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FiftyYearsof ContinuousteamerEvolutionBy Charles B. Palmer, Zima Corp., retired, Spartanburg, S.c.

In the summerof 1949,withthe inkbarely dry on my bachelor degree inChemical Engineering, I sawmy

, first continuous dye range steamerand was mystified by its operation.Cloth going into the steamer through aslot in the top of the entry wall andexiting the steamer through a waterbath at the end of the steamer madesense. But why was all that steamgushing from the entry and why wasthe atmosphere inside the steamer socloudy? Why was this steamer leakingsteam from so many points where therolls went through the steamer walland what was the purpose of the pul-leys on each of the top rolls? Theycertainly were not being drivenbyanything unless that broken leatherstrapping lying near the steamer hadsomething to dowith it. It was a quicktrip through this plant without muchtime for questions, and shortly there-after I went to work in a batch process-ing plant.

Thirteen years later, I visited severalmore continuous fabric processingplants specifically to study the pro-cesses and the equipment.And what Isaw in the way of dye range steamerswas nothing but wider models of thesame steamer describedpreviouslywith somewhatbetter steaming condi-tions but with all of the deficienciespresent to varying degrees. I then se-lected similar steamers for a plant thatwas on the drawing boards. Nothinghad changed in the interim, and I sup-posed that was the way it should be!WAKEUP CAllIn retrospect, I think steamer improve-ments were not made in the interven-ing years because nobody asked forAATCC REVIEW

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them. Plant production people, whoknew most about the process, wereproducing acceptable product; plantengineers, who more than anyone elseselected the equipment for a plant butknew least about the process, saw noreason to change; and the machineryproducers certainly had no interest inchanging their models because of theengineering and retooling costs in-volved. There were only two majorsuppliers of continuous wet processingequipment in the United States in the1950s, and they were quite satisfiedwith the status quo.

Gradually, things were happeningthat literally forced fabric and machin-ery producers to sit up and take notice.Our economy increasingly becameglobal. European and Japanese ma-chinery manufacturers were offeringequipment to the United States thatlooked and operated differently inmany respects but could be purchasedat competitive prices. In the 1970s,wehad an energy crunch followedby thereturned popularity of 100%cottonfabrics in the 1980s.Emerging nationswith significantly lower labor rateswere taking "our" business and pro-ducing fabrics on new equipment moreefficiently. It was a wake up call weheeded; those who didn't are no longerwithus.Continuing ImprovementsIn the ensuing years, many improve-ments weremade in continuouswetprocessing equipment. These weredriven by the need to be competitive,increase speed, conserve energy, im-prove process results, and the influx oftechnically trained people who recog-nized the problems and were not will-

ing to accept themwithout trying toovercome them. Everything was sub-ject to question and the phrase "wealwaysdid it this way" gradually dis-appeared from wet processing plants.For this desirable state of affairs tooccur, it was absolutely necessary forplant production, technical, and engi-neering personnel to meet together,reach agreement about machineryrequirements, and very much becomea part of the decision making teamthat clearly presented these require-ments to the machinery manufactur-ers. The results were excellent witheven the most staid suppliers makingsome effort to fulfill those require-ments. Both suppliers and users ben-efited in what came to be recognizedas a win-win situation.Similaritiesof SteamersBefore we go further, let us considerthe similarities of the steamers underconsideration. Tight strand steamers ina fabric dye range, conveyer and rollerbed steamers in a fabric preparationrange, a type of festoon steamer in acarpet dye range, and steamers forcontinuous dyeing of pile fabrics allhad one thing in common. They usedcopious amounts of steam becausemuch of the steam consumed wasexhausted to the atmosphere (hencesteam billowing from entry and exitslots) in order to keep those steamersfilled with steam to the exclusion ofall'.

