When Dustin Stuyt and his team sought solutions to extend the life of tertiary sizer teeth in Syncrude’s ore crushing units, they looked internally to the Research and Development department for ideas.
The collaboration resulted in new technologies that could see oil sands mining and extraction equipment of all kinds running for years before they need maintenance.
Syncrude has been tackling material wear issues since production began in 1978. The abrasive nature of oil sand combined with the extreme temperatures throughout the year in Northern Alberta have played havoc on shovel teeth, grader blades, and tertiary sizer teeth in particular. As equipment and technology have changed, so have the solutions to these issues. The ultimate goal is to extend equipment performance as long as possible before replacement is required.
The company’s Leading Edge Advanced Performance (LEAP) project was created five years ago to look at extending the life of equipment in direct contact with oil sand and rock materials. Dan Wolfe, senior associate, Mechanical with R&D, leads the project and their work on tertiary sizer teeth has revealed viable solutions including friction welding technology adapted from the aerospace industry.
Tertiary sizers are the final step in wet crushing technology used at Syncrude’s North Mine operation to process oil sand and prepare it for hydrotransport. After oil sand is broken down by crushers in the field to about the size of a beach ball, the material has water added to it while it passes through two sets of sizers before being sent to Extraction. In secondary sizing, those beach ball pieces become the size of a volleyball, and after tertiary sizing the pieces are softball size or smaller.
Syncrude’s North Mine uses a wet crushing technology that mixes crushed oil sands with water through secondary and tertiary sizers to produce a slurry for bitumen extraction. New technology developed for the sizer teeth has the potential to extend unit run life 10 times longer than is currently achieved.
The magic happens in the tertiary sizers.
– Dustin Stuyt
“It’s the last step where oil sand is mixed with water and chemicals to convert it to a slurry of finer particles that can be easily transported to Extraction,” says Dustin Stuyt, a senior engineer with Equipment & Reliability Engineering.
Unlike other extraction technologies on site where screens reject materials larger than a specified maximum before the remainder enters the hydrotransport system, the use of sizers allows everything to be fed into the system allowing for greater bitumen recovery and fewer maintenance issues along the way to Extraction. There are four of these systems operating in parallel at North Mine.
The sizers consist of four rotating shafts about five metres long with fist-sized teeth. There are 432 teeth on each of the shafts on the tertiary sizers for a total of 1,728 in a machine. Over a typical run of 2,000 hours, more than 10 million tonnes of oil sand will pass through the system before the teeth will need maintenance, with the tertiary sizers taking the brunt of the wear.
The wear issue is significant in the sizers, because if you lose one inch off the teeth, larger materials get through and you’ll start damaging equipment downstream.
– Dan Wolfe
Dustin’s Extraction team and R&D tested a number of options for the tertiary sizer teeth with various degrees of success – including a test that both he and Dan referred to as a horrific failure – until they discovered two tungsten carbide options with serious potential.
Tungsten carbide is a dense, metal-like substance about two times heavier than steel and up to 10 times harder. It’s the hardest material commercially available to Syncrude and wears extremely well, but it is prone to cracking when attached to steel with traditional joining processes.
The first option to the team was teeth sourced from a US-based company specializing in tungsten carbide products. They developed a sizer tooth with broken bits of tungsten carbide recycled from hard rock drills embedded in the first centimetre of the tooth.
“These teeth cost less than what we’re currently using and so far the results have shown they can last about twice as long,” says Dustin.
Tertiary sizer teeth ready for action. The teeth are made from solid blocks of 25-millimetre thick tungsten carbide clad with a Kovar coating and attached to the segments using a friction welding technique.
The new teeth are being attached to the sizer segments as maintenance rebuilds take place. Using the previous teeth, the team budgeted for nine rebuilds per year but the new, lower-cost sizer teeth could reduce rebuilds to as few as three per year – meaning millions of dollars in annual savings.
“We think the teeth could process up to 30 million tonnes of ore before they need replacement,” says Dustin. “With the addition of small tungsten carbide studs between the teeth, we are seeing better product for hydrotransport and our wear rates have dropped off by 50 per cent since the wet crusher was commissioned.”
A second option, while more complex, is showing even greater potential. It involves cladding solid blocks of 25-millimetre thick tungsten carbide with a Kovar coating, and attaching them to the segments using a friction welding technique. Kovar is a unique iron-nickel-cobalt alloy that expands and contracts like the tungsten carbide material. When Kovar cools from the cladding operation it doesn’t create residual stress at the bond line. Without the Kovar coating, a crack forms when the tungsten carbide is welded to the steel and it doesn’t take long for the block to break off.
Hugh Roth is a senior associate, Metallurgy at R&D, who tested this new technology and introduced the Kovar coating/friction welding solution. “With friction welding the weld takes seconds to make. It is only hot at the interface and the carbide doesn’t know it’s being welded,” he says.
Syncrude is the first company to evaluate this technology and we anticipate it having benefits for a wide range of earth engaging equipment.
– Hugh Roth
Syncrude is analyzing results as they come in and is looking to evaluate the technology for other applications. R&D tested friction welding on grader blades and tertiary sizers this winter with extremely positive results. While regular grader blade edges last about two weeks before they need to be replaced, the test showed potential for them to last an entire season. Additionally, 66 of the friction welded sizer teeth were put into service and all of them showed little to no wear after two months. It’s possible the teeth could last 10 times longer than current teeth, or 20,000 hours.
“It’s a totally different level of capability,” said Hugh. “We can design and operate equipment in a completely different way now that we know materials can last 20,000 hours or more and we can rely on the metal keeping its shape. Outage schedules don’t have to be what they were, and we may not have to build redundancy into our operating equipment.”
While there is excitement for the results to come from this collaboration, Dan believes more can be done to improve wear rates in the future. Developing two parallel solutions for a big problem and applying those ideas to other leading edge issues, means there is more testing to do. And with that, more innovations to come for R&D and Bitumen Production to extend wear life on machinery and equipment.