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Repowering the Welland Canal
John Dodge, Editor-in-Chief -- Design News, February 25, 2008
View fascinating video footage and browse through a photo gallery from DN Editor-in-Chief John Dodge's trip to the Welland Canal.
What weighs 500 tons and gets pushed around by two 30-horsepower electric motors?
The answer is each of the 75-year-old double plate steel mitre gates enclosing the 11 locks comprising the Welland Canal, which links lakes Ontario and Erie. The 27-mile canal and its 50-mitre gates lower a dozen or more ships a day 100m into Lake Ontario or raises them heading into Lake Erie. The locks compensate for the Niagara Escarpment, which forms nearby Niagara Falls.
As a key link in the 2,340-mile St. Lawrence Seaway connecting inland North America to the Atlantic, the Welland Canal could be labeled an unofficial “Wonder of the World” although it’s open to debate if it would fall into the “modern” or “ancient” category. Today’s canal is the fourth version of a remarkable man-made waterway connecting the two easternmost Great Lakes since 1829. And a fifth canal with five “super locks” is in the talking stage.
(An exhaustive 128-page study examining the Seaway’s traffic patterns, markets, environmental impact and infrastructure condition was released in Fall 2007 and the most critical component in need of updating were its locks. Beside the Welland lock system are the Soo and Montreal/Lake Ontario locks. The Seaway also has five canals. A ship traveling from Duluth to the Atlantic spends 17 hours in the locks and 112 hours sailing).
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Electro-mechanical systems have reliably powered the three major lock systems since the present canal was constructed in 1932. However, high maintenance cost along with safety and reliability factors sparked a debate starting in 2000: Should the Seaway rehabilitate the existing machinery or replace it entirely? They opted to replace it with modern hydraulics from Bosch Rexroth Canada (BRC).
“In 2003 when we made our major estimates, we had a initial benefit to cost ratio of 1:1.4. But in 2004, there was a huge increase in steel prices. We had to redo our analysis based on device prices (so now) the benefits outweigh the costs by a ratio of 1:1.28,” according to Iqbal Biln, the Seaway’s project manager for the hydraulic conversion.
For Biln, working at the Seaway has been much different than his former job as a mining engineer in Australia, Fiji and Sudbury, Ontario. Starting as an inspection and assessment engineer in 1998 to replace a retiring engineer, Biln, a native of The Republic of Fiji Islands, spent 18 months assessing and rating the conditions of gates, bridges, valves, ship arrestors and myriad electro mechanical drives.
“My training in mining says maximize the run for your dollars and money is always scarce. The Seaway has a completely different way of doing things,” he says. His biggest challenge was convincing Seaway management on down to accept change. “Everybody at the Seaway — management, mechanics and technicians — are so resistant to change. They have been doing the same thing for 75 years and they don’t want to change,” he says.
Besides replacement’s lower expense, the hydraulics have proven safer and more reliable.
“There was huge improvement in the safety because there are few moving parts. There’s no machine guarding which was one of our major issues, that is protecting workers from getting caught between the gears,” Biln says. “Mechanics’ clothes and fingers get caught in moving shafts. They would remove the guards for lubrication and not put them back again or would not lubricate because of the guards. And we started to get failures because of lack of lubrication. It was the major cause of a lot of the breakdowns.”
That said, ships still average 11 to 12 hours to get through all the locks and under the eight moveable bridges.
“For customers, there are no significant benefits, but we have a reduced number of breakdowns so there is less down time,” he says. As for manpower, the standard staffing on three operators per lock will remain the same for now. They operate the locks and perform all the lubrication. However, hydraulic oil largely makes the cylinders and pumps self-lubricating.
Rehabilitating a pair of old drives for each set of lock gates would cost $1 million and that would only elevate the system’s condition rating by a point. The Seaway uses a zero-six assessment rating system for the machinery with six being brand new. At that point, the gate machinery systems averaged a three rating, according to Biln.
“If you replace things like gears, bearings and shafts, but the entire framework stays the same, the best you can do is bring the condition rating to four. You can never get up to five or six,” he says. “You can spend a million dollars on two gate drives and what you gain is one condition rating.” That translates to $25 million for rehabbing just the gate drives.
Indeed, rows of worn racks, a jumble of exposed black gears, heavy orange motors and the ever-present smell of grease make for a scene out of a Dickens novel.
