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Three Steps of Preventative Maintenance

But this is only part of the equation. Mill management also requires a top-notch maintenance team to keep the machinery in tip-top shape.

This all relates to the bottom-line, which in today’s North American pulp and paper industry, is essential.

Imperial Oil continues to develop products that allow for smooth operation, as well as helping to establish and enhance preventative maintenance programs.

“A large portion of our research is focused on the resource industry -pulp and paper has always played a key part in that,” says Lorne Brock, Imperial Oil’s product technical advisor, industrial oils and greases. “Corrosion, because of the various fluids and materials that are processed in pulp and paper, is a big part of the problem that affects paper machines.”

Introduced three years ago, Imperial launched Mobil Centaur XHP 221, a corrosion control grease applied to the wet end and press section of the equipment.

“It’s a brand new technology,” says Brock. “The thickener is made from calcium sulphonate, a corrosion inhibitor additive in itself. Roughly 20% of Centaur consists of this additive. In the past, greases were more conventional and you had to put in additives for corrosion inhibition.”

For the dryer section, Imperial has two paper machine oil offerings. Both Esso’s Teresstic N and Mobil’s DTE PM were introduced in the early 1980s, and were reformulated over the years to stay current with machine demands.

“Both were designed for corrosion, long life and to deal with high temperatures,” says Brock. “In the drying section, temperatures can be 100C or more at the bearing interface, the point where you need to have something stable. Usually the bulk temperatures are between 65C and 80C, depending on the application. At the interface, 100C for the bearings is not unheard of and this requires good thermal protection, corrosion control and deposit control.”

Since 1980, developments in corrosion control have focused on enhancements to deal with various detergents and disbursement to keep the equipment clean and to eliminate deposits that form in high temperatures.

“This is where you start to build in your corrosion inhibition,” says Brock, who stresses that while the industry is facing hard economic times, investments by mills in quality oils and greases are essential to keep the machinery operating efficiently.

With mills either being closed or temporarily shutting down some of their paper machines, additional corrosion control is needed for idle periods that could range between months and years. Esso’s Procon was developed for this specific purpose. Procon, a lay-up lubricant (reformulated last fall), is added to the oil (between two and five percent of the volume) prior to the shutdown.

Among its key attributes, Procon protects coated surfaces from corrosion or rust normally caused by unprotected exposure to water or to a humid and corrosive atmosphere, cleans and disperses soluble and insoluble material, displaces water and neutralizes acids left in new equipment by the pickling procedure.

Complete removal of the oils and fluids from a paper machine is essential prior to a re-fill in order to avoid contamination of the new fluids. Reservoirs in these systems range from 1,200 to 7,000 litres.

“There can be up 10 % of the oil still tied up in various bearings and the equipment,” says Brock.

To clean the tanks prior to fluid replacement, Imperial offers Mobil System Cleaner, which is poured in (between two and 10% of the total volume), 72 hours to a week prior to the oil change.

A reliable oil analysis system is necessary, preferably on a monthly basis, to gage the state of the fluids, which helps determine when they need to be replaced and to coordinate that replacement period with preventative maintenance shutdowns.

This analysis will determine whether bypass filtration or other fluids will have to be added to extend the life of the oils. On average, says Brock, oils have a lifespan of five to ten years.

Brock explains that the expense and diligence of sending in monthly oil samples results in savings for the mill.

Team Effort

To Imperial, oil analysis is a team effort, and the company has helped in the creation of Lube Teams teams at plants, which have representatives from maintenance and operations departments, lubrication personnel and an Imperial field technician. LTs meet quarterly, scheduled to coincide with the Imperial field technician’s visit.

Brock says that reports are presented at these meetings from the various departments.

“It’s not just one person,” he says, “it’s the whole team with their areas of expertise having a positive impact on maintenance and the costs of operating a mill.” Feedback from the industry, as well as from original equipment manufacturers is essential to Imperial’s efforts to enhance its greases and oils.

Imperial is key player in industry meetings and associations such as the Pulp and Paper Technical Association of Canada.

“We have a global team of equipment builder contact people and they visit various offices and test centres to keep abreast of developments by OEMs,” says Brock. “They test our products to make sure that they work in the new equipment. We also get feedback from the field. This is very important because the industry in Canada operates with a lot of older equipment.

“You have to make sure that the products are compatible with existing machines and provide a maintenance-enhanced performance for older equipment that may or may not have been upgraded,” he adds. “For example, mills should not have to use different oils for different systems.”

Smoothing the Way

Based in Canton, Ohio, The Timken Company manufactures bearings, coatings, lubricants and related products for the paper industry. The company also offers a wide portfolio of condition monitoring, reliability and repair services.

