FIL AI Eure. Myron L 720 Series II ORP monitor/controllers can be config-ured with bleed and feed switches as well as visible and audible alarms. Myron L Ultrameter and ULTRAPEN …

I N T E R N A T I O N A L

Your Global Source

FILTRATION NEWS

March/April 2013Volume 32 No. 2

www.filtnews.com

• Backwash Filters in Pharmaceutical Process

• Controlling Static Discharge in Hydraulic Systems

• Engineering Principles of Precoating

Myron L Company:Improving RO Systems Through Testing

Myron L Company:

Improving RO Systems Through Testing

• Backwash Filters in Pharmaceutical Process

• Controlling Static Discharge in Hydraulic Systems

• Engineering Principles of Precoating

2 • April 2013 • www.filtnews.com

Published byINTERNATIONAL

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Publication DataFiltration News (ISSN:1078-4136) is publishedbi-monthly by International Media Group, Inc.Printed in U.S.A., Copyright 2013.This publication has a requested and controlledsubscription circulation - controlled by the staff ofFiltration News; mailed bi-monthly as PeriodicalsPostage Paid (USPS 025-412) in Novi MI andadditional mailing offices.Filtration News is not responsible for statementspublished in this magazine. Advertisers, agenciesand contributing writers assume liability for allcontent of all submitted material printed andassume responsibility for any claims arisingthere-from made against publisher.

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IN THIS ISSUEMarch/April 2013, Vol. 32, No. 2

Cover Story | Myron L

Testing for Better System Efficiency 6

Baghouse | Dust Collection

Ensuring Effective Dust Collection in Challenging Environments 10

Chemical | Filtration

Poroplate MaxPore Extended Area Filters For Chemical Processing Applications 18

Backwash | Filters

Automatic Backwash Filter Improves Performance in Pharmaceutical Process 20

Electrostatic | Discharge

Controlling Static Discharge in Hydraulic Systems 24

Hydraulics | Filtration

Combining Filter in Reservoir of Hydraulics 32

Activated | Carbon

Changing Activated Carbon Demand and Supply 34

Precoating | Filters

Engineering Principles of Precoating 40

Product | News

Scientific Dust Collectors Announces New Nozzle Design Feature 46 Pfeiffer Vacuum Introduces Energy-Saving Dry Pumps A 100 L ES 47Sartorius Extends arium Lab Water Family by

Three New Product Lines 48Membrane Technology for Water with Fouling Potential 49

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Cover courtesy of Myron L Company


Editorial Advisory Board

Editorial Board ChairmanEdward C. Gregor, ChairmanE.C. Gregor & Assoc. LLCTel: 1 704 442 1940Fax: 1 704 442 [email protected]&A, Filtration Media

Haluk Alper, PresidentMyCelx Technologies Corp.Tel: 1 770 534 3118Fax: 1 770 534 [email protected] Removal – Water and Air

Jim JosephJoseph MarketingTel/Fax: 1 757 565 [email protected] Filtration

Robert W. McilvaineTel: 1 847 272 0010Fax: 1 847 272 [email protected]. Research & Tech. Analysis

Dr. Graham RidealWhitehouse Scientific Ltd.Tel: +44 1244 33 26 26Fax: +44 1244 33 50 [email protected] and Media Validation

Tony ShucoskyPall MicroelectronicsTel: 1 410 252 0800Fax: 1 410 252 [email protected], Filter Media,Membranes

Scott P. YaegerFiltration and SeparationTechnology LLCTel/Fax: 1 219 324 3786Mobile: 1 805 377 [email protected], New Techn.

Mark VanoverBayer MaterialScience LLCKey Account ManagerTel: 1 314 591 1792Email:[email protected] Systems

Dr. Bob BaumannAdvisory Board Member Emeritus

Andy RosolGlobal Filtration Products Mgr.FLSmidth [email protected]: 1 800 826 6461/1 801 526 2005Precoat/Bodyfeed Filter Aids

Clint ScobleFilter Media Services, LLCOffice: 1 513 528 0172Fax: 1 513 624 [email protected] Filters , Filter Media, Baghouse Maintenance

Gregg PoppeThe Dow Chemical CompanyTel: 1 952 897 4317Fax: 1 942 835 [email protected] Water, Power,and Membrane Technology

Henry Nowicki, Ph.D. MBATel: 1 724 457 6576Fax: 1 724 457 [email protected] Carbons Testing,R&D, Consulting, Training

Brandon Ost, CEOFiltration GroupHigh Purity Prod. Div.Tel: 1 630 723 [email protected] Filters, Pharmaceuticaland Micro-Electronic

Dr. Ernest Mayer E. Mayer Filtration Consulting, LLC Tel: 1 302 981 8060Fax: 1 302 368 [email protected]

Wu ChenThe Dow Chemical CompanyTel: 1 979 238 [email protected] Filtration (liquid/gas)Equipment and Media

Peter R. Johnston, PETel/Fax: 1 919 942 [email protected] procedures

Peter S. Cartwright, PECartwright Consulting Co.Tel: 1 952 854 4911Fax: 1 952 854 [email protected], RO,Ultrafiltration


Cover Story | Myron L Company

ater quality testing isnot only vital to thedesign of an efficient,

cost-effective RO system, it is alsoone of the best ways to preserve sys-tem life and performance.

And with the right instruments,it’s easy to do. Myron L Companymanufactures innovative high qualityportable meters and cost-effectivemonitor/controllers designed to sim-

plify the management of those pa-rameters most critical in screening,treatment, and distribution.

Using an accurate Total DissolvedSolids (TDS) measurement to cor-rectly assess the system load preventscostly mistakes up front. The TDSmeasurement gives users the infor-mation they need to determinewhether or not pretreatment is re-quired and the type of membrane/s to

select. Myron L Ultrameter™ andULTRAPEN PT1™ Series TDS in-struments feature the unique abilityto select from 3 industry standard so-lution models: Myron L 442 NaturalWater™; NaCl; and KCl. Choosingthe model that most closely matchesthe characteristics of the sourcewater yields measurements accurateenough to check and calibrate TDSmonitor/controllers that alert to sys-

Testing for Better System EfficiencyLearn how to substantially improve RO system performance and cut costs using a few basic water quality tests.

By Heather Rekalske, Technical Writer, Myron L Company

W

Figure 1: The Ultrameter Series – Myron L manufactures easy to use multiparameter instruments that make managing basiccritical water quality parameters required for optimizing any treatment fast and simple.

tem failures, reducing downtime andincreasing productivity. The same in-struments provide a fast and accuratetest for permeate TDS quality con-trol. Measuring concentrate values,as well, and analyzing quality trendslets users accurately determine mem-brane usage according to the manu-facturer’s specifications so they canbudget consumption correctly. Thesedaily measurements are invaluable in

detecting problems with system per-formance where changes in the ionicconcentration of post-filtrationstreams can indicate scaling or foul-ing. System maintenance is generallyindicated if there is either a 10-15%drop in performance or permeatequality as measured by TDS.

Membranes such as thin-filmcomposite membranes degrade whenexposed to chlorine. In systems

where chlorine is used for microbio-logical control, the chlorine is usu-ally removed by carbon adsorption orsodium bisulfite addition beforemembrane filtration. The presence ofany chlorine in such systems will atbest reduce the life of the membrane,thus, a target of 0 ppm free chlorinein the feedwater is desirable.

ORP gives the operator the totalpicture of all chemicals in solution

www.filtnews.com • April 2013 • 7

Figure 2: Point Source Sampling – An integrated cell and sampling cup makes the Ultrameter II highly portable. Real-timedata makes fast field analysis possible.


Cover Story | Myron L Company

that have oxidizing or reducing po-tential including chlorine, bromine,chloramines, chlorine dioxide, per-acetic acid, iodine, ozone, etc. How-ever, ORP can be used to monitorand control free chlorine in systemswhere chlorine is the only sanitizerused. ORP over +300 mV is generallyconsidered undesirable for mem-branes. Check manufacturer’s speci-fications for tolerable ORP levels.

An inline ORP monitor/controllerplaced ahead of the RO unit to auto-matically monitor for trends andbreakthroughs coupled with spotchecks by a portable instrument willprevent equipment damage and fail-

ure. Myron L 720 Series II™ ORPmonitor/controllers can be config-ured with bleed and feed switches aswell as visible and audible alarms.

Myron L Ultrameter and ULTRAPENPT3™ and PT4™ portable handheldsare designed for fast field testing andare accurate enough to calibratemonitor/controllers. Myron L meas-urement methods are objective andhave superior accuracy and conven-ience when compared to colorimetricmethods where determination ofequivalence points is subjective andcan be skewed by colored or turbidsolutions.

Monitoring pH of the source waterwill allow users to make adjustmentsthat optimize the performance of an-tiscalants, corrosion inhibitors andanti-foulants. Using a 720 II SeriesMonitor/controller to maintain pHalong with an Ultrameter Series orULTRAPEN PT2™ handheld to spotcheck pH values will reduce con-sumption of costly chemicals and en-sure their efficacy.

Most antiscalants used in chemicalsystem maintenance specify a Lange-lier Saturation Index maximum value.Some chemical manufacturers andcontrol systems develop their ownproprietary methods for determininga saturation index based on solubilityconstants in a defined system. How-ever, LSI is still used as the predomi-nant scaling indicator becausecalcium carbonate is present in mostwater. Using a portable Ultrameter III9PTKA™ provides a simple methodfor determining LSI to ensure thechemical matches the application.

The 9PTKA computes LSI from in-dependent titrations of alkalinity andhardness along with electrometricmeasurements of pH and tempera-ture. Using the 9PTKA LSI calcula-tor, alterations to the water chemistrycan be determined to achieve the de-sired LSI. Usually, pH is the mostpractical adjustment. If above 7, acidadditions are made to achieve the pHvalue in the target LSI. Injections aremade well ahead of the RO unit to

ensure proper mixing and avoid pHhotspots. A Myron L 720 Series II pHMonitor/controller will automaticallydetect and divert solution with pH out-side the range of tolerance for the ROunit. ULTRAPEN PT2, TechPro II™and Ultrameter Series instruments canbe used to spot check and calibrate themonitor/controller as part of routinemaintenance and to ensure uniformmixing. Myron L handheld pH instru-ments are useful for monitoring pHduring excursions, as well.

Water hardness values indicatewhether or not ion exchange beds arerequired in pretreatment. Checkinghardness values directly after thesoftening process with the 9PTKAensures proper functioning and an-ticipates the regeneration schedule.

Alkalinity is not only important inits effect on the scaling tendency of so-lution, but on pH maintenance. Addi-tions of lime are used to buffer pHduring acid injection. Titrate ppm alka-linity values with a 9PTKA for fast fieldanalysis where other instrumentation istoo cumbersome to be practical.

Though testing and monitoringpressure is a good way to evaluatesystem requirements and perform-ance over time, measuring otherwater quality parameters can helppinpoint problems when trou-bleshooting. For example, if the pres-sure differential increases over thesecond stage, the most likely cause isscaling by insoluble salts. This meansthat any degradation in performanceis likely due to the dissolved solids inthe feed. Using a 9PTKA to evaluateLSI and calculate parameter adjust-ments is a simple way to trou-bleshoot a costly problem.

For more information contact:Myron L Company2450 Impala DriveCarlsbad, Ca 92010-7226Tel: 1-760-438-2021 X1223Email: [email protected]: www.myronl.com

Figure 3: Free Chlorine in the Field –The new 6PFCE features an innovativeORP-based free chlorine analyzer exclusive to Myron L products.

FN



hen it comes to selectinga dust collector for a par-ticular environment, the

characteristics of the specific dust to becollected needs to be considered. Whatis the size of the dust? Is it extremelysmall? Is it a mix of sizes? Is it abrasive?Is it hygroscopic, or moisture absorb-ing? Does it agglomerate easily, or notat all? Is it explosive/combustible? Is itcorrosive/toxic/unstable?

