Having spent most of mid-April dealing
with the high style design issues of the Holly Theatre, this past week has seen
a return to the more typical aspects of report writing, including covered
bridges and compliance documentation.
Staring back at me from my computer screen at the moment is PGE’s Faraday
Powerhouse, on the Clackamas River.
“Penstocks” are the feeder tubes
that connect a reservoir to the turbines that spin a generator to create
electricity. They are usually large
concrete or steel pipes that drop significantly in elevation to create “head,” increasing
the force of the water and spinning the turbines efficiently. In more recent projects (post-WWII) penstocks
are typically underwater, at the bottom of a dam, and so unseen. But in an early hydro project, like that at Faraday (which was built
in 1907-1909), the penstocks are exposed and become highly visible features, dropping from the
crest of the dam, down an embankment, to the powerhouse. Faraday's penstocks are typical, in that these early powerhouses tend to have multiple,
smaller, generation units rather than one or two large ones, and so the penstock
lines can be pretty dramatic through repetition. At Faraday there are six
penstocks, five built by 1909 and one, Unit No. 6 (the larger one, at the extreme right above), that was added in 1956.
Faraday’s original penstocks are
of riveted steel, between eight and nine feet in diameter, and are supported by
multiple concrete piers with small semi-circular “saddles” where they meet the steel
penstock itself. This has worked well
for over a century, but where the concrete and the steel meet, water is
trapped. Steel and water are a bad mix,
and one thing you surely do not want is a weak, rusted, spot in steel tube
carrying 1/6 of the Clackamas River at high pressure.
PGE has creatively developed a
solution to repair the damaged spots and then modify the top of the concrete
piers to re-seat the penstocks with a steel-to-steel connection. This will reduce the potential for damage and
allow the Faraday penstocks to continue to operate into their second
century.
People tend to glaze over when I talk about my interest in hydroelectric generation, penstocks, flow lines and the like and many of these early projects are criticized as unnecessary and un-green. That's another rant. Last night I was amused, while watching NBC's filmed-in-Portland fantasy-drama show Grimm, to see that PGE's now-decommissioned Bull Run Powerhouse (built prior to WWI) played a major role. It’s a shame, and an
interesting comment on how our society has changed, that only few people still see
the postcard potential in engineering marvels like these early, small scale, powerhouse projects. Think about that during the next power
outage, or when you drive through a sea of wind turbines.
