lamination and stress study
lamination and stress study
(OP)
in service LPG tank 3000 m3 ,18 bar mawp, sa516 gr.70 , i found lamination in more 5 shells , after return to API 510 to see assessment , it forwarding me to API 579 which say (lamination is acceptable regardless of sizes except(1- in case of no working in hydrogen charging service, 2-locate the lamination out of distance of( 1.8 √ D*t )from major discontinues 'manhole'
i want to make some study of effect of stress to lamination prolongation in case of P.V. working with lamination, and why avoid locate in the area near to manhole ?, wich type of stress may be run?
i want to make some study of effect of stress to lamination prolongation in case of P.V. working with lamination, and why avoid locate in the area near to manhole ?, wich type of stress may be run?





RE: lamination and stress study
RE: lamination and stress study
Generally, laminations and non-metallic inclusions are planar irregularities/anomalies which lay parallel to the two faces of the plate. You can usually see them when you machine or cut through them, as you cut across the thickness of the plate. They do not usually change the cross sectional area of the plate appreciably. You can map their location in a plate by ultrasonic testing (UT) or radiographic testing (RT) through the plate. When your primary stresses are in the plane of the plate, as is usually the case in a PV, the lamination is not too critical as long as it is not too thick. The same applies to compressive loads or stresses perpendicular to the plane of the plate (radial loads/stresses in most PV’s), they just tend to compress the lamination. But, tension perpendicular to the plane of the plate is a different matter, since tensile stresses will tend to pull the lamination further apart, or make it grow at its boundaries.
I don’t have the API or ASME codes in front of me, so I don’t know exactly what restrictions and limitations those codes put on this situation. But, given the above general considerations, they will more than likely tolerate some lamination as long as they aren’t too large (thick) or extensive. The codes will be much more strict about their existence in locations where the actual stress patterns/fields are tri-axial. That is, where the likelihood of through plate stresses is high, such as at a nozzle or manway openings or other transitions and significant discontinuities, which distort the normal stresses and cause significant through plate stresses.
RE: lamination and stress study
We do seem to meet up at this topic periodically, don’t we? Have a nice holiday season.
RE: lamination and stress study
dhengr. RT is not adecuate to detect laminations
Regards
R6155
RE: lamination and stress study
RE: lamination and stress study
Regards
r6155
RE: lamination and stress study
The response provided by metengr is, as usual, spot on.
RE: lamination and stress study
Was by chance during inspection of actual thickness?
Regards
r6155
RE: lamination and stress study
Regards
r6155