Relocation of used LPG Horton Sphere

Look up the typical physical properties for the A516 Gr70 and compare them to your requirements. I don't have access to the ASME Code at present, but I believe that the formulas are in there to calculate from the typicals temperature to your needed temperature.

In general, I think that the material will be fine.

Dear Sir

01. ASTM Grade 70 was first adopted during 1964 and since then there are around 25 amendments to this Standard i.e. almost one amendement every year. Presently 2006 issue is in active. Our spheres were fabricated during 1980-81. If the sphere have to be refabricated at a newer location whether there will be any difficulty to declare that the material confirms to ASTM 516 Grade 70 material and there will not be any ambiguity on material specification confirmation due to the amendments to the standard.

02. Design Philosphies of LPG Bottling Plants in India are being guided by Oil Industry Safety Directorate (OISD-144) Standards. Design code used for fabrication of sphere was BS 5500-1976 but the latest OISD standard stipulates that Single Code to be adopted for design, fabrication, inspection and testing i.e. ASTM and BS shall not ne combined. But in this case ASTM 516 grade 70 material and design code BS 5500 was used. Since the sphere has to be rafabricated after relocation as per latest OISD Standard, old design code of BS 5500 will be no longer relevant and entire design calcualtion such as minimum thiickness etc should be recaluated as per ASME Sec VIII.

03.Further design pressure was 19.25 Kg/cm2 and minimum required thickness was 35 mm with 1.5 mm Corrosion allowance. Present requirement is 14.5 Kg/cm2. Is it correct to recaluclate the thickness as per the reduced pressure requirement in standard as the MDMT requirement reduces with the reduction in thickness of the plate.

Kindly correct me if my understanding of point no 2 and 3 is not correct.

Regards

kjs

By all means recalculate to ASME Sec VIII for the lower pressure. You are fabricating from used materials so take the opportunity to have some material samples analysed for chemistry and tested for physical properties. This way you know exactly what you're dealing with.

My experience with most material standards has been that the changes are very small, and don't generally affect the physical properties. If they do, then new classes within that standard are created. In the case of ASME, most of the addenda changes are to correct editing and typographical errors.

Sir

Due to reduced deisgn pressures minimum thickness will be definitly lesser than existing 35 mm. MDMT reduces with any reduction in minimum thickness requirement.

Under such cicumstances existing MDMT which is stipluated as -27 deg C will not remain applicable.

Hence for the reduced thickness MDMT also should be recalacuted.

Whether my understaning is correct for the above.

In order to keep everything consistent, all the engineering figures should be recalculated to the new operating parameters. Since most engineers like myself worship at the Altar of Overkill, your redundancy figures (safety margins) are sure to please. Even the insurance underwriters will be happy as long as you have material testing results in hand to back up your figures.

Testing will be a small price to pay for the comfort and confidence of working from "Knowns".

I think it will be ok to use this material but you have to perform PWHT as per BPVC