Three costly mill problems lead to three reliability-based solutions, Solutions!, Online Exclusives, December 2004

Excessive machine vibration in one mill, critical equipment failures in another, and a need for improved mill operations in a third were producing costs ranging from US$ 200,000 to US$ 1,200,000. To solve each problem and contain these costs, each mill turned to SKF, a global supplier of products, customer solutions and services incorporating rolling bearings, seals, mechatronics, and lubrication systems.

An SKF reliability specialist performs a
diagnostic test at the client’s mill.

Mill 1: Excessive vibration
The first mill experienced excessive machine vibration from a supercalender stack, with vibration worsening when the mill ran at speeds above 1325 feet per minute. This excessive vibration was creating roll damage that cost the mill $500,000 in only one year for replacing ruined rolls. Just as important, the vibration kept the mill from running at its design speed. Also, although the mill had been experiencing these problems for several years, the root cause was still unknown. Seeking a solution to this ongoing problem, the mill management went to SKF Reliability Systems for help.

Mill management saw the problem as:

• High vibration, especially in the lower part of the stack
• Roll barring or flat spots on the paper rolls
• Broken rolls, both paper and steam
• Failed bearings, predominantly from thrust loading
• Reduced operating speed in an effort to reduce failures, leading to reduced production.

The solution:
The SKF Reliability Systems solution was developed from a Machine Reliability Assessment (MRA) process to improve calender stack reliability. The assessment involved:

• Listing probable causes for symptoms
• Using advanced technologies, like Operating Deflection Shape analysis, to gather multi parameter data and analyze connections to probable root causes
• Making improvement recommendations on roll misalignment
• Improving alignment with machine enhancements and precision installation procedures

The paper mill quickly benefited from improved roll alignment, reduced roll vibration, and reduced roll damage. The cost of replacing rolls at US$ 500,000 was eliminated, and running the machine at its design speed of 1,450 fpm increased paper production.

How the MRA program works:
Machine reliability and maintenance issues are frequently complex, and the solutions require special tools and expertise that are not always available on-site. SKF offers service packages designed to help keep this critical element in the production process running more efficiently. SKF Reliability Specialists are trained to use the most up-to-date practices and specifications whenever applicable.

In the MRA process, a team of reliability specialists reviews the entire machine, examining both operational and engineering aspects of the system to develop a complete solution. Activities include:

• Operating deflection shape analysis
• Lubrication analysis and recommendations
• Advanced vibration analysis
• Precision maintenance
• Bearing maintenance
• Bearing mounting and installation
• Seal application review

Mill 2: Critical equipment failures
The second mill was experiencing frequent and unexpected failures of critical equipment. This created a culture of reactive maintenance and gave rise to significant operational reliability problems.

Mill management saw the problem as:

• Unexpected failures
• Reactive maintenance
• Mill production below capacity
• High waste rates

Together, these problems contributed to a loss in excess of a million dollars.

The solution:

The SKF Reliability Systems solution was to bring in the Proactive Reliability Maintenance (PRM™) program, using the technologies and processes required to improve reliability. The solution process included the following steps:

• Assess the total mill, including operational reliability and maintenance processes
• Apply critical component mechanical and advanced condition monitoring expertise to pinpoint failure-causing points
• Use the PRM process to maintain reliability improvements and eliminate unplanned downtime

The paper mill succeeded in reducing unplanned downtime by 70% and reducing the waste rate by 30%. In addition, the improved reliability led to record production rates. The successes reinforced the proactive cultural changes that occurred. The total positive impact for the mill is US$ 1,200,000 and counting.

How the PRM process works:
Most traditional forms of predictive maintenance will form a sustained maintenance loop, whereas the SKF Proactive Reliability Maintenance (PRM) process forms a continuous improvement loop. Each of the following four steps builds on one another to prevent repetitive failures or problems.

Step 1 is to design a Predictive Maintenance (PdM) system specifically for the plant, based on information provided by an SKF assessment that provides an understanding of the parameters that affect plant and equipment effectiveness. The PdM system includes activities such as: vibration analysis and bearing monitoring, thermography, and lubrication analysis.

The PRM process may also highlight the need for additional activities during maintenance, such as geometric alignment, precision balancing, lubrication, filtration and sealing improvement.

Step 2 is to make a diagnostics and root cause analysis. SKF Reliability Systems engineers will diagnose the root cause of problems and determine corrective maintenance actions, such as machine realignment, changing the lubricant, or replacing a damaged component.

Detailed machine diagnostics can be conducted on site or at an SKF remote diagnostics facility using SKF Condition Monitoring. Physical analysis on the damaged components may also be required to determine the root cause of the failure. This information is used to prevent the same type of failure from recurring.

Step 3 is to measure improvement using Key Performance Indicators (KPIs). KPIs are performance improvement targets established jointly between SKF and the customer. They may cover a wide range of factors, from bearing performance to plant availability. Where possible, once a KPI is achieved, a new target is set to facilitate continuous improvement.

