This paper deals with application of contemporary liquid sealants based on methyl - methacrylate, so called anaerobic sealants. Applications include reliable sealing of threaded joints in pipeline installations (cold and hot water pipelines, steam pipelines, gas pipelines, cooling and air-conditioning, pneumatics and hydraulics). Economy of anaerobic sealants application as well as important advantages of this contemporary sealing technique in comparison with traditional one has been considered in particular.U radu je razmotrena primjena suvremenih tekućih brtvenih materijala na bazi metil-metakrilata, tzv. anaerobnih brtvila. Primjene obuhvaćaju pouzdano brtvljenje navojnih spojeva u svim vrstama cijevnih instalacija (vodovodi, toplovodi, parovodi, plinovodi, rashladna tehnika i klimatizacija, pneumatika i hidraulika). Posebice je razmotrena gospodarska opravdanost tih brtvenih materijala i značajne prednosti koje ta suvremena tehnika brtvljenja ima u odnosu na klasične postupke

Josip Stojšić

Marija Somolanji

Zlatko Tonković

English

Hrčak - Portal of scientific journals of Croatia

1Introduction2Sealing methods and materialsUvodMetode brtvljenja i brtveni materijaliOne of the most important tasks while drafting, makingor maintaining any pipeline installation is to preventleakage of gases or liquid media by sealing pipe-threadedjoints. That implies various communal and industrialpipelines such as cold and hot water pipelines, steampipelines, gas pipelines as well as technically highdemanding pipe systems in cooling and air-conditioning,pneumatics and hydraulics. Pipe-threaded joints areextremely dynamic systems due to vibrations, changingpressures or changing temperatures, which complicate theirreliable sealing. Unintentional leakage of media from anyelement of pipe supply systems is uncontrolled leakage. Insuch a manner, uncontrolled leakage of natural gas performsa great risk for people and material property. Regardingduration, leakage intensity can cause disaster by producingflammable and explosive compounds in combination withair [1].Nowadays two types of threaded joints are mainly usedin pipe installations, metric (M) and pipefitting (Whitworthform, R). In the case of metric threaded joint, threads(external and internal) are parallel, and fittings must betorqued with the application of sealing material to minimizevoids. Pipefitting threaded joint has parallel internal threadand taper external thread. Sealing of such threaded joint isaccomplished by screwing external into internal thread withthe application of proper sealing material until the joint istight. Main task of the sealing material is to fill in clearancesbetween threads.Improperly assembled joints are most often the reasonof leakage that can lead to life danger situations, thereforesealing of threaded joints is particularly important.The ideal sealing method is to achieve a joint with tightthread connection. In doing so, theoretically there is no needfor the application of sealing material. It is possible to55Z. Tonković, M. Somolanji, J. StojšićISSN 1330-3651UDC/UDK 621.643.4-762APPLICATION OF CONTEMPORARY MATERIALSFOR SEALING PIPE THREADED JOINTS-Zlatko Tonković, Marija Somolanji, Josip StojšićThis paper deals with application of contemporary liquid sealants based on methyl - methacrylate, so called anaerobic sealants. Applications include reliablesealing of threaded joints in pipeline installations (cold and hot water pipelines, steam pipelines, gas pipelines, cooling and air-conditioning, pneumatics andhydraulics). Economy of anaerobic sealants application as well as important advantages of this contemporary sealing technique in comparison with traditionalone has been considered in particular.Keywords: anaerobic sealants, pipe - threaded joint, sealing methodsProfessional paperU radu je razmotrena primjena suvremenih tekućih brtvenih materijala na bazi metil-metakrilata, tzv. anaerobnih brtvila. Primjene obuhvaćajulacija (vodovodi, toplovodi, parovodi, plinovodi, rashladna tehnika i klimatizacija, pneumatika ihidraulika). Posebice je razmotrena gospodarska opravdanost tih brtvenih materijala i značajne prednosti koje ta suvremena tehnika brtvljenja ima u odnosu naklasične postupke.pouzdanobrtvljenje navojnih spojeva u svim vrstama cijevnih instaKljučne riječi: anaerobni brtveni materijali, cijevni navojni spoj, metode brtvljenjaStrukovni članakPrimjena suvremenih materijala za brtvljenje cijevnih navojnih spojevaPrimjena suvremenih materijala za brtvljenje cijevnih navojnih spojevaTechnical Gazette 16, (2009), 552 -58achieve absolute tightness of the joint with preciselycompiled thread. In practice, on the other hand high costs offitting and problems with fulfilling tolerances usuallydemand the application of sealing methods with additionalvarious sealing materials.For sealing threaded joints in pipeline installations,according to regulation EN 751, non-curing