石油和天然气工业用合金钢和碳钢螺栓（第二版；生效日期：2017年8月；附录 1：2018年9月；附录 2：2019年3月

This standard specifies requirements for the qualification, production, and documentation of alloy and carbon steel bolting used in the petroleum and natural gas industries. This standard applies when required by an applicable API equipment standard or otherwise specified as a requirement for conformance. It establishes requirements for three bolting specification levels (BSLs). These three BSL designations define different levels of technical, quality, and qualification requirements: BSL-1, BSL-2, and BSL-3. The BSLs are numbered in increasing levels of requirements to reflect increasing technical, quality, and qualification criteria. a) machined studs; b) machined bolts, screws and nuts; c) cold formed bolts, screws, and nuts with cut or cold formed threads (BSL-1 only); d) hot formed bolts and screws < 1.5 in. (38.1 mm) nominal diameter; e) hot formed bolts and screws ≥ 1.5 in. (38.1 mm) nominal diameter; f) roll threaded studs, bolts, and screws < 1.5 in. (38.1 mm) diam