Step 4 involves an operational review process. Periodic review of the improvement program is important to monitor KPI achievement. Results are documented and presented at performance review meetings. Operational review meetings are held to continually refine the PRM process to achieve the best balance of plant asset performance with the PRM process activity cost.

Implementation of a well-managed PRM process will ensure the best possible return on plant assets by managing potential risk. SKF Reliability Systems can guide a mill to establishing its own PRM process, or design, implement and manage the process for the mill. This can apply to the entire plant or any area of it. A full management program will include all the hardware, software, and the technical resources needed to ensure measurable improvements.

Mill 3: Operations improvement
The third mill was already experiencing good reliability, but wanted to improve operations even more by reducing downtime and costs. However, they were not seeking to incur upfront capital investment.

The client challenges were:

• Reliability program not completely effective
• Increased preventable unplanned mechanical downtime
• Higher replacement part stores

All three problems reduced mill output, with a resulting cost of hundreds of thousands of dollars in lost production, maintenance costs, and inventory costs.

The solution:
The SKF Reliability Systems solution was an Integrated Maintenance Solution (IMS™) agreement using the best technologies and processes, as well as addressing the cultural challenge needed to improve plant reliability. The IMS activities included:

• Make a detailed assessment of financial and operating conditions
• Set key performance indicator (KPI) for IMS guarantee of no unplanned preventable mechanical downtime (UPMD)
• Enter into IMS multi-year partnership focused on processes, technologies, and culture to improve mill profit by guaranteeing 30% annual reduction of UPMD KPI
• Assume and improve condition monitoring processes
• Perform root cause analysis and bearing inspection
• Perform precision shaft alignments
• Supply bearings, stock and manage inventory
• Provide new condition monitoring technologies (on-line, portable, and software)
• Improve culture by taking responsibility and improving processes and providing training to maintenance and warehouse staff

The mill achieved improved quality and full machine control with on-line condition monitoring. The mill improved MTBF for auxiliary equipment and reduced labor cost by US$ 90,000. Inventory carrying costs were reduced by 100%, and the guarantee was met by reducing unplanned preventable mechanical downtime by 30%. Total savings were in excess of US$ 250,000.

How IMS contracts work:
Manufacturing companies rely on increasing machine uptime to improve profitability. An Integrated Maintenance Solutions (IMS) contract agreement offers an alternative to current maintenance practices. Within the IMS contract, SKF Reliability Systems improves asset efficiency by providing technical expertise in plant maintenance. Asset utilization is improved and maximum plant efficiency gained.

Step 1: Assessment. The process begins with a detailed assessment of plant efficiency, including component supply costs and maintenance practices. The assessment identifies key problems, enabling the creation of a sound improvement plan. Upon agreement, SKF Reliability Systems personnel are assigned to work at the customer’s site, to strengthen existing maintenance and technical skills and to provide other SKF technical resources. A Proactive Reliability Maintenance (PRM™) process is then established to drive the improvement plan.

Step 2: Trouble-free supply. Reducing all costs associated with purchasing, supplies and inventory management is an integral part of an IMS contract. Working in close partnership with our Authorized Distributor network, SKF will reduce transaction costs, release capital tied up in inventories, and guarantee that replacement parts are available and delivered when needed.

Step 3: Maintenance strategy. Analysis of the maintenance strategy applied across the plant and to each machinery asset will allow effort to be re-focused on critical tasks, to ensure that maintenance activity adds value to the business result. SKF Reliability Systems can also fully integrate all aspects of maintenance into EAM/CMMS systems.

Step 4: Proactive Reliability Maintenance™ (PRM). Through the defined process mentioned earlier, best practice condition monitoring activities are used, the root causes of problems are diagnosed and corrective actions taken to eliminate recurrence.

Step 5: Technology upgrades. Part of the ongoing activities of an IMS contract is to adopt new technology to improve machine performance whenever possible. These might include:

• Plant re-engineering, using the latest component design solutions
• Oil cleanliness systems to prolong lubrication life and minimize effects of contamination
• Use of the latest condition monitoring technology to reduce the cost of data collection and ensure better machine diagnostics

Step 6: Machine maintenance. Precision maintenance tasks can be supervised or performed by skilled SKF engineers to ensure effective machine overhaul. This includes techniques such as laser alignment, rotor balancing and critical bearing installation and lubrication tasks.

Step 7: Training. Keeping staff maintenance skills up-to-date is an important step in achieving IMS performance goals. SKF Reliability Systems provides detailed training courses to cover aspects of precision maintenance that directly impact the overall return on assets, including: precision maintenance skills, bearing maintenance and service, condition monitoring skills, and management of maintenance.

An IMS contract agreement is a partnership that incorporates a performance-based payment structure. The IMS contract agreement guarantees that SKF will perform to a specified level. The annual contract fee may include bearing and seal consumption, upgraded condition monitoring equipment, software tools and support, and the SKF technical resources to determine, correct and eliminate repetitive machinery problems.

About the author:
Colin Roberts is Head of SKF Group Technical Press, and can be reached by email at colin.roberts@skf.com. For more information about the SKF Group, visit the website: www.skf.com.