Tasked with planning a scheduled turnaround at its Mahkeses in situ oilsands facility at Cold Lake, Imperial Oil’s engineering team needed to solve the problem of how to minimize downtime and lost revenue. The scope of this shutdown included replacing three of seven modules within each of the plant’s two heat-recovery steam generators. It was the first time since the facility’s startup in 2003 that entire modules, rather than just individual tubes within the modules, needed to be changed out.
The conventional approach to this type of job involves disconnecting the old modules within the heat exchangers and lifting them out by crane, one at a time. The new modules are then lowered into place, again one at a time, and everything is welded up.
For Imperial, this would have meant six lifts out and six lifts in, which would have required 30 days above and beyond the 58 days needed for the rest of the turnaround. In other words, the heat-exchanger module replacement was the critical pass in the shutdown.
The solution, which won the company an APEGA (Association of Professional Engineers and Geoscientists of Alberta) 2015 Summit Award in the Project Achievement category, was simple enough: the three modules that needed replacement were welded together and lifted out as one unit. They were then replaced by a three-pack of new modules.
Two lifts out. Two lifts in. Thirty days saved.
In theory, this seems as simple as scooping up two dropped loonies at one go rather than bending over twice to pick them up separately. But nothing is simple when each of Imperial’s three-module units weighed over a million pounds, requiring a special 188-foot crane (about 17 storeys tall). Then all of that brute lifting power needed to be deployed with the utmost precision within the tight confines of an industrial plant that allowed for just six inches of free space on either side of the module units.
A lot of talk about creative thinking and its importance to oilsands development sometimes misses the point that much of the progress in the industry falls squarely on the shoulders of engineers, whose jobs routinely require problem-solving ingenuity. In fact, the creative spark that generates a new idea is often the easiest part of a project. The bigger challenge is everything that comes after—the planning, the engineering, the management of the risks and the collaboration needed to execute effectively. This was certainly the case with Imperial’s Mahkeses Heat-Recovery Steam Generator (HRSG) Replacement Project.
“We had to have a lot of trust in our contractors. We had a lot of oversight. But we also let them do what they do best,” says Vi Nguyen, project manager for the HRSG replacement.
It’s difficult to overstate the amount of planning and collaboration that goes into any successful oilsands turnaround. Planning for the Mahkeses shutdown began in 2011, two years before its 2013 commencement. And while the idea for the bundling the modules came easily enough, selling that idea to the original equipment manufacturer of the heat-recovery modules and to Imperial management was a bit of a challenge.
The manufacturer was resistant at first because the modules weren’t designed to be moved as a package. Meanwhile, Imperial’s management wasn’t keen to venture into uncharted territory and risk a module unit crashing to the ground in a heap of twisted metal, possibly destroying part of the Mahkeses plant.
“So on both sides, contractors and management, we had to work through the technical challenges and the risks,” says Imperial project executive Andrew Hodgetts. “Internally, we had to make sure we understood the risks and had appropriate mitigation in place and that we could communicate this to our management so they could trust us to execute.”
A big part of the in-house engineering work came down to creating an effective way to bind together the modules. The team settled on using engineered beams to which three modules could be welded.
“The new modules going in were also pre-welded together to take as much work out of the shutdown [timeframe] as possible,” Nguyen explains. “We would only need to do the final connections once it was all lifted into place.”
There were only four lifts total, but they were big ones. The heavier of the two outgoing module units weighed 1.12 million pounds, while the lighter one weighed 1.06 million pounds. A crane with a total capacity of 1.6 million pounds (and a lift capacity of 1.3 million pounds at the required 50-foot radius) was sourced, but it would have to be brought in from Hawaii where it was on a job just prior to the Mahkeses shutdown.
To haul just one HRSG module required a 243-foot semi truck and multiple tandem-trailer rig. Each of these modules measures about 71 feet by 36 feet, which is large enough to make the tractor look like an overachieving toy truck.
Unfortunately, there was just one such trailer set in existence, and the Mahkeses turnaround alone would require a total of six hauls. The project would have to be slotted in among another 20 module hauls to other oilsands facilities during the busy oilsands construction and turnaround season. The risk of a trailer breakdown was real and had to be considered carefully.
“We were delivering into January,” says Jason Parsons, the company’s opportunity manager on the HRSG replacement project. “Road bans come into enforcement in February, weather dependent. This shutdown was in May. If we didn’t have all our modules by the time the road ban came into enforcement, we would have to wait until December to get the rest of the modules. So we would miss the shutdown.”
To square the odds of getting the modules delivered on time, Imperial decided to have another trailer built.
“In our world, it’s really about risk management,” Hodgetts says. “The second trailer gave us more schedule flexibility so that we had the assurance we would get all our deliveries before the spring road ban.”
With that sorted out, another Imperial engineering team tackled site prep and designed a series of foundations on which the modules could be set and welded into units. Global lift experts reviewed the lift plans. Three-dimensional modelling and animation were used to identify potential interference with existing site infrastructure. When the modules were finally welded together, a series of test lifts were executed to verify that the module units would lift without tilting off centre.
The big day arrived with a blue sky and hardly any wind. Execution of the first lift, after two years of planning, went ahead almost anticlimactically without a hitch, on time and on budget. Ditto for the second module unit a number of days later.
“When both units are down, the power lines are disconnected, so we’re not selling electricity into the grid and we’re not producing, so that total downtime is what you want to minimize, and we kept that down to just 19 days,” Nguyen says.
The old modules were then cut apart and trucked away for disposal.
Collaboration was the meat and potatoes of the HRSG replacement project, which achieved a sterling safety record. Apart from the original module manufacturer and the transportation contractors, numerous other parties were involved on tasks ranging from the mechanicals to the module welding and tie-ins. A union workforce and various other groups had to be coordinated and rotated through the site—all of which is really nothing new for an oilsands project, but each new job adds to the knowledge of what makes for effective collaboration.
The bigger takeaway, however, came from employing an alternative approach to HRSG module replacement. The company saw that there is a better way that can offer superior economics and also be used at its other projects in the future. Along with that comes a greater tolerance for pushing boundaries and raising the bar for innovative solutions at Imperial—and possibly within the industry as a whole.