Implementing technological advances in a vintage mechanical drive design will result in a more efficient, durable system that can meet increased production demands.

The quality of mechanical drive system components has evolved and improved over the years. Advances in drive system design, manufacturing capabilities, and materials technology allow existing components to be replaced with more durable and efficient equipment with significantly higher power densities.

Technological improvements
Some of the greatest advancements in drive system components have occurred with the girth gear set, consisting of a gear and pinion. Material technology, manufacturing techniques, and rating standards have changed, and now provide uprating and upgrading opportunities to facilities with vintage mechanical drive system designs.

First, material technology for steel castings has been refined, resulting in techniques that have drastically improved quality, integrity, and component hardness. In the 1950s, state-of-the-art in material technology could produce gear blanks with a hardness of only 180 HB (typical) or 225 HB (maximum) and pinions with a hardness of 265 or 285 HB. Now, with the availability of high hardness girth gears and through-hardened or carburized pinions, durability and strength rating increases can be realized with the installation of such components. When installed as a replacement for an older drive system, these latest technology gears and pinions can achieve durability rating increases exceeding 100 percent and strength rating increases exceeding 50 percent.

Second, manufacturing methods have improved component quality. Tooth accuracy of pinions and gears is significantly greater because of modern machinery used in the manufacturing process. The gear tooth quality that 1950s or earlier vintage gear cutting equipment could produce is in the range of AGMA 6 for gears and 8 for pinions, compared with today's available quality levels of AGMA 10 for gears and 12 for pinions.

Third, the equipment rating standards developed by the American Gear Manufacturers Association (AGMA) have changed. In an attempt to quantify difficulties that arose in the manufacture of such large gears, rating methods differed for open girth gears and enclosed gears. Originally, the AGMA reduced the rating of large gearing, such as girth gears. Now, because of improved materials and manufacturing methods, rating standards more accurately model the actual performance of all gears.

Options
Depending on the required increase in production and the budget, there are different uprating and upgrading approaches to achieve the necessary output level: replace pinions, recut girth gears, replace girth gears, uprate the gear drive and couplings, or a combination of these options.

Replace pinion in girth gear set.
Taking into consideration improvements in materials, manufacturing, and rating standards, a higher hardness pinion can be installed to increase the power density and production level of a vintage girth gear set.

AGMA rating practices allow a rating increase by increasing only the hardness of the pinion. The replacement pinion can be either through-hardened or carburized, depending on the rating increase desired.

It is important to note that the rating increase from replacing the pinion assumes the girth gear is in like-new, as-manufactured condition. This is typically not the case and, therefore, the full rating increase may not be realized. An exact value for adjusting the rating of the girth gear set due to gear wear or damage cannot be assessed without a thorough inspection of the gear.

When replacing a girth gear set's pinion, tooth modifications can be performed. Grinding the new pinion's teeth to specific modifications will increase load carrying capacity and operating contact, and extend service life.

For a typical application such as a grinding mill, a significant production increase may be possible by increasing the number of pinion teeth. This results in a lower total gear ratio, which increases the mill's speed and, in turn, production ability. The exact speed increase depends on the original number of pinion teeth. For example, increasing the number of pinion teeth from 19 to 20 will increase the mill's speed by 5.3 percent. A 4.5 to 6.25 percent increase in speed is possible when adding one additional pinion tooth. But an increase in speed will put the driven equipment closer to a system's critical speed. The original equipment manufacturer should be consulted when making this change.

Increasing the number of pinion teeth may require that the girth gear set's center distance also be increased. Allowance for this is usually available in the pillow block foundation bolt holes. If not, the bolt holes can be slotted to accommodate the increased center distance.

When implementing any system upgrade that will increase speed, remember that the motor must be capable of providing the extra power required to drive the system at the increased speed. This is typically not a problem, as most systems draw less than full motor power. If a facility is operating at motor nameplate power, adding additional cooling to the motor can usually increase the motor power. When faced with this situation, the motor manufacturer should be consulted for a proper recommendation.

