Priest Rapids Scroll Case

Over the last 30 years, heavy pitting, corrosion and impact has wreaked havoc on the steel in immersion, including scroll cages, penstocks, etc

Priest Rapids Dam bears the name of the water feature on the Columbia River near the home of the Wanapum, a small band of indigenous people who have lived in the area since time immemorial. The dam began generating power in 1959. It has a rated generating capacity of 950 megawatts of power.

Over the last 30 years, heavy pitting, corrosion and impact has wreaked havoc on the steel in immersion, including scroll cases, penstocks, etc. Coal Tar Epoxy has been the go to coating for corrosion prevention, but during the recent rehabilitation of units 1-3, it was noticed that the coal tar was losing half its thickness in less than 2-years causing management and engineering to consider a different coating system. Enter Tnemec company and the consideration of a High Performance Coating option.

"I was contacted by Grant County to provide a more abrasion and impact resistant option", remarked Rick Gilbreath with TNW, Tnemec. "The Engineering team wanted to explore a new and improved technology that could buy a longer life-cycle".

Tnemec Perma-Shield Series 431 is a ceramic filled highly cross-linked epoxy that is designed to provide abrasion and impact resistant 10x more than standard epoxy, including coal tar. Its 10 year history in similar environments and over 20 ASTM test methods covering permeability, abrasion, and impact gave the owners enough comfort that it was specified for the next 8 units.