Contemporary approaches regarding to infrastructure are more and more directed to new materials development for natural gas and other installations. The most recent development and application of the new materials pertain to sealant materials for sealing of threaded joints in gas pipeline installations and installations for other media. Based on provided analysis, gas leaking on threaded joints in home metering and control units sealed with hemp was affirmed. Considering that in practical work in the case of hemp, sealing threads are made by a thread tool and during threading, the tool lubricates, the influence of impurities on sealing with anaerobic sealant compounds has been tested. Experimental work includes testing of three different anaerobic sealing compounds with three material combinations in threaded pipe joints (steel – brass, brass – brass and brass – aluminium) on three different temperatures (-20 °C, 25 °C and 100 °C).Trenutačni su pristupi, koji se odnose na infrastrukturu, sve više usmjereni na razvoj novih materijala za izvođenje plinskih i drugih instalacija. Najnovija dostignuća i primjena novih materijala prvenstveno se odnose na smjese za brtvljenje navojnih spojeva plinskih cjevovodnih instalacija, te cjevovoda za druge medije. Provedenim je ispitivanjima potvrđeno propuštanje prirodnog plina na navojnim spojevima kućnih regulacijskih stanica brtvljenih kudjeljom, što je potvrđeno provedenim ispitivanjima. U instalaterskoj praksi navoj na cijevima izrađuje se pomoću nareznica koje se prilikom narezivanja navoja podmazuju. Ispitivanjem se utvrdio utjecaj onečišćenja na brtvljenje spojeva pomoću anaerobnih brtvenih smjesa. Eksperimentalnim radom ispitana su tri različita anaerobna brtvila s kombinacijom tri materijala u navojnom spoju (čelik - mesing, mesing - mesing, mesing - aluminij), pri trima različitim temperaturama (-20 °C, 25 °C i 100 °C)

Josip Stojšić

Pero Raos

Zlatko Tonković

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1IntroductionUvodApplication of hemp and non-curing sealingcompounds is quite common in developing countries fordifferent installation types, especially in natural gasinstallations. In spite of careful assembling, industry isfaced with leakage problems of such joints after few years ofexploitation. Nowadays, most of the countries andespecially industrial developed countries devote great careto development and application of sealing materials forsealing of threaded joints in gas pipeline installations andinstallations for other media.Main task of thread sealants is to prevent leakage ofgases and liquids from pipe joints. All such joints considerbeing dynamic due to vibrations, changing pressures orchanging temperatures, which makes special requests onthem. With the growth of natural gas usage, possibilities ofrisk are also increasing, and for that reason, it is necessary todirect all attention to the tightness of sealed joints in gasinstallations. For sealing threaded joints in gas pipelineinstallations, according to regulation EN 751 non-curingsealing compounds, polytetrafluoroethylene (PTFE) tapesand anaerobic polymer sealants can be used.Non-curing jointing compounds that are made of oiland fillers, mostly combined with hemp, are one of theoldest methods for sealing threaded joints. Jointing is easierbecause of lubricating threads. However, they can squeezeout under pressure, have poor solvent resistance, and do notwork on parallel threads. Solvent-based jointingcompounds are also an old method of sealing threadedjoints. It provides lubrication and jams in gaps, extrude lesseasily. Disadvantage is that they shrink during cure assolvent evaporates and fittings must be re-torqued tominimize voids.11Z Tonkovi , P  Raos, J  Stojši. ć . . ćISSN 1330-3651UDC/UDK 620.197.6 : 678.7] : 621.643.414APPLICATION OF ANAEROBIC THREAD SEALANTS IN NATURAL GAS PIPELINESZlatko Tonkovi , Pero Raos, Josip Stojšić ćContemporary approaches regarding to infrastructure are more and more directed to new materials development for natural gas and other installations. Themost recent development and application of the new materials pertain to sealant materials for sealing of threaded joints in gas pipeline installations andinstallations for other media. Based on provided analysis, gas leaking on threaded joints in home metering and control units sealed with hemp was affirmed.Considering that in practical work in the case of hemp, sealing threads are made by a thread tool and during threading, the tool lubricates, the influence ofimpurities on sealing with anaerobic sealant compounds has been tested. Experimental work includes testing of three different anaerobic sealing compoundswith three material combinations in threaded