Replace pinion and recut girth gear.
Recutting the teeth of a girth gear restores the original tooth form and makes it possible to take full advantage of a new pinion (see Fig. 2). In addition, the gear structure is completely inspected during the recutting process and any defects are repaired. This provides the structural integrity required to transmit the increased torque. Defects in the gear structure are identified by nondestructive testing methods, such as magnetic particle and ultrasonic inspection, and weld repaired (see Fig. 3). If required, weld repairs are made before the girth gear is completely stress relieved and/or heat-treated to ensure proper integration of the repair with the base metal (see Fig. 4). All surfaces of the gear are machined to ensure dimensional accuracy and geometric tolerances that meet or exceed the original design.

A complete design review is undertaken to validate all aspects of the gear and pinion design and manufacture. This updates the design with current design methodologies and rating practices.

The new tooth surfaces also yield increased efficiency benefits. A recut gear operating with a new pinion restores the gearing to 99 percent or greater efficiency (see Fig. 5). This can translate into significant operating cost savings. For example, a 1 percent increase in efficiency for a 1000 kW (1341 hp) mill will result in savings of $3500 per year, using an electricity cost of $0.04 per kWh.

Fig.2 Representative tooth damage that can be repaired by recutting the teeth.	Fig. 3 After cleaning, nondestructive testing identifies defects in the gear blank structure that then are removed.
Fig. 4 The defects identified and removed in Fig. 3 have been finish weld repaired. The repaired areas are not visible after the gear blank is painted.	Fig. 5 Major tooth damage has been removed and the tooth-working surface has been restored to like-new condition. The remaining damage is minor and will not affect the operation of the gear.

The cost of refurbishing a girth gear will vary, depending on the amount of repair that is required. Typically, refurbishing an existing girth gear is 30 to 50 percent of the cost of a new gear. The exact final cost heavily depends on the amount of weld repair required.

Replace pinion and girth gear.
A third uprating option is replacing both the pinion and girth gear. This allows the use of the latest design methodologies and rating practices, and takes advantage of the improvements in manufacturing and materials technology.

Replace gear drives and couplings.
Uprating the girth gear and pinion is useless if the main gear drive and/or couplings cannot transmit the increased torque. In some situations, these components will need to be uprated or replaced with new counterparts.

The gear drive can be replaced with a higher hardness gearing. For a gearbox with through-hardened gearing, the typical uprate using only a carburized pinion is 15 percent. Replacing both the pinion and gear with carburized elements will result in an uprate of up to 50 percent.

At the same time the gearing is replaced, new bearings using latest material and manufacturing technology should be installed. Bearing manufacturers have released E-type spherical roller bearings that have significantly more load carrying capacity than similarly sized standard bearings. The typical uprate using E-type bearings in place of standard bearings is 15 percent.

Rating practices for bearings include adjustment factors for lubrication, cleanliness, and load zone. These factors can either increase or decrease the calculated life of a bearing. The result is a much better understanding of the actual operating life of the bearing. New seal design technology such as Taconite, Magnum or noncontact also can be installed during a gear drive upgrade to provide better leak protection, reduced operating temperatures, and longer seal life.

New seals with higher allowable operating temperatures, such as Viton seals, are additional technological improvements that can upgrade and uprate a vintage drive system.

Shaft couplings have experienced a similar uprate over the past 30 years. New materials and manufacturing processes have increased shaft coupling power density 70 percent for grid-type couplings. The rating of gear-type couplings has increased at least 55 percent, size for size. In essence, a dimensionally interchangeable coupling with a much higher rating can be used or a smaller coupling with the same rating can be installed to significantly reduce costs.

There are many ways to increase the power density of existing mechanical drive systems in order to meet increased production demands. Improvement of materials, manufacturing techniques, design methodologies, and rating practices over the past 40 years has resulted in mechanical drive systems that are no longer a limiting factor in achieving higher production goals. MT

Bill Hankes is engineering manager, mill products at The Falk Corporation, P. O. Box 492, Milwaukee, WI 53201-0492; (414) 937-4566; e-mail bhankes@falkcorp.com; Internet www.falkcorp.com

Robert C. Baldwin, CMRP, Editor

Zero value gaps: Products or services custom fitted to each customer to maximize the value each receives. Values, of course, are different for different customers. They want the product or services tailored to their needs, delivered at the appropriate time, and at a price point that makes the deal satisfactory.