sealingcompounds, polytetrafluoroethylene (PTFE) tapes andanaerobic sealants [2] can be used.Non-curing joining compounds are one of the oldestmethods for sealing threaded joints. They are various liquidand paste compounds based on oil and grease, mostly withthe addition of filler. These sealing compounds lubricateand completely fill in threads. However, this kind ofthreaded joint can squeeze out and has poor solventresistance on aggressive media, so that is why it is not aproper method for parallel threads.Solvent - based joining compounds are also an oldmethod of sealing threaded joints. Sealing effect isaccomplished by curing compound due to the evaporationof solvent. These compounds lubricate threads while fitting,fill small clearances and it is not possible to squeeze themout as easy as non curing compounds. Disadvantage is thatthey shrink during cure as the solvent evaporates andfittings must be re torqued to ensure full sealing. Assuranceagainst self torque is based on the presence of abrasionwithin threads.Hemp and polytetrafluoroethylene (PTFE) tapes arecategorized as solid sealing materials, where the mostcommon ones are PTFE tapes. PTFE tapes act as lubricantand simplify fitting, give a good initial seal and have goodsolvent resistance on aggressive media (chemicals). It is theonly organic sealant allowed for gaseous oxygen.Unfortunately, PTFE tapes lubricate (low abrasion) also inoff direction so the risk of spontaneous torque is very high.Dynamic loads may accelerate creep, causing leakage overtime [3].Due to low abrasion of threads, it is necessary to givehigh initial seal that can cause high stress and threadcracking.Application of PTFE tapes in hydraulic systems isoften restricted because small tape particles can separateand by that block the system bores causing expensiverepairs.The most effective contemporary sealing method for---56Application of contemporary materials for sealing pipe threaded joints- Z. Tonković, M. Somolanji, J. StojšićTehni ki vjesnikč 16, (2009), 552 -58metallic threaded joints from technical and economicalpoint of view is the application of liquid polymer sealantsbased on methyl – methacrylate, so called anaerobicsealants.The most recent development in sealants polymeric(methacrylate) anaerobic sealants. Those materials ofvarious consistencies (from liquid, low viscose to highdensity, paste) cure to insoluble, tough, plastic thread fillersthat prevent leakage regardless of the pressure or torqueapplied. Those sealants are called anaerobic because theycure only without presence of oxygen.The most important advantages of anaerobic sealants incomparison with conventional ones are:Prompt and easy assembling of joints: lubricate duringassembling, sealing of external or internal thread isclean and quick directly from package or dosagedevice, seal regardless of assembly torqueEasy to clean remains of sealing: anaerobic sealantscure only inside of threaded jointEasy and reliable disassembling of joints: no corrosionon threaded joint, controlled unscrewing torquedepending on applied material type (low, medium orhigh toughness)Reliable sealing regardless of assembly torque: seal tothe burst rating of the pipeExquisite chemical resistance on most of industrialmedia (acid, alkali, lubricant, etc.)Medically and ecologically acceptable: when curedanaerobic sealants are completely neutral and by thathave a permission for appliance in food industry andwater supplyDVGW (Deutscher Verein des Gas- und Wasserfaches)authorization: for safe application in gas installations,Good temperature persistence: depend on materialtype, from – 55 230 °C in permanent exploitation.Disadvantages of anaerobic sealants refer to theirrestricted usage in the presence of oxygen and strongoxidize media or in case when working temperatures reachabove 230 °C. These sealants are not usually applied forsealing threads with diameter greater than M 80 3").When acting with active metals liquid anaerobicsealants react as accelerant of polymerization (Tab. 1) [4].3Anaerobic sealantsAnaerobni brtveni materijaliare;;;;;;to +R!!!!!!!!Passive materials in general have poor or do not haveaccelerant function therefore different chemical substances,so-called activators must be applied on one or bothassembling areas to accelerate and ensure complete curingof sealing compounds. The most important characteristicsof liquid anaerobic sealants are:have increased tangentially toughnesshave good temperature persistencefast curingeasy to dosedo not require special handling of assembling areasgum and seal joint at the same timehave exceptional persistence on various mediahave good endurance due to vibrationshave good endurance due to permanent dynamic stress.Anaerobic sealants have specific course of curingsignificantly conditioned with threads material type, sealingcompound thickness, curing temperature and appliedactivators. According to the mentioned factors qualitativecourses