By Stacy Heston, CLS, PMP, CMRP, OMA, Lubrication Subject Matter Expert, Allied Reliability Inc.

Lubrication practices are often overlooked as a potential time and money saver for a plant.  However Cargill Charlotte has found that by optimizing their lubrication task intervals, utilizing specific grease volumes, and implementing an oil analysis program, the overall reliability of their manufacturing process, as well as, the healthy status of their lubricated components has increased.
In 2009, Allied Reliability performed a Reliability Centered Lubrication Current State Analysis at the site to determine the state of the lubrication program.  Through the assignment of a score to different lubrication activity and practices, the site’s lubrication program was benchmarked on several parameters including program documentation, management structure and practices, storage and handling, etc.  By assigning a score, the benchmarking activity becomes more objective and less subjective allowing for a definitive path forward.
When Allied Reliability arrived on site, “the site had run amuck with lubricants everywhere, it was all about the flavor of the month…” where lubrication was concerned, and “no structure existed for the scheduling of lubrication tasks,” says Andy Nolan.  As a result of the Current State Analysis, it was determined that a RCL walk down was needed to bring the site up to speed with industry best practices for lubrication.
Shortly after the Current State Analysis, Allied Reliability began the development of a Reliability Centered Lubrication Program at the site.  The program design began with a full walk down of all lubricated components on site.  During the walk down phase, all data pertinent to the development of lubrication specifications, interval calculations, and lubricant quantity calculations is gathered.  This phase sets the stage for the remaining program design as the accuracy and content of this data is the core to a strong program.
During the walk down, opportunities for optimizing intervals are identified as well as opportunities for optimizing the lubricant list.  Optimization does not always mean an increase in intervals or a decrease in the number of lubricants on site, rather it is the assignment of calculated intervals that are specific to the component and takes into account the specific operating conditions the component is exposed to.  Essentially, the same bearing may be exposed to wash down practices and heavy debris requiring an increased interval, such as 30 days to account for these environmental exposures.  However, the same type of bearing operating at the same speed with limited exposure to moisture and no exposure to debris may have an interval of 360 days.  This deviation in intervals means that the bearing with the more aggressive environment and operating conditions receives the more aggressive treatment.
When the Charlotte site began the implementation phase of their RCL program, the lubricated components were in poor health.  Approximately 60% of the oil lubricated assets were considered to be in the red, or in a state that did not meet industry best practices for contamination control, operating temperature, etc.  Within three months, the percentage decreased to approximately 40%.  By the end of 2010, 100% of all oil lubricated assets had achieved a green status.