Zero learning lags: Management of the entire life cycle of knowledge--from creation to dissemination. It is suggested that the components of a zero learning lag organization include an environment for learning; management of the knowledge in useful chunks; and an infrastructure supporting seamless integration of computing, communication, and content technologies.

Zero management: Every person in the organization has the ability and the permission to do whatever needs to be done in order to produce value for customers. It is implied that people and teams are aligned with the corporate whole.

Zero resistance: A process in which there are no obstacles to performing whatever tasks are required. Zero resistance requires that individuals have achieved personal mastery of tasks and that they are empowered to follow them through.

Zero exclusion: All people and organizations who need to be involved are included--automatically--with neither physical nor technological boundaries to limit accessibility. The Zero Time organization is a proactive organization that anticipates, senses, and responds to the environmental changes influencing completion of the corporation's mission and goals.

Reliability and maintenance practices and technologies fit nicely into these Zero Time buckets:

• Proactive maintenance and RCM advance the cause of zero value gaps
• Condition monitoring and computerized maintenance management systems facilitate zero learning lags
• Autonomous maintenance is the essence of zero management
• TPM is based on zero exclusion
• Planned maintenance promotes zero resistance.

What time is it in your maintenance operation? MT

Symptom: Your CMMS has become too slow.
This can occur for several reasons that have nothing to do with your CMMS software. First, when was the last time you archived old work orders? If your system is bogged down with 75,000 old work orders, a software upgrade is not going to help. Most reputable CMMS provide for the archiving of old work orders.

Also, what has changed recently? Is your server now handling more PCs than before; are there other applications on the network that have been added that might impact the speed of your network or your server? One of our clients installed a DOS-based application on their non-dedicated server. Every time they fired up their old spreadsheet software, the speed of the CMMS dropped by 50 percent. They were convinced it was the CMMS until shown otherwise.

Also, is your CMMS database engine being used by other software applications? Sometimes you're not just sharing your server, you're sharing your database as well. If it's tuned to work well with one application, it can have an impact on your CMMS. You also can suffer performance issues if the other software is causing a significant number of hits on the engine, cutting down on the amount of processing time left for you.

Symptom: Your CMMS doesn't have features that others do.
CMMS vendors are always adding new bells and whistles, and sometimes people feel behind the times with their current application. That's a typical feeling and may very well be founded; however, there are a few little things that you should check first.

Have you been keeping your current CMMS up to date? Almost all vendors offer a maintenance program for their software to ensure that you get bug fixes, new version of the software (with--surprise, new features!), etc. However, what often happens is that in budget cutting somewhere along the lifespan of the software, someone decides not to renew the maintenance on the CMMS. It seemed like a good idea at the time, but can leave you with an out-of-date application.

What about re-training your staff on the software? Most CMMS training is done in the same manner a bad gene is passed on--it is done by an employee (now long gone and retired in Barbados) who trained a handful of people, who trained a handful of people, and so on. Each generation of training lost more and more of the skills until they sometimes reach the point where the staff is convinced the CMMS is nothing more than a work order engine. Sometimes when you're convinced your CMMS can't do something, you need to crack open the manual to find out if it's possible in the first place.

Also, are the new features you've read about in brochures, etc., really going to add to your maintenance department's productivity, or do they just look good? This is the old adage of being the sizzle, not the steak. You get the idea that the new functionality will be a big help, when in reality, it's not practical for your operation.

Symptom: Your CMMS doesn't work with other company applications.
The CMMS as an enterprise-wide application is not a new concept, but often not implemented correctly. Also, the maintenance department often is on the low-pecking order for new software, meaning that the accounting, purchasing, or enterprise management software your CMMS used to connect with has been upgraded or changed while your CMMS remains the same. That, or you never attempted to integrate your CMMS to any other application(s).

