Why vitrified claySpecific weight KN/m322Bending tensile strength N/mm215 - 40Mohs hardness 8Modulus of elasticity N/mm2 50.000Coefficient of thermal expansion 1 / K 5.10-6Thermalconductivity W/m.K 1,2The most important properties which might be required for calculationpurposes are listed in the following table:The material vitrified clayVitrifiedclaypipesandfittingsareproducedfromtherawmaterialsclay,grog(chamotte)andwater.Theglazeappliedtotheproductsbeforefiringconsistsofmainlythesamebasiccomponentsplusmetallic oxides for colour. During drying at a temperature of approx.110Cmostofthewaternecessaryforshapingisextracted.Thesubsequentfiringattemperaturesrisingupto1200Ccreatesacompletely new material by sintering. This vitrified clay has exceptionalpropertiesinrespecttochemicalresistance,mechanicalstrength,impermeabilityandhardness.Highlydevelopedmanufacturingandpreparation techniques have made it possible to upgrade an alreadyprovenproduct,theconsistencyisguaranteedbyqualitycontrol.Vitrifiedclaypipesaredesignedforsewersoperatingongravityinmunicipal and industrial applications.Steinzeug | Keramo pipes and fittings are manufactured to a harmo-nisedEuropeanstandardEN295,whichspecifiesrequirementsforvitrified clay pipes and fittings with flexible mechanical joints fordrainsand sewers. National reference can still be recognised by two lettersindicating the country (e.g. BS EN 295 stands for British Standard EN295; whereas DIN EN 295 is the translation of EN 295 into the Germanlanguage). EN 295 consists today of 8 parts :EN 295-1 = RequirementsEN 295-2 = Quality control & samplingEN 295-3 = Test methodsEN 295-4 = Special fittings, adapters, accessoriesEN 295-5 = Perforated pipes & fittingsEN 295-6 = ManholesEN 295-7 = Jacking pipesEN 295-10 = PerformancerequirementsQualitycontrolThe Standard EN 295PipesandfittingsmeettherequirementsoftherelevantclausesofEN 295 in all respects. Compliance wit the requirements is monitoredand recorded by the internal quality management system to ISO 9001of each manufacturing plant. Quality supervision may also be carriedoutbynationalcertificationbodies,suchasMA39(Austria),AFNOR(France)BENOR(Belgium)andDINCERTCO(Germany).Batchtestcertificates for specific product supplier are provided upon request.2Properties of vitrified clayChemicalresistanceVitrifiedclaypipesandfittingstothespecificationofEN295areresistanttochemicalattackinapH-rangefrom0-14.Forspecialcircumstances or application, the chemical resistance may be deter-mined by the use of the test in clause 10 of EN 295-3.3Biological induced H2S-corrosionTheformationofH2Sinsewageisaconsequenceofthenaturalbiological decomposition of sulphur containing organic and inorganicmatter (proteins, sulphates). H2S mainly forms under anaerobic condi-tions by sulphate reducing bacteria (desulfovibrio desulfuricans) in theslimeofamaturedsewerandtoalesserextentbybacteriologicalprocessesinthesewage.IngravitysewerstheformationofH2Scommences after the oxygen originally present in the sewage has beenconsumedbymanifoldbiologicalprocesses.ThisisfollowedbytheanaerobicdecompositionwithaneverincreasingformationofH2S,whichslowlyescapesintotheseweratmosphere.Turbulenceinthesewage stream increases the escape of the gaseous H2S. The forma-tion of H2S is supported by long sewage flows, low flow velocities andhigh sewage temperatures.TheformationofH2SandtheoxidationintoH2SO bybacteria(e.g.thiobacillus thiooxidans) living on the moist surface of the sewer occursnot only in gravity sewers, but also and more severely in pressure pipelines, where, due to the absence of an atmosphere, continuously idealconditionsforthesulphatereducingbacteriaprevail.Thebiologicalinduced H2S-corrosion has its effects only above the surface level of thesewage stream, where the sulphuric acid reacts with the lime contentofcement-boundpipematerials.OnconcretepipeswhichcontainlimestoneastheaggregatetheeffectsofbiologicalH2S-corrosionshowlaterthanonthosehavingquartzisticaggregate.Ingeneralaprogression in corrosion of concrete sewers having a constant pres-ence of hydrogen sulphide in the sewer