pipe joints (steel – brass, brass – brass and brass – aluminium) on three different temperatures (-20 °C, 25 °C and100 °C).Keywords: anaerobic polymeric sealants, gas installations, leakage of natural gasPreliminary notesTrenutačni su pristupi, koji se odnose na infrastrukturu, sve više usmjereni na razvoj novih materijala za izvođenje plinskih i drugih instalacija. Najnovijadostignuća i primjena novih materijala prvenstveno se odnose na smjese za brtvljenje navojnih spojeva plinskihProvedenim ispitivanjima potvrđeno prirodnog plina na navojnim spojevima kućnih regulacijskih stanica brtvljenih kudjeljom, što jepotvrđeno provedenim ispitivanjima. U instalaterskoj praksi navoj na cijevima izrađuje pomoću nareznica koje se prilikom narezivanja navoja podmazuju.Ispitivanjem se utvrdio utjecaj onečišćenja na brtvljenje spojeva pomoću anaerobnih brtvenih različitaanaerobna brtvila s kombinacijom tri materijala u navojnom spoju (čelik - mesing, mesing - mesing, mesing različitč čcjevovodnih instalacija, te cjevovoda za drugemedije. propuštanjesmjesa. Eksperimentalnim radom ispitana su tri- aluminij), pri trima im temperaturama (-20°C, 25 °C i 100 °C).jeseKlju ne rije i: anaerobne polimerne brtvene smjese, plinske instalacije, propuštanje prirodnog plinaPrethodno priopćenjeIstraživanje primjene anaerobnih brtvenih smjesa u plinovodnim sustavimaIstraživanje primjene anaerobnih brtvenih smjesa u plinovodnim sustavimaTechnical Gazette 16, (2009), 111 -14One of the solutions is also polytetrafluoroethylene(PTFE) tapes that give a good initial seal; they can resistchemical attack and it is the only organic sealant allowed forgaseous oxygen. At the same time, they also act as alubricant and resist solvents. Unfortunately, PTFE tapeslubricate also in off direction, facilitating fittings to loosen.Dynamic loads may accelerate creep, causing leakage overtime [1].The most recent development in sealants is polymeric(methacrylate) anaerobic sealants, which cure to insoluble,tough, plastic thread fillers that prevent leakage regardlessof the pressure or torque applied. Some of the mostimportant advantages of these anaerobic jointingcompounds are that they lubricate during assembling, sealregardless of assembly torque, seal to the burst rating of thepipe, provide controlled disassembly torque years later, donot cure outside joint (easy clean-up) and by that preventcorrosion on threads, give the lowest cost per sealed fitting.The leaking of the gas from commercial pipelines is notonly safety problem; it should also be regarded as direct lossof financial resources for gas distributors. Therefore, it isnecessary to determine positions and frequency of the gasleaking as well as to analyze the possible causes of leakingand to give the eventual solutions to improve sealing.To set the natural gas consumer in motion, workperformer has to make the home metering and control unit(MCU) and to seal all the elements safety.An analysis of thegas leaking in home MCUs has been performed in thedistributive region Osijek (locations Višnjevac, Josipovacand city area of Osijek). The installation systems of 3 barinlet pressure have been analyzed. Each MCU consists of2Leaking analysisAnaliza propuštanjaeight threaded pipe joints (schematically presented inFigure 1), all sealed traditionally with hemp and non-curingjointing compounds.12Application of anaerobic thread sealants in natural gas pipelines Z Tonkovi , P  Raos, J  Stojši. ć . . ćTehni ki vjesnikč 16, (2009), 111 -14Figure 1Slika 1Schematic overview of MCU (A – The major cock, B – dielectricconnector, C – filter, D – regulator of the pressure, E – gasflow-meterand F – flexible gut)Shematski prikaz ku ne regulacijske stanice (A – glavna slavina,B – dilektri na spojnica C – filtar, D – regulator tlaka, E – plinomjeri F – fleksibilno crijevo)ćčGas leakage on each considered MCU, has beencontrolled using a foam-detecting agent [2]. The consideredjoints have been in operation during the last 5 years.In the location of Višnjevac a total number of 1366MCUs (10928 threaded joints) has been analyzed. Totalnumber of leaking joints was 967 or 8,85 %. Figure 2 showsgas leaking frequency on each position of threaded joints inthe location of Višnjevac.2.1Results of leaking analysisRezultati analize propuštanja2.2Discussion of the leaking analysis resultsRasprava o rezultatima analize propuštanjaThe analysis has shown an unacceptably high numberof threaded joints, in which gas leakage has been detected.There are many factors influencing the reliability. It mightbe the thread length, uncorrected cutting tool, sealingmaterial or man work. However, the analysis has shown thatone of the most important factors is the applied sealingmethod. According to