First and foremost, check with your current CMMS vendor and see if they allow or can provide integration to whatever software you want to link up with. More often than not, the larger vendors are more than willing to do so if you can specify what that linkage needs to be and how it will work.

Keeping fasteners tight, particularly threaded fasteners, seems like a simple task, but the moving nature of the machinery they are used on is what makes them so troublesome. How nails and rivets work is fairly well known. But because the physics of the threaded fastener is not as well understood, it tends to cause the most problems.

Causes of loosening
Threaded fasteners are employed primarily to clamp objects together using tension. Rotary force or torque imposed on the fastener provides that tension. Problems occur when this clamping load deteriorates.

About 85 percent of the torque and effort of tightening a bolt is absorbed by the friction in the threads and under the head. Only 15 percent produces clamping load. Therefore, high torque may be absorbed by high friction and not produce tension. Torque is not the most precise method of controlling clamping load, although it is the most common. When bolt and nut manufacturing is closely controlled, the tension produced in a bolt for a given torque varies up or down by 15 percent.

Although it is always the first suspect in any case of lost clamp, vibration, as commonly perceived and observed, is not capable of bolt loosening by itself. If vibration is violent enough to cause shifting of the threads, then it will cause loosening, and in only 50 to 100 cycles. However, vibration that violent is usually perceived as shock, shudder, or impact. Toward the end of the loosening cycle, common vibration can and will rattle the fastener loose. This is why it often takes full blame for loosening.

The actual cause of loosening is side-sliding or shifting of the threads. The empty space between the threads of a nut and bolt leaves room for movement that leads to self-loosening and loss of clamping force. The friction in the threads and under the head of the bolt is reduced to zero when the clamped parts and threads slide sideways to the bolt axis.

Each time this happens, the bolt can unwind by itself. The loosening process of a non-locking fastener starts with the first motion. It normally takes less than 100 side motions to completely loosen a bolt.

This shifting can occur any time the side force exceeds the friction between surfaces, as produced by the clamping load. There are three common causes of shifting:

• Bending. Bending of parts causes stress on the friction surface. If slip occurs, the threads and head also will slip. Each slip causes a partial downhill or unwinding slip in the threads. After 50 to 100 of these, the bolt is completely loose.
• Thermal expansion. Differences in temperature or in clamped materials can cause the same effect as bending. If the effect is strong enough to cause side-slip, then downhill slip also will occur and loosening will result.
• Applied loads. The impact of loads applied directly to the fastening point can cause side-slip as well.

Any one or combination of these conditions can occur from shipping trauma, extreme heat or cold, or just plain abuse. The effects are cumulative and self-accelerating. As these affect clamping load, there is increased probability that side-sliding will occur.

Threadlocking
Various methods and devices have been employed over the years to reduce or prevent loss of clamping load in threaded fasteners.

The earliest attempts involved the use of lock wires and split pins in conjunction with nuts and bolts with holes drilled in them. Although effective, these measures had some serious drawbacks. Each fastener had to be the correct length, and the holes had to be aligned on each individual bolt. Consider the difficulty and time required using this method to assemble numerous parts requiring many threaded fasteners.

As fastener manufacturing skills improved, more complex methods of threadlocking were developed. Two of the most common mechanical methods of threadlocking are thread distortion and the use of washers. Although these methods can be effective for short-term threadlocking, anaerobic threadlockers can provide short-term, long-term, and even permanent tightening when necessary.

Liquid threadlockers
The first chemical threadlockers, developed by Loctite, eliminated many of the design faults and shortcomings of threaded fasteners. Chemical threadlockers are anaerobic liquids that cure to a tough, solid state when activated by a combination of contact with metal, and a lack of air. The resulting cured material is a thermoset plastic that cannot be liquefied by heating, and resists most solvents.

