Contamination Control in Highly Contaminated...

2007 Conference Proceedings 515

/ Contamination Control

AbstractThe iron, coal, precious metal, and mineral mining industries are

among the most challenging environments in which lubrication andhydraulic systems are required to operate. These mining facilitiessubject L&H systems and components to extreme levels ofcontamination that are rarely seen in other manufacturingenvironments. In addition, the massive scale of the processesensures that every instance of lost production, scheduled orotherwise, results in great material and labor expense as well as lostrevenue. Finally, as these processes continue to grow older whilesimultaneously being pushed harder, the cumulative wear and tear onequipment is reaching a critical stage.

In one situation that we will describe, an iron ore processingfacility was shown to be able to reduce the material and laborexpenses associated with replacing lube oil pumps by more than$2.3MM annually. Remarkably, the one-time cost associated withupgrading the oil conditioning equipment was less than $200K,resulting in a first year annualized savings of over $2MM.

In this paper, we will present details of this application as well asothers in which it has been shown that even highly contaminatedenvironments can be economically upgraded through the proper useof high performance fluid filtration solutions. Other examples:

• Concentrator bearing lube oil systems were originally designedusing fifty-five resin bonded, nominally rated filter elements(2.5” by 30”). As a result, element life, fluid quality, andchangeout efforts were less than optimal. These systems arebeing upgraded to utilize seven high capacity pleated elements,significantly extending element life and reducing changeout timeand effort – without any existing housing modifications orprocess changes.

• Obsolete screen type filters that had been requiring custom builtfilter elements (the original manufacturer had ceased productionsome time back) have been replaced with substantially smaller,high performance technology. The result is a significantreduction in equipment footprint as well as overallimprovements to the fluid condition while simultaneouslyreducing operating costs.

• Nominally rated and bypass prone duplex filtration systems havebeen replaced with high capacity, Beta rated simplex filtrationsystems, resulting in ISO cleanliness code improvements of 2-4classes and the elimination of filter bypass.

• In an underground mining application, small volume, splashlubricated gear boxes that have never had in situ fluidconditioning have been upgraded using panel mounted kidneyfiltration systems that remove both particulate and moisture

contaminants, significantly extending fluid and equipment lifeand eliminating unnecessary maintenance shutdowns.

IntroductionFor years, original equipment manufacturers, lubricant

manufacturers and suppliers, educators, and other industryspecialists have advocated the use of high efficiency fluid filtrationand conditioning devices to protect high performance bearings andmachinery. In support of this effort, there has been a significantvolume of data generated, documenting that the investment inupgrading these critical processes is worthwhile. As a result,substantial improvements have been made in the conditioning of thelubrication and hydraulic fluid used in many high speed or closetolerance applications.

At the same time, lower speed, lower tolerance processes areoften overlooked or ignored when strategic planning determineswhich processes and equipment would benefit most from improvedfluid conditioning practices. Historically, there are a number ofreasons given as to why these processes should be omitted fromfluid conditioning upgrade plans:

• The process and/or environment is too highly contaminated

• The cost and frequency of element changeout would be too highif filtration was improved

• The existing filtration systems are too old

• The gearbox is so small; the oil can be dumped when it gets dirty

• The clearances in the machinery are so large; better fluidconditioning is unnecessary

In reality, improvements to these types of processes can alsoresult in significant bottom line value while simultaneously improvingequipment reliability. With properly sized filtration technology andattention to the mitigation of contaminant ingression, most processesare not too dirty, and the changeout frequency and cost are notnecessarily prohibitive. In other cases the machine clearances andloads may be extremely large and particles in the sub-50 micronrange may not be thought to be particularly harmful to the primaryequipment, but when pumps, control valves, etc., are also given fullconsideration, the overall cost of contamination in these processesmay still prove to be very high.

ContaminationThe most common method for assessing the condition of L&H

fluids is bottle sampling. In many cases, bottle samples are sent toan outside lab periodically. This can be performed monthly, quarterly,or annually, depending on the size of the system and how critical it is

By: David Kolstad, Porous Media

Contamination Control in Highly Contaminated Environments

LE Papers Final.qxp 4/16/2007 11:33 AM Page 515

to the overall process. The results are then monitored for significantchanges over the course of time. For particulate contamination, themost common method of reporting these results is through the ISOCleanliness Code.

