Masiku ano m'mafakitale, mapaipi achitsulo amagwiritsidwa ntchito pazinthu zosiyanasiyana komanso m'mitundu yambiri, yomwe imakhala yowala. Mwa iwo, ASTM A106/A53/API 5L GR.B chitsulo kalasi B, monga chinthu chofunika zitsulo chitoliro, amakondedwa ndi mainjiniya ndi opanga p ...
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