The purpose of threadlockers is to lock and sometimes seal threaded components without changing fastener characteristics or altering torque-tension relationships. In addition, chemical fasteners offer a number of other advantages over mechanical tightening methods:

• Breakloose and prevailing torque. Liquid threadlockers find their way into tiny imperfections of threads. As they cure, these imperfections serve as molds for thousands of tiny keys that resist fastener movement in any dimension.
• Anti-corrosion. Because threadlockers fill the voids between threads, they block the entry of moisture, preventing corrosion and subsequent seizure.
• Strength control. Most threadlockers are graded by their various strengths and characteristics into distinct classifications. The different formulations of Loctite threadlockers, for instance, are distinguished by the color of the threadlocking material: low-strength is purple, removable is blue, permanent is red, and the penetrating formula is green.
• One size fits all. Because they are liquids, threadlockers do not come in different sizes. The same bottle that locks in a tiny screw also can be used on a large bolt. Stocks of various size mechanical threadlockers are no longer necessary.

Selecting the right threadlocker There are several key factors to consider when choosing a threadlocking compound:

1. Shear strength. If all threaded fasteners were designed never to be removed, then only one type of threadlocking compound would be necessary, the strongest available. Most assemblies that are held together with threaded fasteners will, with varying frequency, need to be dismantled for repairs, maintenance, or adjustments. Consequently, threadlockers of various shear strengths are available.
2. Cure speed. The cure speed of threadlockers can vary, depending on several factors, including temperature, base metal, surface treatments, clearance between parts, and surface cleanliness. The use of chemical primers can speed cure and result in higher ultimate strength.
3. Gap filling requirements. Most threaded fasteners are designed with some clearance between their mating surfaces. Larger clearances between mating surfaces require more product to fill them. Thixotropic liquid threadlockers will easily fill clearances in threaded fasteners, without migrating to other areas of the assembly. Where a higher shear strength product is required, and product migration is considered a potential problem, a higher viscosity compound is recommended.
4. Operating environment. Both chemical resistance and operating temperature should be considered when selecting a liquid threadlocker.

The chemical resistance properties of threadlocking compounds vary between different grades. The most popular anaerobic products will generally resist water, natural or synthetic lubricating oils, fuels, organic solvents, and refrigerants.

Like most organic materials, threadlockers lose strength at elevated temperatures. Most show significant strength retention at temperatures up to 300 F (150 C). Hot-strength formulations can increase this working temperature to 450 F (230 C) for those applications where it is considered necessary.

Removability
The most common myth about liquid threadlockers is that once they are cured, they cannot be removed. In fact, all threadlocked fasteners can be removed. Different grades of threadlocker can be used depending on the task. Fasteners secured with low- and medium-strength grades can be removed with common hand tools. Those secured with high-strength grades can be removed by applying heat for a specified time.

Threadlockers are not just for specialized uses, either. They perform effectively on fasteners and threaded assemblies of any type and size, in any kind of equipment. MT

Information supplied by Robert A. Valitsky, a manager of technical communications at Loctite Corp.'s North American Engineering Center, 1001 Trout Brook Crossing, Rocky Hill, CT 06067; (860) 571-5416; Internet www.loctite.com

There is universal agreement that improved machine performance can control and reduce manufacturing costs. That was the goal of Coors Brewing Co., Golden, CO, when it commissioned a maintenance benchmarking study of its can and bottle packaging lines and the warehouse operation.

The study results compared the maintenance operations at Coors to a world class model and other companies in similar industries. The benchmarking process, developed and administered by Charles Brooks Associates, Inc., uses a grading system to determine a company's level of maintenance effectiveness.

Although the brewery's maintenance operations performed better than most of the comparison companies, two major opportunity areas were identified: planned maintenance and mechanic training.

As a result, Gene Rowe, senior consultant, and Coby Frampton, partner and president of Charles Brooks Associates; and Paul Altimier, director of can packaging at Coors, designed a program for the company that later became known as Reliable Predictable Manufacturing (RPM). The goal of RPM is to improve equipment performance and control or reduce manufacturing costs.