The results are reported as either a 2 or 3 number classification.The classification would generally be in the form of 18/16/13 or in theshort form as 16/13. The numbers represent the ISO Class (Figure 1)for particle counts in the sizes ranges of 4 μm and larger / 6 μm andlarger /14 μm and larger – or just the 6 μm and 14μm classes for 2number results.

Based on the example for ISO results of 18/16/13, the actualnumber of particles per size range is shown in Figure 2. One aspectof this method of cleanliness classification that should be recognizedis that each time a sample moves up one ISO Class, the level ofcontamination can potentially be doubled. For example, if the ISOclass for any one number in the code increases by just one point (i.e.from 18 to 19) the allowable contamination level doubles. In Figure 3the particle counts for an ISO classification of 19/16/13 are shown.As can be seen in the data, the number of potential particles in the 6

and 14 micron size range remain unchanged, but the allowablenumber of particles in the 4 micron range has doubled.

Equipment life extension is a useful tool for assessing the long-term value to a specific process that would be associated withimproved fluid conditioning methods. Different types of life extensiontables have been printed in a number of Noria publications. In Figure4, we have reprinted the data from one of these tables, which isapplicable to heavy mining equipment such as gear boxes.

As shown in the data, even moderate improvements in fluidcondition can have a significant impact on the useful life of the typeof equipment commonly used in the mining industry. This, in turn,can have a measurable impact on plant throughput (less downtime)as well as maintenance expenses (reduced labor and materials). Forexample, equipment normally operating at ISO 24/21 would beexpected to last twice as long if the fluid was maintained at ISO19/16, and three times as long at ISO 17/14.

Example 1: Eliminating Pump FailuresAt one iron ore mining facility, the circulating oil pumps in the

concentrating area of the plant had a long history of failure after onlya short time in service. The process was comprised of 16 zones,each with 3 lubrication circuits, for a total of 48 lines. The pumps inthis application were typically lasting just a few weeks, resulting inan annual replacement cost of $48,000 per line or $2,300,000 totalper year.

A review of the historical oil analysis revealed that all of the lubeoil systems were almost constantly in a highly contaminatedcondition. Continuous operation with this level of contamination wasthought to be the root cause behind the history of excessive pumpfailure. Examination of the process indicated that:

1. The nature of the manufacturing environment ensured that highrates of contaminant ingression were likely to continue.

2. The filters being used were of a nominally rated style or sockfilter style (Figure 5). In this application, the filters had atendency to surface load with contamination, causing theelements to have a limited dirt holding capacity. As a result, thepressure bypass around the filter housing would generally be atleast partially open.

3. The housing design relied on a compression nut on the elementto create the element seal. This type of sealing mechanism

516 2007 Conference Proceedings

Figure 1: ISO Classes

Figure 2: ISO Cleanliness Reporting

Figure 3: ISO Cleanliness Reporting

Figure 4: Life Extension Factors for Gear Boxes




made fluid bypass at the upper and lower element sealingsurfaces quite likely, further limiting the filtration effectiveness.

Following the process review, it was concluded that the best way tominimize pump failures would be to make significant improvements tothe overall fluid conditioning methods. Making these upgrades with theexisting housing design did not appear practical; as a result the customeropted to replace the old style sock filter housings with new housings thatwould be better suited to the application. The new housings (Figure 6)had several features that were going to be beneficial:

• Each line would have a single housing with a single element,6.5” by 38” long

• The elements had a pleated configuration,offering an extended surface area tomaximize the overall dirt holding capacity

• The element sealed into the housing usingan O-ring seal, preventing fluid bypass

• The housing used a quick-opening clampstyle closure to make element changeoutless time consuming

• Multiple filtration grades are available: 25micron filtration was chosen as a startingpoint with the potential to lower the ratingto 12 or 6 micron in the future.

Initial results indicate that the lines that havebeen upgraded are maintaining very high levelsof fluid quality. The primary mills have seencontamination ratings of ISO 15/13/11 and thesecondary mills are at ISO 18/15/12. At the 14micron particle size range, this equates to acontaminant reduction of 99.9%. Mostimportantly, they have been able to operate theupgraded lines for over a year without pumpfailure.

The associated costs of the upgrade have been minimal. The costto purchase and install the filter housing: less than $4,000, with anannual filter usage of $1,000-$2,000. Based the original annualizedmaintenance cost of $48,000 per line, the upgrade is projected toachieve a first year savings of more than $40,000 per line (or$1.9MM overall).

