OCTG ndiye chidule cha Oil Country Tubular Goods, makamaka amatengera mapaipi omwe amagwiritsidwa ntchito popanga mafuta ndi gasi (zobowola). Machubu a OCTG nthawi zambiri amapangidwa molingana ndi API kapena zofananira nazo.

Pali mitundu itatu ikuluikulu, kuphatikiza chitoliro chobowola, casing ndi chubu.

Chitoliro chobowola ndi chubu cholimba chopanda msoko chomwe chimatha kuzungulira pobowola ndikuzungulira madzi akubowola. Amalola kuti madzi akubowola kuti akankhidwe kudzera pabowolo ndi mpope ndikubwerera ku annulus. Paipiyi imakhala ndi kupsinjika kwa axial, torque yayikulu kwambiri komanso kuthamanga kwamkati.

Chotengeracho chimagwiritsidwa ntchito kulumikiza chitsime chomwe amabowolera pansi kuti apeze mafuta. Mofanana ndi ndodo zobowola, zitsulo zamapaipi azitsulo zimayeneranso kupirira kugwedezeka kwa axial. Ichi ndi chitoliro cham'mimba mwake chachikulu chomwe amachilowetsa m'chibowo ndikuchiyikapo simenti. Kulemera kwake kwa casing, kuthamanga kwa axial, kuthamanga kwa kunja kwa miyala yozungulira, ndi mphamvu ya mkati yomwe imapangidwa ndi madzi amadzimadzi zonse zimatulutsa axial tension.

Chitoliro cha chubu chimalowa mkati mwa chitoliro chifukwa ndi chitoliro chomwe mafuta amatulukamo. Tubing ndiye gawo losavuta kwambiri la OCTG, lolumikizana ndi ulusi mbali zonse ziwiri. Mapaipiwa atha kugwiritsidwa ntchito kunyamula gasi wachilengedwe kapena mafuta opanda mafuta kuchokera kumalo opangira kupita kumalo, omwe amakonzedwa pambuyo pobowola.