A common requirement was and isthat the steam must be saturated forbest results in a dye or preparationrange. Conversely,desuperheatedsteam; i.e., unsaturated, causes myriadproblems ranging from badly soiled

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and difficult-to-clean interior rolls andsurfaces to poor fabric quality result-ing from improper preparation condi-tions damaging fibers, and dyeingprocesses not reaching optimum end-point with consequent fabric appear-ance or quality problems.PROPERTIESf STEAMSteam-saturated or superheated-is acolorless gas and is lighter than air.Only if it condenses in the steameratmosphere does it look cloudy andthis condensation is normally causedby air entering the steamer with thefabric or through leaky seals whereroll journals pass through steamerwalls. Such condensation must beabsolutely minimized to obtain satis-factory results.Wet SteamSaturated steam, sometimes called wetsteam, is steam that can contain noadditional water.Therefore it cannotdry roll surfaces or fabrics in contactwith it to their detriment. Saturatedsteam, at sea level, in a steamer opento the atmosphere, is always at 212F.You can find this and other usefulinformation in any set of steam tables.JThe one I use was published in 1933,but the information in it neverchanges; it is not debatable. In theatmospheric steamers, you may havesensors telling you differently, but Iguarantee they are being fooled (byradiation, for example) and they arefooling you.Dry SteamBoilers usually produce steam withvarying degrees of superheat; i.e.,steam that is "dry" and can absorbwater until it becomes saturated. Themore degrees of superheat (actualsteam temperature under pressureversus temperature of saturated steamat the same pressure) the more prob-lems you will have, which is why youmust superheat in one of several ways.In most cases, you simply add water tothe steam by passing it through a sumpor spraying water under pressure into

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the main delivering steam.This lattermethod sounds simple, and it is if youcontrol the amount of water beingadded. But, it has a high maintenancerequirement because spray nozzlessupplying the water clog easily and,under the best conditions, you cannotachieve true saturation. For this reason,early steamers had a wet bottom, orsump, through which steam, underpressure, was passed to provide therequired steam atmosphere.Wet BottomsThe wet bottom works well if thesteam supply pressure and the steamvelocity entering the sump are lowenough and the height ofwater in thesump is high enough to allow thesteam to condense in the sump andboil the sump to provide saturatedsteam to the steamer.But wet bottomswere not designed to make thathappen.

Consider that a really deep sump of2.5 ft only exerts 1 Ib/in2of hydraulicpressure on the bottom of the sump.Steam of many times that pressure issparged into the sumpwith the resultthat the sump eventuallyboils, butsteam continues to pass through itwithout becoming fully saturated (i.e.,the difference in pressure betweensteam and sump depth means thatmuch steam passes through the sumpand into the steamer atmosphere with-out first condensing).External SumpThe answerwas to design and build anexternal sumpwith a minute watervolume compared to a steamer wetsump but with a sufficiently high wa-ter column and internal mechanisms toensure that steam passing through itwould alwaysbe saturated and avail-able in the quantities required. Anadded bonus was that this externalsump operated at atmospheric pres-sure, was totally reliable, and mainte-nance free.

Such a sump has been availablefrom Kiisters Corp. for many yearsnow and used with all type of dyeing

and preparation steamers. Most inter-esting is that the external sumpwasdeveloped and first used in the carpetindustry before being scaled down insize for application to fabric prepara-tion and dye steamers.Heinz Gruber, an associate ofEduard Kusters Machinenfabrik ofKrefeld, Germany,but located in theUnited States in Dalton, Ga., the heartof the carpet industry, was familiarwith external sumps. These were nor-mally operated under pressure that, inthe United States, meant that the exter-nal sump would require anASMEcode, making it more expensive tobuild and limiting its construction tometal fabricating shops licensed byASME. Heinz took the idea and itsdeficiencies to the engineers atKusters Corp. in Spartanburg, S.c.,with the result shown inFig. 1, anexternal sump operating at atmo-spheric pressure with input steampressure of only a few pounds persquare inch.CARPETNDUSTRYSTEAMERPROBLEMSThe carpetindustry'sproblemwasidentical to the problem found in thefabric industry but magnified manyfold by the weight of carpet passingthrough a carpet dye steamer.Al-though acid or pre-metalized dyeswere used, it was shown conclusivelyin the 1980s that saturated steam was arequirement. Furthermore, its compo-sition had to be constant throughoutthe dye run.

Fig. 1. External sump design by KOsters.

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Fig. 2. Type I steamer schematic.