Example 2: Reducing Element Consumption At another facility, the bearing lubrication systems were designed

with slipstream filtration and cooling circuits. Each of the ninereservoirs has a circulation system consisting of a pump, duplexfiltration housing, and a water cooled exchanger. The fluid is pumpedfrom the reservoir through the filters and the cooler and back into thereservoir.

Operating Conditions: ISO 220 or 320 OilReservoir Volume – 1,200 gallonsReservoir Temperature – 80-110 oFCirculation Rate – 135 GPM

Each of the filter housings was 24” in diameter and held a total of55 nominally rated, resin bonded filter elements (2.5” by 30”).Depending upon how rapidly the elements fouled and how quickly theflow was switched from the on-line to the stand-by housing, elementchange-out could require anywhere from 4 to 12 hours ofmaintenance labor. Furthermore, during system upsets, situationshad occurred where a single filtration circuit consumed over 600 filterelements over a 2-3 day period.

Review of the system revealed the following:1. During element change-out, maintenance had to insert a cup

and spring assembly into the top end of each element and thencarefully close the cover on the vessel. If any of the springswere dislodged or askew, the element would not seal.

2. If elements were allowed to run too long before switching to thestand-by housing, they could collapse onto the support bars.When this happened, the support v-bars had to be removed andeach element manually cut off of each bar.

3. The elements were 2.5” by 30” depth style elements. With 55elements, the system was limited to 86 square feet of mediasurface area. At 135 GPM, this creates an element flux rate of1.6 GPM/ft2.

4. Due to high contamination levels, oil samples were not testedfor particulate contamination.

5. During system upsets, maintenance efforts needed to becompletely focused on changing filter elements, preventing othernecessary maintenance tasks from being completed.

The objectives of the project upgrade were to protect thelubricated equipment through improved fluid quality, extend the life offilter elements, and to make element change-out quicker and easierfor maintenance. In order to improve fluid quality, the plan was toupgrade the housing using elements based on high performance

Figure 5: Sock Filters

Figure 6: New Filter Housing


microfiber media technology, which were Beta rated at βx=1,000. Inaddition, all internal seals would be positive O-ring style seals,preventing potential fluid bypass.

To make change-out quicker and easier, the number of elementswould be reduced from 55 to 7, each significantly larger at 6.5” by28” long. Each element would have a handle for ease of removal andthe need for springs and sealing cups has been eliminated.

Finally, since the new elements were of an extended area, pleatedconfiguration, the surface area of each element was increased to 46ft2, resulting in a total surface area of 322 ft2, resulting in nearly 4times the usable filtration area and a more appropriate 0.4 GPM/ft2flux rate.

The process was accomplished in the following manner:• All of the filter elements, v-bars, and seat cups were removed

(Figure 8)

• A machined 2” high spacer ring (23.5” diameter) was positionedat the bottom of the housing

• A new tube sheet (Figure 9) with semi-permanent elementsupport cores (Figure 10) was placed on top of the spacer ring

• Compression bars were installed to secure the tube sheet andspacer ring in place as well as ensure proper sealing of spacerring O-rings

• The new elements were installed and the vessel put intoservice (Figure 7)

The first systems placed into service indicate that the upgrade hassuccessfully achieved the project’s goals. The filter elements haveachieved a 4 month service life and are maintaining excellent fluidquality. Oil analysis indicates contamination ratings of ISO 20/15/13,a substantial improvement over the initial ratings of >ISO 24. Basedon the life extension table shown in Figure 4, this would be expected

to extend the life of the processing machinery by 4-5 times.

The one-time capital cost for upgrading each of the systems wasless than $4,000 per vessel. Operationally, with an element life of 4months, on-going operating costs will be less than $6,000 per year,per system. While the resin bonded cartridges were quiteinexpensive (< $4 each), after all materials, labor, and the higherfrequency of change-out are factored in, the operating cost of thesystem with improved fluid quality will be equal or less than theoriginal system.

Example 3: Obsolete EquipmentThe gearboxes on the primary crushing stage at an ore mining

facility were originally equipped with a large serial filtration system.The system was comprised of two 24” diameter filter vessels inseries. The ISO320 lubricant was pumped from the reservoir, throughthe filters – the first housing held 32 wire screen elements, thesecond held 32 pleated paper style elements. Downstream of thefilters, the fluid went directly to the gearbox. In order to prevent anypotential for oil starvation to the crusher, an external bypass line wasalso installed around the housings. If the combined filter differentialpressure became too high, the bypass was intended to allowuninterrupted flow to the gearbox.

