API SPEC 20E:2017

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 referenced by an applicable API equipment standard or otherwise specified as a requirement for compliance. An annex for supplemental requirements that may be invoked by the purchaser is included.
This standard establishes requirements for three bolting specification levels (BSL). 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 severity in order to reflect increasing technical, quality and qualification criteria.
This standard covers the following finished product forms, processes, and sizes:
a) machined studs;
b) machined bolts, screws and nuts;
c) cold formed bolts, screws, and nuts (BSL-1 only);
d) hot formed bolts and screws < 1.5 in. (38.1 mm) nominal diameter;
e) hot formed bolts and screws > or = 1.5 in. (38.1 mm) nominal diameter;
f) roll threaded studs, bolts, and screws < 1.5 in. (38.1 mm) diameter;
g) roll threaded studs, bolts, and screws > or = 1.5 in. (38.1 mm) diameter;
h) hot formed nuts < 1.5 in. (38.1 mm) nominal diameter;
i) hot formed nuts > or = 1.5 in. (38.1 mm) nominal diameter.