Heavy WeightQuick change color application alreadyhad become commonplace,whichmeant that one color lot followedan-other into the steamer without interrup-tion. Carpet weight variedwidely, andit was not uncommon for 70 oz lyd2carpet carrying 300% of its weight indye liquid to follow a 40 oz lyd2carpetwith its weight of dye liquid into thesteamer.The heavier carpet demandedalmost twice asmuch steam,which theboiler could supplybut that thedesuperheater, regardless of sump orspray in line type, could not immedi-ately desuperheat.Until steam conditions eventuallystabilized, carpet of varying shade wasproduced (i.e., off quality carpet orcarpet that could not be shipped withthe remainder of the dye lot). Thedevelopment of the external sumpsolved this problem. It was engineeredto handle the easily calculated steamvolume requirement of the heaviestcarpet to be dyed and was capable ofswitching instantaneously to lowercarpet weights and back again tohigher carpet weights without variationin steam quality. Furthermore, thechange in steam volume was con-AATCC REVIEW

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Fig. 3. Type II steamer schematic.

trolled automatically by an RTD sensorfeeding its signal to a simple control-ler. (More about the control methodlater since it was first developed about10 years prior to the external sump.)Energy CostsThe energy crunch of the 1970s hit thecarpet industry particularly hard be-cause of the heavy weights they pro-cessed. Early carpet steamers re-sembled fabric dye range steamers inthat they had top entry and exits.Steam was supplied through a sump orfrom bottom sparge lines deliveringsteam supposedly superheated by aspray-in-line desuperheater.

In the example used, this Type Isteamer (Fig. 2) billowing steam fromexit and entry was consuming 14,000Ibs/hr of steam, which had becomeveryexpensive.2 With energy costsrapidly increasing, it did not take longto design, build, and sell the Type IIsteamer (Fig. 3) with low entry andexit slots. This simple change reducedsteam consumption to 7,700 Ib/hr, butthat only provided some breathingroom to develop the Type III steamer(Fig. 4), which consumed only 4,700Ib/hr, roughly one-third the amount of

the TypeI steamer and very close tothe calculated amount of steam re-quired by a 100%efficient process.The company fromwhich this data wascollected said their steamer was savingthem $250,000 per year!CloudControlThe TypeIII steamer had entry andexit slots even lower than the TypeII.Unlike the others, however, steam wasintroduced from sparge lines in thetop, and the amount of steam wascontrolled by measuring the tempera-ture of the "cloud" formed in the areaof the interface between steam and airat the bottom of the steamer.By vary-ing steam flow to satisfy a setpointmeasured in the "cloud" below thecarpet path through the steamer, thesteamer remained filled with steam butnone was exhausted. The carpet con-sumed only the steam the dye processrequired and none was wasted. If forany reason, and there were some legiti-mate ones, it was necessary to provideexcess steam and exhaust a controlledamount, the control system could eas-ily handle this requirement.The "cloud control" also was devel-oped by engineers from Kiisters in

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Fig.4. TypeIII steamerschematic.

Spartanburg,S.c. It resultedin asteamerwithsteamon top andair onthe bottom similar to the "open bot-tom" Arioli steamer used in the wetprinting industry but with a distinctlydifferent control principle. Years later,when the external sump was developedand added to these steamers, theybecame ideal for the process.fABRIC fOllOWSFollowing on the heels of the steamerdevelopments in the carpet industry,the same principles were applied tofabric preparation steamers.Theyworked just as well, reducing steamconsumption to the amount requiredby the process plus an insignificantloss to radiation. Many steamers ofthis type (Fig. 5)were sold and most

had exhaust ducting at the entry andexit lips because the customers couldnot believe that the steamer did notrequire an exhaust.Some owners continue to add asurplus of steam and run their exhaustfans; others have blocked their exhaustducts for further steam savings. Steamsavings when operating these steamersas intended recover their cost in aboutone year. The external sump has beendownsized to accommodate thissmaller equipment and, as expected,eliminates all steam problems oftenencountered in preparation equipment.FabricDye SteamerThe last bastion of resistance to mod-ern steamer design was the tight strandfabric dye steamer. During the last 20years, dyehouse managers grudginglygave up the top entry for mid-entry andfinally for true bottom entry (Fig. 6),fearing all the time that they might bedoing wrong even though each changeresulted in improved conditions.They even liked the "cloud control"

principle, but absolutely would notconsider eliminating overflow; i.e., theexcess steam that then had to beexhausted from the lip. No need forthe steamer manufacturer to argue overthat point; his control system wouldhandle it with a simple change insetpoint.Much more difficult was to con-vince the dyer and the dye supplier'stechnical people that you cannot oper-ate an atmospheric steamer above

