the sealing technology magazine - flowserve · pdf fileinto a new product, the flowserve st...
TRANSCRIPT
ENSURINGPHARMACEUTICAL
PROFITABILITYState-of-the-artmechanical seals helpPharma Manufacturersmanage uptime
Flow Solutions DivisionBW Seals
Durametallic SealsPacific Wietz Seals
Pac-Seal
VOL. 15, NO. 1
T H E S E A L I N G T E C H N O L O G Y M A G A Z I N E
FTF0403_C1_CVR.qxd 2/23/04 1:52 PM Page 1
Chemical manufacturing requires the stan-dard repertoire of chemical engineeringknow-how and process hardware. From
fertilizer to pharmaceuticals, each processingline uses similar pumps, mixers, vessels and reac-tors. However, one significant differencebetween producing ordinary chemicals and life-saving drugs is the degree of cleanliness andsterility imposed on the latter. A contaminatedbatch of drugs can’t be reprocessed if a mechan-ical seal fails.
Fighting the tideTime moves in only one direction, and thatpresents a particular difficulty for the pharma-ceutical industry. The moment a research labsecures a patent on a new drug formulation, theclock starts counting down the 17 years it takesfor the protective cloak to vanish. Bringing thenewly patented pharmaceutical to marketrequires that it undergo a rigorous FDA testingregimen, an activity that can consume a largepart of the limited window of opportunity thepatent provides.
Perhaps years later, if the trials prove success-ful, the drug company has relatively little timeleft to recoup its research and developmentcosts. While their patent protection is in effect,
pharmaceutical companies routinely bestow ahigh degree of care and maintenance on theequipment that produces the new drug and itsrevenue stream.
When the protection expires, however, theformulation enters the public domain.Manufacturers of generic drugs are then free tomake the same material. An increased supply inthe marketplace tends to drive down the priceeither manufacturer can demand. With thebasic economics so dramatically changed, it’snatural for the drug’s developer to start cuttingcosts, perhaps by switching to less expensivehardware and alternate raw materials.
Doing the mathApplying a cost-cutting strategy to specialtyitems, such as mechanical seals for top entrymixers, can backfire. First of all, the cost of amechanical seal is a tiny fraction of the totalinstalled cost of a processing line. Second, thecost of a seal is small compared to the value ofthe contents in a reactor or mixer, which can beworth thousands of dollars per pound.
Instead, traditional engineering economics,and its long view that accounts for the relation-ship between purchase cost and operating cost,should be the final arbiter in matters of compo-
2 www.flowserve.com Face to Face
cover story
ENSURINGPHARMACEUTICAL
PROFITABILITYThe value of a vessel’s contents is not agood guide for seal selection. Pharmamanufacturers must also consider uptime.
FTF0403_02_03_Bennett.qxd 2/23/04 1:49 PM Page 2
nent selection. “Greater uptime,” says TomBennett, Flowserve marketing manager, “ismore cost-effective than the original low price.”
The heart of a pharmaceutical plant is aninterconnected, interdependent network ofreactors and vessels, each of which must func-tion reliably to manufacture product economi-cally. Successful operation requires streams ofintermediates and raw materials to cometogether at the right time, in the right amount,in the right vessel. Starting with relatively inex-pensive raw materials and intermediates, theplant adds value by processing them into a finalproduct that’s more valuable than the sum of itsparts.
The natural tendency is to use the highestquality seals for vessels that process expensivematerials, while those that process lower-costmaterials are equipped with low-cost seals. Itlooks good on paper, but ignoring seal reliabil-ity is false economy. When margins are thin, atolerance for unplanned downtime is an extrav-agance no plant can afford. A seal failure in anupstream vessel handling low-cost material initi-ates a chain of events that halts production ofthe high-value final product. Overall, the valueof a vessel’s contents isn’t a good guide for sealselection.
Designed for successUsing a seal specifically designed for the phar-maceutical industry, however, is a way to ensuresuccess. For years, Flowserve has offered its QBseries seals for API and ANSI pumps. These stan-dard single, balanced, multi-spring pusher sealsare available in single and dual seal configura-tions for general service, primarily in the petro-chemical and chemical industries. The QB sealsare API 682-compliant and boast a solid historyof success with environmentally restricted prod-ucts that must meet EPA and OSHA regulations.