All these are necessary considera-tions, related to the dust being col-lected, but the dust is not the only

factor to consider. It is essential that theproperties and conditions of the gasstream entering and passing throughthe collector be also factored into thechoice of a dust collector.

Gas stream characteristics have asignificant – and sometimes greater –impact on equipment selection thandust characteristics. The combinationof the dust and gas stream characteris-tics can make for some challengingequipment selections. Let’s look at justa couple of the more common gasstream characteristics and their impacts

on selecting an appropriate collector:temperature, moisture, and chemistry.

TEMPERATURETemperature – especially high tem-

perature – affects not only the selectionof filter media, but the constructionmaterials of the collector, and the filterstyle – bags or cartridges. Temperaturecan also influence the method of filterreconditioning/cleaning and the totalrequired filter area. (The required filterarea is driven by the required air vol-ume and the reasonable filtration veloc-

Ensuring Effective Dust Collection in Challenging EnvironmentsBy Tom Godbey, Senior Application Specialist, Donaldson Torit

W

Figure 1. Filter Media Performance Characteristics – based on increasing temperature conditions.

Xinxiang Tiancheng Aviation Purification Equipments Co. Ltd.

Our company specializes in designing & manufacturing and supplying many kinds of filters,

complete filtrating equipments and their elements with different materials according to your

drawings or new & old samples.

Xinxiang Tiancheng Aviation Purification Equipments Co. Ltd.No. 1, Chuanye Road, Dvelopment Area, Xinxiang City 453003, Henan

P.R. China

Contact Person in China: Mr. Li Minghao

Tel: +86-13673735086 Fax: +86-373-3520026 Website: www.tchkjh.comEmail: [email protected] • [email protected]

Contact Person in USA: Mr Liu Shengyuan

Tel: 4015881868 • [email protected]

For airplane For special vehicle

For coal machinery

For fluid cleaning systemFor dust collector of cement industry

For ultrafilter


ity, commonly referred to as the Air-to-Media Ratio.) Higher temperature con-ditions usually require moreconservative filtration velocities.

There are many different filtermedia available with known charac-teristics. Figure 1 is an example of a

Filter Media Performance Character-istics Chart showing the temperaturelimitations and other attributes of var-ious commonly available filter media.It would seem relatively simple to se-lect filter media by the process ofelimination, and, it can be simple IF

you know the other characteristics ofthe gas stream.

However, not all media are suitablefor all types of collectors or condi-tions. Fiberglass, as an example, isnot generally considered suitable forenvelope-shaped pulse jet collector


Figure 2. A dust collector and ducting that is insulated to ensure condensation control.

bags – just as spunbond polyester isnot generally considered suitable forshaker style collectors. So the operat-ing temperature and available mediafor temperature can influence thetype of collector being considered.

As mentioned earlier, temperature

can also influence materials of con-struction for the collector. This in-cludes the type of metals, gaskets, orpaint as well as special requirements forinsulation for both moisture and acidcondensation control, or personnelsafety. See example in Figure 2.

And, finally, it is important to re-member filtration velocity is impactedby changes in the density of the gasstream. Increases in temperature andthe total volume of filtered air in-crease with temperature, so tempera-ture influences collector size.




MOISTUREHigh moisture levels can have both

negative and positive effects on the per-formance of dust collectors. Whenmoisture levels are higher, precautionsmust be taken to prevent condensationon not only the filter media but also onthe interior sidewalls of the collectorbody and hopper to avoid an obviouseffect of moisture interacting with thedust – mud. See example in Figure 3. Itis often difficult, if not impossible, toremove mud from a filter media by nor-mal pulsing or shaking. It is even moredifficult to try and get any air move-ment through the mud, thus the value

in maintaining an interior temperaturein the collector above the moisture andacid dew points.

Maintaining the collector wall tem-peratures above the moisture dew pointcan be equally important, especially onthe interior walls of the hopper. The in-terior walls of the hopper are typicallythe coldest temperature inside a collec-tor, and it is not unusual to see mois-ture condensation on the interiorhopper walls while the temperature onthe media is well above the dew point.

Consider the impact of dust fromthe filters being pulse cleaned, fallingonto the wet hopper walls. The result

is dust not sliding smoothly downthe hopper walls as intended, butsticky dust eventually bridgingacross the discharge opening, effec-tively shutting down the operationjust as if mud were formed on thebags themselves.

Preventative action to keep theseissues from developing can take theform of insulation of the housing oradditional heating elements on the ex-terior of the hoppers. Some environ-ments even require heating of thecompressed air used in pulse cleaningto prevent the collector from passingthrough a dew point because of the

Figure 3. Filter media that illustrates the negative impact of excessive moisture within a dust collector. The mud that resultsis difficult – if not impossible – to remove from a filter by normal pulsing or shaking.

Update or list your company in our 2013 Buyers’ Guide.Deadline is May 31.

Email: [email protected]: www.filtnews.com/buyersguideFN.html


Baghouse | Dust Collectionchilling effect from expanding com-pressed air released during each pulse.

While condensation is an extrememoisture condition, problems canarise from just elevated moisture lev-els without condensation actually oc-curring. Hygroscopic dust such assugars, salts, and lime actively absorbmoisture from a gas stream and canbecome very difficult to dislodgefrom filter media.

As a general rule, dust collectorsperform best when the relative hu-midity of an air stream containinghygroscopic dust is kept at or below40% RH. The use of hydrophobic orfluorocarbon-treated media can en-hance dust release characteristics ofthe media filtering these dusts, re-sulting in more stable pressure lossacross the filter media and longer in-tervals between filter replacements.

The challenges associated withhigh moisture levels are relativelywell known and predictable. How-ever, low moisture levels with hightemperatures and dusts such asmetallic salts can become even morechallenging. At high temperaturesand low moisture levels, metallicsalts (as well as other dusts with sim-ilar characteristics) behave as if eachdust particle has the same electricalcharge. The particles repel each otherand agglomeration of small particlesinto larger particles can become neg-ligible. Since dust particles must ag-glomerate for collected dust on themedia to be dislodged and migrate tothe hopper, if dust never agglomer-ates, the particle size stays the sameand the air currents just transportdisturbed dust back to the media tobe re-deposited. This means dust

would never migrate into the hopper.With some dusts, this effect is severeenough that it can actually be advan-tageous to introduce moisture intothe air stream, often in the form ofsteam, to promote agglomeration.Unfortunately, many times dusts withthese characteristics are not recog-nized until after the collector is al-ready in operation. Yes! Withmoisture, the challenge can be eithertoo much or too little!

CHEMISTRYChemistry is that broad term en-

compassing a multitude of contami-nants, the most common being acidgases, but also including condensablecompounds, hydrocarbons, VolatileOrganic Compounds (VOC), andothers. Acid-forming compoundssuch as Sulfur Oxide (SOx) and

Update or list your company in our 2013 Buyers’ Guide.Deadline is May 31.

Email: [email protected]: www.filtnews.com/buyersguideFN.html

Chlorine (CL), which are commonbyproducts of combustion, are in-cluded in this grouping. These com-pounds, when combined withmoisture, (also a byproduct of com-bustion) have the potential to formacids when the temperatures in thesystem drop below their acid dewpoints. Each of these present chal-lenges in materials of construction,surface coatings, insulation, and fil-ter media selection. Gas streams withmixtures of several of these contam-inants represent even more challengeand require a thorough review of theprocess and performance priorities.Many requirements will cause con-flicts, so the final collector selectionwill require tradeoffs such as higherinitial capital cost for a special coat-ing but a longer collector life, or alonger interval between filter re-placements but at the expense of ahigher cost filter media.

CONCLUSIONSEach of these gas stream charac-

teristics offers common challenges inthe selection and operation of dustcollection equipment, but gasstreams with combinations of thesefactors offers great challenges. Theanswer for one process may not bethe best answer for what would ap-pear to be a similar gas stream. As anexample, Polyphenylene sulphide(Ryton) media may be an excellentselection for a hot SOx-laden gasstream from a coal fired boiler. How-ever, it may not be a good selectionfor hot SOx-laden gas from a coalfired kiln when a kiln induces signif-icant amounts of excess air and as aresult, produces higher oxygen con-tent than the coal fired boiler. In thishot moist flue gas environment,Ryton media can be subject to a lossof physical strength due to oxidationas oxygen levels exceed 8%. Boilerflue gases are rarely above that level,

but the excess air from the kiln candrive oxygen levels well above thatlevel. Thus, a polyimide (P84) mediamay be a better selection eventhough it has a lower resistance tothe acids.

The point is: to make properequipment selections for challenginggas streams, the full characteristics ofthe gas stream must be known. Sowhen an inquisitive dust collectorsalesman/engineer starts grillingabout process, trust his intention.His primary goal is to prevent sur-prises during commissioning and op-eration that might occur becausesomething was left unknown in theplanning phase. No one likes thosetypes of surprises, and everyone isbetter served by facing the challengesup front.

For more information contact:Donaldson Company, Inc. Website: www.donaldsontorit.com

FN

Chemical | Filtration


he chemical processing industryis one of the world’s largestusers of industrial filtration

equipment. Filters are used in a widerange of liquid process applications inchemical plants, including filtering theraw materials, additives/pigments/cata-lysts, water/liquid waste generated by theprocess, and the finished product itself.

The most commonly used filters inthe chemical processing industry arebags and cartridges. These are typicallyconstructed of cotton, synthetic poly-mers, fiberglass, or other non-metallicmedia. While acceptable for most ap-plications, they are generally not suit-able for temperatures above 400-500˚ F(except for fiberglass, which is capable

of higher temperature exposure), andare incompatible with some chemicals.Therefore, alternative materials of con-struction must be used in many cases.

While the initial cost of the abovenoted bags and cartridges are very low,the total cost of use can be very high.Factors such as labor to change-out fil-ters, production loss during change-outs, operator exposure to potentiallyhazardous chemicals during change-outs, and cost to properly dispose ofused filters should be considered.

Considering the chemical compati-bility and temperature limits, as well asthe total cost of use of non-metallic fil-ter bags and cartridges, reusable porousmetal filters are often the best choice

for chemical processing applications.But, in order for porous metal filters tobe economically viable, they must becapable of economical regeneration insitu, or economical external chemicalcleaning must be available.

Purolator Advanced Filtration re-cently introduced a technology that ad-dresses these challenges. Poroplate®MaxPore™ extended area filter basketshave been specifically designed for hightemperature, corrosive environments,and can be cleaned in place for reuse,or removed and chemically cleaned.

Poroplate MaxPore baskets are con-structed from stainless steel (or higheralloys) sintered wire cloth laminatedmedia (Figure 1). This media has a 40+

Poroplate MaxPore Extended Area FiltersFor Chemical Processing ApplicationsBy Mark Willingham, Purolator Advanced Filtration

Figure 1. Sintered wire cloth media Figure 2. Poroplate MaxPore cross-section

T

year proven service record in a varietyof high temperature, high pressure andcorrosive applications, and is availablein ratings as low as 2µ nominal. Themedia consists of multiple layers ofwoven wire cloth, which are diffusionbonded (sintered) in a furnace to createa highly permeable filter laminate witha permanently fixed pore size. Themedia can be configured as a surfacemedia, or as a progressive pore sizemedia, which yields up to 4x higher

dirt holding capacity. Both configura-tions can be backwashed/back-pulsedto regenerate the baskets.