atmosphere can be expectedwith 3 - 6 mm/y. Vitrified clay pipes are immune to sulphuric acidSO4H S2H SO2 4H S2MechanicalresistanceThe mechanical resistance of vitrified clay has developed enormouslyduring the last decades. Nowadays, a vitrified clay pipe up till DN 600has the same mechanical strength as reinforced concrete pipes fromthe series 135. Normally, the installation is done on a sand bedding of90(EN295,chapter2.9).Ifthereisanydoubttothisrespect,Steinzeug|Keramoofferastaticcalculationestablishingthemosteconomic and reliable installation method, free of charge.Resistance to high-pressure cleaningThe requirement included in the ZPWN 295 standard is met (resistancewith regard to a standardized maintenance cleaning test at 120 bar anda deblocking test at 340 bar). Here again, vitrified clay scores consid-erably better than many other types of material.HydrauliccapacityVitrified clay pipes have and hold a smooth inner surface (wall rough-nessbetween0,02and0,05mm).Especiallyinthecaseoflimitedslopes, this offers quite some advantages. Because of the high erosionresistance, vitrified clay can even be used for slopes up to 10 m/sec.,withoutanydangerofmaterialdeterioration(forconcretee.g.themaximum slope is only 3 m/sec.). See also EN 295, chapter 2.16.4High abrasion resistanceVitrified clay has high abrasion resistance, which is equally true for theglaze and the rest of the wall. Abrasion values encountered in the testsareapproximately0,08mm,whichismuchlowerthanthetypicalabrasionvaluesof0,2mmto0,5mmafter100 000loadcyclesmeasured using the Darmstadt test as specified in the EN 295 standardor the maximum value of 0,25 mm in the ZPWN1 295 standard. Abrasiondoesnotaccelerateevenwithextendedloadcycles,suchasupto400 000,incontrasttowhatisoftensuggestedindatasheetsforcompetitive materials. The depth of abrasion remains limited to 0,3-0,8mm after 400 000 cycles. Compared with the large wall thicknesses ofvitrifiedclayjackingpipes,thatrepresentsanegligiblelossofwallthickness.1 ZPWN 295 is an internal manufacturer standard of STEINZEUG | KERAMOTemperatureresistanceVitrifiedclayhasalowheatexpansioncoefficient.Compensatingmeasures are superfluous. In case of sudden temperature shocks, itcan be necessary to take protective measures (such as a cold waterbuffer). In the latter case, or in any case of doubt, you should pleasecontact our technical advisor. See also EN 295, Part I, Chapters 3.8 and3.9.CorrosionresistanceVitrified clay material is resistant to all types of chemicals over the entirewall thickness. The resistance of the vitrified clay material and seals istested using chemicals, including sulphuric acid at pH 0 and NaOH atpH 14, in conformance with EN 295 and ZPWN 295.DurabilityThevitrifiedlifecycleiscalculatedtobe80upto100years(LAWAdirective A 250), even in the hardest conditions. Furthermore, vitrifiedclay is the only material that resists regular rinsing and unclogging bymeans of high water pressure techniques. This means that vitrified claypipecanalscanbewrittendownoveralongerperiodandthatmaintenance,renovationandreplacementcostscanbelimitedtoamuch lower level.EnvironmentalfriendlyTherawmaterialsformanufacturingvitrifiedclaypipeareclayandrecycled materials from the ceramic industry. Mining of the raw mate-rials and subsequent restoration of a natural environment take place inanenvironmentallyfriendlymanner.Inaddition,theenvironmentalimpact of manufacturing of vitrified clay is relatively small comparedwith most other types of sewer materials. The long service life of vitrifiedclay is an additional decisive factor in this regard. No polluting productsare generated at the end of the life cycle.5EconomicconsiderationThemanagementofdomesticandindustrialwastewatertransport,infrastructureandtreatmentismostoftenalocalgovernmentissue.Theauthorityisobligedtopayparticularattentiontotheeconomicaspects. These include the one-off cost for construction of the sewerline and the operation and maintenance cost (subsequent cost).The cost for construction of a sewer line is determined largely by thelocation and the type of construction. A