Cathodic Protection In Cold Climate

Valve Case Studies

Water Division

David Raymond, C.E.T.

Technical Assistant

Region of Ottawa-Carleton

951 Clyde Avenue Ottawa, Ontario K1Z - 5A6

ABSTRACT

This paper reports on two case studies of valves that were part of the water supply system for the Region of Ottawa-Carleton (ROC) in Canada. It also presents data on the relative costs of system replacement versus cathodic protection to prolong the life of water mains.

Keywords: ductile iron, cast iron, corrosion, cathodic protection, exothermic weld, water pipes

INTRODUCTION

The Region of Ottawa-Carleton (ROC) in Canada has more than 900 kilometers of ductile iron main and more than 800 kilometers of gray cast iron lined main in the water infrastructure along with approximately 28,000 valves. Some of the ductile iron pipe installed in 1971 to 1989 already shows signs of corrosion and failure.

The rehabilitation program could not replace the water main at the rate required to maintain a minimal backlog of rehabilitation work. This would compromise the infrastructure quality and lead to more reactive programs, than to the more proactive approach.

It was imperative to identify methods of prolonging the water main and valve life either indefinitely or until replacement of the main and / or valves could be completed in a cost-effective manner. The Region reviewed various methods that other cities had adopted as their programs to defer the rehabilitation of these water mains. Test sites and different methods were developed to ensure the best practice method was implemented. In order to understand the best methods of corrosion control and prevention, a study was conducted on typical installations to determine the types of corrosion experienced and the appropriate means of corrosion control.

PAGE 1 2 3 4 next