After the media has been con-structed in panel form, it iscut/formed/welded into various diame-ter cylinders, which are concentricallyarranged to maximize the effective filterarea. Each of these cylinders consists ofan inner and outer cylinder, open onone end and joined together by a solidring at the other. A flow channel is cre-ated between the inner and outer wallsof each cylinder, similar to the flowpath of a wall flow filter. This dual-sided arrangement further increases fil-ter surface area. In its final form(Figures 2 and 3), the Poroplate Max-

Pore extended area basket has up to 23ft.2 of filter area and fits into a baskethousing that would normally hold a sin-gle filter basket with only 4 ft.2. This ad-vantage in effective filter area can be usedin several ways – to reduce the numberof filter housings/valves/piping needed innew installations, to increase filter life, toreduce pressure drop, and to increase theflow rate through the filter.

A typical Poroplate MaxPore basketis capable of flow rates of up to 300

gpm (of water or fluid of an equivalentviscosity) with a clean pressure drop aslow as 1 psi.

Poroplate MaxPore baskets can beused in standard bag/basket housingswhere they can be removed for cleaningwhen dirty, or cleaned in place. Thepreferred flow direction is from the bot-tom of the basket up and through themedia, then out the top of the basket.Cleaning in place is typically accom-plished by reversing the flow and push-ing clean, filtered liquid back throughthe media with approximately 100 psi.The pressure can be applied by air/gas,or the clean liquid itself.

The chemical processing industrytoday has a number of filtration prod-

ucts to chose from, and the final selec-tion of which type to use in each appli-cation should be determined by anumber of factors, as mentioned earlierin this article. The initial cost, as well asthe total cost of use must be considered.

Poroplate MaxPore extended areafilter baskets have many unique per-formance characteristics such as highflow rates with low pressure drop, fil-tration ratings as low as 2µ, ability tobe regenerated, compatibility in appli-

cations with high temperature, highpressure, and corrosive chemicals.These characteristics should be consid-ered when making the final selectionfor chemical processing applications.

Mark Willingham is Vice President ofSales for Purolator Advanced Filtration.He has 30 years of experience in the fieldof porous metal filter products for appli-cations in the oil & gas, chemical pro-cessing, nuclear power generation,polymer, and general industrial markets.

For more information contact:Purolator Advanced Filtration/Martin Kurz (MKI)Tel: 1-336-217-3822Website: www.purolator-facet.com

Figure 2. Poroplate MaxPore cross-section Figure 3. Poroplate MaxPore cross-section and full size basket


FN


Backwash | Filters

ith the patented back-wash principle, theLenzing Technik Opti-

Fil® has the ability to filter down tovery small particle sizes, while havinglowest amounts of reject losses. Thismakes it the perfect choice, whenevervaluable products are filtered.

THE LENZING OPTIFILOriginally, the technology was de-

veloped for high-viscosity spinning so-lutions and has recently beenredesigned for the microfiltration ofwater and other low-viscosity fluids.

The Lenzing OptiFil is a fully auto-matic, continuous system that worksaccording to the principle of depth,surface or cake filtration, depending onthe selected type of filter material. Ametal or synthetic fiber fabric or fleece

is used as filter media, retaining parti-cles of different sizes either inside oron its surface. After the pre-determineddegree of contamination has beenreached, the filter material is cleanedby backwashing a small quantity of fil-tered medium, with continuous filtra-tion during backwashing.

In detail, the filter material of theLenzing OptiFil is installed outside aperforated supporting structure (“per-forated drum”). In case of cake filtra-tion, a very thin filter cake (of typically0.5 – 2mm) is formed inside the holesof the perforated drum during the fil-tration from the inside (Room P1) tothe outside (Room P2). During thepartial backwash from “Room P2” (Fil-trate) to “Room P3” (Reject), the cakeis completely discharged within a fewseconds, using a small amount of fil-

trate to force it out of the filter. Newcake formation already starts duringbackwash and is typically finished re-sulting in clear filtrate within less than10 seconds.

Figure 1 shows the operating prin-ciple and setup of the filter in detail.

In applications with valuable basematerials, the Lenzing OptiFil revealsits big advantage of low rejectamounts due to the patented back-wash principle.

THE APPLICATIONThe low reject amount was the

major reason for a renowned multina-tional pharmaceutical company, basedin the Netherlands, to install the Lenz-ing OptiFil in the production of a drugfor treatment of high blood pressure.

In this process, a fermentation

Automatic Backwash Filter Improves Performance in Pharmaceutical ProcessBy Stefan Schöpf, Stefan Strasser and Lisa Ertl, Lenzing Technik

WFigure 1: Operating principle of the Lenzing OptiFil.


broth is put into a reaction tank to-gether with enzymes and mixed witha “kieselguhr” type of filter aid. Thedistribution density of this filter aidis shown in Figure 2, which illus-trates that it contains very fine parti-cles, and even smaller with less thanten microns.

After finishing the reaction, themixture is pumped into a centrifugewhere the enzyme solids are filtered.However, a certain amount of filter aid,typically the fraction of the smallerparticles, always migrates into the fil-trate. Those filter aid residues need tobe removed prior to the downstreamultra filtration step. Previously, dispos-able bag filters made out of high qual-ity 10µm monofilament were used forthis pre-filtration step.

In Figure 3: Process Flow Diagram,the process implementation of theLenzing OptiFil is shown. It replacesthe previously used bag filters, situatedbetween the centrifuge and the ultrafiltration unit.

IMPROVEMENTSCost for filtration:With each batch produced, up to ten

bag changes were necessary.The previously installed 10µm

monofilament bags have already beenmade out of a rather costly material.

However, much more crucial was thefact that with each bag change about 30

Figure 2: Distribution density of the filter aid.

Backwash | Filters


liters of the very expensive base mate-rial were lost. Extrapolated to the batchvolume, the product losses amounted

to between 5% and 10%.Through implementation of the

Lenzing OptiFil, product losses for a

whole batch where reduced to less than1%. This means higher yield and there-fore more product output with eachbatch. Additionally, no manual filtermaterial change occurred due to the au-tomatic cleaning.

Filtrate quality:Even though premium quality filter

material was used for the bag filter, thefiltrate quality was fairly poor for tworeasons: (1) For reaching reasonablelife times and change intervals (highdirt holding capacity), a rather large fil-ter area per flow volume had to be in-stalled. This required filter area led tosedimentation effects in the bag, result-ing in a non-uniform cake formation inthe filter bag. (2) Furthermore, eventhe best monofilament material madeof polymer filaments has a rather highvariation in pore sizes, meaning thatthere are many pores being larger than10 µm.

Both effects led to a poor perform-

Figure 3: Process Flow Diagram

ance of the downstream ultra filtrationunit, resulting in a low flow ratethrough the membrane, so that it be-came a bottleneck.

As the Lenzing OptiFil is operatingan automatic backwash system, it wasdesigned for achieving the highestflow/time instead of focusing on thedirt holding capacity. This led to amuch smaller filter area (only about10% of the bag filter system) and there-fore to a uniform cake formation aswell as high quality filtrate, shortlyafter backwash. Additionally, a specialstainless steel weave was used, alsowith 10µm pores, but with a muchmore uniform pore size distribution.

Therefore the actual filtration perform-ance is close to 1µm!

By using the Lenzing OptiFil, theflow through the ultra filtration systemand the module lifetime could be in-creased significantly so it does nolonger represent a bottleneck in theprocess.

Workplace, Health and Convenience:The fermentation broth contains

ammoniac, which leads to high odornuisance along with each bag change.

The Lenzing OptiFil is a com-pletely closed system. A double act-ing mechanical seal with athermosyphone system was chosen to

seal the rotating shaft to the outside,leading to zero emissions during op-eration.

Productivity:Since the application of the Lenz-

ing OptiFil, the company has beenable to finish a batch in much lesstime, leading to a significant increasein production.

For more information contact:Lenzing Technik GmbHTel: +43 (0) 7672 701-3479Fax: +43 (0) 7672 918-3479 Email: [email protected]: www.lenzing.com/technik

FN


Correction:

In the February 2013 issue of International Filtration News, the article on page 20: “Integrated Dual Membrane Systemsfor Drikning Water Production” was compiled by the following industry experts:V. García-Molina (1), O. Ferrer (2), B. Salgado (1), A. Fiaz (1), I. Martín (2), J. Mesa (3), X. Bernat (2)(1) Dow Chemical Ibérica, Autovía Tarragona Salou s/n, 43006 Tarragona, Spain(2) CETaqua, Centro Tecnológico del Agua. Carretera d’Esplugues 75, Cornellà de Llobregat 08940 Barcelona, Spain(3) SGAB, Sociedad General de Aguas de Barcelona. Av. Diagonal 211, 08018 Barcelona, SpainFor more information on the article, email: [email protected]


he phenomenon of static elec-tricity and resultant static dis-charge is typically associated

with a shock that occurs after walking oncarpet with rubber-soled shoes or stock-ing feet and subsequently touching an-other surface. In fact, in the abovescenario, it is possible for a person tocarry out an Electrostatic Discharge event(ESD) of over 30KV. The micro-electron-ics industry has a history of dealing withthe presence and dangers of static elec-tricity and has taken many precautions toprevent electrostatic discharge from oc-curring. These precautions include wriststraps, anti-static garments, groundedworkstations, and environmental con-trols including humidity and air ioniza-tion. As with the micro-electronicsindustry, hydraulic and lube oil systemdesigners and users need to be aware ofESD, the damage it can inflict on systemcomponents, and where to look for it.This paper will ultimately assist the sys-tem designer and user on how to preventESD from occurring, including the use ofstatic control filter elements.

INTRODUCTIONAn initial experience with ESD on a

hydraulic system was in the lab at Parker’sHydraulic Filter Division. A flow test wasbeing conducted on a filter assembly andit was a cold, dry January day. The testfluid was a pre-filtered ISO 46 hydraulicoil and the filter media was a micro-glasscomposite with 10um rated filtration ef-ficiency (β10>200). The first indicationthat something may be occurring was atapping sound inside the filter housing.As the flow rate increased, the sound wasmore frequent and pronounced. As theflow rate decreased, the sound would be-

come inaudible. When the flow test con-cluded and the filter assembly was disas-sembled, engineers noticed someevidence of arcing and pitting on the ele-ment locator and the element end-cap.

An earlier customer occurrence re-garding ESD on a hydraulic system wason an off-line filtration skid at a North-ern Ohio automotive plant. Here, thecustomer was filtering ash-less ISO 46hydraulic oil using a 4um rated effi-ciency filter, again in the wintertime.This time, the customer observed a rum-bling, or sound similar to thunder, in thehydraulic reservoir. After removing thereservoir cover, arcing resembling smalllightning bolts was also observed.

Both of these two ESD experienceshad several things in common:

• Clean Oil – an ISO cleanliness code of <15/13/10 was measured via particle counting on both systems

• Efficient filters– 10um efficiency or finer (β10>200)

• Micro-glass filter media was utilized in both cases

• Environmental - low humidity• Relatively high flow densities or high velocity thru the filter media

• Relatively low system temperatures (<50°C)


Controlling Static Discharge in Hydraulic SystemsBy Bruce Shane, Engineering Manager, Parker Hannifin Hydraulic Filter Div.

T

The use of static control filter elements can prevent ESD in hydraulic systems.


These ESD issues could have beensolved in several ways, but perhaps notby the most efficient or even acceptablemeans. In the Parker Lab it was initiallyconsidered as an anomaly that engi-neers could solve by doping the oilwith an anti-static additive. In the au-tomotive customer case Parkerchanged the filter housings from singlelength to double length in order tolower the face velocity thru the filtermedia. These two solutions are not al-ways possible or desirable, but bothmay have been preferred over ignoringthe situation. In this paper follows a re-view of more of the issues concerningthe effects of ESD on a system and waysto eliminate it.

WHY ESD OCCURSESD (Figure 1) can occur when the

charge generation interfaces of two dis-similar non-conductive surfaces (inthis discussion we will mainly considerthe oil and filter media) slide across orare in contact then separated. The re-sultant charges are carried by the oil

downstream to a conductive surfacewith low potential and a voltage dis-

charge occurs (see the aforementionedcustomer experience). ESD also occurs

Figure 1 – Arcing between filter element media and center support core, and alsobetween filter element end-cap and filter housing.


if the filter media is significantlycharged by the same contact and sepa-ration from the oil and the dischargeoccurs in or near the filter housing (seethe experience in the lab).