line laid through a green fieldwill cost less than a sewer along a major street. In both cases, however,the cost of the pipe material is only a fraction of the entire cost of theproject.Theoperatingandmaintenancecostarethebasisofthechargeslevied for use of the sewer. These costs represent a constant expense.Thecalculationoftheanticipatedmagnitudeoftheseexpensesistherefore even more important than that of the construction cost. Theserunning costs include:- Capital expenditure - Depreciation- Maintenance - AdministrationItcanbeassumedthattheestimatedcostformaintenanceandadministration will be the same for all sewers. With regard to the capitalexpenditure (interest and amortization) and the rate of depreciation, adifferentcostmustbeanticipated,dependingonthepipematerial.Features such as resistance to corrosion and chemical attack, abra-sion, temperature, as well as their impermeability, sewers constructedfrom vitrified clay have an above-average life-span. The higher cost forinterest on the capital required to the purchase of vitrified clay pipes asthe chosen material as opposed to cheaper less permanent materialsis therefore more than compensated.Destruction and road re-building20%Soil excavation and sheeting49%Lowering groundwater level9%manholes11% Pipe material:Delivery, installationand embedment11%Economic viability Share of pipe material cost in pipe layingComposition of the municipal sewage chargesSteinzeug | Keramo Paalsteenstraat 36 3500 HasseltSource: DUDEY. J., PECHER R., ATV - Survey: Sewage ChargesService life6AssembliesTheseshallremainwatertightwhentestedatinternalorexternalpressures of 5 kPa (0,05 bar) and 50 kPa (0,5 bar).The joint under such internal or external pressure must not show anyvisible leakage when further be subjected to:Angular deflection: (after 5 mm draw)Nominal size Deflection per meter (DN) of deflected pipe length100 - 200 80 mm250 - 500 30 mm600 - 800 20 mm> 800 10 mmPipes and fittings of the same jointing system, of the same nominal sizeand the same pipe class are directly interchangeable.Uniformity of pipe class during installation is a prerequisite.Forallapplicationsitmustbeobserved,thatjointassembliesareguaranteed to withstand cyclic temperature changes of -10C to +70Cand chemical attacks from normal sewage and other harmful effluentsin concentrations from pH 0 (sulphuric acid) to pH 14 (caustic soda).1. Vitrified clay socket pipes for open trenchThe jointsIt is imperative that tight flexible joints are formed when individual pipesand fittings are assembled to form sewers. The pipe and joint are partof a unique system that together ensures easy assembly, reliability andlong service life. For this reasonsealing elements are factory installed. Joint L to jointing system F (EN 295) Joint K to jointing system C (EN 295) Joint S to jointing system C (EN 295)Jointing systemsC and F to EN 295StructuraldesignBuried pipe lines can be stressed by backfill and traffic loads. In specialapplications additional risk may result from temperature influences andinternalpressures.Instructions for the calculation of the load bearing capacity of sewershave been published by the Abwassertechnische Vereinigung ((ATV) -German Sewage Engineering Society) in ATV-A 127 (Worksheet 127).When carrying out the calculation, a basic distinction must be madebetween the two available types of pipes. Flexible pipes permit closeinteractions between load, deformation of the cross section and loaddistribution. The computation of the likely deformation risk is decisivein the choice of material suitability.Rigid pipes do not deform under load and interaction between defor-mation and stress distribution do not occur. The stress computation setagainst the permissible rupture stress is decisive for the suitability.Vitrified clay pipes are rigid pipes.Products7Calculatingthereservesforstressbearingtheidentificationofthefollowing details is essential: Type of soil, specific weight, angle of internal friction Traffic loads Superimposed loads (e.g. buildings) Designed slope of trench walls Type of trench shoring Trench width at