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A Watchful Eye at Bonneville Dam


Exactly 200 years ago, and 17 months after leaving St. Louis, surviving a harsh, 4,000-plus mile overland journey through unexplored territory, and nearing their long-sought destination – the Pacific Ocean- explorers Meriwether Lewis and William Clark led their intrepid Corps of Discovery through the spectacularGorge on the mighty Columbia River. Here they encountered ferocious rapids, often requiring labored portages around them.

Today, the Columbia Gorge is still spectacular but its rapids are long gone, submerged under 48 placid miles of Lake Bonneville behind the Bonneville Lock and Dam, whose 18 giant gates stretch 1,450 feet to maintain the upriver reservoir some 60 feet above the torrent on the downstream side.

Forty miles upstream from Portland, Ore., Bonneville Dam was the first of a series of hydroelectric dams that transformed the Pacific Northwest. Construction by the U.S. Army Corps of Engineers began in 1933, and the dam was dedicated in 1937 by President Franklin Roosevelt. Its cost was $88 million, and it is now designated a National Historic Landmark.

In mid-July, just a few months short of that 200-year anniversary, Jerry Carroll, maintenance manager of Bonneville Dam, could be found gazing down at the cavernous Powerhouse #1, with its 10 main and one smaller Kaplan generating units. These, together with the eight main and two smaller units in Powerhouse#2, are capable of producing 1.6 million horsepower andover 1 million kilowatts, enough to supply the powerneeds of nearly 500,000 homes.

Carroll laid out a high-priority goal to a visitor from LubesnGreases. We are continually aware of our responsibility to use oil in an environmentally sound manner, he said. An oil spill into the river would be a

huge issue throughout the area. Our procedures and installed systems are designed to keep oil out of the river, as this is a concern to be avoided at all costs.

His colleague, Mechanical Crew Supervisor Steve Culbertson, added, A spill is the most critical oil event, when oil reaches the river or the oil/water separator. A release, on the other hand, is still considered to be serious but its a smaller event, such as a drip which does not reach the river or separator. We can collect this oil or clean up a release by wiping by hand or vacuuming, or other ways.

During Carrolls 11 years at Bonneville, rarely has there been a spill from the roughly 500,000 gallons of petroleum products on site, most of which is oil. He pointed to the level of control and said, If anyone spills even so much as a cup of oil anywhere on the project, we are required to report it to our environmental compliance coordinators. When we change oil in a generating unit we make a determined effort to match the amount that goes in with what we take out. The same is true when we move oil from one place to another on site. We attempt o account for all oil, even down to the level of a few gallons. He added with pride, Were getting better with our accounting, too. We train our people to know the system and to take good care of our oil.

Fish First

Careful oil management is not a foreign aspect in most industrial settings, but it is absolutely essential in the watery Pacific Northwest. Here, environmental issues take on an almost religious intensity, culminating in the annual adult and juvenile fish runs up and down the Columbia.

To protect the fish, which are mostly but not entirely salmon, Bonnevilles turbines are set to operate within 1 percent of best efficiency for fish vs. power. This means that the variable-pitch turbine blades inside the system will be set to produce the least amount of turbulence, even at the expense of maximum power generation, in order to allow 98 to 99 percent of the fish to survive transit through the system.

It wasnt so when Bonneville Dam first entered service in the 1930s, but for many years this fish mitigation program has taken precedence over the power generating efficiency rating. During LubesnGreases visit, for example, low water in the Columbia resulted in all 11 of Powerhouse #1s generating units being out of service; in Powerhouse #2, only five of 10 generating units (three main and two small) were online.

Congress and the Roosevelt Administration created Bonneville Power Administration in 1937, to electrify farms and small communities with public power. BPAs wholesale customers now include public utilities, public utility districts, municipal districts, public cooperatives, some investor-owned utilities and a few large industries, such as aluminum. Over the years, it has spent more than $7 billion to support fish and wildlife recovery, including more than $3.5 billion in energy purchases and loss of energy sales due to fish operations.

Inside: Very Old Oil

A considerable quantity of oil in our older powerhouse, #1, which was put in service in the late 30s, is the original oil, pointed out Culbertson. (Powerhouse #2 was put in service in the early 1980s.) We normally overhaul the 18 main generating units every four to five years and at that time we drain the oil, run it through a purifier to primarily remove emulsified water and a few other impurities, store it until the overhaul is completed and then pump it back in. As oil is disposed, we top off the tank prior to bringing the unit back online. Any leakage would be wiped up or caught in our oil/water separator and does not have an avenue to reach the river.

