NG TGN(E) 161 PDF

PURPOSE AND SCOPE

A generic design defect exists in the layout of body extensions incorporated into Blaw Knox L66, L2, L3, L3(c), L8 and L8(c) towers. Some incidence of buckling has been found in members of the body extensions. These extensions are mostly used on tower heights above the standard height. Such extensions were not used in towers that were originally tested.

This problem has been known since 1990 and body extensions have since been modified as part of various overhead line refurbishment schemes, particularly those where tower loading has been increased by the use of larger conductors.

However, the majority of towers supporting original conductors and containing the original body extensions have been in use on the system for up to 40 years without incident.

This document identifies the affected towers.