of curing (achieving declarative toughness ofsealing compound) are shown in Fig. 1 to 4.Fig. 1 shows the course of curing threaded jointconditioned with the threads material type.Fig. 2 shows course of curing threaded jointconditioned with sealing compound thickness (clearancesin threads that sealing compound must fill in completely).Fig. 3 shows course of curing threaded jointconditioned with curing temperature.Fig. 4 shows course of curing threaded jointconditioned with applied activators.!!!!!!!!!Table 1Tablica 1Overview of various materials accelerant characteristicswhile curingPregled katalitičkih svojstava raznih materijalau procesu očvršćivanja[4][4]ACTIVE MATERIALS PASSIVE MATERIALSsteelbrassbronzeother copper alloyshighly alloyed steelaluminumnickelzinctinsilvergoldoxidized jointschrome – plated areasanode areaspolymersceramicsFigure 1Slika 1Dependence on threads material typeOvisnost o materijalu navoja[4][4]57Z. Tonković, M. Somolanji, J. StojšićTechnical Gazette 16, (2009),2 55-58Primjena suvremenih materijala za brtvljenje cijevnih navojnih spojevaAnaerobic sealants are half packed because of theirspecific curing. In this way sufficient presence of oxygenprevents curing in package. Liquid anaerobic sealants canlast at least one year at temperatures of storage from -5 °C to28 °C [4]. Lower or higher temperatures of storage canaffect product quality.4Economics of anaerobic sealants applicationGospodarstvenost primjene anaerobnih brtvenihmaterijalaThe analysis shows that the application of anaerobicsealants is the cheapest way of sealing considering costs andrequired work (Tab. 2) [4].Figure 2Slika 2Dependence on sealing compound thicknessOvisnost o debljini sloja brtvene smjese[4][4]Figure 3Slika 3Dependence on curing temperatureOvisnost o temperaturi[4][4]pri skrućivanjuFigure 4Slika 4Dependence on applied activatorsOvisnost o aktiviranju površine[4][4]Tehni ki vjesnikč 16, (2009),2 55-58586ReferenceLiteratura[1] Tonković, Z.... Contribution to investigation on sealingthreaded joints of the city gas pipelines with anaerobic sealingcompounds, Master thesis, Mechanical Engineering facultyin Slavonski Brod, University of Osijek, 2002[2] EN 751 Standard: Sealing materials for metallic threadedjoints in contact with 1 , 2 and 3 family gases and hot water,1997[3] Raos, P. Contemporary methods of adhesive bonding andsealing in maintenance, 2 International meeting:Maintenance 95, Croatian Maintenance Association, Opatija,1995[4] N. N. Loctite Worldwide Desing Handbook, 2 Edition,Loctite co, Rocky Hill Ct., USA, 1998st nd rdndndApplication of contemporary materials for sealing pipe threaded joints- Z. Tonković, M. Somolanji, J. Stojšić--Direct (material) costs of anaerobic sealants applicationare slightly higher than for ones of conventional application(hemp, PTFE tapes). Average anaerobic sealant amount forone pipe – threaded joint (size R1") is about 0,45 l (put onmanually) or 0,35 l (put on automatically) what is accordingto current prices on Croatian market about 0,90 or 0,70 kn.However, real savings of anaerobic sealants application arewithin indirect costs, such as assembling time (that is a fewtimes less), no additional expenses for re torque, jointcontrols or badly sealed threaded joints. Considering theseelements, even the simplest economic calculation givessignificant advantage to anaerobic sealants application, thefact confirmed in industries all over the western world andlately also in Croatia.Development of contemporary liquid anaerobicsealants enabled, among other, their significant applicationwhile making and maintaining various industrial andcommunal pipe installations. In this group of sealants themost important ones are anaerobic polymer sealants basedon methyl methacrylate. The arguments for increasinglyfrequent anaerobic sealants application are theiroutstanding technical characteristics in comparison withconventional sealants as well as economical adequacy oftheir application.5ConclusionZaključakTable 2Tablica 2Necessary amount of anaerobic sealants for reliable sealing of threaded jointne brtvene smjese za pouzdano brtvljenje navojnog spoja[4][4]Potrebne količine anaerobNecessary amount of sealant, mlPipe – threaded jointAutomatically put on Manually put onR 1/8" (3 mm) 25 40R 1/4" (6 mm) 45 60R 3/8" (10 mm) 60 90R 1/2" (13 mm) 90 130R 3/4" (19 mm) 190 250R 1" (25 mm) 350 450Authors' addressesAdrese autoradr. sc. Zlatko Tonković, ia,n,Croatian Electrical Company (cr. HEP)HEP - Plin Ltd.HR-31000 Osijek  Croatzlatko.tonkovic@hep.hrCroatian Electrical Company (cr. HEP)HEP - Plin Ltd.HR-31000 Osijek  Croatiamarija.somolanji@hep.hrUniversity in OsijekMechanical Engineering Facultyi Slavonski BrodHR-35000 Slavonski Brod  Croatiajstojsic@sfsb.hrMarija Somolanji, dipl. ing.Josip Stojšić, dipl. ing.

Primjena suvremenih materijala za brtvljenje cijevnih navojnih spojeva

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