Brian Moentenich is senior mechanical engineer in the Corps Portland District hydroelectric design center. The average age of the oil in all our power plants is probably over 25 years, he said. In the past we scheduled an oil change when we noticed problems in operations, such as overheating. Now however we look at indicators – the acid number, the RBOT value, for example – and other indicators which show that the additives are all used up and the oil is worn out. Many plants have installed purifiers with particle detectors. In the larger power plants, like Bonneville, well over a half a million gallons of oil are in use.

Carroll added, At $4.00 to $4.25 a gallon we take care of the oil and do not waste any funds on oil that is still serviceable.

Hub of the Action

Kaplan axial flow reaction turbines are the hydropower generating units in use at Bonneville and make up about 40 percent of the Corps of Engineers 400 hydroelectric generating units throughout the United States. The remaining 60 percent (240 units) are Francis turbines, a radial flow impeller turbine with non-movable turbine blades.

Each Kaplan turbine has an intake below the waterline on the upstream face of the dam, adjustable vanes to control the quantity of water entering the turbine housing, and adjustable turbine blades. These blades, like a ships propeller, can be moved inside the housing (called the runner) while the blades are turning. Water exits the system below.

The design heads for Kaplan turbines at Bonneville range from 26 feet to 70 feet across. (By contrast, the Corps largest generating unit, located in Idaho, measures 740 feet across the head.) RPM of the generators range from 54.5 to 400. The smallest Bonneville unit produces 5,000 hp while the eight largest produce 105,000 each.

At the base of the shaft containing the operating mechanism controlling the turbine blades is the hub – the sealed core of the turbine; this hub mechanism contains between 2,500 and 3,000 gallons of oil.

Another 3,000 or so gallons of oil lubricate other aspects of the turbines including the servomotors, the governor system and the shaft bearings. Thats a total of about 6,000 gallons of oil required for each major Kaplan generating unit.

Which Oil to Use?

At present, just two viscosities of oil are being used for all bearings, hub lubrication and the governor pressure system: a lighter ISO 68 oil in Powerhouse #1, and a slightly heavier ISO 100 viscosity grade in Powerhouse #2. In both powerhouses, this product is an R&O oil, so named to highlight its additives focus on protecting against rust and oxidation, a particularly essential requirement in a water environment.

However, Moentenich noted, Powerhouses are moving more toward a single oil. It can be either an ISO 68 or 100 but the tendency is toward the 68 product in all applications. A single oil simplifies the inventory issue, and weve found that the lighter product works well in all the applications.

While were phasing out the heavier 100 oil and moving toward a heavymedium 68 oil, which will eventually be the industry standard in all our units, were not there yet, said Culbertson, sounding a note of hands-on, operational caution. Some projects have had significant trouble when converting to 68. Its basically a trial-and-error process. Currently, Powerhouse #1 uses 68 and Powerhouse #2 uses 100 and the two oils are not mixed.

Carroll added, Both powerhouses have had good success with their respective grades of oil.

Historically, Mobil DTE and Chevron GST oils have been the choice of most Corps powerhouses. More recently, Petro-Canadas Premium R&O Turbine/Circulating Oils have been selected by the Defense Logistics Agency as an approved product which can be purchased off-the-shelf via a simplified purchase-order mechanism. However, individual powerhouses retain the authority to select the brand of oil for use in their equipment.

The technical literature for each of these three products emphasizes their high-quality base stocks, strong ability to separate or release water from the oil – clearly an essential parameter of oils used in an aquatic environment – and their ability to withstand rust and corrosion. (The oils are also used in U.S. Navy ships.) Chevron additionally spotlights the environmental benefit of its GST oil, including not expected to be harmful to aquatic organisms.

A Look Ahead

As Carroll noted, oil leakage is a big issue. The Corps of Engineers calls the oil/water issue a top issue, and Moentenich notes that it is continually looking for ways to reduce the risk of a spill.

On one recent occasion at another site, he said, we had a leak between the stainless-steel seal ring around the turbine blade trunnion. Oil began leaking past the band and the blades. We tried to insert sealant but that didnt work, so we tried welding the bands in place, which was successful. When we notice were losing oil we look for the source and the exit. Typically the sealant or packing is leaking.

The hub is a critical point in the system and we always look for ways to reduce the risk of oil leaking out of the hub, which goes directly into the river. We keep the oil sumps pressurized. In some parts the water pressure is higher, and water may leak in; in others the oil pressure is higher so oil may leak out, Moentenich explained.

Longer term there is the possibility for the use of dry sumps, and some companies have developed this technology. Were not yet ready to use it.

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