... or by sea Hejian Fist Petroleum Equipment Co., Ltd. we have been in line with the principle of "faith-based, quality ... .5% of the nominal thickness.(3) the surface not couplings have folded, hair grain, overburden bed separation grouting, crack, rolling fold ... casing couplings and surface should be smooth and thread, does not allow to have the burr, tear and enough to make thread ...