Hi, Richard...

I'm a new COADE Tank software user.

Now I'm designing a CRT Tank (mat'l A283-C) and need your advice.

DESIGN DATA:
- ID = 17 m
- Height = 16 m
- Design Pressure = Full Liquid+100 mm H2O
- Design Ext Pressure = 50 mm H2O
- Design Temp. = 70 C degree
- Design Liquid Level = 16 m
- Liquid SG = 1
- Corrosion Allowance = 1.5 mm
- Site Class E
- Sp = 0.3
- Ss = 0.75
- S1 = 0.375
- SDs = 0.6
- I = 1.25
- Rwi = 4
- Wind velosity = 25 m/s

After I calculate using COADE Tank, I found this tank is un-anchored, J = 1.0554.
When I checked the calculation output, the value Ai = 0.066964, it means this Ai is got from API equation E.4.6.1-3.

Could you kindly advise wether we can use this Ai value, even when we manually check using API equation E.4.6.1-1, we will get higher Ai value (0.1875)?

Thank you for attention.

Regards,
Amar F

Amar,

You said the report shows the value calculated according to E.4.6.1-3, which is a threshold of Ai≥0.625*Sp*I/Rwi valid for S1≥0.6

First, your S1 is less than 0.6 so you are not in that case!
Second, it seems you are right that the threshold is calculated as 0.5*S1*I/Rwi=0.5*0.375*1.25/3.5= 0.066964, even S1 is less than 0.6.

Why Tank reports such value of Ai instead one based on E.4.6.1-1? I have no idea, I cannot check your output anyway.
Here Intergraph team can help you giving an answer.


About your manually check giving value Ai=0.6*1.25/4=0.1875, I have also some remarks.

- Your SDs value cannot be SDs = 0.6, I don't know from where is coming up that value.
In fact in E.4.6.1-1, API considers SDs which is specific to ASCE 7 and failed to develop a similar formula for non-ASCE sites.
For non-ASCE sites, SDs must be substituted by Fa*Ss (the definition of SDs is given in API 650/ E.2.2 Notations as SDS=Q*Fa*Ss where Q=1 for non-ASCE sites)
I think you must consider SDs=1.2*0.75 for your site E.

-About your value of Rwi, you must see the the table Table E.4, where Rwi=3.5 for non-anchored tanks.

Best regards.

Mario,

Thanks for your feed back.

I'm sorry, I forgot to inform that the tank was designed
based on API 650 11th Ed., Add. 2 as Client requirement, not
the latest one.

In this edition there is no requirement for S1≥0.6;
the equation E.4.6.1-3

Ai≥0.5S1(I/Rwi) = 0.625SP (I/Rwi) is for Site Class E & F.

Regarding Rwi, I would like to inform
- At first I calculated using COADE Tank, and set
as un-unchored tank; Rwi=3.5.
- Since Client requested Anchor Bolt for the tank, then, I re-calculated,
and set as anchored tank.
Rwi = 4. I want to correct, the Ai=0.058594 (not 0.066964 as
my previous info).

Based on my calculation using COADE Tank, the software always
take the smaller Ai value (0.058594), even the equation E.4.6.1-1
will produce higher Ai value.

Pls Integraph team to advise (I utilized COADE Tank ver. 3.30.

Thank you & regards,
Amar F