API Spec 20E

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.