Centralized Lubrication Systems to Improve Mill Operations and Profitability - A Case Study

Note: This article was published and presented within the US paper industry in 1987-1988. and was co-authored by Matti Vakevainen (Enso-Gutzeit Oy) and J.R. Havron (Safematic Inc.)

"Increase Machine Uptime" and "Reduce Maintenance Costs" are probably two of the most common items on a Maintenance Manager's key work objectives list.

This would appear to be conflicting objectives to many Maintenance Managers who fear a reduction in maintenance expenditures will result in a reduction in machine uptime. This could be true in many operations, but the secret to success lies in the approach we take in managing our maintenance resources. 

Reliability experts have long advocated a very basic approach. If we give top priority to eliminating the need for repairs by identifying the major causes for repairs and take appropriate steps to correct them we can in fact, over time, reduce maintenance costs and increase machine uptime.

Applying this in the Pulp & Paper industry our attention must focus on rotating equipment first.

More than any other industry, we depend on rotating equipment such as pumps, motors, reducers, etc. to process our product. We employ more rotating equipment per unit of production than even the chemical or petroleum industry - and the maintenance of that type of equipment consumes at least 30-40% of a typical maintenance budget.

We know that bearings are usually the limiting factor determining the reliability and runnability of rotating equipment. Bearing experts have estimated that fewer than 10% of all bearings reach or exceed their minimum life expectancy. So, if we picked any single item of equipment that causes the most equipment downtime and maintenance costs - in most mills it would have to be bearings.

We know too, that bearing failures can result from several causes. Unfortunately, records of the causes of bearing failures are not usually well documented because it is too commonly accepted that bearings are expected to fail. However, some surveys of bearing failures have show that a very high percentage of them - even in the range of 50-70% are associated with lubrication - either lack of it, too much of it, or contaminated lubricants.

All of this analysis leads to the inescapable conclusion that an effective lubricating process is absolutely essential to achieving increased equipment uptime and reduced maintenance costs – a fact that we all Intuitively know - but often fail to ensure. 

MILL ANALYSIS

Some years ago, the Kaukopaa Mill of Enso-Gutzeit Oy in Finland found themselves in the position of many mills - excessive machine downtime and high maintenance costs with a major culprit being bearing failures. Their response was to establish a working committee - consisting of the Maintenance Manager, and representatives from the production department, a bearing manufacturer, and a lubrication supplier - to establish the causes of these failures and the corrective action to take. As they studied the problem, several factors became apparent:

• The major causes of bearing failures were inadequate or improper lubrication
• Their manual lubrication program, though a formalized program with dedicated lubrication personnel were not as effective as it needed to be
• Their effectiveness was severely impeded by
• Non reliability of people to perform repetitive, routine lubricating casks at specific intervals without the proper perception of their importance.
• Lack of easy and safe access to many lubricating points.
• Environmental conditions such as heat, water, etc. at the machine.

These factors then brought about a review of the process of grease lubrication. In Figure 1, we show a comparison of the manual lubrication process versus automatic lubrication. In the theoretical manual process, a bearing is filled to an optimum volume of grease. Over a period of time, this volume diminishes until it reaches a minimum point – at which time new grease is added to restore it to the optimum volume. In practice however, the process is often as depicted in Figure 1. The bearing is filled to maximum capacity, often to overflowing. After a period of time the volume diminishes to the minimum point before it is refilled. However, when a lubrication time is missed, the volume continues to diminish below safe levels, creating a high potential for bearing damage. As you look at this figure you can see the similarity to a process control situation where you are trying to maintain a certain level in an operating tank by scheduling a man to

come to that tank at a specified time and manually operate a valve to admit enough liquid to restore the volume. It became apparent many years ago, that this vas not a practical way to maintain a level - so automatic controls were developed and installed to overcome the non reliability of a man. Why then not apply the same technology to lubrication by installing a system to automatically add small doses of grease at regular intervals so as to maintain the optimum volume of grease as shown in Figure 1. 

Figure 1 Manual versus Automatic Lubrication

A centralized automatic lubrication system was the solution arrived at by the team - but they considered it very important that certain basic criteria be met. The system had to:

• Be reliable in operation.
• Supply the proper amount of grease at the right time.
• Have flexibility to adjust the amount and timing of doses to precisely fit the needs of the machinery.
• Be expandable to a large number of points

There are of course, several types of automatic lubricating systems on the market, and the committee reviewed three major types for their needs. - the single line system, progressive module system and the dual line system.

The system chosen and installed at Kaukopaa is a dual line system - as illustrated in Figure 2 because this arrangement was considered the most reliable for operation and accurate dosing. It is controlled by microprocessor control centers by means of which the correct lubrication period is provided for each machine. The lubrication center is supplied with a pneumatic pump and a 4-way reversing 'valve. Grease is pumped directly out of the lubricant drum via the reversing valve into the main pipe system, responding to electrical impulses from the control center.

