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API 653 minimum thickness vs API 650 design thickness

API 653 minimum thickness vs API 650 design thickness

API 653 minimum thickness vs API 650 design thickness

(OP)
Why does API 653 provide a higher allowable stress than API 650? The equations are equivalent except for E which is = 1.0 for butt joints.

The tank i am inspecting was constructed to 650 edition 9 appendix F.
It was NOT constructed to Appendix A.
It is 60 ft dia 32 ft tall (4 rings).
t = 0.216 for API 653 and
t = 0.232 for API 650.
The design specific gravity is = 1.5.
A-36 material
Ambient Pressure and Temperature

RE: API 653 minimum thickness vs API 650 design thickness

The minimum thickness per API 650 would be 0.25 in per Section 3.6.1

That being said, they do have larger allowable stresses for A36 in API 653. I think the reason being service history they feel they can cut into the margin?


Anyway, I put an API 650 calculator online and was looking for feedback. I placed it at
http://www.novanumeric.com/samples.php?CalcName=APITanks

Any constructive criticism/feature requests would be useful.

Regards,
Jeff Brubaker

RE: API 653 minimum thickness vs API 650 design thickness

"Houston, we have a problem"

Using my handy-dandy 653 calculator, I get 0.313" for A36 at 23.2 kips [1-ft method]

brubaker's calculator spit out 0.3026"

Nobody is close to your .216"/.232"

RE: API 653 minimum thickness vs API 650 design thickness

Hmmm - I used brubaker and got 0.2914 and by hand and got 0.312 - hmmmm

RE: API 653 minimum thickness vs API 650 design thickness

I matched his numbers in my calculator for course 2.

API 650
Calculating Thickness Per 1FT Method on Course1
Course1
D:60.0
G:1.5
S:23200.0
E:1.0
Cas:0.0
currentHeight:32.0
2.6xDx(H-1)xG/(SxE)+Cas=0.312672413793
Min Plate for 60.0, 0.25
Calculating Thickness Per 1FT Method on Course2
Course2
D:60.0
G:1.5
S:23200.0
E:1.0
Cas:0.0
currentHeight:24.0
2.6xDx(H-1)xG/(SxE)+Cas=0.231982758621


API 653
 Min Plate for 60.0, 0.25
Calculating Thickness Per 1FT Method on Course1
Course1
D:60.0
G:1.5
S:23200.0
E:1.0
Cas:0.0
currentHeight:32.0
2.6xDx(H-1)xG/(SxE)+Cas=0.312672413793
Min Plate for 60.0, 0.25
Calculating Thickness Per 1FT Method on Course2
Course2
D:60.0
G:1.5
S:23200.0
E:1.0
Cas:0.0
currentHeight:24.0
2.6xDx(H-1)xG/(SxE)+Cas=0.231982758621


 

RE: API 653 minimum thickness vs API 650 design thickness

API 653 (I pasted API 650 twice above)
Min Plate for 60.0, 0.1
Calculating Thickness Per 1FT Method on Course1
Course1
D:60.0
G:1.5
S:24900.0
E:1.0
Cas:0.0
currentHeight:32.0
2.6xDx(H-1)xG/(SxE)+Cas=0.291325301205
Min Plate for 60.0, 0.1
Calculating Thickness Per 1FT Method on Course2
Course2
D:60.0
G:1.5
S:24900.0
E:1.0
Cas:0.0
currentHeight:24.0
2.6xDx(H-1)xG/(SxE)+Cas=0.216144578313
Min Plate for 60.0, 0.1
 

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