Components were easily converted from a red state to a green state through the implementation of oil analysis, off line filtration, and monthly inspections.  Oil analysis aids in the identification of in use lubricants that required filtration to clean up solid contaminates, needed refreshing due to changes in additive levels and lubricant properties, or need complete replacement.
Previous to the implementation phase, the site utilized a time based oil change methods, had a multitude of lubricants with no specific requirements for each component, utilized screen breathers, and had no structure for the inclusion of filtration.  Lubricants were stored in drums and in areas that did not provide a clean, temperature controlled atmosphere.  The overall program lacked structure with regards to regrease intervals and amounts, as well as, oil analysis and oil change intervals.
The implementation phase of the RCL Program Design included recommendations for component modification with items such as desiccant breathers, quick connect couplings, level gauges, and sample valves.  These modifications provide multiple benefits for the lubrication program as well as the plant operating structure as a whole.  Level gauges and sample valves allow lube technicians to perform level checks and sample collection tasks with the machine running.  Without these modifications, the machine and possibly the product line would need to be down for the completion of these tasks.  It also saves time from a labor perspective.  A dipstick level indicator involves several steps to determine the level and exposes the lubricant to the possibility of contamination, where as a visual level gauge is nothing more than a quick peek then walk on to the next component.
The Charlotte site followed some very basic steps to manage the program implementation starting with the incorporation of desiccant breathers and other types.  After some experimentation with different types of breathers, there was an eventual shift to the use of trap and hybrid breathers based on the components size and location within the plant.  Of all the modifications, breathers are the least evasive to install, and limits the amount of debris able to enter the sump down to 3µ in size.
The second step included the conversion of mineral based oils to synthetic based oils in the smaller sump components.  Using the current practice of 6 or 12 month oil drains, each sump was converted during the next scheduled oil drain task.  At that time, new intervals of 12 or 18 month were implemented for each sump.  This step applies only to sumps that are too small for oil sampling.
The third step was the implementation of oil sampling practices on sumps within the 4 to 22 gallon range.  This implementation allowed for the extension of oil drains through the monitoring of the lubricant health.  Unlike the second step, these components were not immediately converted to a synthetic oil.  Rather the current lubricant was monitored and cared for until such time the oil analysis results showed a break down in the lubricant properties.  Once the lubricant properties began to degrade, an oil change with conversion to a synthetic occurred.  This maximized the life of the lubricant that was in service before change over without harm to the component.
*During lubricant drains, additional modifications were implemented while the sumps were empty such as the installation of level gauges, quick connects, and sample valves.
Once the oil lubricated components had been addressed, the fourth step was implemented.  The fourth step was the mass implementation of the grease lubrication routes that were developed based on the walk down phase.  These routes were provided in an electronic format which is downloadable to a pda, or other handheld device.  The routes were grouped together based on location within the plant, lubricant required, and interval.  The interval and re-grease volumes are calculated using gathered data to ensure the right amount of lubricant is delivered at the right time.
At the onset of the RCL design, this location had 1 overworked lubrication technician.  Now, they have 1 lubrication technician who is able to complete all required tasks within a timely manner because a solid program structure has been implemented to address all aspects of lubrication.  Task intervals have been optimized to ensure over and under lubrication is not an issue, and oil drain intervals have been extended.  Additionally, lubrication related failures have decreased allowing focus to shift from putting out fires to maintaining the current state.
“We now have a set program that anyone can follow with component state data being collected regularly to ensure appropriate actions are taken to avoid lubricant and component failure.  We have structure and focus.”

By: T.J. Garten, IR/MCA Specialist

Bean Conditioner – Horizontal Rotary Vessel

Synopsis

Fault

Summary of Action

Supporting Data

Figure 1: Pre-repair Demodulation Spectrum

Figure 2: Pre-repair Historical Data

Figure 3: Pinion Wear

Figure 4: Broken Welds on Pinion Gear Pillow Block Pedestal

Figure 5: Post-repair Demodulation Data

Conclusion

The corrective action taken during the repair of the failed trunnion bearing resulted in an altered elevation of the rotary vessel. The attempts to adjust for this were inadequate and resulted in a changed mating pattern between the pinion gear and bull gear assemblies. Over time, the increased impacting caused the pinion shaft to deflect, breaking the welds on the pedestals. This deflection also caused an angular misalignment between the pinion shaft and the gearbox output shaft. The level of misalignment may also have been affected by utilizing dial indicators for precision shaft alignment rather than the on-site laser alignment equipment. As the trunnion rollers wear, the clearance between the pinion gear and bull gear’s high spot decreases, resulting in increased shaft deflection. The increased shaft deflection results in transmitted vibration to the feed screw platform and torsional stress on the gearbox output coupling.Future corrections need to take into account all clearances and their effect on correlating components. Monitoring of adjusted components should be within days of adjustments and load changes. Installation of remote accelerometers on the pinion gear shaft pillow blocks would allow for quicker analysis of shaft misalignment, bearing condition, and pinion gear mesh frequencies.