 Figure 2 Dual Line Automatic Grease System 

The reversing valve alternates the pressurization of the two main pipes. Branch lines from the main pipes are led to each of the machines to be lubricated, terminating in dosing modules.  

The dosing modules are positive displacement piston units, hydraulically operated by changing pressures in the main feed lines in both directions and alternately lubricate two individual lubrication points with precisely measured doses of grease.

This system fully met the criteria established for an automatic lubrication system.  

Reliability: The dual line system ensures grease ' will be forced into the bearing by utilizing the full pressure of the grease supply line - up to 2500 PSI - as the motive force on the dosing module piston, but limiting it to just that required, so as to protect the bearing. This eliminates the use of springs and their consequent exposure to breakage. An automatic control and monitoring system ensure proper operation of the system and provides an alarm if a disturbance occurs - such as a low level in the grease supply or a break in a grease supply line. 

Proper Dosage: The individual dosing modules, which are positive displacement piston units, are sized according to each bearing need and can be precisely adjusted within its range to give an exact dosage as calculated from the bearing dimensions. Timing is set and continuously controlled by the microprocessor control unit. With this arrangement, different sized bearings within the system can be properly lubricated. 

Flexibility: The volume of grease supplied to each bearing each cycle can be adjusted as well as the timing of each lubrication cycle for banks of bearings so that the precise needs of each bank of bearings can be met without affecting other banks.

Expandability: The modular construction of the system permits it to be expanded or reduced as the numbers of lubrication points vary with equipment changes, either as new banks of bearings with specific needs. or as additional dosing modules within existing banks. This feature made it possible for Kaukopaa to start with a small system and expand it to a very large system across the total mill.

Here are some of the more difficult areas that have been addressed by Kaukopaa:

Paper Machine Wet End

The wet end of a paper machine is typically a difficult environment for lubrication because it involves most of the things that are death on bearings – it is hot, wet and corrosive. This combination of conditions requires that bearings be lubricated frequently to protect them from contamination and corrosion. It was found that most mills try to manually lubricate these bearings every 2-7 days. However, these same environmental conditions at the wet end - as well as the safety considerations in getting to the less accessible bearings while the machine is running - make it unlikely that the desired schedule was actually achieved regularly. In addition, when the bearings were greased, the oiler often pumped them completely full until the grease oozed out – so that he would know that the water had been pushed out. As the grease warmed up and expanded, the excess then dripped onto the frames and into the white water system - bringing down the wrath of the papermakers. In the opinion of the study committee, this was a natural application for an automatic grease system, but they recognized there were some special considerations:

• With the large volume of water intrusion into the bearings, it was important that - the grease dosage be large enough to ensure that the wet grease in the roller path of the bearing be completely replaced each cycle. Research by the supplier of the automatic system and a major bearing manufacturer had shown that very small frequent doses did not do this and the small amount of new grease was quickly contaminated. They found that a larger dose at a less frequent interval - generally in the range of 48 hours - was necessary. Consequently, they installed larger dosing modules than they would have used on similar sized bearings in other applications, so as to achieve this optimum volume.
• The system had to be installed in such a way that there were no components requiring unnecessary removal when the wires and felts were changed - and the system must not suffer damage when these changes were being carried out. Utilizing the experience of the system supplier, all the components were located in a manner that eliminated interference with wire and felt changes as shown in Figure 3.
• The corrosive conditions at the wet end dictated that all materials - dosing modules and piping - be of 316 ELC.

Figure 3 Automatic Lubrication - Paper Machine Wet End

Kaukopaa has completed these installations on four of their five paper machines and is now working on the fifth. 

Dryer Felt Rolls 

As in so many mills, Kaukopaa found that grease lubricated dryer felt rolls were the largest source of bearing failures on the machine. Here too, environmental conditions had a great effect on a manual lubrication effort. The excessive temperature and humidity - as well as the safety hazards - made it difficult to ensure a regular lubrication schedule. In addition, the high temperatures oxidized and hardened the grease in the bearing housing - making it difficult to get fresh grease in manually. By installing individual dosing modules that supplied small doses of fresh grease at intervals of 6-8 hours. these problems have been eliminated and the bearings properly lubricated. 

Pulp Mill and Bleach Plant

The Pulp Mill and Bleach Plant offered a challenge with a large number of varied types of equipment with grease lubricated bearings in wet and corrosive conditions. Kaukopaa installed an automatic system that regularly greased these equipment items such as:

• Brownstock and Bleach Washers
• Agitators
• Pumps
• Electric Motors

Altogether they now lubricate a total of 950 bearings in these areas with this system. 

Wood Room and Barking Area.

The old Wood Room and Barking area presented a similar challenge, but the automatic system was successfully applied to:

• Barking Drums
• Chippers
• Chip Screens
• Bark Presses
• Conveyors

In some cases, such as conveyor chains. automatic oiling systems were installed to properly lubricate them. Because of the success of these automatic systems, the new Wood Room and Barking area that was built in 1980 included the same type systems as part of the original construction. 