Given QB’s success in chemical plants aroundthe country, Flowserve engineers believedstrongly that they would serve equally well in thepharmaceutical industry. Although they will sealand perform well in that venue, they faced onemajor hurdle for use in drug manufacturing:they simply don’t comply with FDA standards.
Reacting to the perceived market need, theFlowserve engineering and design teams inKalamazoo, Mich., rose to the challenge. Theymodified specific elements and features of thestandard QB seal to bring it into compliancewith FDA standards. When tested, the prototypeseal hit a home run in its first turn at the platein a pharmaceutical beta site.
Buoyed by the success of that collaborativeeffort, the design team refined the prototypeinto a new product, the Flowserve ST seal. It’s adouble, liquid-lubricated contacting sealdesigned specifically for bottom entry applica-tions. The ST seal joins a lineup that includesthree other Flowserve mixer seals (liquid bar-rier, contacting gas barrier and non-contactinggas barrier) used successfully in pharmaceuticalcompanies around the world. As Bennettsummed it up, “Inlet to outlet, we cover all of aplant’s seal needs—and the pharmaceuticalindustry is no exception.” ❚
Face to Face www.flowserve.com 3
PREFERRED PRODUCTS FOR THE PHARMACEUTICAL INDUSTRY
Historically, the sealing industry has focused on the chemi-cal and petroleum industries, but there is increasing needfor products specific to the pharmaceutical/biotech industry.Interest is growing in alternatives to the compression pack-ings commonly used for mechanically sealing mixer equip-ment. At Flowserve’s Flow Solutions Division, ongoing R&Dprograms have resulted in proven products that meet thesespecial needs. Visit www.flowserve.com/seals for moreinformation.
• ST—double liquid lubricated contacting seal specificallydesigned for bottom entry vessel applications.
• QBW—A double dry contacting seal.• VRA—A single, outside, dry-running pusher seal designed
specifically for use in top-entry agitator/mixer services.• ML-200—Mixer seals configured to operate with non-
contacting gas barrier technology.• MD-200—Mixer seals configured to have contacting
faces operated with a gas barrier.• MW-200—Mixer seals configured to operate with a
liquid barrier.
The Flowserve ST seal is a double, liquid-lubricated
contacting seal designed specifically for bottom
entry applications.
FTF0403_02_03_Bennett.qxd 2/23/04 1:50 PM Page 3
While other segments of industry haveslowed, the pharmaceuticals industry is
currently enjoying growth. There are manyunique types of equipment in a typical pharma-ceutical plant, but the top entry mixer remainsthe most commonly sealed equipment, super-seded only by the pump. As we learn andunderstand the unique requirements of thepharmaceutical mixer we can design refine-ments into the basic mechanical seal that willhelp our pharmaceutical customers maximizeoperational MTBPM. To intelligently select anddesign these features into the mechanical sealrequires that we understand five operating con-ditions that affect the operational success of amechanical seal.
CryogenicsUnlike the chemical processing industry, thepharmaceutical industry sometimes requirestheir equipment to operate in the cryogenicregime. This is usually done to control vaporpressures or reaction speed while minimizingthe risk of introducing biological infection intothe batch. While most seal components toleratecryogenic temperatures well, elastomeric sec-ondary seals have difficulty tolerating cryogenictemperatures. Perfluoroelastomers become brit-tle below 0 °F. Special compounds of fluoroelas-tomers can tolerate temperature down to minus40 °F. EPDM elastomers regularly extend thelower temperature limits to minus 40 °F and tol-erate steam cleaning, but they have a narrowerband of chemical compatibility than a typicalfluoro or perfluoroelastomer. Careful consider-ation must be used when selecting secondaryseals to be used in cryogenic applications.
DebrisThe product in a typical top entry mixer in thepharmaceutical industry tends to be an inter-mediate product. The vessel normally will besterilized or chemically cleaned betweenbatches, but it is also very important to keepany seal contaminates out of the batch duringthe process run.
To avoid product contamination from the
seal requires prevention of the normal day-to-day seal wear debris from falling into thevessel. Another concern is that if there is aseal failure the accelerated wear rate willintroduce large amounts of debris to thebatch and perhaps ruin the batch. Thedebris well, a passive cup-like device belowthe seal’s wearing surface, is the most com-mon method of collecting the debris beforeit falls into the batch. The assumption is, ofcourse, the debris falls into the debris welldue to gravity. Any collected debris in thedebris well is swept away between batchesusing gas or liquid in any number of flushconfigurations.
