.2.
For Self-Supporting Roofs:
Compression Area shall be ≥ Cross-sectional Area calculated in 5.10.5 or 5.10.6 as applicable.

5.10.5.2 Participating Area @ Roof-to-Shell Joint shall be determined using Figure F.2 & the Nominal Material Thickness – Any Corrosion Allowance shall be ≥ P D^2/8 Fa tan θ.

Mohd Yaseen

• https://files.engineering.com/getfile.aspx?folder=8b18c234-8568-4de0-9e31-2

(5.10.5.2 The participating area at the roof-to-shell joint shall be determined using Figure F.2 and the nominal
material thickness less any corrosion allowance shall equal or exceed the following:
where

A= p*D2/(8 *Fa* tanθ )

This formula is for calculation of the minimum required compression ring cross section area. The area determined using Figure F.2 ( with net thickness = thickness - CA ) SHALL NOT BE LESS THAN THE AREA CALCULATED BY ABOVE FORMULAE !!

Dear HTURKAK;

Thanks, its clear now.

Mohd Yaseen