Don’t Let the title fool you, this is a great and very short case study!  Allied Reliability SME Aubrey Green examines a dilemma at a salt evaporation plant in upper NY.  Read it for yourself here:

Radio Frequency Interference on Commtest VBx Series Data Collectors from Improperly Grounded Equipment

Ricky Smith SME for GPAllied examines the common roadblocks and excuses surrounding maintenance planning.  Ricky will walk you through steps that can take you from where you are to ‘World Class’.  Article as printed in the July issue of Asset Management and Maintenance Journal.  Read it for yourself here:

Maintenance Planning is Too Hard in my Workplace

GPAllied Subject Matter Experts Chris Colson and Doug Plucknette dive into how equipment reliability delivers low-cost, energy-efficient assets at plants around the world.  As published in the July edition of Uptime Magazine.  Read it for yourself here:

Clean, Green & Reliable

Every year Reliabilityweb publishes an eBook on top tips, opinions and viewpoints from industry thought leaders and subject matter experts from around the world.  Stacy Heston, Subject Matter Expert in Lubrication was featured in this 2011 edition with her tips on data entry.  Read it for yourself here:

Things to do and think about 2011- DATA

John Schultz, with co-authors Rick Baldridge and Tim Goshert, wrote an artilce on Reliability and Healthy Assets. Read it for yourself here:

“Nourishing Reliability and Healthy Assets”

Jeremy Davis, alongside co-author Hunter Golden, wrote an artilce on tension belts  that is featured in the February/March Edition of “uptime” Magazine. Read it for yourself here:

Relieving the Tension

SUBMITTED BY: John H. Williams

TITLE: Vibration Analyst

EQUIPMENT: 700 HP Frick ammonia compressors.

TECHNOLOGIES APPLIED:
Vibration analysis and Ultrasound.

PROBLEM DESCRIPTION:

Vibration readings came into alarm on #6 Frick ammonia high stage compressor. Vibration readings taken on the outboard side of the male and female compressor screw bearings continued to rise. Readings went into alarm in April. Work order was written to repair compressor. Work was submitted for approval. Unit was shut down until work was completed.

INVESTIGATION:

Base line reading on male screw conveyor 12/14/2005

Readings into alarm on 4/14/2006

Readings after repairs 11/6/06

CONCLUSION: Compressor refurbished and bearings replaced. New readings were taken above. The unit was able to be repaired in place with significant costs savings versus sending compressor out for repairs. Problem was located before any damage happened to screws or compressor head. Bearings were found to have significant wear after 10 years of running time and poly metallic bearing cages had broken down. A spacer for the thrust bearings was found to be in backwards also.

Thrust Bearing                                  Bearing Cage Gone

IN SUMMARY:

When suspect readings show up, you can check bearings for cage failure by shutting down the compressor and turning machine coupling over by hand. Listen with mechanic’s stethoscope and you should hear the rollers hitting as the shaft turns over. The bearing cage is usually the first thing to fail on these compressors.

It’s much better to locate the problem now before catastrophic failure.

SUBMITTED BY: Jamie Duart

TITLE: Level III Vibration Analyst

EQUIPMENT: Carbon Furnace Draft Fan

TECHNOOGIES APPLIED:  Vibration

PROBLEM DESCRIPTION:
The Carbon Furnace Induced Draft Fan is an overhung, radial blade fan mounted on top of the carbon furnace. It is a direct-drive, variable speed application. Vibration amplitudes vary greatly from month to month and overall vibration is over 1 in/sec on some surveys. A long history of work orders exist in our CMMS system ranging from physical removal of fan for cleaning to bearing replacement to adding mass and stiffness.  

INVESTIGATION:

Analysis: With many variable speed applications vibration data goes in and out of alarm from survey to survey. In many cases this is a result of resonance.  Resonance is when a forcing frequency such as imbalance, misalignment, looseness, bearing defects, gear defects, etc., coincides with a natural frequency. The natural frequency may be that of the rotor itself or may be that of the support frame or foundation or even drive belts. It was suspected that the Carbon Furnace Induced Draft Fan at our facility was experiencing resonance and different testing methods were employed and much research was done to prove our theory. 

Comparative Analysis:  On the following page is a horizontal, vertical and axial view of the coupling side fan bearing on the Carbon Furnace Induced Draft Fan. The spectrums show that the readings in the horizontal direction are significantly higher than in the other two directions. One of the characteristics of resonance is that it causes much higher vibration in one direction as compared to the other tri-axial directions. When resonant, it is common for the resonant direction to be 5 to 15 times higher than in the two other directions.

