The latest NTSB Safety Alert can be applied to Process Safety! It speaks to the critical nature of “joinment” using a B-nut on fuel, oil, and air lines on aircraft. It also addresses over-torquing or under-torquing as a failure mode for this joint.
A B-nut is a common term for a nut that provides the clamping force to create a reliable seal in lines (such as fuel, oil, or air lines on a reciprocating or turbine engine) installed on an aircraft. If a B-nut is improperly secured (either torqued too much or not enough), a loss of engine power or an engine fire could result.
Under- and over-torqued B-nuts could cause fuel, oil, or air leaks depending on where the B-nuts are installed; over torqued B-nuts could also result in
deformation and damage to a line. Fuel or oil leaked onto a hot engine could result in a fire. B-nuts are exposed to vibration and thermal expansion and contraction during aircraft operations; therefore, it is critical that maintenance personnel ensure that the B-nuts are properly secured.
CLICK HERE for the full alert