The RPM process includes many of the elements of other improvement processes such as critical component analysis, equipment upgrading, planned maintenance, and performance evaluation. It differentiates itself through the use of Defined Equipment Standards (DES) as the basis for maintaining and operating equipment, as well as being the vehicle for achieving employee participation, skills enhancement, and production/maintenance cooperation.

The 20 steps required to implement RPM are shown in the table "Steps for RPM Implementation." The first eight have to do with proper planning and setting the stage for change. The last 12 steps outline the implementation of the DES, modification of preventive maintenance routines and audits, and mechanic training. While quite specific in application, DES is essential in implementing Total Productive Maintenance (TPM) and Reliability Centered Maintenance (RCM).

To insure that the project goals were being met, a baseline was established measuring unscheduled downtime, quality, and production.

Monika Seiler, the plant's RPM process manager, and Rowe involved the hourly mechanics and electricians from the onset to gain support for the RPM process. They developed the DES, prepared updated preventive maintenance (PM) routines, and conducted extensive, formal peer-level training. They also made presentations to upper management explaining their work and the benefits that were accruing. Hourly maintenance personnel took ownership of the analysis of line performance data and developed specific action plans to correct recurring problems.

Understanding how the program works and how it will affect them was essential in gaining their confidence and cooperation. The mechanics and electricians were empowered by the knowledge that they had an opportunity to participate in and assist with the development of a key business strategic program that would affect the company's bottom line. In order to request program funding, the supervisors, mechanics, and their appointed peer leaders met with L. Don Brown, senior vice president, operations and technology, to voice their support of and commitment to the program.

In order to determine the pilot production line, the team analyzed downtime data and identified the line with the greatest problems.

The variables analyzed were quality, production data, unscheduled downtime, and maintenance spending. Can Line No. 10, it turned out, produced the most can defects and received the most maintenance dollars.

Can Line No. 10 was broken down into major equipment systems or subassemblies. An analysis of subassembly downtime and maintenance cost determined which subassemblies were causing the can defects.

Next, current machine settings were identified, documented, and evaluated with input from mechanics from all shifts. Not unusual with many companies, each mechanic used a different setting. After gaining consensus from the mechanics, machine settings were adjusted to a set standard and were documented. This standard setting became part of the DES.

Once the can line's collator was upgraded and set to the new machine standard, can defects were reduced by 87 percent. After further evaluation, a variable speed drive was added to reduce pressure from the accumulator table, thereby eliminating all defects that prevented shipments.

Machine performance was monitored at the set standard and adjustments were made as necessary to optimize machine and line performance. When optimal machine and line performance were achieved, the machine settings were documented in the DES. Maintenance personnel took digital pictures of each machine and documented how the settings were achieved.

The use of digital pictures proved to be an important training tool as well as a creative way to document the DES for all the line equipment.

As a result, PM procedures were modified to reflect changes in the machine settings and new PM procedures were developed. Machine audits also were developed and implemented to assess the level of maintenance received and the current machine condition to ensure optimal machine performance.

Detailed PM procedures were developed once the optimal level of PM was achieved, and entered into the computerized maintenance management system.

At this point, the training process was begun to train mechanics on the new machine settings and PM procedures. A technical job skill training process called the Analytical Method of Training (AMT), used by Charles Brooks Associates since 1971, was implemented.

It begins with a thorough analysis of training needs, followed by standardization on the best trainable method. Once the method is known, skill development begins with peer-level instructors providing training until the trainee can perform at the expected level. When single-cycle skill has been achieved, the stamina buildup phase begins. The entire process is measured and monitored through extensive testing and performance demonstration.

Through an improved planned maintenance process starting with Defined Equipment Standards and mechanic training, reduced maintenance costs and improved efficiency can be achieved. The involvement and assumed ownership of the program by hourly employees, supervisors, and managers assures long-term results can be realized. MT

Katherine Berntzen and Gene Rowe are consultants with Charles Brooks Associates, Inc., P. O. Box 11758, Charlotte, NC 28220-1758; (800) 868-3553; e-mail rtt@charlesbrooks.com