Natural Frequency and Resonance Detection: Component natural frequencies can be detected utilizing several different methods including Impact/Impulse Natural Frequency Testing (also referred to as a “Bump Test”) and Run-up and Coast-down Testing.  Impact Naturally Frequency Testing should be performed with the piece of equipment shutdown and could not be performed due to production schedules. A Run-up Coast-down Test was the best option in this case and we employed a technique of this test called a Bode’ Plot. This Plot consists of two different plots – one of amplitude versus RPM and the other of phase versus RPM. Past vibration history showed that the Coupling side fan bearing, horizontal position showed the most response and was the point chosen for our testing. The results of this test can be found on the next page. Data shows that the characteristic 90-degree shift and rise in vibration amplitude seen at resonance occurs at approximately 64% of these units operating speed or 1360 RPM. 

Questions arose as to whether this resonance may have been caused by the fan being out-of-balance or misaligned. These conditions could have been the forcing frequencies that coincided with the structures natural frequency and resulted in resonance excitation. A laser alignment had been performed immediately before conducting the Run-up/Coast-down test and the assumption was made that this was not the forcing frequency responsible for the resonant condition. The phase shift that had occurred at 1360 RPM and the steady decrease in vibration as RPM was increased to 2081 RPM was uncharacteristic of an out-of-balance condition. Attempts to balance this fan would likely have been unsuccessful without changing the natural frequency of the structure. This natural frequency may be lowered by adding mass or raised by adding stiffness.

Physical and Analytical Research: Closer examination of the structure confirms that support and stiffness is inadequate. Conversations with Robinson Fans (the manufacturer of this fan) stated that they recommend the foundation supporting the assembly weigh a minimum of five (5) times the weight of the assembly (motor, fan, bearings, shaft and base). In this case the assembly weighs approximately 3700 lbs. total.  Five times this amount would be an approximate value of 18,500 lbs. Since this fan sits on two I-beams mounted to the top of a furnace it is doubtful that the base approaches this value. The tank-like construction of the furnace may not be able to support a massive foundation like what is recommended. 

The fan company representative also addressed our concerns about the A-frame base that the motor and fan bearings are mounted to not being adequate to dampen frequencies excited by the fan. He explained that the weight of the base assembly (including the motor and fan bearings) provided by Robinson was roughly ten (10) times that of the fan and should provide adequate damping (fan and shaft weight is approximately 320 lbs. and the motor, base and fan bearing weight totals approximately 3700 lbs.).

Another concern we had was that this fan may not have been designed for a variable speed application and that we were exceeding the fans operating speed or operating at a critical frequency of the fan. Robinson explained that they typically design their fans with a critical speed at least 40% above the maximum speed rating. Maximum speed listed on the fan curve is 2183 RPM and currently the fan does not exceed 2081 RPM.

RECOMMENDATION:
After careful review of the data including vibration analysis, fan company recommendations and work order history in our CMMS system it has been determined that the best course of action would be to relocate this fan to the level above the furnace. This would allow installation of a more substantial base to change the natural frequency of the unit and eliminate the resonant condition that is occurring.

CONCLUSION:

In April of 2006 the Carbon Furnace ID Fan was moved from the top of the Carbon Furnace to a newly constructed platform on the level above. Structural I-beams were added and a concrete pad was poured. Fan vibration was checked upon startup and levels were found to have risen at 2081 RPM from approximately .25 in/sec to nearly .5 in/sec. Although vibration amplitudes had risen there was little change in phase. Phase only fluctuated about 30 degrees from 40 to 100%. Vibration amplitude did see a slight rise at about 80% but did not appear to be a resonance (characteristic phase shift was not present). Time constraints prevented completion of a precision field balance but running speed vibration was lowered to approximately .25 in/sec. Balancing was accomplished the following month with final readings of .04 in/sec at 2081 CPM.

Below are pictures of the new structure as well as pictures of the old location on top of the furnace.