pipe crown Depth of cover Pipe diameter, strength, etc.Theresultofthecomputationgivesthefactorofsafety.Ingeneralapplications a safety factor of 2,2 is required for vitrified clay pipes.Flexible manhole connectionsLayingLaying commences at the lowest point of the line. Make sure that socketand spigots are clean, apply the recommended lubricant to the sealingelement(s) and push the spigot fully home into the socket manually withthe aid of a crowbar and a wooden timber or mechanically with the aidof an approved assembly device.The type of bedding required is determined by a structural analysis. Onsupplying the necessary details (e.g. type of soil; trench design; loads;life loads; additional loads) we can perform such structural analysis withour recommendations for pipe bedding and pipe strength class free ofcharge.It is important to ensure that the soil around the base of the pipe is firm.Loose soil should be well compacted mechanically. Soft soil should beremoved and replaced by non-cohesive soil. The bed at the base of thetrench should be prepared in such a way that the pipe, when laid, issupported along the length of its barrel. Recesses should be formed toaccommodatethesockets.Inordertoavoidpointorlinearloadingvitrified clay pipes should not be laid on stony soil or directly on rock.Water test to EN 1610Thefollowingtablecontainsthevaluesforthepermissiblewateraddition (l/m) at an allowance of 0,15 l/m during the test period of 30minutes.DN Water addition DN Water addition100 0,05 l/m 400 0,19 l/m125 0,06 l/m 450 0,21 l/m150 0,07 l/m 500 0,24 l/m200 0,09 l/m 600 0,28 l/m250 0,12 l/m 700 0,33 l/m300 0,14 l/m 800 0,38 l/m350 0,17 l/m 1000 0,50 l/mTightness: testing with water (W) or air (L)Water test to EN 295When pipes or pipe sections are tested with water at ambient tempera-ture, the water addition W15to maintain the pressure of 0,5 bar shall notexceed 0,07 l/m of internal surface without leakage.Direction of flowDN Test period DN Test period100 3,0 min. 400 5,5 min.125 3,0 min. 450 6,0 min.150 3,0 min. 500 7,0 min.200 3,0 min. 600 8,0 min.250 3,5 min. 700 10,0 min.300 4,0 min. 800 11,0 min.350 5,0 min. 1000 14,0 min.Air Test to EN 1610The air test is a convenient alternative to the usual water test. Pipelinescan only be deemed faulty after the unsuccessful completion of awatertest.ForperforminganairtestonalinemadefromSteinzeug|Keramoproducts, we recommend the following procedure:- Applyapressureequivalentto100mbar(ensureadequatesafetymeasures are implemented)- Observe the period for the air test with an intitial pressure approxi-mately 10% in excess of the required test pressure of pO to settle 5min. for DN 500; DN/100 in min. for > DN 500- During the following test periods the air pressure must not drop morethan 15 mbar82. Vitrified clay jacking pipes for pipe jacking or micro-tunnelling2.1 Economical and ecological advantages Microtunnelling takes place beneath existing service lines. The safe-guarding or diversion of these is either minimal or unnecessary androad surfaces arent damaged. Ability to construct sewers without problems and in a cost-effectivemanner near buildings or historic areas since settlement of the soil isavoided and expensive trench sheeting is not required. Once jacked,thesewerisbeddedinidealcircumstancesandthankstotheimportant wall thickness, can take very high loads. Theamountofsoiltobeexcavated,transportedanddumpedisrestricted to the volume of the sewer line. There are important costadvantages in contaminated soils, in water-catchment areas, in soilswith a high water table and weak soils. Sincethegreaterpartoftheworkoflayingasewertakesplaceunderground and as the space required at ground level is small, lifeand commerce can go on virtually undisturbed.Pipe-jackingresultsinsignificantlylowerlostsalesformerchantsthan the open-trench method of pipe laying, which impairs or pre-vents access to their businesses. Noise, dirt and smell are minimized.The jacking doesnt depend on weather conditions. As a rule traffic can continue to flow when microtunnelling is beingemployed since the site facilities