2l2F. So they placed their sensorsclose enough to the steamer roof andpressurize the roof sufficiently to radi-ate the sensor and get the reading theywish, while the steamer continues toexhaust 2l2F steam from the bottom.They were satisfied with the result, thesteamer manufacturer was satisfiedwith the result, and with the additionof the external sump, the process re-mained in control regardless of howyou fiddled with it!OTHERMPROVEMENTSSealsWhile the developments aboveweretaking place, lesser known improve-ments were being made that wereapplicable to all steamers, since allsteamers have rolls whose journalspass through the steamer walls. Manyof these rolls must be driven, and all ofthem must be sealed sothat steamdoes not escape wherever a roll passesthrough the steamer wall. Until theadvent of the non-lubricated seal, theseseals leaked, and required lubricationthat often got into the steamer withconsequent problems.The non-lubricated seal correctedthose problems as well as eliminatinghalf the lubricating points on asteamer. The seal itself was not reallynon-lubricated. It was made of plasticinside a stainless sandwich and lubri-cated by condensed steam.As long asthe seal was properly made and ad-justed, it did not leak. If it failed, re-placement was simple.

Fig.5. Fabricpreparationsteamerwithexhaustducting. Fig.6. A true bottomentry steamerdesign.JULY2002 WWw.AATCC.ORG

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Drive ChangesAnother improvement involved themechanical drive to be found on therolls of a roller bed steamer.The tradi-tional double sprocket on each roll andconnecting chains was replaced withsingle sprockets and a single continu-ous chain contacting only a singletooth at a time on each sprocket as thechain slowly drove the rolls of a rollerbed steamer. This was so successfulthat maintenance disappeared, neitherchain nor sprockets wore out, and themarket shifted away from conveyer toroller bed steamers, which also offeredfabric handling advantages.Finally,in the 1990s,there was astrong shift from DC toAC rangedrives. These new drives had manyadvantages including less expensiveand lowermaintenance AC motors.Computer programs made these drivesversatile but more sensitive and pro-vided the ability to process fabricunder lower controlled tension.

At lower tensions roll problems likeout of round, not level, or not alignedshowedup as fabric creases (that pre-viously were eliminated by highertensions) and consequent off quality.Steamer rolls became larger in diam-eter and weremanufactured to tightertolerances. Roll centers were short-ened. And selected rolls were drivenby individualmotors. The product wasbetter and its quality certainly was.MODERNSTEAMERSThe modern dye range steamer nowhas an external sump to supply satu-rated steam at atmospheric pressure, a"cloud" temperature sensing and con-trol system to provide precisely theamount of steam the process requires,a lowor true bottom entry, and theabsence of steam gushing into theroom. Roll diameters are almost twicethat of the 1950s and no more than oneroll in 20 yards is driven but by indi-

vidual motors rather than by sprocketsand chain or by pulleys and belts.Seals do not leak and the steamerremains cleaner and easier to cleaninside and out.You can still see its1950s forerunner in the functionalaspects of the steamer, but the modernversion that evolved from it is thesalvation of a high speed dyeing pro-cess and will help keep us in businessa while longer.References1.Keenan, 1.H. and F. G.Keyes, Ther-modynamic Properties of Steam, JohnWiley and Sons Inc., New York, 1936.2. Palmer, C. B., American DyestuffReporter, Vol. 75, No.8, August 1986pp18-20.

Author's AddressCharles Palmer, 153Highbridge Dr.,Spartanburg, S.C., 29307.

AATCC REVIEW JULY 2002