Even with the original filtration system in place, the oil in thesystem would continuously buildup excessively high levels ofcontamination. As a result, once a month, maintenance would needto bring a portable filter cart to each of the 3 lines to provideadditional fluid cleaning.

The root cause of the continuous contamination buildup appearedto be due to the system’s spring loaded bypass valve (Figure 11)being open nearly all of the time, allowing a significant amount of thefluid to remain unfiltered. Initially, the set point of the bypass wasincreased to prevent it from being open at all times. This, in turn


Figure 7: Filter Vessel Figure 8: V-bars & Seat Cups




caused the filters to see the entire system flow and contaminationload, and as a consequence, they required change-out morefrequently than operation would like. As a result, the valve wasreturned to the original setting.

At the same time, the original manufacturer had stoppedmanufacturing the screen style elements. Another manufacturer hadagreed to custom manufacture a replacement element, but after ashort period of time ceased production as well.

Examination of the pleated paper style elements indicated that theymay be unsuitable for continued use as they did not provide highcontaminant holding capacity, particularly with the high viscosity fluidbeing used in this application.

The potential for upgrading the filters in both housings wasevaluated. The plan was to eliminate the screen filters as they weretoo coarse. Secondly, they wanted to upgrade the pleated paperstyle elements with a synthetic media to get more consistentfiltration efficiency and higher dirt holding capacity. After additionaldiscussions with the maintenance technicians and engineers, it wasfelt that the space constraints within the work area made continueduse of the large housings impractical. The original filtration systemrequired a 3’ by 6’ floor space and overhead piping interfered with theability to easily change filter elements.

Preliminary fluid sampling indicated that if they were able tocontinually keep a fluid filtration system in service and withoutbypass that it should be possible for a new filtration system to keepup with the rate of contamination ingression. With that in mind, theexisting filtration systems were completely removed and discarded.Since the new systems would use quick-opening v-band closures,element change-out could be accomplished quickly and without tools.

With this in mind, a target element change-out frequency of onceevery 2 months was chosen as an acceptable rate.

New triplex full-flow filtration systems, with a significantly smallerfootprint (approximately 18” by 30”), were installed (Figure 12). Anintegral manifold on the new systems enabled the flow to be evenlysplit between three housings, each with a single 6.5” by 38” filterelement. The GenesisTM glass microfiber filter elements provide highdirt holding capacity and are rated for 25 micron solids removal. Inaddition, the elements have an optimized deep pleat configurationthat allows for extra life.

Knowing that the systems were already highly contaminated,flushing equipment was brought in to clean the fluid prior to startingoperation of the new triplex filtration units. In operation, theupgraded system has been able to maintain acceptable fluid quality(ISO 20/16/14) as well as meeting the target change-out frequency ofevery other month.

Economically, the cost per change-out has been reduced from$1,869 to $1,020 per line. Based on 3 lines, each requiring 6 change-outs per year, the new systems are projected to reduce operatingexpenses by $15,282. The payback cycle for the capital equipmentupgrade will be approximately 18 months.

Example 4: Nominally Rated FiltersOEM equipment manufacturers often select filtration equipment

based on the least costly technology that will attain an acceptableequipment life. In many cases, the primary goal is to simply getthrough the warrantee period. Within lubrication and hydraulicsystems, one way to do this is to minimize the physical hardwarebeing used to house the filtration elements. As a result, it is notuncommon for filtration systems to be subjected to excessive flux

Figure 9: New Tube Sheet Figure 10: Filter Elements

LE Papers Final.qxp 4/16/2007 11:34 AM 19

rates and/or nominally rated filter media, either of which can limit theuser’s options for improving fluid quality.

Elements operating at high flow rates per unit surface area (fluxrate) can limit system performance in several ways. In aggressivelysized applications, a significant portion of the filter surface area maybe required to simply maintain fluid flow, making it impractical toincrease fluid filtration efficiency. If an attempt is made to increasefiltration efficiency while continuing to use the same style filter media,the element life may become too short for sustained operation.

At the same time, nominally rated elements can create limitationsas well. In one particular application, the OEM equipment consistedof a set of two filter housings in series, each containing a single 6” by28” bag style filter (Figure 13). This type of filter element iscomprised of a single layer of polymeric media with a very open porestructure. Since it is a single bag, the element surface area is limitedto less than 4 ft2 per element, limiting the overall dirt hold capacity ofthe element format. Even if a bag was manufactured from moreefficient filter media, the high flux rate would cause element life tobecome prohibitive.