Why is ESD more prevalent today? There are several primary reasons,

and the main ones are as follows:

Filtration - As the hydraulics in-dustry changed from on-off hydrauliccontrol systems to more sophisticatedand compact proportional controlsystems, the requirements for filtra-tion grew. The filtration efficiency re-quirements evolved from a 20 micronto 10 or even <5 micron “absolute”(β5>200) particle removal. Cellulosefilter media, due to its large fiber sizeand lack of void volume that couldnot meet the requirements for effi-ciency, capacity and low pressuredrop, was replaced by micro-glass.Base micro-glass is non-conductiveand has tight fiber matrices that pro-vide maximum surface contact withhydraulic oils that are often also non-conductive.

Environmental - Many hydraulicsystems operate in environmentallysensitive areas where leaks or spills ofhydraulic fluid may result in contami-nation of the soil or nearby waterways.Conventional anti-wear hydraulic oilsare formulated with conductive metal-containing performance additives,which can possibly remain in the envi-ronment in the event of leaks. How-ever, these metal additives also providesome level of conductivity, dependingon the specific oil. In contrast, ash-lessoil, several synthetic oils, and dielectricoils do not have these conductive addi-tives. Typically, oil specification sheetsdo not mention conductivity values,but these can be measured using a con-ductivity probe. ASTM D4308 (1) is thestandard used to measure the rest con-ductivity of hydrocarbon fluids by aprecision meter (2).

Figure 2 shows how oil conductivitycan be measured using a digital con-ductivity meter.

System Efficiency - More compacthydraulics allows for both lighter andlower cost vehicles and systems, but

this typically results in higher flow ve-locities. This includes not only the fil-ters, but other components as well –including hose and fittings. This highvelocity condition will typically in-crease static charge generation in thesystem and limit the allowable timethat the static charge has to dissipate.Smaller reservoirs are also the norm,which limits the relaxation time of anystatic charge that occurs and limits itsability to slowly dissipate. Also, lightweight, but non-metallic (non-conduc-tive), reservoirs are now commonlyused on mobile equipment.

WHAT ESD DOES TO A SYSTEMLeft uncontrolled, ESD can damage

system components where the dis-charge takes place. The constant arcingcan eventually pit the surface, reducingthe component’s functionality while re-leasing contamination into the systemto perhaps do more damage.

Figure 3 shows pitting from ESD onanodized aluminum component.

ESD can also damage the filter ele-ment. Micro-glass media for hydraulicand lube systems can have a mean pore

Figure 2. Oil conductivity can be measured using a digitalconductivity meter.

Figure 3. Pitting from ESD on anodized aluminum component.



size of < 2 um. Any arcing that takesplace can burn large holes in the mediamatrix allowing contaminant to passand damage downstream system com-ponents.

Figure 4 shows burnt polymer pleatsupport mesh from arcing.

Studies have suggested that varnishis formed due to thermal and oxidativedegradation of oil. It also has been sug-gested that the localized heat generatedfrom a static charge discharge can reachseveral thousand degrees – hot enoughto cause localized thermal degradationof the oil. Varnish can harm the systemin several ways, such as sticking servo-valves, plugging filters, and build-upon metallic surfaces (heat exchangers,reservoir walls, bearings, etc.). Manu-facturers of combustion turbines havelong recognized this relationship ofstatic discharge causing thermal degra-dation and subsequent varnish forma-tion in turbine lube oils.

Figure 5 shows varnish build up onmetal surfaces in a system decreasingsystem efficiency and reducing compo-nent life.

MEASURING & DETECTING ESDThe amount of static electricity in a

fluid system is an unpredictable phe-nomenon that can come and go basedon the time of day, time of year, ambi-ent and system environmental condi-tions, and the amount ofcontamination – particulate or water. Itis sometimes difficult to determine

when and where to measure suspectedESD. However, the best diagnostic ap-

proach would include measuring andmonitoring the same way under the

Figure 4 – Burnt polymer pleat supportmesh from arcing.

Figure 5. Varnishbuild up on metalsurfaces in a systemdecreasing systemefficiency and reduc-ing component life.



same conditions. Audible tapping or ticking sounds

near the filter housing as describedearlier, is perhaps the most commonmeans to determine if ESD is occur-ring. If the system filter is located in anoisy area, a stethoscope should beemployed.

A hand held static field meter(3) is aneasy, quick, and non-intrusive methodto determine if static charge is buildingup in a system. The field meter willmeasure up to 40KV, is battery pow-ered, and can be used anywhere. If userstarts seeing voltage readings above4kV with the static field meter theyshould suspect that ESD events are oc-curring somewhere in the system.

Figure 6. Shows an electrostaticfield-meter that can be used for locat-ing & measuring static charges aroundcomponents in a system.

The combination of a voltmeter anda high voltage probe adapter(4) is an-other instrument that can be used tomeasure static electricity. This ap-proach can be more intrusive depend-ing on the system, is typically lesssensitive, and is best suited for meas-

urements near the surface in a reser-voir where the fluid is entering. Thisset-up can be customized by modify-ing or changing the end probe to athermocouple style adapter to meas-ure inside the fluid stream, which canenable a more quantitative voltagemeasurement.

Figure 7 shows a digital voltmetercoupled with a high voltage probethat can measure up to 40kV and canbe used for locating & measuringstatic charges in the oil stream and in-side reservoirs.

Static charge is an unpredictablephenomenon, and issues with incon-sistent results can occur using eithermeasurement approach. The point toremember is that both devices offer ameans of measurement that can detectstatic charge and allow the user tomonitor the system and take con-structive measures to control ESD.These measures are described in thefollowing section.

CONTROLLING ESD The velocity of oil flow thru the fil-

ters can be decreased by increasing thefilter media surface area, which can bedone in several ways. First, many filterconfigurations have extended canisteror bowl lengths which, when retrofit-ted, may cut the velocity in half withan increase in filter’s footprint in themajor axis. Second, filter assembliesare normally part of a family for abroad flow rate range. By upsizing tothe larger size product in the family,velocity thru the filter media will be re-duced. Also, splitting flow betweentwo filter assemblies will decrease thevelocity thru the filter media by half.While these solutions may eliminateESD, they have several drawbacks in-cluding labor & material cost, addi-tional size & weight, and may bedifficult to retrofit on existing systems.

As discussed earlier, the more effi-cient a micro-glass filter element, themore static electricity is typically gen-erated. By switching to a more open fil-ter media including perhaps cellulosemedia on the in-line system filter, inconjunction to installing more efficientoff-line filtration at low flow velocity,ESD can also be eliminated. This solu-

Figure 6. An electrostatic field-metercan be used for locating & measuringstatic charges around components in asystem.

Figure 7. A digital voltmeter coupledwith a high voltage probe can measureup to 40kV and can be used for locat-ing & measuring static charges in theoil stream and inside reservoirs.

Figure 8. Static control filter elementsreduce charge generation and offer adrop in solution to existing installed fil-ter housings.

tion, however, would also increase cost by way of the off-line pump-motor-filter group and associated hardware. Inaddition, it would also increase the risk of system compo-nents being damaged by unfiltered particles before the off-line filters are able to capture them.

Adding an anti-static additive to the oil may temporar-ily eliminate ESD, but this would require monitoring andre-doping, plus these additives typically contain carcino-gens, which may make them unsuitable for environmentalreasons.

Switching to conductive oil could also eliminate ESD,but some environmental fluid maintenance issues couldexist. Of course this option would not be possible in thecase of dielectric oils, as functionality and safety could becompromised.

Increasing the fluid piping size, reservoir size, eliminatingareas of turbulence, and removing air from the system, allcan reduce the possibility of ESD occurring. However, trade-offs in system size and cost need to be considered.

While a combination of the above solutions may help,several significant compromises in system performance,weight, cost, and sustainability may be required to reduceor eliminate ESD.

STATIC CONTROL FILTER ELEMENTS While several possible system and fluid modifications

have been discussed, the simplest solution would appear tobe the utilization of a modified filtration technology that re-duces the voltage generated by micro-glass filter media andthe possibility of ESD occurring. Static control filter ele-ments can provide all of the positive filtration characteristicsof micro-glass filter media, i.e., low pressure drop, high fil-tration efficiency and dirt holding capacity, but at the sametime reduce the static charge generated in fluid systems.

This proprietary media technology is unique in that ittakes advantage of the media morphology, triboelectricpropensities of materials, and the use of conductive fibers.No large stainless steel fibers are present in the media matrixthat can affect the porosity of the filter media and potentiallymigrate downstream to damage system components. Also,this approach does not require the element to be groundedto be effective, no modifications to existing filter housingsare required, and it offers a straightforward drop-in solutionto existing installed filter housings. The result is a reductionin static charge generation and ESD.

Figure 8 shows static control filter elements that reducecharge generation and offer a drop in solution to existing in-stalled filter housings.

Laboratory tests show a significant reduction in voltagegenerated by static control filter elements in a test standfilled with ash-less hydraulic oil with rest conductivity of<60 pS/m. For this test, a standard micro-glass Beta4um©>200 efficiency rated element with 30 GPM rated flowwas tested along with a similarly rated static control element.Voltage measurements were taken and recorded as the flowrate was increased from 0 to the rated flow. Also, auditorytests were carried out to determine if any sounds suggesting

Electrostatic | Dischargestatic discharge were noted during thetests.

Results from the test shown in theTable 1, and also in Figure 10 show thatthe tests conducted using the staticcontol elements did not display any ev-idence of static discharge and the peakvoltages recorded were a magnitudelower in value than standard elements.

Figure 9 shows Static Charge TestCircuit – Voltage measurements takendirectly after the test filter and also inthe reservoir.

Further tests were carried out withelements rated at Beta 10um©>200with similar results, although the peakvoltages were less for both the standardand static control types of filter ele-ments shown in Figure 10.

In Figure 10 illustrates test resultsthat show the difference in voltage gen-erated in a hydraulic system using stan-dard micro-glass and static control filterelements.

In addition to laboratory testing andvalidation, field trails were conductedthat resulted in lower static charge gen-eration and the elimination of ESD eventswhen using static control filter elements.

The first was a turbine lube skid at apower plant where a rumbling soundwas noted in a multi-element filter ves-sel fitted with Beta 10um©>200 filterelements. The customer was usingGroup II lube oil and also noted someevidence of arcing on the filter elementend-caps and support cores duringchange-out. Once the vessel was fittedwith a drop-in replacement of staticcontrol filter elements, all of the audi-ble sounds ceased and no more evi-dence of arcing were seen duringfurther scheduled change-outs.

For a second field trial, a manufac-turer of bulk oil storage and dispensingsystems was having difficulty dispens-ing a filtered ash-less oil into plasticcontainers. The stream exiting the dis-pense nozzle had so much static elec-tricity that it would not flow in astraight predictable path into the con-tainer. By fitting the dispensing filterwith a static control element, the flowstream into the contanier became con-

Figure 9. Static Charge Test Circuit – Voltage measurements were taken directlyafter the test filter and also in the reservoir.

Figure 10. Test results show the difference in voltage generated in a hydraulic sys-tem using standard micro-glass and static control filter elements.

Test Results for Beta 4um© > 200 Filter Elements

Filter Element Max. Voltage (V) Tapping Sound

Standard > 10K Yes @ 4kV+Static Control < 1K No

Table 1.


sistent and predictable.In yet another field trail at a power

plant, the customer was operating a du-plexing filter in the center position andallowing both sides to provide filtrationdue to ESD.

