In Episode 1 of this two-part “soap opera,” our protagonist Whyr T. Heckawe corresponds with senior project engineer Dug E. Syner about some suspicious goings-on at the Lost Lake hydro project
By Tom Spicher
- Dug E. (D.E.) Syner, senior project engineer with Turnkey Ops. Ltd. in Burymdeep, Ontario, Canada
- Whyr T. (W.T.) Heckawe, project manager, Lost Lake Project, owned by Unlimited Waterpower Ltd. in Camp Bichemorre, Yukon Territory, Canada
Our story takes place via standard postal correspondence.
We have determined the cause of our problems to be your organization’s environmental and hydrologic assessments for the Lost Lake Project. Because it was thought that the black-nosed sucker was nearing extinction and the Quichdeel River held the only remaining population, our plan to dam the river for a storage pool was dropped in favor of an off-stream plant and enlargement of an existing “dead” lake 700 feet higher than the plant site. This meant we would use a reversible unit for off-season pumping and peak load generation. We now know this fish is considered a detrimental addition to the trout and salmon streams and can be found in many streams in the area. Nonetheless, we proceeded with our decision to build the reversible, off-stream unit.
The pondage we added increased our surface drainage area from 40 square miles to more than 300. The usable lake elevation is only 15 feet, however, due to the use of a 2-mile-long natural channel leading to our intake structure. After pumping for two summers to fill the reservoir, we have completed our first generating season.
After each pump season, we had to rebuild various parts of the unit. First, our intake allowed sand to enter and we damaged our seal rings. Because we passed too much water through the upper rings, the upper drains cavitated badly at each elbow. That first winter, as you recommended, we pumped epoxy into the voids above the runner to fill that zone and reduce the vent size. The next season, we had to add water to our thrust bearing cooler because the bearing seemed to be overheating. After that second summer, we had to replace our thrust bearing and its runner plate with the spares.
Those first two pumping seasons also caused much cavitation and erosion damage to our runner. The first year repair was at our expense because of the exclusion for abrasive damage in our two-year warranty. Lining our tailrace pool eliminated the abrasive problem the next summer, but we still had lots of cavitation damage that you said was due to “aggressive” water conditions causing our “stainless steel” runner to corrode. We tested the water and find it has a neutral pH but is supersaturated with nitrogen and oxygen from the natural stream above our plant site. This 13 chrome-4 nickel alloy seems to have several types of corrosion present. Large pits form that are filled with a black oxide, a red haze exists over most of the surfaces, and several areas have wavy, linear rust patterns in the direction of water flow.
Based on your recommendation, we repaired the pitting damage from erosion, corrosion and cavitation with more than 300 pounds of 18-8 stainless wire following the contour of the templates you supplied. We had to split the templates because the blades were too thick to fit inside them. We were careful to place them horizontally at each of the three blade heights identified on them for the (pump) intake edge. Of course, we had to make additional relieved templates to handle the added weld material and step them down as we ground the blades to final shape.
Because all the procedures followed were at your direction, we wonder if the cavitation warranty could be extended; the short summers only allowed 6,000 total hours of pump operation in the first two years. We also wonder how this could be described as cavitation-free operation.
After rebuilding the rotor to accommodate the inward collapse of the upper stator due to the low-strength concrete, we discovered the threaded fasteners holding the rotor arms were stretching. We had to replace all of them with high-strength fasteners. The hydraulic torque wrench required to install them to a reasonable pre-tension cost an additional C$20,000. We also discovered that the finger plates on the stator were held down with a system including high-strength non-magnetic bolts and spring-type lock washers. All of these had vibrated loose. A local trapper said he had a similar problem with lock washers, and his solution was to remove the washers and “torque the hell” out of the bolts. That seems to have worked this past year.
An Alaskan fisherman also showed us how to decrease much of our vibration by better balancing of the unit. It was while installing several 30-pound weights on the spider that we discovered the 10-inch crescent wrench you were missing from your tool box. You can probably polish off the burn marks, but the worn jaws make it pretty useless. Fortunately, it was wedged so tightly that it just rubbed the upper support ring without hitting the insulation.
We bought an eddy probe system the fisherman recommended that measures the runout at our bearings. We were able to reduce the speed-no-load runout to 30% of the previous runout and the full generating load runout to about 20% of the “acceptable” National Electrical Manufacturers Association standard.
Some additional benefits have accrued from the quieter operation. It is now obvious the noise is coming from the pump-turbine. Removing the wrench took care of most of the upper screech.
During our first week of operation, we encountered several bits of information and additional problems. The mole-driven, unlined tunnel does not have any significant hydraulic losses. This was discovered when an intended brief excursion to full gate left us without enough servo power to close the wicket gates. When we went to emergency closure of the head gate, it didn’t operate because the trashrack had failed and passed into the gate slot. Fortunately, the lower spherical valve worked and we were able to slow and stop the unit.