In operation, it was found that the nominally rated filter elementswould initially begin to build differential pressure very quickly. Oncethe differential pressure began to rise, operations would generallypartially open a bypass line (bypassing both filtration stages). As aresult of contamination, it had become necessary to drain, discard,and replace the lube oil several times per year. Over recent periods,it had become necessary to do so an average of 5 times per year.With each system containing 200 gallons of oil and more than 40systems total, this resulted in the consumption of 40,000 gallons ofoil. At $4-$5 per gallon, the material cost alone would be $160,000to $200,000 per year.

In order to increase oil life, it was necessary to increase filtrationperformance while at the same time obtaining a suitable filter life andoverall operating cost. To do so, the duplex filter assemblies wereremoved and replaced with a single filter assembly. The newassembly utilized a high capacity pleated style filter element, withmicrofiber media and wire screen support for use with high viscositylube oil (Figure 14).

A manual bypass line was also installed so that element change-out could be performed without needing to shut down the entireprocess. However, the original pressure bypass line was removed toprevent unwanted filter bypass.

Since being upgraded, periodic oil samples have shown that thefluid quality is now being properly maintained. Average ISOCleanliness codes range from 19/17/13 to 18/15/12, compared to21/19/14 prior to upgrading. This cleanliness improvement reflectsthe elimination of approximately 75% of all contaminants from thesystem. Since the elements were designed for long life and the oilcirculation rate is low, the system flux rate is also low. As a result,they have been able to limit filter changes to approximately 4 elementchanges per year. At $340 per element, the total operating cost of


Figure 11: Bypass Valve

Figure 12: Triplex System




each system becomes $1,360 per year ($54,400 for 40 systems).

At the same time, they have been able to reduce the frequency ofoil replacement dramatically, now averaging 1-2 changes per year.This amounts to a total oil consumption of 8,000 to 16,000 gallonsper year or, based on the previous cost of oil, oil expenses arereduced to $32,000 to $80,000. If the filtration costs are alsoconsidered, the total operating cost has been reduced by $65,000 to$114,000 per year.

Example 5: Gear Box UpgradesOn small volume systems such as gear boxes, it is not uncommon

for manufacturers to eliminate on-line filtration altogether. In thesesituations, when the oil becomes contaminated, the users are advisedto drain the fluid and refill with new oil. Unfortunately, it is oftendifficult to fully drain the system, especially if the system is designedwith any sort of external piping. When this happens, the condition ofthe new oil is immediately diminished through mixing with the highlycontaminated old oil.

In a particular deep mining application, the maintenance requirementsand lost operating time associated with maintaining a number of smallgear boxes became an issue. The location of the systems made routineservice very difficult, and there was resulting concern that this couldlead to very serious and costly equipment failures.

Evaluation of the application led to the outlining of several keydesign parameters.

• Space was constrained, so an overall size envelope of 10” by20” by 20” (including element change clearance) was requested

• For ease of installation, the unit was to be designed to mountdirectly on the side of each of the gearboxes

• On occasion trace moisture could enter the system, so waterabsorbing elements were required along with particle filters

• The ambient environment had the potential to damage spin-oncanisters or plastic housings, so rugged aluminum construction

was going to be a benefit

• Since there was no oil circulation system, a dedicated pumpwas integrated into the assembly

The systems were installed on each of the gear boxes as a kidneyloop filtration circuit (Figure 15). Using a 1 GPM gear pump,designed for continual operation, oil is drawn from the reservoir,through a 3 micron filter element, followed by a water absorbing filterelement. The clean oil is then returned to the reservoir.

Following installation, all of the facility’s oil reservoirs have beenable to maintain ISO cleanliness levels of 16/14/12 with no moisturecontamination being detected. Going forward, it is expected that thisimproved fluid conditioning will ensure a long life for the lubricant aswell as minimize the potential for gear box failures.

Summary These examples illustrate some of the different strategies and

technologies that can be applied to lubrication and hydraulic systemsthat are situated in environments prone to high levels ofcontamination. And, more importantly, they have enabled operationsand reliability teams to significantly increase the quality of lubricantand hydraulic oil conditioning within their facilities, ensuring bettermachinery life as well as extending fluid life.

Figure 13: OEM Duplex

Figure 14: Simplex Upgrade

Figure 15: Panel Mount Duplex


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