This cut the flow rate thru the filterelement in half. While this approachapparently eliminated previously notedESD, maintenance personnel had tomonitor the pressure drop continu-ously to make sure element change-outwas done well before it was customary.By installing static control filter ele-ments, the duplex was able to be oper-ated with one side off-duty with nospecial provisions for change-out of the

spent filter elements.

CONCLUSIONElectrostatic discharge in a fluid sys-

tem is a phenomena that can causedamage to the fluid, system compo-nents, and filter elements. Steps canbe taken when designing a new systemto minimize the posibility of staticcharge generation but these often havedraw backs that may include additionalcost, size, and weight. Choosing fluidswith increased conductivity also maynot be possible as these typically aredesigned & optimized for specific ap-plications. The utilization of static con-trol filter elements can provide a

convienent drop-in solution for bothnew and exisiting systems reducingcharge generation and the resultingstatic discharge.

For more information contact:Bruce ShaneParker Hannifin Hydraulic Filter DivisionTel: 1-419-644-0222Email: [email protected]: www.parker.com

REFERENCES1. ASTM D-4308 STANDARD TEST METHOD FOR ELECTRI-CAL CONDUCTIVITY OF LIQUID HYDROCARBONS BYPRECISION METER.2. Emcee Electronics (www.emcee-electronics.com)3. Simco-Ion (www.simco-ion.com)4. Fluke Instruments (www.fluke.com

FN


igher power densities anddecreased size are two majordesign criteria that are driv-

ing the hydraulic industry and as aresult bringing thermal performanceto the forefront. In many systems thereservoir is the only heat sink thatprovides cooling, and the rule ofthumb – volume equal to 2.5-3 timesthe pump flow, which allows for thisheat exchange – has become imprac-tical. The importance of operating atthe proper temperature is difficult tounderstate. For example, the sensi-tivity of oil viscosity to temperatureinfluences lubrication and leakages.A 20˚ C rise in temperature can re-duce the viscosity by one half, result-ing in the compromise of immediateperformance as well as the longevityof the system components. As a re-sult, manufactures are respondingwith an array of products that reduce

the overall footprint and compressthe package size by combining func-tionality and performance.

The most prominent products in-tegrate a combination of reservoir,filter and radiator. The location ofthe reservoir in the circuit is fixeddue to its function of feeding thepump in an open loop. The filter andcooler, however, can swap positions,which have implications on the over-all performance. Further, integrationof a thermal or pressure bypass and aradiator fan have costs and benefitsthat must be considered.

The traditional approach of themobile industry is to install inde-pendent components with the coolerdownstream of the filter, shown inFigure 1. The utilization of the ther-mal bypass is not compulsory but de-termined by application and often apressure relief valve in its place.

Often the bypass valve is built intothe outlet of the filter assembly. Thisinstallation ensures that full flowpasses through the filter and only theneeded flow across the cooler. Returnline radiator cores are typically sizedto minimize pressure drop and rarelysee spikes in excess of 100 psi. Thislow-pressure location ensures the fil-ter will see little backpressure allow-ing a low to medium pressure returnline installation. One performanceadvantage of locating the filter here isthat it will help prevent fouling as themachine ages. Radiator fouling is theresult of debris building up or con-taminates reacting with the core ma-terial. In extreme cases this foulingmay cause pressure to build and ad-verse consequences on the up-streamcomponents including the filter.

Figure 2 shows the filter installeddownstream of the radiator core and

H

Hydraulics | Filtration

Combining Filter in Reservoir of HydraulicsBy John Trott, Design Engineer, Parker Hannifin Corporation

Figure 1: Filter installed before cooler Figure 2: Filter installed after cooler


thermal valve. This configuration al-lows for the use of an in-tank filter,which takes further advantage of thereservoir volume, saving valuablereal estate while using a large filterelement. By virtue of the filter loca-tion, a performance advantage maybe realized should the radiator core,with intricate geometry, shed dirt.Radiator manufactures are aware ofthis and often provide cores to acleanliness specification of a maxcontaminate weight and size, whichhelp alleviate some concern.

As designers integrate components,they are faced with choices that willhave variable suitability for the enduser. On systems that combine the fil-ter, reservoir and core, the location ofthe thermal bypass must be consid-ered. If the design requires the bypass,either temperature or pressure, to beplumbed into the system externallythen the filter assembly along with theradiator may also be bypassed. If sizedproperly, this is not a problem becausethe bypass setting is such that opera-tion corresponds to the element by-pass setting. This means that if theflow is in bypass through the thermalvalve at low temperatures it wouldalso be in bypass as dictated by the fil-ter element assembly. But if the valveis improperly sized then bypass of thefilter may occur for an extended pe-riod of time. Another point to con-sider is that the combination offunctionality also makes it difficult toutilize these systems in closed loopapplications where full flow may berequired for cooling and filtration butonly cause drain and leakage flow forthe reservoir.

Furthermore, the system designmust allow for the reduced volume.The reservoir volume serves manyfunctions only one of which is re-lieved by integrating a cooler. The de-aeration and exchange capacity needconsiderations on their own merit.For example, systems that requiremoderate to large exchange volumes,such as those with larger cylinders oraccumulators, are often not suitablefor these integrated products.

While these new products are of-fering advantages, there are tradeoffs

that must be deliberated. The type offilter used, the system contaminategenerators, thermal bypass location,and reservoir function must all be de-ciding factors that will lead to theirsuccessful implementation.

For more information contact: John TrottParker Hannifin Corp. Hydraulic Filter Div. Tel: 1-419-644-0224Email: [email protected]: www.parker.comFN

Read more articles online at www.filtnews.com


Activated | Carbon

ctivated carbons (AC) ascommercial sorbents gottheir jump-start during

World War II. When Germany was ap-plying chlorine gas on allied troops,U.S./ Britain/ Russian and the Japanesecut off the supply of coconut-shellbased activated carbon for gas masks, alife or death AC application, to protecttroops against toxic chlorine gas. TheU.S. government contracted CalgonCarbon near Pittsburgh, Pa., andBarneby-Sutcliff near Columbus, Ohio,as part of the Manhattan project, to de-velop a new and available feedstock orparent raw material to manufacture ac-tivated carbons for gas masks. Thesetwo government contractors developeda process based on bituminous coal asraw material to make AC material forgas masks. In this application, AC actsas a chemical reducing agent, whensmall amounts of water are present, to

convert chlorine gas to harmless chlo-ride ions. Carbon is a reducing agentsimilar to copper metal and chlorine isan oxidizing agent.

After the Great War the first majoruse of coal-based AC was municipaldrinking water plants, to remove indus-trial and natural organic matter con-taminations and improve chlorine tasteand odor. AC removes water-soluble or-ganics by physical adsorption. This wasbefore the EPA, when major surfacewaters were heavily contaminated. EPAregulations have become a driver forAC water and air purifications.

DEMAND TO RISEThe Freedonia Group has provided

an independent world future demandfor activated carbon(1). The authors andcolleagues presented this article infor-mation at the 30th International Acti-vated Carbon Conference (IACC-30) in

Pittsburgh, Pa.(2). Table 1 contains the world projected

activated carbon demand in thousandsof metric tons. World demand for acti-vated carbon is expected to increasemore than 10% per year from 2011through 2016 to 1.9 million metrictons, according to World ActivatedCarbon, a new study from the Freedo-nia Group.

Figure 1 contains the global netgrowth by application sector for fiveyears(3). It is obvious that most of thegrowth is from North America air andgas purification. The use of powderedactivated carbon injection to removemercury at coal burning electric powerplants and municipal waste to energy,are the users of AC.

The Freedonia Group reports thatthe high rate of growth will be due toregulatory changes in the U.S., andChina’s 12th Five-Year plan (2011-2015) to improve water and air qual-ity in the nation, and expandingproduction of edible oils, beverages,and sweeteners in much of the rest ofthe world.

The activated carbon market inChina will be driven by more than reg-ulation, and will advance at a slightlylower rate than sales in the U.S. Whileimplementation of the newest Five-YearPlan will bolster activated carbon use,gains will also come from increasingconsumption by industry, as demandfor activated carbon rises faster thanthe world average. The 12th Five-YearPlan will also lead to greater use of ac-tivated carbon in water treatment andin air purification.

Consumption of activated carbon atthe household level, in tap point-of-useand whole building point-of-entry

Changing Activated Carbon Demand and SupplyBy Henry Nowicki, Wayne Schuliger, George Nowicki and Barbara Sherman

Figure 1. Projected net growth by application sector over the next five years.

A


water filtration systems, will boost de-mand, as individuals demand betterquality drinking water.

Several other nations will also ex-perience rapid growth. For instance,India is expected to surpass Germanyto become the fourth largest marketfor activated carbon in 2016 (behindJapan, China and the U.S.) with salesrising on increased food and beveragemanufacturing and increased levels ofwater treatment. India is becoming amajor supplier of coconut char andcoconut based AC(4). Many other na-tions in the Asia/Pacific region, alongwith many in Central and SouthAmerica, Eastern Europe and theAfrica/Mideast Region, will exceedhistorical growth levels as industrial,water treatment and food & beverageproduction markets for activated car-bon grow.

Like all projections into the future;they should be taken with a grain ofsalt. But, from a manufacturer or usersviewpoint these projections help

guide planning, investments and pur-chasing contracts. As demand goesup, expect higher prices and AC de-livery problems. It takes years to getnew manufacturing plants up andrunning. AC users may want to lock-in longer-term contracts to guaranteesupply at agreed to prices. Not all ac-tivated carbons are the same thus it iscritical that manufacturers providewhat the individual market applica-tion types need, to best solve theirproblems.

SIX AC APPLICATION TYPESSince all activated carbons are not

the same, it is important that manu-facturers provide what AC users needfor their applications. Dr. Greenbankhas classified AC users into six typesof applications. The upper part ofTable 2 provides Greenbank’s deci-sion tree for classification into sixtypes. The starting feedstock and themanufactured final pore structures oradsorption spaces determine wherethe AC can and cannot be best used

Table 1. World activated carbon demand (thousand metric tons)

% Annual growthItem 2006 2011 2016 2006-2011 2011-2016

AC demand 877.6 1180.0 1930.0 6.1 10.3North America 250.9 325.0 642.0 5.3 14.6Western Europe 158.5 180.0 228.5 2.6 4.9Asia/Pacific 316.0 464.5 729.5 8.0 10.0Other 152.0 210.5 310.0 6.7 8.0


in the six activated carbon applicationtypes. The Greenbank activated car-bon classification into six types alsoprovides examples in the lower sectionof Table 2 for the six applications.

The Gravimetric Adsorption EnergyDistribution or GAED test method,initiated by Michael Polanyi some 100years ago and modernized by Manes-Greenbank and others, is a quick, low

cost and relevant test method to deter-mine an AC sample’s adsorption en-ergy (AE) distribution and itsassociated pore volume and thus thesix AC application types, for GAEDsample runs. Also, GAED testing hasenabled many real world solutions forrefractory problems for the activatedcarbon industry(5).

The adsorption energy (AE) distri-bution and their individual AE associ-ated pore volume of different ACmaterials determine the different phys-ical adsorption applications rangingfrom Type I heavy AC loading applica-tions to Type 6 ultra trace loading ap-plications. For example, in theautomotive application of hydrocar-bon vapor emission control the AC hasno high AE sites, because this applica-tion demands loading and un-loadinglarge volumes of hydrocarbon vaporemission. Additionally, GAED pro-vides Butane Activity and ButaneWorking Capacity (BWC) valuesequivalent to the ASTM approved testmethods. GAED can quickly, accu-rately, and at low cost reveal this AE-pore volume information, whichallows rapid classification into the sixapplication types.

GAED has helped many to makebetter AC purchasing and used ACchange-out decisions. Recently wepresented a platform talk on advan-

Activated | Carbon

Table 2

tages of GAED over classical testmethods to make purchasing andchange-out decisions(6).

