Mechanical Engineering
McKay Hydro Station Turbine Runner Upgrades
The McKay Hydro Station is a remote, unmanned facility located at the headwaters of the Penobscot River in northern Maine. The station is owned and operated by Great Northern Paper (GNP) and part of the largest private hydro system in Maine. The McKay Station contains three turbine-generator units with a total installed capacity of approximately 40 MW. These units generate 40 Hz electricity for GNP’s local paper mills and are critical to the owner’s core business. However, by the mid 1990s, the three Francis runners were reaching the end of their useful life. GNP engaged the services of Devine Tarbell & Associates Inc. (DTA) to study these units and develop a program for runner replacement and upgrade.
DTA’S hydro mechanical and electrical engineers conducted a detailed study of the existing units at McKay Station. The scope of services included dewatered turbine inspections, index performance tests, and development of rehabilitation and upgrade alternatives, along with cost and energy estimates. Based on this study, the owner decided to replace and upgrade the Francis runners with the objectives of decreasing cavitation, increasing and reshaping operating efficiency, and increasing annual production. DTA prepared specifications for runner replacement and rehabilitation of the turbine-generator for all three units. Our scope also included turbine and installation bid evaluation, turbine vendor design review, turbine manufacturing shop inspections, field supervision of the turbine-generator disassembly, rehabilitation, installation, commissioning, and field performance testing with flow measurement.
These runner upgrades were planned carefully and sequentially to minimize the outages and lost generation. The first runner was ordered in November 1997, unit disassembly began in July 1998, and the new runner was in production by October 1998. Disassembly of the second unit began in December 1998 and its new runner was online by March 1999. The third new runner was installed and commissioned in February 2001 as part of frequency conversion of the entire station from 40 to 60 Hz.