In addition to the difficult applications mentioned above, Kaukopaa has extended their automatic lubrication systems to "On Line" coaters, wrapping lines and the Evaporator/Recovery area. It is their plan to continue to apply automatic lubrication systems to appropriate new applications until they have reached a minimum number of manually lubricated points. Their system design and modular construction lends itself very readily to this expansion. 

Figure 4 illustrates their schedule and the extent to which Kaukopaa has automated their lubrication throughout the mill. As you can see, Kaukopaa now relies heavily on their automatic lubrication systems. From their systematic analysis of their problems, their determination to solve them and their careful application of this technology, they have expanded their automatic system across the entire plant and have accepted it as a normal and effective maintenance tool.

RESULTS

Of course, the proof of the system is in what it does for them. .In the beginning of this paper, we followed a process of analysis that indicated that an effective lubrication process could help increase equipment uptime and reduce maintenance costs by minimizing bearing failures. As you know, records are not always readily available to document such items as well as we would like, but some specific applications have convinced the management of Kaukopaa chat their objectives are being met. 

Figure 4 Automatic Lubrication Systems Installed

Equipment Uptime

Because of the profit value of equipment running time, reduced downtime is the major reason to eliminate bearing failures. 

Prior to 1975, No.2 Paper Machine experienced 5-10 lubrication related bearing failures a year. Since the installation of an automatic lubrication system in that year, this failure frequency has been reduced to zero. This translates into 30-60 hours of additional machine time and a profit gain of $90.000 to $180.000 annually. 

Total maintenance downtime on this machine has decreased from a level of 470 hours in 1973 to a level of 148 hours in 1986 as illustrated in Figure 8 (below). While other applications have not been as well documented, Kaukopaa is confident that reliability has significantly increased on other paper machines as well as in the Pulp Mill, Wood Room, etc. which are so hard to quantify. Figure 5 illustrates how the total productive output of Kaukopaa has increased even though there has been a shift from heavier board grades to lightweight fine papers on one machine. 

Maintenance Costs

Figure 5 indicates a rather dramatic decline in total maintenance costs. Using 1982 as an index of 100%, and with the effects of inflation removed, you can see that total maintenance cost has decreased from an index of 108% in 1979 to an index of 85% in the 1987 budget, a total decrease of 23%. Without revealing confidential data, we can only say this represents an annual savings of several million U.S. dollars. 

Figure 5 Total Maintenance Cost vs. Production 

Because maintenance costs are impacted by so many factors, it would not be realistic to suggest this decrease was due solely to improved lubrication procedures. However, there are clear indications of a major role in the following areas: 

Reduced Bearing Failures: This of course is the direct objective of automatic lubrication. Though figures vary from application to application, bearing failures with the automatic system have been reduced by about 50% - simply because lubrication failures are eliminated by supplying the bearing with the right amount of clean grease at the right time. Such a decrease results in savings not only on the cost of the bearing and the labor to install it - but also the cost of labor and material to repair the secondary damage that often occurs - usually on premium time. 

Reduced Lubrication Labor (Figure 6): With an automatic lubrication system, labor is limited to periodic inspections and the changing of grease supply drums when empty. Figure 6 illustrates how the annual man-hours for lubrication and preventive maintenance have decreased from 37,000 in 1976 to 20,000

in 1986 - as compared to the increasing number of bearings covered by automatic lubrication, starting from zero in 1976.

This has enabled Kaukopaa to combine the duties of lubrication and preventive maintenance into one craft and reduce the crew size from 20.to 12 men.

Figure 6 Lubrication Labor vs Automated Lubrication Points

(See updated chart Fig 7 below)

 The chart also shows how production continued to increase over the same period of time. 

Figure 7 Updated Lubrication Labor vs Automated Lubrication Points 

Reduced Lubricant Usage: By eliminating the overfilling of bearings, total mill grease usage has - been reduced by 15% while still providing lubrication - even though there have been additions of new equipment and some manual lubrication routes remain

Improved Cleanliness: The reduction in grease usage represented wastage in grease which had previously ended up on the equipment or the surrounding area. Its elimination definitely improved the cleanliness of the mill - particularly on the paper machine. 

Safety: Last, but far from least, was the improvement in safety conditions - not only be eliminating the hazards of waste grease on the equipment and floor - but also in minimizing the exposure of lubricating personnel to moving parts and inaccessible areas.

In summary, Kaukopaa has found that:

• The old way of doing things is not always the best way
• A systematic approach to problem solving can be extremely helpful to maintenance
• Bearing failures do not have to be accepted as a normal event
• State of the Art technologies are available to help maintenance do their job
• Maintenance costs can be reduced while increasing equipment uptime.

While we have been referring to Kaukopaa as a case history, similar references can be made to many of the mills in Scandinavia. 

Although it is difficult to quantify the number of different systems in operation, we do know there are over 200 paper machines operating with wet end lubrication systems. It is interesting to note an increased interest in these technologies by U.S. paper mills and I foresee a time in the future when their usage will be as widespread here as in Scandinavia. 

Figure 8 Maintenance Downtime #2 Paper Machine