“For the paper industry, application solutions through product enhancements are key,” says Barclay Simmons, Timken’s application and service engineering specialist. “Such improvements in our portfolio include quiet bearings for refiners with noise sensitive controls and engineered solutions for compromised lubrication conditions and corrosive environments.

“We offer a range of bearing design modifications to meet the demands of and solve common problems for the industry,” he adds. “One modification, known now as the W906A, is for large bore paper machine bearings and is designed to solve the long-time problem of fractured inner rings and rollers. The advanced metallurgy of this modification minimizes unplanned downtime and improves overall productivity.

“Coatings and engineered surfaces provide another reliable solution for harsh environments common in the industry,” he adds. “Timken Thin Dense Chrome (TDC) coating is uniquely designed to provide protection against rust and etching for increased performance in harsh and corrosive environments. The TDC coating can be supplied for virtually any design or style of bearing we manufacture.”

Simmons notes that engineered surfaces can be applied to the rollers of a spherical roller bearing to deter bearing failure and increase bearing life in marginal-lubrication environments and low-speed conditions.

Customer Specification

Todd Thorsen, Timken’s market manager for the pulp and paper industry, says that mills are demanding customer-specific solutions for unique application issues.

“Customers demand engineering support and product modifications for paper machinery,” he says. “Our engineering teams work closely with paper customers to recommend the right product solutions that improve equipment performance and extend bearing life.

“A service that is growing in popularity in the paper industry is bearing repair,” he adds. “This provides an alternative, both in cost and time, to buying new bearings by extending the life of bearings already in service. A high-quality repair prog
ram can address the challenge of determining if and when a bearing can be repaired. A repaired bearing, depending on the required level of service, can often be returned to like-new specifications.

“It is essential to follow proper bearing handling practices,” he adds. “Preventing bearing damage begins before a bearing is placed into operation and must be considered at times of inspection, cleaning, installing, removing or repairing.” Another key factor is condition monitoring. “Reliable products and services help eliminate the guesswork associated with machine maintenance and may prevent unscheduled downtime,” says Thorsen.

“Our application engineering team works with customers to determine the optimal bearing design and operating conditions for the application,” he notes. “Our service engineering team works alongside the mill’s maintenance team to provide on-site bearing maintenance, installation, repair and training support.”

Lubrication -Vital to the Process

Lubrication, says Cheryl Mendoza (EIT) of SKF Canada Limited’s application engineering department, plays an integral role in bearing performance, with its primary function to completely separate the moving surfaces in a bearing, namely the rolling elements and the raceways. Prevention of metal-to-metal contact within the bearing is key in avoiding surface wear and fatigue, which can very quickly lead to premature bearing failures.

“In order to prevent bearing damage it is important that a lubricant of adequate viscosity is chosen,” she says. “This will depend on the bearing size, operating temperature and speed. Additives, such as extreme pressure (EP) or anti-wear (AW), can be used to enhance the lubrication characteristics.

“In addition to proper lubricant selection, it is also important that bearings be regularly re-lubricated, whether manually or through an automatic lubrication system,” she adds. “Ensuring that the bearings are always fully coated will not only guarantee separation of the metal surfaces, but will also protect the bearing from corrosion, especially in a humid environment.”

Typically two types of lubrication are used in rolling bearings -grease and oil.

Grease lubrication, says Mendoza, is more easily retained inside the bearing housing due to its consistency, which is particularly beneficial for inclined or vertical shafts.

“It can also be applied to seals to form an added barrier against external contaminants,” she says. “However grease lubrication tends to generate more friction and heat in the bearing, often acting as an insulator. Oil lubrication, on the other hand, can conduct heat away from the bearing and can be used as a lower friction alternative for applications where speed and temperature are high.

“It can be applied through an oil bath, where the oil sits in the bottom of the housing and is swept up into the bearing by its rotational movement or through oil circulation, where the oil is continuously pumped through the bearing. If an oil circulation system is used, there is the added benefit of being able to cool and filter the oil before it returns to the bearing.

CARB, the newest bearing made for the Pulp and Paper industry, was developed by SKF. “Most of the recent R&D has been on making existing products better” says Mendoza. “This can be in terms of manufacturing methods, improved steel quality, special coatings, etc. The lifespan of our products varies. There have been some instances whereby bearings have lasted decades. In 2006, the International Standards Organization (ISO) adopted the SKF Life Theory in ISO 281. SKF life theory factors in fatigue load limit, indicates the load limit where any applied load under this will lead to infinite life based on fatigue failure, lubrication and contamination. What really influences life are the ‘other’ factors -lubrication, contamination, mounting and dismounting practices.”