Cargo Tank Design

[victorpbr]

Hi,

First of all, I`m not quite sure if this is the proper place for this post, if not, please advise me.

I'm studying the design of Cargo Tanks for the transport of Hazardous Products, specifically the transport of refrigerated CO2. In my country (Brazil) we have a local regulation that is supposed to guide the design that is strongly based (not to say a copy) of the CFR regulations, on the CFR and DOT the cargo tank I'm looking into is specified as MC-331.

I had some trouble intepreting my local regulation, so I went to the CFR 178.337 to see that if maybe the text in english was more clear to me. However, did not help much.

Here is the text from CFR 178.337

The tensile or compressive stress resulting from normal operating longitudinal acceleration or deceleration. In each case, the forces applied must be 0.35 times the vertical reaction at the suspension assembly, applied at the road surface, and as transmitted to the cargo tank wall through the suspension assembly of a trailer during deceleration; or the horizontal pivot of the truck tractor or converter dolly fifth wheel, or the drawbar hinge on the fixed dolly during acceleration; or anchoring and support members of a truck during acceleration and deceleration, as applicable. The vertical reaction must be calculated based on the static weight of the fully loaded cargo tank motor vehicle, all structural elements, equipment and appurtenances supported by the cargo tank wall. The following loadings must be included:

(1) The axial load generated by a decelerative force;
(2) The bending moment generated by a decelerative force;
(3) The axial load generated by an accelerative force; and
(4) The bending moment generated by an accelerative force

Now my questions, say this is a semi-trailer, and I have two points of support at the back(R1) and front(R2) (tandem suspension and kingpin). What load should be multiplied by 0.35, R1 or (R1+R2)? Should the tandem weight be included in R1?

Once I figure out the load to be applied, I have to select the proper location of it to calculate the moment. My current interpretation is that the load is applied at road surface level when decelerating and at the king pin level when accelerating, is that correct?

Thank you for your attention and Merry Xmas

 

[r6155]

See Pressure Vessel Design Manual 4th edit., by D. Moss , "Transportation and erection".

Regards
r6155

 

[victorpbr]

Hi r6155

Just took a look on your reference, unfortunately did not helped much. The method used by the author is different than the indicated by CFR 178.337, and is primarly focused on the stresses on the saddles.

My focus now is getting a better understanding of the CFR "method". The closest I found was ASME XII, really close, however there are some minor changes.

 

[r6155]

victorpbr
I forgot ASME XII. It is easy to understand. Figure 1-1.4 is clear and complies with DOT.

Regards
r6155