A 50-hp slip ring motor powering two winches pays out and pays in an inch and eighth steel cable that threads through the gate on pulleys and then anchors to the lock wall. The winches simply reverse direction to open and close the gates. The mechanism is nothing fancy although divers would have to occasionally perform a dangerous task of rethreading cables after one snapped from ice or debris.
“If there is any restriction in the motion of the gate, there is the slip mechanism in the drives, but sometimes they wouldn’t work and when they don’t, the cable breaks. The bottom part of the gate is 40 feet under water. So we have to bring in divers to replace the cables so we’d be looking at down times of eight to 16 hours depending on how bad the problem is,” says Biln. These problems are eliminated by the new hydraulic drives.
Thanks to proximity switches and linear transducers, another advantage of the hydraulics is speed control to slowly start the gate moving and to slow it down as it approaches the mitre (fully closed) position with the corresponding gate. A gate also slows down when it retracts into its recessed location in the lock wall, thus minimizing wear on the mitres and aging gate hinges, comprised of a pintle on the bottom and two eyebars on the top. The electro-mechanical gear had only one speed from cycle start to finish, inflicting shock loads on the gate hinges.
The switches are the primary position control device and a gate has four, each monitoring a single position: open, closed, nearly open and nearly closed. At the fully closed position, the pair of gates stop within two inches of each other. Another proximity switch monitors the position when the gates are mitered (touching each other) against the weight of water. Acting as a backup, the linear transducer monitors the cylinder rod and as such, always knows the position of the gate.
“For all the mass (each door is 500 tons, remember), we go from 0 to 15 percent, then to 100 percent. Then one of the switches tells the cylinder to decelerate as its closes,” says Wayne Scutt, a technical consultant with Bosch Rexroth Canada. The gates open in about 75 sec and close in the same amount of time, but can cycle at 60 sec for ice clearing during the winter months.
The Taintor valves were also electromechanically driven with 15-hp motors aided by counterweights to fill and drain the lock chambers. There were six different types of electromechanical drives that required extensive maintenance and lubrication. A single hydraulic cylinder and extension shaft in some cases replacing a rack and pinion greatly simplified this mechanism.
Finally, the dozen ship arrestors, which were in the most need of rehabilitation, are powered by an electric motor which through a series of gears and a bascule system lower and raise a tapered boom to place a four-inch diameter steel cable across the lock to prevent ships from drifting into the lock gates. As part of the hydraulic conversion project, the Seaway has redesigned the entire ship arrester drive system and replaced the bascule system with a boom adaptor which is now operated with two hydraulic cylinders resulting in better reliability and control.
So with the completion of a pilot project on the south end of Lock 6 East over the winter of 2003-04, Bosch Rexroth Canada embarked on a five-year program to supply hydraulic systems and controls to convert all the locks from electro-mechanical to fluid power. The construction work at the site takes place when the Seaway shuts down for about 10 weeks in the winter depending on the weather’s severity. If you need convincing about the existence of global warming, the Seaway re-opened on the earliest date in its history on March 20 for the 2007 navigation season.
The hydraulic conversion work is in its fourth year with Locks 2 and 3 on tap for replacement this winter. Work on Locks 2 and 3 commenced in early December 2007 and picked up steam when the Seaway closed at midnight Dec. 29. The core work of replacement begins once the locks are drained.
“We do so much in eight to 10 weeks in subzero temps, but when we press the button for the first time, everything has to work,” says Biln. Indeed, once the locks are drained, wind whistles through the lock chambers, making for a challenging work environment. The hydraulic conversion project will be completed next winter with the conversion of Locks 1 and 8. Two seasons were required for Locks 4, 5 and 6 because they each contain westbound and eastbound lanes. As such, they are known as “twinned flight locks” because they are two-way and each lock feeds immediately into the next.
Total cost of the project including construction nets out to between $61to $62 million, according to Biln. BRC’s piece of that is $24 million for the design and supply of hydraulic systems and controls.
While installation is during the winter, there’s plenty of other work occurring during the rest of the year. “We have to look at upgrading (machine) communication, what types of wires are running and how we interface with Ethernet and other protocols,” says Scutt.
The PLCs, motor control panels and HMI interfaces are made and programmed at BRC’s Burlington, Ontario facility and brought down to a factory conveniently and coincidentally located in the City of Welland hard by the canal. “Half the job for us is programming,” says BRC Application Engineer Peter Nywening.
The power units are made in the Welland factory, and once tested, are transported to the site at installation time and permanently wired. “At Welland, we marry them wire for wire, pump for pump, valve for valve to make sure everything is running and communicating properly and that we have the control we are expecting. Then we tear everything down and bring in the next pair (of controls),” says Scutt.
