Maintenance & Reliability
Moving the annual shutdown to every 18 months
May 2, 2017 - When a kraft pulp mill has to shut down for 10 to 14 days every year for scheduled maintenance, millions of dollars are spent, and millions more in revenue from lost production are not coming in — resulting in a significant impact on cash flow and a company’s quarterly results. There is enormous pressure not only from management, but also from investment analysts, to complete these shutdowns on time and on budget.
May 3, 2017 By Martin Fairbank PhD
But what if that annual outage could be extended out to every 18 months or even longer?
At PaperWeek Canada this past February in Montreal, Que., a session was held on shutdown strategy, featuring three mills that presented their experience with extending the period between major shutdowns. The panel was hosted by Eric Ashby, general manager of Domtar’s Windsor, Que., mill and newly appointed chair of Paptac’s executive council.
Predictive and preventive maintenance
First to present was Ryan Kazakoff, maintenance superintendent and shutdown coordinator at Domtar’s Kamloops, B.C., mill. He told the audience that four to five years ago, the shutdown budget and costs at his mill were not under control. In spite of meetings held year after year on how to improve the shuts, the same items came up each time.
He decided it was time to change their approach. They did some benchmarking within Domtar, with other pulp mills in the industry and even in other industries, to compare shutdown cycles and documented some best practices. One of the first follow-ups was to instill better discipline in their planning, execution and improvement cycles.
While the benefits of a shutdown that is planned and executed efficiently are easy to understand, an intriguing idea emerged from looking at some other mills — extending the period between shuts from 12 months to 18 months or longer. Intuitively, one would think this is more risky. With a longer period between scheduled shuts, there might be more breakdowns, necessitating unscheduled downtime. But if it’s backed up by better predictive and preventive maintenance, these risks can be mitigated. Looking at historical records of unscheduled breakdowns, Kamloops determined through Pareto analysis that 80 per cent of the risk comes from 20 per cent of the equipment.
Typically, the two pieces of equipment in a kraft mill that drive the critical path for a shutdown schedule are the recovery boiler and the continuous digester. And Kamloops’ analysis showed that the actual time used during the annual shuts for working inside these two pieces of equipment amounted to only 50 per cent of the shutdown window for the recovery boiler and 20 to 25 per cent of the shutdown window for the digester. This means the length of the scheduled shutdown does not necessarily have to be longer when it is held less often.
Kamloops’ expectation was that with a longer period between shutdowns, over a three-year cost cycle, the cost of industrial cleaning and mechanical, electrical and instrumentation repairs would go up. On the other hand, with only two shuts instead of three over a three-year period, the cost of several other items would subsequently decrease, including scaffolding, rental of equipment and trailers, contractor overhead, training and chemicals.
A forward-thinking approach
The second presenter was Bob Ostaff, kraft pulp production manager at Resolute’s Thunder Bay, Ont., mill. They were looking for ways to become more cost-competitive, and since the annual outage has a large impact on costs, they looked at how to move to an 18-month cycle without incurring additional risk. At first, they faced a lot of skepticism from operators, whose reaction was: “The equipment is not being taken care of now, and you’re going to do less maintenance?” But the message from the corporate level was: “A lot of mills in the industry are doing it already, so why can’t you?”
Resolute selected the Thunder Bay mill to pioneer the 18-month process, because in this case, a shutdown not only meant lost revenue from pulp production, but also from the sale of renewable power to the Ontario grid. Resolute decided the benefits of a successful implementation would be high.
In the last couple of shutdowns, the mill had not hit the targeted budget or timeline, so they had to develop a plan. They set up a review process using personnel from the mill, the corporate office, suppliers and regulatory agencies to look at what they did in the past and what would need to be done in the future. In the past, they had never really had a shutdown planning group, so that was one of the first changes made — three employees now do nothing but plan the 18-month shuts using a more rigorous approach.
One advantage of this new approach is that they are now able to prepare detailed job packages, with pictures, procedures, and safety and environmental information. These packages are sent out to contractors for quotes, and the mill now has the power to negotiate better prices on these contracts, because both sides know exactly what the job being quoted on involves.
Thunder Bay’s vision of success for this exercise includes reduced maintenance spending on shuts, with production risks mitigated, improved reliability, and important lessons that can be transferred to other Resolute sites.
One of the barriers that had to be overcome to implement the new strategy at all the mills presenting at PaperWeek was the effect on employees. When the annual shutdown was traditionally held in spring, employees planned their lives around it, and it was a good fit with the spring thaw season, when log trucks are regulated to carry lighter loads. With an 18-month schedule, a shutdown could take place in the spring, or sometimes in the fall, or not even in a calendar year at all. Having a shutdown in the fall could require some employees to be on site when they traditionally take vacation for hunting season. Communication with employees about the how, when and why of a new strategy is very important, as it helps gain employee buy-in, ensuring its success.
The process of moving away from an annual shutdown requires a lot of patience and dedication. Ostaff stated a five-year plan as a requirement, and Kazakoff opined that it will take six to seven years to fully evaluate and optimize the longer time cycle.
A pit-stop strategy
The third speaker at the session was Vincent Charbonneau, assistant maintenance superintendent at the Domtar Windsor mill. He is planning the mill’s first 18-month shutdown for October 2017. To support the longer period between major shuts, Windsor uses a “pit-stop” strategy of shorter shuts for cleaning when production rate is decreasing due to bottlenecks, approximately every six months. For example, they use short pit-stops of two days to descale the lime kiln. They also take advantage of these pit-stops to carry out non-destructive testing inside the digester.
A risk of moving to less frequent major shutdowns is the possibility of a major failure occurring to a pressure vessel, such as the recovery boiler or the digester due to corrosion. Pulp mills have to persuade their insurers that they are taking all necessary steps to mitigate this risk, by performing predictive and preventive maintenance. Non-destructive testing, such as ultrasonic inspection of welds and boiler tubes, is a useful tool, as well as vibration testing and oil analysis of rotating equipment. Physical inspection is important too. Ostaff mentioned “rats in the digester” — it turned out he was not discussing rodents but Remote Access Technology, a company that inspects and services difficult-to-access areas through technicians who use ropes and harnesses to get to these areas, saving pulp mills from having to erect scaffolding.
All these mills have learned that a longer shutdown cycle requires a much more effective shutdown planning, budgeting and execution strategy. Equipment reliability is of paramount importance to reach their goal of more production days over a three-year cycle.
This article was originally published in the Spring 2017 issue of Pulp & Paper Canada.
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