4:1 Safety Factor - PV Elite 1

[pperlich]

Is there a setting in PV Elite to design to the current code (VIII-1), but at a 4:1 safety factor?

 

[TGS4]

A couple of things:

1) THERE'S NO SUCH THING AS A SAFETY FACTOR!

2) the last time that the design margin against the minimum-specified engineering ultimate stress was 4.0 was prior to the 1999 Edition. You may want to look at that.

3) why would you want to use the current Edition with old allowable stresses?

 

[pperlich]

1) Yes, I understand that. What terminology would you prefer? We both know what I mean.

2) I am aware.

3) Customer wants warm and fuzzies, idk.

This is a question about options/settings in PV Elite software, not about tank design specifics.

 

[dig1]

What I have done is create a custom material using the pre-1999A design margins. The only time we run into this is when we are requested to make a modification to a vessel that was pre-1999 and the Owner or more often the AI has requested/required current rules for a new component (example a new nozzle) but wants the design margin for the component the same as w/ the original code of construction.

BR,

Patrick

 

[JStephen]

We have a regulatory body that mandates vessels with a 4:1 safety factor. (I think ASME changed, and they never got around to it, I don't think there's any deep thought that went into this requirement.) But the software we use also has an option for that.

 

[pperlich]

I used to use DesignCalcs, and it had an option for 4:1. Now we are using PV Elite.

I will manually decrease the allowable stress in the material data screens for each component. Luckily, this is a pretty simple design.

JStephen, which regulatory body are you referring to?

 

[TGS4]

The proper term is "design margin against minimum-specified engineering ultimate strength".

A custom material is the way to go.

 

[Don56]

DOT mandates a 4:1 ratio.

 

[JStephen]

"Metal thickness for pressure tanks shall be sufficient to withstand the highest expected working pressures with a four to one factor of safety."

https://www.tceq.texas.gov/assets/public/legal/rules/rules/pdflib/290d.pdf

(page 68)

 

[pperlich]

Don56, Do DOT applications typically get built to Section VIII? Not my industry.

JStephen, I figured you would say Texas.

 

[victorpbr]

DOT CFR 49 specifies ASME VIII div 1 as code of design and construction and to use a design margin of 4 on ultimate strenght. However in my opinion it is very outdated, ASME XII uses the same allowables as VIII. Don`t know the current practice though if DOT is accepting ASME XII designs or is still enforcing the use of old allowables and section VIII.

 

[bpv66]

ASME Section XII has yet to be adopted by DOT.

 

[Don56]

pperlich, CFR 49 178.337 for MC331 class vessels mandates ASME Section VIII design and construction and the old 4:1 stress factor.