available references [3] andcorresponding standards and producer's recommendationsas well as based on own experience [4], a significantimprovement could be the application of anaerobic-curingjointing compounds instead of traditional sealing methodusing hemp and non-curing compounds.The experiences in application of anaerobic jointingsealants for natural and commercial gas installations inEurope vary from country to country. Their applicationstandardizes DIN EN 751-1 (DIN 30 661), BS 6956-7 andsome company-internal standards (e.g. Italgas, Gaz deFrance etc.).In Croatia, there are no large-scale applications ofanaerobic sealants in commercial gas installation pipeworks. However, the analysis has shown an excessiveleakage in some parts of the analyzed commercial gasinstallation, traditionally sealed with non-curing sealants incombination with hemp.Therefore, the authors have conducted experimentalinvestigations in which anaerobic sealants have beenapplied in some positions of the commercial gas pipelinesFigure 2Slika 2Gas leaking frequency in the location of VišnjevacUčestalost propuštanja KRS-a u VišnjevcuIn the location of Josipovac the 718 MCUs (totalnumber of threaded joints is 5744) have been analyzed.Total number of leaking joints is 638 or even 11,11 %.Figure 3 shows gas leaking frequency on each position ofthreaded joints in the location of Josipovac.Figure 3Slika 3Gas leaking frequency in the location of JosipovacU estalost propuštanja KRS-a u JosipovcučIn the city area of Osijek 87 leaking positions on totalnumber of 1320 analyzed threaded joints were detected(6,59 % of leaking joints). Figure 4 shows gas leakingfrequency on each position of threaded joints.Figure 4Slika 4Gas leaking frequency in the city of OsijekU estalost propuštanja KRS-a u Osijekuč13steel aluminium joints (M3), all assembled by usingvarious sealants (S1, S2 and S3).-Z Tonkovi , P  Raos, J  Stojši. ć . . ć Istraživanje primjene anaerobnih brtvenih smjesa u plinovodnim sustavimaTechnical Gazette 16, (2009), 111 -14and compared them with the same positions on pipe worksealed traditionally.According to available literature, our experience andpreliminary investigations performed [5, 6] there are threemain factors influencing the sealing performances of thethreaded pipe joints. They are sealing compound, workingtemperatures and fitting material combination.In the investigations an experimental design, whichincludes 3 factors at 3 levels in 5 runs [5] giving a total of135 experimental runs, has been applied. Summarized, allfactors and level values are shown in Table 1.3Experimental  nvestigations3.1Design and course of the experimentiEksperimentalna istraživanjaPlan i tijek pokusa--All experimental procedures have been conductedaccording to DIN 2999 on R¾" pipe fittings with parallelinternal threads and taper external threads of Withworthform. Sealing performances (output variables) at each runhave been qualitatively measured using a foaming leakcontrol agent after exposure to an internal pressure of 3 barduring 24 hours. Additionally, the unscrewing torque wasmeasured at the end of each experimental run. Figure 5shows the experimental setup.In only one experimental run at S1/M1/T2, a moderateleakage from the joint was noticed. Afterward checking hasshown an inadequate degreasing of fitting threads, whichinhibited compound wetting ability to the surface of thefitting threads. However, assuming proper fittingdegreasing, all sealing compounds considered give veryreliable sealed joints.As expected, higher working temperatures decreaseunscrewing torque, but with no influence on sealingperformances. This correlation was observed at allcombination of factors. Figure 6 shows this correlation forsteel brass joints (M1), Figure 7 shows correlation forbrass brass joints (M2), and Figure 8 shows correlation for3.2Results and discussionRezultati i raspravaTable 1Tablica 1Influencing factors and their levelsUtjecajni faktori i njihove razineFactors LevelsS1 Loctite 577S2 Loctite 511A Sealing compoundS3 Loxeal 58-11T1 - 20 °CT2 25 °CB Working temperatureT3 100°CM1 Steel-BrassM2 Brass-BrassC Fitting material combinationM3 Brass-AluminumFigure 5Slika 5Experimental setupEksperimentalni postavFigure 6Slika 6The influence of temperature and sealant on unscrewingtorque at steel-brass joints (M1)Utjecaj temperature i brtvene smjese na moment odvrtanjakod spojeva čelik-mjed (M1)Figure 7Slika 7The influence of temperature and sealant on unscrewingtorque at brass-brass joints (M2)Utjecaj temperature i brtvene smjese na moment odvijanjakod spojeva mjed-mjed (M2)020406080100120140160T1 T2 T3Temperature levelUnscrewingtorque,NmS1/M1S2/M1S3/M1020406080100120140T1 T2 T3Temperature levelUnscrewingtorque,NmS1/M2S2/M2S3/M2Tehni