DeflectionTop entry pharmaceutical mixers have one ortwo impellers attached to long shafts. They areeasy to seal, as long as the mixer design ade-quately addresses run-out, squareness andvibration. A rigid shaft and mounting platformgreatly contributes to the life and success of amechanical seal.
There are many factors that can contributeto shaft runout and perpendicularity prob-lems during operation. Highly viscous prod-ucts, filling or emptying the tank during shaftrotation, manufacturing tolerances, thermalexpansion, pressure deformation, and sparg-ing are all examples of conditions that canmodify the relative position between theequipment shaft and seal mounting plate dur-ing operation.
At elevated temperatures and pressures thesingle most destructive form of misalignmentis the lack of perpendicularity between thecenterline of rotation of the shaft and the sealmounting plate. There are seal designs, suchas flexible stator designs, that minimize theaffect of perpendicularity due to manufactur-ing and assembly tolerances. Operational per-pendicularity issues are generally not resolvedwith seal design.
Increased shaft runout (dynamic motion ofthe shaft in the radial direction) induces apendulum-like motion through the mixer
4 www.flowserve.com Face to Face
selection
SEALING PHARMACEUT IFive factors for selecting seals for top entry mixers.
FTF0403_04_06_Smith.qxd 2/23/04 1:50 PM Page 4
bearing, which degrades the perpendicularityof the mating surfaces at the seal. As mixerpressures and temperatures increase, alongwith requirements for decreased leakage andincreased seal life, shaft run-out and square-ness have become known as vitally importantto the success of the mechanical seal.
When the seal manufacturer must provide abearing in the seal package the size and cost ofthe package increases. The trick is to know anddesign for the direction and magnitude of theforces the bearing and seal housing must with-stand. The fact that the seal contains a bearingdoes not alleviate the mixer manufacturer fromproviding an otherwise concentric and perpen-dicular seal platform.
It is important to recognize that the mixerdesign, including the size of shaft, may bemodified for competitive reasons.
Temperature ControlThe double wet seal that uses flush Plan 54with water, ethylene glycol or oil as a barrierfluid has been widely accepted in the mixingindustry. The double wet seal tolerates tran-sient temperature and pressure swings andmaintains an absolutely positive seal betweenthe vessel and the atmosphere. The liquid bar-rier fluid makes it easy to control the seal cavitytemperature. In hot applications, the barrierfluid flow keeps the seal’s O-rings lubricatedand cool. Under cryogenic conditions, barrierfluid flow keeps the seal faces and O-rings at anacceptably warm temperature. Moderation ofthe temperatures at the inboard o-rings nearestthe source of heat or cold enhances the sealreliability.
Another temperature control used in con-junction with flush Plan 54 includes a coolingcoil or a cooling jacket around the seal. Inextreme temperature cases the jacket helpsthe Plan 54 flush system pull heat out of theseal area.
A cooling spool is a type of cooling jacketthat is installed between the seal housings andthe mixer vessel. When extremely high or lowtemperatures are present in the mixer vessel
the spool moderates seal cavity temperature byphysically blocking heat flow from or to theseal cavity. The spool is an extremely effectivemethod for maintaining the elastomers atmoderate temperatures. With a spool andjacket working in unison to moderate temper-ature in the seal cavity the pressurized barriersystem can often be simplified to a simple pres-surized, no flow, system.
Materials of constructionThe most common metal used for mechanicalseals in the pharmaceutical industry is 316SS.This alloy has a good blend of strength, weld-ability, chemical resistance, and economy. Ifadded corrosion resistance is called for, upgrad-ing to alloy C-276 is common. C-276 is a ther-mally stable, high nickel alloy with good thermalconductivity. Another suitable alloy is 20 SS.
When used in extreme temperature applica-tions seal designers must account for thermalexpansion and contraction of all materialsapplied to the seal. The wider the range oftemperatures the more important it becomesto consider the thermal properties of the sealmaterials and how they interact with the mixermaterials.