WHAT GAED TEST REVEALSIn a recent case study, six applica-

tion types were determined for a client.Our laboratory evaluated two activatedcarbon samples noted below as CC-242and CC-243 to provide information onthe markets that their material couldand could not be used commercially tocompete with present benchmarkknown activated carbons. The threebenchmark commercial AC were wood-,coal-, and coconut-based products. Sam-ples were run on GAED to define theirAE and pore volume distributions andthus where the materials had an appli-cation type or a competitive advantagecompared to benchmark AC. TheseGAED runs are summarized below inTable 3, as cc adsorption space foreach applications type per 100 cc ofthe AC tested.

This information tells us that theseclient materials are most useful fortrace removal of contaminants fromwater and air. Samples CC-242 andCC-243 materials are expected to becompetitive with commercial presentwood-, coal-, and coconut-based acti-vated carbons in type IV, V and VI ap-plications. Since trace removals arewhere the drinking water market istoday, they are apparently well posi-tioned in this marketplace. With theupcoming new disinfection rule, mate-rials with more high AE sites will be-come more valuable. High adsorptionenergy sites are required to removetrace trihalomethanes from drinkingwater supplies.

TRACE CAPACITY NUMBERA modified GAED method is avail-

able to selectively reveal the high AEsites. In GAED the challenge gas is1,1,1,2-Tertrafluorenethane (TFE). Inthe trace capacity number (TCN) de-termination method, the challenge gasis Tetrafluoromethane (TFM), becauseTFM is more difficult for AC to adsorbthan TFE.

In the drinking water purificationcase, where water soluble at very lowconcentration needs removed, the AC

with finest available pores is best, be-cause it provides the highest adsorptionenergy (AE) pore volume, which isneeded to remove it from water. Exam-ples of these molecules are Vinyl chlo-ride, Methyl-tertiary butyl-ether(MTBE), Geosimin, MIB, etc. MTBEwas added to gasoline to provide betterignition auto starting, but MTBE iswater-soluble and has a bad taste andodor at low ppb. MTBE has contami-nated groundwater from leaking under

ground gas storage tanks, and MTBEwas later banned by the EPA. The resultis that some ground water drinkingwater supplies are now contaminatedwith MTBE. About half of the U.S. pop-ulation use groundwater as the sourcefor drinking water and AC is the bestavailable technology to purify water.Again, the high AE sites are required toremove MTBE from water.

To determine the best AC for tracewater soluble Geosimin, MIB, MTBE and


Table 3

similar cases, Calgon Carbon Corp. de-veloped a test method called Trace Ca-pacity Number (TCN). AC materials thatadsorb TFM require pore structures withsmallest adsorption spaces and thus high-est adsorption energies. A paper on TCNhas been accepted for presentations(7).

The author regularly provides shortcourses on how the GAED benefits acti-vated carbon manufacturers and users(8).The course also covers specific issues ofinterest to course attendees. This courseis the introductory course for the acti-vated carbon school, which is designedto provide the needs of the different sec-tors of AC.

CONCLUSIONNew test methods such as Gravimetric

Adsorption Energy Distribution (GAED)and Trace Capacity Number (TCN) areneeded to select the best AC for adsorb-ing trace and ultra trace water-solublecontaminants from air, water, or organicsolvents. The present ASTM and AWWAtest methods are not powerful enough tosolve many of the major new medianeeds, such as catch and release ofmethane and carbon dioxide. This iswhen the TCN test method is needed.The activated carbon industry has de-mand for additional projected AC thenext five years at 10%. This is expectedto result in shortage of supply and in-creased prices. It takes a couple of yearsto provide new AC manufacturing plants.In order to supply the proper AC porestructure for existing and new emergingmarkets demanded by green chemistryand sustainable and environmental busi-ness, some new starting raw- or parent-materials are needed to manufacture AC.An example of new starting material tomake unique, new AC was presented byNeal Megonnel(9).

GAED has other applications besidesphysical adsorption: It provides differ-ences between competing AC, enables lo-cating positions of chemical impregnantsinto AC, determines the outer and inneractivities to determine if the AC particlehas a significant activity gradient, revealswhen AC is used and needs replaced andmany other applications for GAED.

GAED provides Characteristic Curves,polynomial equations to calculate load-ing as a function of aqueous- or vapor-phase concentration, isotherms forcompounds of interest, trace- and mid-adsorption capacities, BET surface area,pore size distribution. GAED test methodhas many advantages over classical ACsuch as iodine, molasses and BET surfacearea(6). There are still many good oppor-tunities to do R&D to develop newneeded products and services.

UPCOMING 2013-2014 CONFERENCESTwo International Activated Carbon

Conferences and Activated CarbonSchools are planned in 2013 - 2014:Pittsburgh, Pa., September 25-26, 2013and Orlando, Fla., February 20-21,2014.

For more information on papersand Carbon Conference registration:Tel. 1-724-457-6576Email: [email protected]: www.pacslabs.com

Acknowledgments

Authors acknowledge Dr. Mick Greenbankfor providing ideas for six sectors for AC ap-plication types and Dr. Hugh McLaughlin foruse of Figure 1 presented at the 30th Inter-national Activated Carbon Conference on Oc-tober 4, 2012 in Pittsburgh, Pa.

References1. www.freedoniagroup.com2. Henry Nowicki, “Demand and Supply for Activated Car-bons Next Five Years.” International Activated Carbon Con-ference poster. Pittsburgh, PA Oct 5, 2012. 3. Hugh McLaughlin, “The Changing Activated Carbon Mar-ketplace: New Demand and Supply Change.” 30th Interna-tional Activated Carbon Conference on October 4, 2012 inPittsburgh, PA.4. Srilal Weersingle. “Journey from Coconut Shell to BlackGold.” International Activated Carbon Conference on Octo-ber 5, 2012 in Pittsburgh, PA.5. Go to www.wcponline.com and type Nowicki in upperright search box to view some prior articles on GravimetricAdsorption Energy Distribution or GAED full characterization.6. Henry Nowicki. “GAED Test provides Advantages overClassical Tests: Iodine, Molasses, and BET Surface Area forPurchasing and Used GAC Change-out Decisions.” 30th In-ternational Activated Carbon Conference. Pittsburgh, PAOct 4-5, 2012.7. Henry Nowicki, “TCN Test Method for Expanding Acti-vated Carbon Industry” accepted for 31st International Acti-vated Carbon Conference, Honolulu, Hawaii February 7-8,2013.8. Henry Nowicki, Ph.D. PACS short course titled “ActivatedCarbon Adsorption: Principles, Practices, Applications andOpportunities.” Monthly public classes are offered and atyour time and place.9. Neal Megonnel, “Advanced Carbon Dioxide Capture utiliz-ing PVDC Based Activated Carbons” International ActivatedCarbon Conference on October 4, 2012 in Pittsburgh, PA.


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Engineering Principles of PrecoatingBy Jose M. Sentmanat, Consultant

ince the first diatomaceousearth filter aids made theirappearance, clearer filtrates

have been obtained than was ever pos-sible using filter cloths or screens bythemselves. The art of precoating, be-cause of the tremendous variety of fil-ter aids and filter designs, requires anunderstanding of some fundamentalsbefore satisfactory filter performancecan be attained.

Precoating is an operation designedto deposit a layer of diatomaceous earth(or some suitable material) on the filtermedia. The filter media can be a fabriccloth, wire screen, porous stone, sin-tered metal or almost any permeablematerial. It should be noted that thismanual applies mainly to pressure leaffilters or candle filters. Primarily, thepurpose of the precoat is to preventblinding or plugging of the media andto provide clean cake discharge. Precoatalso produces clarities superior to thatprovided by the media alone and helpsprolong the useful life of the media.

In addition to diatomaceous earth,paper fibers, perlites, activated or nat-ural clays, carbons and metallic saltshave specific uses when applied as pre-coat material. Commercial grades of di-atomaceous earth may be obtained toprovide particle retentions from 2 mi-crons down to sub-micron range.

Selection of a precoat material is de-pendent upon the nature of the solidsto be removed in a commercial scale fil-tration. Factors to be considered are:

1. Apparent micron size of the haze, turbidity or precipitate

2. Settling rate of the solids3. Solids %/Wt. of the feed liquor4. Solids density5. Solids characteristics, i.e.,

granular, slimy, coarse, fine, etc.

Some of these factors are not as crit-ical for the selection of the precoatingmaterial as they are for filter design andfluid flow. However, all are importantas design criteria for the overall filter-ing operation.

Important physical properties of fil-ter aids, which must be considered inselecting a precoat material, are:

1. Relative inertness2. Proper micron retention3. Uniform particle size distribution4. Adequate porosity5. Ample void volume6. Normal settling rate7. Low bulk density8. Moderate material cost

Two common filtering materials,which cannot be used as precoat mate-rials in leaf filters, due to their rapidsettling rates, are sand and anthracite.

In any unknown liquid-solid separa-tion problem, where the nature of thesolids is unknown, a simple vacuumfunnel or bomb filtration test will sup-ply most of the data required. It may benecessary to evaluate the solids in thelaboratory to determine a firm basis forpilot runs or full-scale operations.

Filter cloths up to 50-micron reten-

tion are not critical of slurry concentra-tions to produce a desired precoatthickness and rapid clarity. However,more open weaves and wire clothsabove 50 to an absolute maximum of250 microns are very critical of theslurry concentrations employed tobridge the interstices. The maximumreliable width of an aperture, which canbe bridged by diatomite with a mini-mum slurry concentration, is 0.005”.

Commonly employed wire screenmeshes, which are recognized as stan-dards in the filtration industry are:

• 24 x 110 Plain Dutch Weave (0.016”/0.11” wire diameters)

• 70 x 80 Mesh (0.007”wire diameter)*

• 60 Mesh twilled (0.011” wire diameter)*

• Various grades of “PZ” wire mesh (also known as Reverse Dutch Weave)

*It should be noted that these two gradesare not as commonly used as in the past.

Where corrosion is not a factor, theselection of screening having the largestwire diameter provides the longestscreen life. Enlargement of the aper-tures by the abrasive action of the silica

S


diatoms (which are constantly shiftingposition from pressure stresses duringthe rise of cake resistance) is the causeof eventual wire failure. A predictablelife of 5 years or more is not uncom-mon (in the absence of corrosion) forstainless screening in these meshes.

Table I is useful for determining pre-coat amounts and concentrations for fil-ters equipped with heavy duty screeningdescribed previously. The table providesnorms for ultimately safe values.

*Wet Density of a filter aid is thevolume produced in a centrifuge tubefrom a weighed amount of slurried inwater and centrifuged to a constantlevel. Specific Gravity produced time62.4 is the wet density.

In some cases, a system engineeredto this data, may permit 10-15% dilu-tions if experimenting proves it to befeasible.

Media with smaller micronic reten-tion capabilities than those describedabove can economize on precoatamounts proportional to the reductionand concentrations. The gallons perpound of precoat can be inversely in-creased, provided the required protec-tion from progressive blinding is notimpaired (see Table II). Precoats of lessthan 3 lbs. per 100 square foot on fabriccloths are not generally practical. How-ever, reductions to 1 lb. per 100 squarefeet can be made with high densityliquors and very tight media in applica-tions requiring low rates of flow perunit area and great filter size to producecommercial volumes (i.e., cane sugarliquors or beet sugar thick juice).

It may be noted here that refine-ments of precoating amounts and con-centrations to achieve the ultimateeconomy of operation can be under-taken. These refinements should bebased upon pilot tests, laboratory eval-uation or prior experience.

SETTLING RATESOnly brief mention has been made

of the raw feed solids as a factor influ-encing precoat operations. Some solids,such as colloids, slimy organics, gyp-sum or gelatinous materials do nothave commercial settling rates, whichlead to clarification by this means. Also,even when assisted by flocculating

agents plus costly pH adjustments, set-tling rates are cumbersomely slow. Theuse of filter aids effectively solves thisproblem by containing the solids as theslurry passes through the media. Thisis much like floc settling in a tank, clar-ifying the liquid in the process.