The excursion into overspeed uncovered a few more minor problems with the generator rotor and braking system. Because of the size of the unit, we were able to place a man and small portable mill into the pole piece slots to mill them back at the top and restore a uniform generator gap when the unit is at speed and load. This puts a bow in the pole piece at rest, but it pretty well straightens out at speed. That aspect is difficult to measure, as you might expect. The milling was set back a little when the mill jammed in the slot, trapping the operator. It took us 12 hours to remove it, and we had to find a new mill operator after that episode.
As we were finishing the generating season, the pump-turbine runner cracked. Apparently, our extensive welding and epoxy filling of the vents caused stresses sufficient to start a crack in the runner crown. The nature of the crack indicates it probably started during our overspeed run and gradually progressed. When the crack finally let go, it cracked the head cover. Our spherical valve had leaked oil and wasn’t operable for a few hours. Fortunately, we were able to add oil to the system and close the valve before the water flooding the plant entered the governor oil sump or motor/generator. It took us two days to pump out the plant and rescue the two men who were trapped atop the spherical valve cabinet. They were ungrateful about our efforts and the whole experience, and after recovering from hypothermia they left the job.
It was about this time that we discovered the unusual early rains we have been experiencing were refilling our reservoir. This means we cannot unwater the intake channel without a cofferdam. That added expense of a canal headworks is beginning to look like a bargain compared to the helicopter installation of such a cofferdam. A road to the area would also have been valuable to bring in heavy machinery and service the area. We need to redesign and rebuild the trashrack and intake channel to prevent the frazil icing that caused the original rack collapse.
The severe anchor icing in the headworks channel also reduced our head and caused some air entrainment near the end of the season. We were operating at full load and had to overgate to get the necessary power. The bubble that traveled up the tunnel must have been substantial. When it hit the gate structure, it lifted the gate, hoist and bonnet out through the shaft and about 50 feet up the hillside. The reversing hydraulic shock traveled down the tunnel and penstock and probably was the final straw for the cracked runner. Coincidentally, the tunnel plug has started leaking and we have to maintain pumps for the 12 to 15 cfs flow running alongside the penstock. The bubble did clear out the remnants of the trashrack and left them next to the channel near the gate structure.
When the shock and reversed flow hit the 2-mile-long natural channel, it was cold enough to cause a flash freeze of the channel somewhere. In any case, when the brakes came on the excessive oil vapor and brake/brush dust slurry we had been complaining about caught fire. With the flood and fire, we had a pretty busy time for a few hours. We were surprised at the rate of pressure reduction in the penstock and our fire water lines. Apparently, the bubble had taken much of the remaining water from the 7-mile-long tunnel as it traversed up the 2% slope. We were able to suppress the fire as the last of the usable pressure disappeared.
The water ejected from the 18-foot-diameter, 30-foot-deep gate shaft eroded much of the surrounding hillsides. The slides backfilled our intake and gate shaft with dirt and toppled many of the trees we had worked so hard to preserve during construction. The recent rains are adding to this problem.
Now the reason for our concern about the environment and hydrology studies is that the two undisturbed years in the reservoir allowed those black-nosed suckers that were pumped up to breed at a fantastic rate. The rains are forcing us to pass water through the bypass and the suckers are moving downstream. The Frost Bite Club and local fishermen are threatening to sue if we don’t turn off the water and stop them. When we were generating, about 96% of the 6-inch-long migrants were surviving. The bypass and flip bucket operation gives about a 90% survival, but that is too much for the local trout and fishermen. If we allow the overflow spillway in the North dam to operate, that will send the water into the north-flowing Pristine River and eventually into the Yukon River, which has never had black-nosed suckers.
We would like to blow the fuse plug in the South dam and drain the reservoir back to its original size. Unfortunately, we haven’t finished clearing that channel area sufficiently for that to be anything but a disaster.
We also have local objections to that. It seems that the past two years the weather has moderated dramatically because of the reservoir. The previously almost barren rocky slopes have erupted in vegetation, the sheep population is on the rise and some goats, elk and moose are now seen in the area. The local guide is booked solid for the next four years and would sue if we reduced the reservoir. The local hunters, bird and animal watchers, farmers and even fishermen want the reservoir retained. Locals are netting the suckers and selling them to canneries for twice the price of coho salmon. It seems the 12- to 15-inch adults precisely fit some gourmet cans and taste really good. The rains have extended the growing seasons and all sorts of agriculture is starting in the high valleys to the east.
Those crazy suckers will take a fly and fight harder than any trout or grayling. Two fly-in fishing services are now operating service to the lake with amphibious planes. Someone said that some musky fingerlings have been successfully transplanted to the reservoir, but I can’t verify that.
I appreciate the last letter with the Hydro Wheels turbine maintenance manual, but I think we need more than that. Please let us know how to treat this dilemma. We have also gotten a letter from Ducks Unlimited thanking us for the many bays and nesting areas we have created.
P.S. The locals have heard about your good work and want to name the falls created by the leaky east dam after you. It would be called D.E. Syner Falls.
Stay tuned for next month’s episode of As the Runner Turns. Does W.T. Heckawe get justice at last?
Tom Spicher owns Hydro Y.E.S., a consulting company, and is a member of the Hydro Review editorial advisory board.
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