Metals may be purchased to conform withGRAS (Generally Regarded as Safe for inci-dental product contact) and may be electrop-olished and passivated.
Face materials may include combinations ofcarbon graphite, silicon carbide, ceramic andtungsten carbide. Of these, only carbon is con-sidered to be soft. One face of a dry runningcontacting seal will usually be carbon, whileliquid-lubricated seals can use any combina-tion, of hard-on-hard or soft-on-hard faces.Seal specifications should state if material cer-tification is required.
Secondary seals and gaskets also may be fab-ricated from GRAS compounds (GenerallyRegarded As Safe). Pharmaceutical applica-tions don’t necessarily require GRAS materialof construction, so specifications from thebuyer should be clear in stating the require-ments for o-ring material certification. ❚
Face to Face www.flowserve.com 5
selection
T ICAL TOP ENTRY MIXERS
FTF0403_04_06_Smith.qxd 2/23/04 1:51 PM Page 5
In Europe, double mechanical seals conform tothe requirements of Deutches Institute fur
Normung (DIN). This is the German nationalstandards organization that cooperates with theInternational Organization for Standardization(ISO) in the development of international stan-dards. In Europe, and especially Germany, theDIN standards serve a function similar to that ofthe ANSI standards in the U.S., according toGordon Fagg, FlowServe pharmaceutical indus-try specialist, based in the U.K. In the U.S.,products that conform to the ANSI standardshave become almost like commodity products.The situation is different overseas.
Original equipment manufacturers in Europeproduce high-quality processing equipment,such as mixers and agitated vessels, for saleworldwide. Each mixer is custom-engineeredand fabricated with components that conformto DIN standards. But, conforming to DIN stan-dards does not imply dimensional standardiza-tion, as it does here.
Vessel designThere are three places an agitator can beinstalled on a vessel. The top-mounted agitatoraccounts for an estimated 90 percent of theinstalled base. In this configuration, the seal typ-ically resists only the vapors in the freeboard vol-ume of the vessel. When installed on the bottomof a vessel, the agitator seal must keep theprocess liquid contained. Finally, for the agitatormounted in the sidewall of a vessel, the sealholds back vapor or liquid, depending on thedepth of the contained fluid. There are threeseal types that can be used on agitators:
• Wet seals (MW-200).• Dry contacting seals (MD-200).• Dry non-contacting seals (ML-200).
A wet seal in a top-mounted mixer holds backvapors because the pressure applied to the bar-rier fluid inside the seal exceeds the pressure inthe vessel. The pressurized barrier fluid canmigrate across the seal face and weep on theinside of the vessel. Designers use a sanitarygland or a debris well to capture such leakage. It
can also be drained periodically using suitablepiping and valves.
Dry, non-contacting seals on bottom-mounted agitators present a different problem.A process upset can force process fluid betweenthe seal faces. No longer separated by a thinlayer of gas, the seal faces come into contactwith each other, thus compromising theprimary seal. The outboard seal isnow the primary defenseagainst leakage until the theseal cartridge is repaired.
Side-mounted agitators useeither dry contacting or wetseals. Dry running seals usepressurized dry nitrogen,although some processes andapplications need humidi-fied nitrogen to maximizeseal life. The faces in a dry con-tacting seal are generally fabri-cated of carbon and a preferred hard face. Sincethe faces physically touch each other in service,wear always produces some minute level of finecarbon particulates. Some industries, such aspharmaceuticals, cannot tolerate any level ofcontamination. If carbon dust is unacceptable,the best option is a gas, non-contacting seal.
RetrofittingAlthough German designers prefer wet seals,end users may find it necessary to use otherstyles. Even some European OEMs are slowlymigrating to dry, non-contacting seals.Nevertheless, like every mechanical compo-nent, sooner or later a seal needs to be replaced.In Europe, retrofitting a DIN-based agitator sealrequires physical measurements of the old unitbefore a new unit can be selected.