The process engineer must be awareof and recognize the importance of thesettling rates of filtering materials in thefeed liquor at process temperatures.This vital data usually escapes notice oris even ignored. But, it is the criteria,which can spell success or failure withfull-scale filters.

Settling rates may be determined bysedimentation. A 1000 ml. graduate isa convenient means of measuring thefeet per minute rate of settling by tim-ing the settled volume. The filter aidmaterial is thoroughly agitated withprecoat liquor at the proper tempera-ture in the graduate and allowed to set-tle. By measuring the settled depthagainst elapsed time, a curve can be

drawn establishing the % settled solidsagainst time in minutes. Since this set-tling or sedimentation is not typical ofthe conditions encountered when fill-ing a tank or pumping prefilt feed dur-ing actual production, a practicalsolution is required to maintain uni-form suspension. This may be solvedusing the time required to settle 10% ofthe filtering materials in the followingmethod:

HEIGHT OF LIQUID SUSPENSION IN FEET = FEET TIME IN MIN. TO SETTLE 10@ x 2 MEAN MIN.

A properly designed precoat systemhas two major requirements:

1. It must prevent withdrawal of any portion of the contents of the system until the filter tank is full.

2. It requires a filling rate or flow velocity, which produces a rate of rise within the filter in excess


of the settling rate of the filtering materials (as determined previously). This must be calculated for the maximum cross section of the filter tank to produce an even precoat layer.

While it is evident that the precoat

rate may be one-half the filtering rate,all conditions being equal, since at mid-leaf during filtration, one half the flowhas been removed as filtrate; precoatsshould be applied at maximum rates forminimum time. However, an accuratedetermination of the filtering materialsettling rate, directly concerns Body

Feed or Admix operations. The propor-tional feed of filter-aids during produc-tion operations (Body Feed or Admix)will be discussed in a supplement.

In almost all precoat applications, agiven precoat thickness is an unneces-sary precaution. Filter aid precoats, dueto the fact that they are so low in ap-plied wet density and contain billionsof particles, will provide an amplethickness with the amounts shown inTable I with corrections shown in TableII for tighter media.

In many cases with tight media,rapid clarity and good cake release (atcompletion of the filter cycle) are ob-tained with only a film layer. Greaterprecoat amounts are many times un-avoidable when:

1. Slurry volumes are excessively large when using open media.

2. Pumping rates are not adequate to uniformly suspend filtering materials at all levels in the filter tank.

3. Precoat slurry is not evenly distributed in all parts of the vessel, causing sparse concentrations in portions of long, horizontal, small diameter tanks.

4. Flow through the media is more rapid in some areas than others, such as areas nearest the leaf outlets from lack of proper hydraulic balance.

5. Filtrate piping dropping directly to lower level preparation tanks, causing a siphon and premature flow through the leaves. This may occur during filling as soon as the leaf outlets are covered and before the vessel is full of slurry.

METHODS OF PRECOATING Selection of the precoat slurry liquid

is primarily a process consideration,but is generally the process liquor asraw feed or clarified liquor from a priorfiltration cycle. Water is acceptable foraqueous solutions or a solvent in non-polar fluids when dilutions can be tol-erated. When, due to process



considerations or if dilution is imprac-tical or costly, the precoat fluid must bedrained before the prefilt feed is started.

Please refer to illustrations 1-3 onpage 42:

1. Most clarifications use a precoattank, having enough volume to fill thefilter and inter-connecting piping,with sufficient volume remaining inthe tank to continue agitation. Theprecoat tank is normally sized to con-tain a volume of liquor 1-1/4 theamount contained in the filter and pre-coat piping. Precoat tanks should bedesigned with a bottom outlet to theprecoat pump suction with enoughdepth or baffled to avoid a vortex. Ag-itation, either with a mixer or by recir-culation flow, must be adequateenough to suspend the filter powderand provide enough roll to thoroughlywet the dry material without manualassistance. Vent lines from the filter tothe precoat tank, should be approxi-mately 1/3 the size of circulating flowpiping to promote air displacementand rapid filling. The precoat pumpmay be a separate unit designed andpowdered to provide adequate per-formance. Or, the main prefilt (sys-tem) pump can be used with athrottling valve adjusted to the desiredflow. In this latter case, selection of theproper characteristics for all condi-tions is very critical. Centrifugalpumps are commonly used because oftheir universal applications, but othertypes of pumps are used for precoatingin many industries.

When the wet density of solids in theprefilt feed are above a specific gravityof 1 and relatively low in ppm, prefiltfeeds can be utilized for precoating withgood economy and simplification ratherthan filtrate or other cumbersome mul-tipurpose procedures. When it is under-stood that an average precoatconcentration containing 1 lb. of filterpowder in 20 gallons of water repre-sents a slurry of 6000 ppm, the volumeof the powder–compared to 1 specificgravity solids id 2–1/2 to 4 times thecontamination. But, of most signifi-cance is the void volume available forenvelopment of the colloids. While the

useable voids for filtration varies witheach grade or class of material, therange of voids will be from 60 to 75%.

This phenomenon provides a work-able rule that may be stated: Whensolids are 1/10 or less the precoat con-centrations in PPM–use the feed liquorfor precoating. This, as inspection willshow, is a safe ratio, and can be refinedby preliminary tests to produce thegreatest benefit without sacrificing thepurpose of the precoat.

Following are examples of practicalmethods, which use this principle:

2. GRAVITY FILLA precoat tank with sufficient vol-

ume to serve the filter is located over-head. Powder is introduced to theprecoat tank, suspended to uniformity,and then dropped to the filter tank inconjunction with starting the prefiltfeed. Filtrate, whether cloudy or not, isreturned to the precoat tank for thenext fill.

The success of this method depends

upon the filter to develop mixing anduniform distribution of the preparedslurry to the diluted concentration. Inthis instance, the gravity precoat tankmay be of less volume than the filter.

3. PRECOAT FUNNELA funnel, generally used on Vertical

Leaf Filters up to 150 square feet ofarea, provides substantially the same re-sults where filter aid quantity is lessthan 50 lbs. A prerequisite to thismethod is an efficient internal mixingand baffling of the feed to achieve theuniform distribution throughout thetank, which is required for precoating.

The funnel may be charged withprepared slurry or by bucketing in sev-eral gallons of liquor to a dry powder.The funnel valve is opened and theslurry allowed to gravity flow to thetank. The funnel valve is closed and theprefilt pump started.

Cloth dressed filters are most adapt-able to this method of precoating assmaller quantities of filter aid, with re-



sulting economies, may be used. Thisis illustrated in Tables I and II.

4. INJECTED PRECOATSIf a gravity set-up is inconvenient,

it is obvious a pump can be substi-tuted in 2 to make the same deliveryof suitable slurry to be combined withprefilt feed. Refer to illustrations 4-5on this page.

The frequent charging of precoattanks by use of instrumentation, ratherthan manual operation, implementsmuch of the objectives desired to re-duce labor and provide instrument re-liability for positive quality control.Proportional admix injection (knownalso as body feed) of concentrated slur-ries combined with the prefilt feedliquor may be used upon start up of thefilter to provide a suitable precoat.

Concentrations of up to 1 lb. per gal-lon may be used as the slurry for injec-tion. For gravity introduction, a seriesof probes, each positioned for theamount of charge, are programmed toopen and close the drain valve at theappointed time. This drain valve shouldnot be located at the bottom of the tankwhere settled powder will accumulate,but should enter the tank at a low levelwith a drop pipe to the interior near thebottom. A clean, timed, fluid back flushabove the valve will purge the line ofpowder slurry. A pumped slurry intro-duction, based on this principle, pro-vides a combination pump start withvalve opening using the same side-en-tering outlet described for gravity pro-portioning. But flushing the siphon lineis combined with simultaneously flush-ing the pump and the discharge lines toprevent resulting failures from powdersettling. Otherwise, probe levels, tanksizes and calculated powder mixturesremain constant.

RATE OF PRECOAT DEPOSITION There is some value in predicting the

time required to deposit a givenamount of precoat layer. Clarity mustbe produced rather promptly with asufficient precoat layer established toprovide good cake release at comple-tion of the cycle. Minimal precoats willfail if the volume turnover is not suffi-cient to reach the desired layer. As allprecoats are applied by flow in a givenvolume, the rate of deposition is a func-tion of the rate of slurry reductionwithin the system. The following tableillustrates the rate of change in whichtime of the circulation volume N di-


vided by the rate, and percent deposi-tion is the fraction of amount Cf/Co tothe original.

Two circulations will deposit about90% of the precoat charge. A gain willbe obtained when the precoat vehicle isclean liquor, as some additional precoatwill be deposited before contaminationbecomes a factor.

A filter feed rate at the mayor crosssection of the filter vessel, no less thantwice the observed settling rate, assuresbuilding uniform cake over the entireheight of the immersed leaf. As thecake grows, it displaces volume in theleaf zone and rate of rise increases. It isimportant to maintain distribution inthe early portion of the production pe-riod at low-pressure drop. By sustainingpermeability, filtrate volume may be in-creased by as much as 10%.

Clarity-Time Relation: Clarity pro-duced from a given precoat mix, whenusing a powder of proven efficiency isa function of the rate per unit area, con-centration of the slurry and retention ofthe media.

Refer to Table II for other media.Multiply above mean times by column(1) for the type of media employed.Dense media will give almost instanta-neous clarity. Caution is suggested toemploy sufficient time to produce a full-scale use of the precoat charged for ad-ditional protection to the media andsatisfactory cake discharge. See Table III.

FILTRATIONWhile the preceding deals primarily

with Precoating, we want to add someobservations on Filtration and ProperFilter Selection.

In an article in the June 26, 1972,CHEMICAL ENGINEERING, Dereck B.Purchas, consultant chemical engineer,goes into full details about “FILTRA-TION”. Here is an extract of his com-ments from that article where he states:Achieving truly trouble free filtration inindustrial installations requires a lot ofattention to five major areas:

• Definition of the filtration problem• Selection of the appropriate filter or filters

• Selection of the filter medium or media

• Selection of auxiliary equipment• Control of operating conditions

In defining the filtration problemthere are so many factors in a typicalfiltration problem, it is often difficultto think that a problem has been fullydefined before a specific type of filter-ing equipment can be recommended orconsidered. It is because of this thatmany manufacturers or consultantshave their own questionnaire to befilled out by the prospective client. Theperson or persons that must fill-inthese questionnaires must be as com-plete as possible in listing the processconditions and answering the ques-tions in these forms. Unfortunately, insome cases, the required data to com-plete these forms may not be availableor known sufficiently by the personcompleting the form and sometimes itis recommended to try to prepare arepresentative sample of the processliquor to be furnished to performbench scale testing so that the resultsmay be scaled up to the determine theactual production units. The question-naire resolves the possibility of notasking the right questions when dis-cussing the application with a client.Such test also determines the filterabil-ity of the process liquor and in a smallscale helps determine what pretreat-ment if any is necessary or what filter

media and filter aid is best for the ap-plication.

It is important to define the degreeof clarity required in the applicationand not vague expectations such as“good clarity”. Equally important isproviding an accurate percentage ofsuspended solids and particle analy-sis. It is important to know if all ofthe suspended solids are to be re-moved and how the removed solidsare to be disposed or if further pro-cessing is required.

Full understanding of the filtrationduty is a prerequisite in the selection ofthe filter equipment. Pretreatment ofthe process liquor is very important be-cause that will determine how it will fil-ter. The shape, size and particledistribution of the suspended solids isan important factor. In the selection offilter, the various types must be consid-ered such as centrifuges, gravity filters,compression filters, pressure filters andvacuum filters.