ki vjesnikč 16, (2009), 111 -1414joints. All of the three tested sealing compounds areadequate to be used for threaded joints R ¾" at = 3 bar intested temperature range from –20 to 100 °C. However, thedifferences in unscrewing torque value have been noticed.The highest values of unscrewing torque at all of the testedtemperatures have been detected at threaded jointsinvolving steel – brass combination of fitting materials(M1), and the smallest values at brass – aluminiumcombination (M3). From the practical point of view apossible limitation for application is a relatively highunscrewing torque, which is achieved by using somecompounds and/or large fitting diameters. In this casedisassembling the joints using standard manual tools couldpossibly be problematic.In further research we will apply anaerobic compoundsin the sealing of chosen home metering and control units(MCU) in the distributive region Osijek aiming to researchtheir long-term behavior.p5ReferencesLiteratura[1] Raos, P.; Hnatko, E.; Tonković, Z.str.[2] Raos, P.; Samardžić, I.; Tonković, Z./Katalinić, Branko (ur.) (ISBN 3-901509-19-4). Beč :DAAAM International Vienna, 24.-27.10.2001. str. 397-398.strć, Z. Contribution to investigation of sealing of thethreaded joints of the city gas pipelines with the anaerobicsealing compounds, Master thesis, Mechanical engineeringfaculty in Slavonski Brod, University of Osijek, 2002..Application of AnaerobicPolymeric Sealants in Gas Installation Pipework // PPSRegional/European Meeting / Saha, Petr (ur.). Zlin : PolymerProcessing Society, 15.-18.08.2000. 203-204Experimentalinvestigation on aplication of anaerobic polymeric sealants ingas installations // Annals of DAAAM for 2001 &Proceedings of the 12th International DAAAM Symposium[3] EN 751 Standard: Sealing materials for metallic threadedjoints in contact with 1st, 2nd and 3rd family gases and hotwater, 1997[4] Raos, P. Contemporary methods of adhesive bonding andsealing in maintenance, 2nd International meeting:Maintenance 95, Croatian Maintenance Association, Opatija,1995, . 6.2-6.9[5] Tonkovi[6] HSUP - P 600, Technical regulations for gas installations,Zagreb, 2002Furthermore, as an illustration, Figure 9 showsinfluence of various fitting materials (M1, M2 and M3) onunscrewing torque of threaded joints assembled by usingvarious sealants (S1, S2 and S3) at constant temperaturelevel of – 20 °C (T1).Figure 8Slika 8The influence of temperature and sealant on unscrewing torqueat steel-aluminium joints (M3)Utjecaj temperature i brtvene smjese na moment odvijanjakod spojeva čelik-aluminij (M3)It is very clear that disassembling characteristics of thejoints strongly depend on fitting materials used. Fittingsmade of steel - aluminium combination (M3) give thelowest values of unscrewing torque at every sealant andtemperature applied. This is because aluminium is a passivematerial, which inhibits full cure of anaerobic sealant.An investigation of gas leaks in home metering andcontrol units (MCU) has been performed in the distributiveregion Osijek. The analysis has shown an unacceptably highnumber of threaded joints (all sealed traditionally withhemp and non-curing sealants) in which gas leakage hasbeen detected. Further analysis has shown that one of themost important factors influencing leaking possibility is theapplied sealing method. Therefore, an experimentalinvestigation of sealing characteristics of somecommercially available anaerobic sealants was conductedaiming to improve traditional sealing method using hempand non-curing compounds.The results obtained in experimental investigationaffirmed the possibility of applications of all three testedanaerobic sealants at any combination of considered fittingmaterials and temperatures aiming to give safely sealed4ConclusionZaključakAuthors' addressesAdrese autoradProf. dr. sc. Pero RaosEng.r. sc. Zlatko TonkovićJosip Stojšić, BSc.Croatian Electrical Company (cr. HEP)HEP-Plin Ltd.HR-31000 Osijekzlatko.tonkovic@hep.hrUniversity of OsijekMechanical engineering faculty in Slavonski BrodHR-35000 Slavonski Brodpraos@sfsb.hrUniversity of OsijekMechanical engineering faculty in Slavonski BrodHR-35000 Slavonski Brodjstojsic@sfsb.hrApplication of anaerobic thread sealants in natural gas pipelines Z Tonkovi , P  Raos, J  Stojši. ć . . ć0102030405060T1 T2 T3Temperature levelUnscrewingtorque,NmS1/M3S2/M3S3/M3020406080100120140160M1 M2 M3Fitting material combinationUnscrewingtorque,Nm S1/T1S2/T1S3/T1Figure 9Slika 9The influence of fitting material and sealanton unscrewing torqueUtjecaj materijala spoja i brtvene smjese na moment odvijanja

Istraživanje primjene anaerobnih brtvenih smjesa u plinovodnim sustavima

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