Pumps and valves are made in the U.S. and Germany and are standard BR catalog items. The cylinders, however, are custom made in BR’s Boxtel, Holland plant. Motors are acquired on the open market.
Drawing on Bosch Rexroth’s vast experience in hydraulics and waterway locks, the work started with concept videos and once those were approved, designing the cylinders, rods and power units began. The design phase included a number of firsts for both BRC and the Seaway.
“When we put out our specifications, we had asked that all drawings be done in AutoCAD and DWG files. We changed our mind and accepted (Autodesk) Inventor as the main package upon request by BRC,” says Biln. Driving that decision was the fact that Inventor is 3D and AutoCAD is 2D. The conversion was BRC’s first 3-D project.
“We saw this as an opportunity to move to 3D to visualize the stuff a lot better. Inventor was a little bit of a learning curve,” according to Ben Gilmore, BRC’s lead drafting designer for the project. “I’d say we got out the concept drawings in a couple of months. We ate a lot of pizza and were working pretty quick.”
Using Inventor, cylinder and rod sizing was determined. “We did a lot of analysis before we ordered equipment and then we did the simulation on loads to find out the operating conditions and profiles. When we commissioned them on site, the load on the cylinders were within five percent of what we had calculated. Those were very good numbers and efficacy of design,” says Biln. The hydraulics run at 50 to 60 percent of the continuous operating load.
Just as challenging as designing the power units and cylinders was sizing them for pre-existing spaces. And some are installed below ground in wells.
“We had to see how we would fit this all together. That’s when we came up with the videos and proposed locations (to determine) general sizing for our power units (PU). All PUs fit into existing rooms on the canal where all the existing machinery is. Theirs comes out and ours goes in. They had to fit through doors (and hatches),” Gilmore says. Some of the PUs weigh as much as 10 tons dry.
“A guy on each corner. We’re Canadians. We’re strong,” jokes Scutt.
Getting the power units into these damp concrete edifices was a tricky balancing act requiring multiple construction cranes. Often they had to be tilted to fit through doors and roof bulkheads. After all, the buildings, some of which has to be modified, were constructed in 1932 to house the electro-mechanical machinery that lasted three quarters of a century.
“In the first year on the double lane flight locks, we had to move the equipment from the mainland over the canal into the center pier. When you are moving that weight with a crane over that span, it presents a challenge,” Gilmore says. “In some cases, we lowered it into the empty canal and craned it back up.”
3-D software also allowed BRC to perform it own finite element analysis instead of sending out the work to a third party, according to Gilmore.
“When this project came up, we trained ourselves on Ansys Design Space. We took on a few things we did not have a lot of experience with like all the cardanic rings (supports for the cylinders) and put them through FEA and did all the testing on the computer without making a prototype. That’s something that could not have been done with 2D,” says Gilmore.
Bosch Rexroth won the bid on this choice job based on past performance and price and they could also provide a complete solution, according to Biln.
“We did not want to piecemeal the work out. A lot people out there will provide a component or a part, but not a complete system. (We wanted) a single point of accountability. Everything is assembled and fully tested before it is shipped to the site. The cylinders, power units and controls are shop tested. Rexroth has the facilities in Welland to do that,” he says. Other bidders for the job, he says, were Magnun Hydraulics and Berendsen Fluid Power.
“On the other side, we at the Seaway have the expertise to retrofit everything. We rely on our engineers to take this design from Rexroth and adapt it to our locations,” Biln says, adding that installation each year is bid out to a mechanical contractor.
Was there ever a time Seaway officials thought BRC was in over its head?
“We asked for special controls, leak detection systems and self-diagnostics which were a challenge for Rexroth. These features were something they had not done in the past, but they were able to deliver,” says Biln. The only failure so far was what Biln describes as a “mini-mess” from a hose rupture. BRC also replaced a few leaking gate cylinder seals.
The Welland Canal has been BRC’s biggest project and represents a big bump up in the size and scope of project it can handle.
“This project stretches our capabilities and forced us to be more innovative. It sets the benchmark for future projects we will be able to handle because of the tools we have at our disposal,” says Jim Lambert, a designer for BRC hydraulics. Adds Gilmore: “We have confidence and experience in taking on a (big) job like this. It’s a different playing field and the next level.”
View a photo gallery and fascinating video footage from DN Editor-in-Chief John Dodge's trip to the Welland Canal.
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WELLAND CANAL: A FLUID-POWER MASTERPIECE
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