I have recently been asked to procure some line pipes on a client's behalf. The specs are API 5L X65, NPS 4 inch x 3.50mm wall thickness. The closest thickness specified in API 5L is 3.58mm and that was waht I specified after obtaining client approval.

Two very reputable manufacturers have replied to our enquiries saying that they are unable to achieve that specified wall thickness. They claimed that it compromises the strength of the material.

May somebody enlighten me if this claim is true or are there any limitation on the wall thickness of line pipes?

NH Liew