National Grid is in the process of investing over £150m on the refurbishment of OHL lattice steel work towers over the RIIO period.

Current asset policies require the replacement of steel work identified as Grade 4 (in accordance with TG4) or worse and this policy is being reviewed by a steel work strategy team. One of the outputs of this team has been the identification of a need to consider the in-situ remediation of Grade 4 tower steel work on main structural members as the volumes of steel work involved are extensive and current methodologies require several circuit outages or a lengthy double circuit outage to complete the works.

Faced with a growing capital programme and the need to minimise circuit outages, it is necessary to consider alternative methodologies to resolve this problem.

The key issues to be addressed by this project are therefore the identification, recording and remediation of Grade 4 steel work on primary structural members of National Grid's lattice steel towers under outage & non-outage conditions.

Objectives

This project will consider a range of technologies, as employed in other industries, for the remediation of structural steel work. It will assess the suitability of these technologies for use on lattice steel structures carrying live 275kV and 400kV conductors.

The 3 key deliverables of this project will be:

• The adaptation of recognised methodologies (techniques for cleaning the steel and combinations of products for re-coating it) for remediation of structural steel work and the demonstration of the effectiveness of this solution (through trials and accelerated weathering tests) for use on National Grid's overhead line towers during outage & non-outage conditions

• The creation of a procedure/manual to support ongoing implementation of the techniques developed

• Development of a training package to ensure consistent recording & communication the condition of the steel work prior to and after remediation.