Following filter selection – it isequality important to select the type offilter media – such as filter cloths, wiremesh, sintered wire mesh, and mem-branes. Consideration must be given tothe porosity, particle retention, filtercake release and cleaning of the media.In the case of the filter cloths, the com-patibility with the process liquor mustbe considered. Whether it should be

woven or non-woven, temperature lim-itations and performance of the clothare to be given consideration.

The selection of auxiliary equipmentis to be considered also – the size andfeatures of the precoat mixing tank,type of mixer, type and capacity of theprecoat pump and the feed pump, bodyfeed mixing tank, and mixer and pump.

Last but not least is the recommen-dation to read published articles on pro-cessing magazines and those publishedby the filter aid manufacturers and filtercloth and wire mesh suppliers – all pro-vide a lot of helpful information in con-sidering filters and filtration systems.

The writer has compiled this manualfrom various sources that he has readand compiled in over 49 years in thefield of filtration. The similarity of com-ments or notes in this manual withpublished information is simply thefact that those sources have been con-sulted in the compiling of notes andcomments in this manual. The writerdoes not claim any or all in part to beoriginally his.

For more information contact:Jose M. SentmanatLIQUID FILTRATION SPECIALIST, LLCTel: 1-936-756-5362Email: [email protected] Website: www.filterconsultant.com



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cientific Dust Collectors(SDC) recently announcedthe next generation of nozzle

cleaning technology for reverse pulsejet dust collectors. SDC’s unique newcleaning nozzle provides an improve-ment in cleaning technology thatachieves superior performance even atlower compressed air levels. Theselevels can be as low as 80 psig. SDChas a new technical paper that ex-plains this feature.

SDC has used nozzle based clean-ing systems for pulse jet collectors inthe manufacturing industry for over

32 years. The key to the performanceof this cleaning system is the scien-tific design of the cleaning nozzle.This patented technology providesmore induced cleaning air into thefilter media than any other systemavailable. SDC’s nozzle is able to in-crease the cleaning velocity to super-sonic flow even at these lowercompressed air levels thus saving en-ergy and money.

For more information visit: www.scientificdustcollectors.com

Scientific Dust Collectors Announces New Nozzle Design Feature

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SDC develops new nozzle.

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Product | News

he dry pumps A 100 L withtheir compact dimensionswere specially developed for

flexible integration in semiconductorproduction facilities. These dry multi-stage Roots pumps are ideal for cleanapplications such as load-lock cham-bers and transfer chambers as well asfor all other noncorrosive applications.

Despite their compact dimensionsthe pumps provide high pumpingspeeds and short pump down times.Today, the A 100 L pumps are installedworldwide in all leading semiconduc-tor fabs. These pumps are suitable foroperation in clean rooms.

The further development, the A 100L ES, cuts energy consumption by upto 50% (ES = Energy Saving). Its pump-ing speed is significantly higher in thelow-pressure range. Additional benefitsinclude a lower final pressure and re-duced noise level.

The innovative and fully inte-grated ES module reduces energy useto a minimum in the low-pressurerange. This significantly reduces op-erating costs. To illustrate the point:annual savings per pump total up to7,900 kWh. This corresponds to 3.9tons of CO2.

At a typical 300 mm semiconductorfab level equipped with 1,300 loadlockpumps, the energy saving adds up to 10GWh, or about 360 k€ or 5,100 tonsof CO2 per year.

In addition to energy savings, thefinal pressure of the A 100 L ES is re-duced to 7x10-4 mbar (hPa). Thisopens up new potential applications re-quiring an enhanced pumping capacitycombined with low pressure. The noiselevel is also reduced from 58 dB (A) to55 dB (A). The A 100 L ES rounds offthe energy-saving product family ofmedium duty process pumps in theA3P series and the harsh duty processpumps in the A3H series.

Pfeiffer Vacuum Introduces Energy-Saving Dry Pumps A 100 L ES

TPfeiffer VacuumEnergy-SavingDry Pumps A100 L ES

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he Sartorius technology grouprecently extended its success-ful arium® lab water family by

three new product lines: the arium proultrapure water system, the arium ad-vance pure water system and the ariumcomfort combination system. These newproduct lines generate Type 1 to Type 3ultrapure and pure water, delivering theright water quality for any laboratory ap-plication. The highlight of these newlines is the arium comfort series. In ad-dition to providing ASTM Type 1 ultra-pure water, this space-savingcombination unit also produces Type 2and Type 3 pure water.

CONSISTENTLY HIGH WATER QUALITYLow quantities of organic contami-

nants in water are all it takes to have anegative impact on laboratory tests.The new arium ultrapure water systemsdeliver water quality that meets, andeven exceeds, the ASTM Type 1 Stan-dard. Its integrated UV lamp preventsmicrobiological growth, thus reducing

the TOC content (Total Organic Car-bon = degree of organic contamination)to a minimum. If a Sartopore® 2 steril-izing grade filter is used on arium, ul-trapure water is practically free ofmicroorganisms when dispensed. As aresult, arium ensures consistently highwater quality and results that are al-ways reproducible in mission-criticallaboratory applications, such as cellcultivation and chromatography.

FAST, SAFE SUPPLY OF LAB WATERPure water is stored in the new

arium bag tank system, which consistsof a closed housing with an integratedsingle-use bag. Inside this bag tank, pu-rified water is protected from secondarycontamination. This ensures consis-tently high water quality over a rela-tively long storage period and thusreproducible results. The bags can bequickly and easily exchanged as neededand do not have to be chemicallycleaned, as is the case with conventionalwater storage containers. This mini-

mizes downtime and reduces mainte-nance costs, while simultaneously in-creasing safety for users, who do nothave to handle any dangerous chemi-cals. The arium bag tanks are availablein a choice of 20, 50 and 100 liters.

ECONOMICAL WATER PURIFICATIONThe arium iJust software controls a

valve on the concentrate drain based onthe data measured for CaCO3 and CO2.As a result, iJust optimizes the quality andusage of pure water, extending the life ofthe downstream ultrapure water systems.All functions of the arium laboratorywater systems can be controlled by touch-activated functions on the display – evenwhile the user is wearing gloves. The newarium laboratory water systems are avail-able as bench top, wall-mounted or built-in units that provide various dispensingoptions and offer flexibility for integrationinto any laboratory environment.

For more information visit:www.sartorius.com

Product | News


Sartorius Extends arium Lab Water Family by Three New Product Lines

Sartorius’ arium product line

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pecialty chemicals companyLANXESS is now offering threenew types of Lewabrane mem-

brane separation elements for reverse os-mosis. The new products are availablenow for waters with strong fouling po-tential. The new membranes have a sur-face area of 37.2, 34.4, and 8.4 squaremeters (equivalent to 400, 370, and 90square feet). Lewabrane RO B400 FR andLewabrane RO B370 FR have a diameterof 201 millimeters (8 inches), whileLewabrane RO B090 FR 4040 has a di-ameter of 101 millimeters (4 inches).

All Lewabrane products comprise apolyamide composite membrane,wound in several layers to form a spiralwound element. “Our membrane sepa-ration elements are characterized by ahigh degree of polymerization and a lowsurface charge, which in itself reducesthe accumulation of dissolved solids atthe membrane surface,” said AlanSharpe, head of the RO MembraneStrategic Project at LANXESS’ Ion Ex-change Resins business unit. Further-more, a special feed spacer has beenincorporated in the newly developed FRtypes. “The new membrane elementswere designed to generate greater turbu-lence in the feedwater channel, meaningthat less solids accumulate on the mem-brane surface,” Mr. Sharpe explained.

In membrane separation, fouling de-scribes the process by which dissolvedsolids (colloids) form deposits on themembrane surface, leading to a reductionin separation capacity. The new FR ele-ments from LANXESS reduce this kind offouling, thereby extending maintenanceintervals and increasing output capacity.

The separation elements, manufac-tured at LANXESS' Bitterfeld site inGermany, were engineered specificallyfor industrial water treatment. Thefields of application include the desali-

nation of brackish and low-salinitywater with a high potential for organicor biological fouling.

LANXESS EXPANDS SOFTWARE TOOL The Ion Exchange Resins business

unit has expanded its design tool for in-dustrial water treatment. UsingLewaPlus, complete systems can now bedesigned, for example, employing differ-ent separation processes. Explained Dr.Jens Lipnizki, Membrane ApplicationsManager at ION: “Until now, LewaPluswas only capable of engineering reverseosmosis and ion exchange systems sepa-rately. With the expanded version, a re-verse osmosis process can now beengineered with a downstream ion ex-changer and, if necessary, even with anintermediate degasification system.” Thisis a typical application for water treat-ment in power plants.

LewaPlus consequently is the onlysoftware application that can design anentire reverse osmosis process with down-stream ion exchange, and the only onethat can integrate in its calculations post-treatment involving a degasification sys-tem or chemical addition. Some industrial

applications require the addition of saltsto reduce the corrosive properties of thewater or to adjust the pH. “Ultrapurewater, for example, literally extracts ionsfrom the metal surfaces in a waterpipeline, which leads to oxidation and vis-ible damage in the form of corrosion,” ex-plained Dr. Lipnizki.

SEAMLESS DESIGNThe LewaPlus design software is a

comprehensive tool for engineering sys-tems that use Lewatit ion exchange resins(IX) and Lewabrane membrane elementsfor reverse osmosis (RO). The applicationcalculates RO system configurations andtheir output, including feed pressure andpermeate quality. “The combination ofmembrane separation and ion exchangeensures that efficiency and economy gohand in hand. The membrane elementsdeliver a stable, lower-salinity permeate tominimize the salt load in downstreamprocesses, thus helping to achieve an effi-cient price-performance ratio,” Mr.Sharpe explained.

For more information visit:www.lewabrane.com

Membrane Technology for Water with Fouling PotentialLewaPlus design software now also for reverse osmosis with downstream ion exchanger

The membrane separation elementsin LANXESS’Lewabrane rangecomprise a polyamidecomposite membranewound in several layers to form a spiral wound element.Photo: LANXESS AG

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Specialists in Mergers, Divestituresand Acquisitions of filtration

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ALL OTHER COUNTRIESKen NorbergEditor, International Filtration NewsPO Box 265Winchester, TN 37398 USATel: 1 202 681 2022Email: [email protected]

A2Z Filtration Specialities 15 www.a2zfiltration.comAFS Conference Ins. Back Cover www.afssociety.orgAir Filters, Inc. 9 www.airfilterusa.comAshby Cross Co. 41 www.ashbycross.comContract Pleating Services 22 www.solentech.comDexmet Corporation 45 www.dexmetfilter.comDopag (US) Ltd. 37 www.dopag.usDurr Ecoclean, Inc. 29 www.durr-ecolan.comFlow Ezy 36 www.flowezyfilters.comGusmer Enterprises 31 www.gusmerenterprises.comIndustrial Netting 35 www.industrialnetting.comInt’l Filtration News - Buyers’ Guide 16 www.filtnews.comJCEM-USA 5 www.jcem.chLenzing Technik GmbH 23 www.lenzing.comMagnetool Inc. 47 www.magnetoolinc.comMetalex 43 www.metlx.comMetcom Inc. 35 www.metcomusa.comMonadnock 25 www.mpm.com/nonwovenMyron L. Company 1 www.myronl.comOrange Reseach 21 www.orangeresearch.comPerCor Mfg. 23 www.percormfg.comPerforated Tubes 17 www.perftubes.comPhifer, Inc. 3 www.phifer.com Rosedale Prod. Back Cover www.rosedaleproducts.comSealant Equipment 27 www.sealantequipment.comSolent Technology Inc. 39 www.solentech.comSonobond Utrasonics 33 www.sonobondultrasonics.comSpinTek Filtration Inside Front Cover www.spintek.comXinxiang Tiancheng Aviation 11 www.tchkjh.com

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