Flowserve is the only supplier offering thethree styles of seal that can be installed in thesame cartridge housing. Users of DIN standardseals now can change seal types without havingto modify the agitator or vessel. The FlowserveSeries M DIN standard seals are currently avail-able in sizes from 40 to 220 mm. ❚
6 www.flowserve.com Face to Face
FLOWSERVE READY FOR OVERSEAS MARKETSA new “three-in-one” concept infiltrates the European and Asian markets for double mechanical seals.
global presence
ML-200
FTF0403_06_07_KEY_2.qxd 2/23/04 1:51 PM Page 6
®
Worldwide ContactsFLOWSERVE WORLDWIDE
HEADQUARTERS
5215 North O’Connor Blvd.
Suite 2300
Irving, Texas, 75039 USA
Phone 972 443 6500
www.flowserve.com
UNITED STATES
Diane Treadway
Phone 909 296 2464 x3062
Fax 909 719 4474
EXPORT SALES / UNITED
STATES
Luisa Alexander
Phone 269 226 3913
Fax 269 226 3800
CANADA
Gail VanPelt
Phone 416 292 2877 x241
Fax 416 292 5190
EUROPE - THE
NETHERLANDS
Marjan Vaesen
Phone 31 165 581400
Fax 31 165 581442
EUROPE - GERMANY
Beate Haselhoff
Phone +49 (0)231 69 64 0
Fax +49 (0)231 69 64 248
ARGENTINA, BRAZIL, CHILE,
PARAGUAY, BOLIVIA
Danny Puharre
Phone 55 11 4231 6328
Fax 55 11 4321 6329
EXPORT SALES /EUROPE-
MIDDLE EAST-AFRICA (EMA)
Carolien Zehetgruber
Phone 31 165 581188
Fax 31 165 581442
PUERTO RICO, CARIBBEAN
Cynthia Marrero
Phone 787 884 6262
Fax 787 884 6535
ASIA, PACIFIC
Kok Kong Wong
Phone 65 68465100
Fax 65 67471963
MEXICO, CENTRAL
AMERICA, VENEZUELA,
COLOMBIA, ECUADOR, PERU
Raymundo Rodriguez
Phone 52 5 567 7170
Fax 52 5 567 4224
Globally, Flowserve Flow SolutionsDivision operates nine regional,
state-of-the-art manufacturing facilities toprovide sealing solutions as a singleresource for the improvement of end usercustomer rotating equipment operations.In conjunction with its alliance customers,the Flow Solutions Division has improvedoperational efficiencies to world-classstandards.
Unlike traditional purchasing agree-ments, the Flowserve strategic alliance con-cept is a reliability-focused process to helpkeep customer equipment running andplants operating. The alliances begin with acomplete survey of all the customer’s rotat-ing equipment and application variables.
Flowserve alliance programs are focusedon optimizing seal and rotating equipmentperformance, achieving dramatically im-proved MTBF, reducing inventory throughstandardization and driving down totalcosts associated with rotating equipment.
The result: Fewer equipment failures,less downtime, less inventory, and in-creased overall profitability.
To meet the end user need for cost reduc-tion, increased seal life and minimal down-time, the Flow Solutions Division has over 35Quick Response Centers (QRCs) located instrategic areas around the world. Typicalfacilities are equipped with modern manu-facturing capabilities that include seal repairand reconditioning, as well as the ability todesign and produce complete seals.
QRCs are staffed with knowledgeableCustomer Service Representatives to expe-dite the customer’s needs and deliveryrequirements. Application Engineers areready to assist in seal and system recom-mendations, on-site troubleshooting andfailure analysis. ❚
Global Presence, Local Support
FTF0403_06_07_KEY_2.qxd 2/23/04 1:51 PM Page 7
Increase your production reliabilitywhile reducing product contamination
with Flowserve sealing solutions.The products and expertise to keep you up and running
We offer a range of mixer seals for dry or wetrunning applications as well as dry nitrogenbarrier gas seals, both contacting andnon-contacting. Based on years ofresearch and lab testing, ourproducts are designed for yourproduction criteria, includingfeatures that reduce processequipment downtime andmaintain strict qualitystandards such as:
• CIP - clean in place seals
• electro-polished finishes
• sterilizable seals
• sanitary designs
• seals constructed of FDAacceptable materials
• seals designed for mixers,centrifuges, dryers, fermentors,and stills
We know that keeping your pharmaceutical processequipment operating while keeping product contaminationto a minimum is your utmost concern. At Flowserve, wehave a complete range of sealing products that havebeen accomplishing this in plants around the world.
© Flowserve, 2004
FTF0403_BackPage_Ad.qxd 2/23/04 1:52 PM Page 8