in the region of the start shaft can bekeptcompactandtargetandintermediateshaftscanbecoveredafterconstruction.Majortrafficreroutingduetoopen-trenchcon-structioncausessignificantamountsoftimetobelostduetodetoured traffic and time spent on the detour route. That is accom-paniedbyhighadditionalcostsintermsofworkhours,fuel,roadsurface wear, environmental damage, accidents, and material dam-age to vehicles.92.2 Additional propertiesHigh longitudinal resistanceVitrified clay jacking pipes generally have greater wall thicknesses thancorresponding standard vitrified clay sewer pipes. That results in highcrown pressure ratings and high resistance to ground and traffic loads.Strength in the length direction is the most important factor for jackingpipes, because they must withstand the high jacking forces necessaryto overcome the resistance of the cutting face and the external pipesurface. According to the EN 295 standard, the longitudinal compressivestrength of the surfaces that transfer the force between pipe sectionsmust be at least 75 N/mm. Steinzeug | Keramo guarantees a value ofat least 100 N/mm. That is higher than the values stated for other typesof current jacking material. It allows very high jacking forces to be used,although this capability is only partially utilized in practice. The glazedouter surface of the pipe strongly reduces friction between the pipe andthe surrounding soil.Long service lifeAfterbeingproperlyinstalled,vitrifiedclaypiperequiresverylittlemaintenance. As vitrified clay scores very high with respect to all therequirements that must be imposed on sewer pipes, vitrified clay pipesattainverylongservicelives.Theimportantpropertiesmentionedabovedonotdegradeovertime.Thatsespeciallytrueforjackingpipes, because they are structurally overdesigned for their subsequentuse and optimally bedded in the ground.Jacking under railwaysSteinzeug | Keramo jacking pipes are manufactured and inspected inaccordancewithinternalandexternalcontrolprocedures.Theyaredescribed in the EN 295 standard and the ZPWN 295 standard, whichcontainsanumberofmoresevererequirements.Certificatesofap-proval for jacking under railway lines are also available for these vitrifiedclaypipes.TheyconfirmthatthepipesmeettherequirementsoforganizationssuchastheDeutscheBundesbahn(GermanFederalRailways), and the certification process include cyclic tests to demon-strate resistance to fatigue phenomena in the presence of alternatingloads. Microtunnelling will not harm existing vegetation. Roots in the line ofthe sewer are only cut away in the region of the cross-section of thecutterhead.Inadditionmeasurestolowerthelevelofthegroundwater are not needed provided suitable construction techniques areemployed. In groundwater collection areas and soils with subsidencerisks, pipe-jacking provides additional benefits.10The couplingsDN150: GRP CouplingThe coupling consists of glass-fibre reinforced polypropylene. Vitrifiedclay DN 150 jacking pipes can be connected to Steinzeug | Keramostandardpipesdirectlywiththejackingcouplingorviathemetalbanded M couplings (spigot-spigot).d1 dMdkd3e bl1Direction of jackingkd1dMdKd3e bKl1Direction of jackingDzpacking ring in rubber elastomer for DN 200 to 300, in particle board for DN 400 to 500Skd1dMdk d3e bkl1Direction of jackingProfiled ringskParticle boardDzDN200-500: stainless steel coupling type 1Thecouplingforpipesinthesediametersconsistsofacontouredstainless steel ring, V4A type EN 1.4571, with an integrated mouldedrubberseal.Theringhasahighchromeandnickelcontentandarelativelysignificantmolybdenumcontent.Thepackingring,whichtransmitsthejackingforce,isintegratedandformsaunitwiththemoulded sealing ring. For diameters up to DN 300 the packing ring ismade from rubber elastomer and for DN 400 - DN 500 from fibreboard.The sealing rubber contours not only guarantee tightness, but ensurefullprotectionfromtheingressofsoilandgroundwaterduringthejacking.DN600- 1200: stainless steel coupling type 2 and pre-stressing ringSteinzeug | Keramo jacking pipes DN 600 - DN 1200 are delivered witha stainless steel (V4A type EN 1.4571) coupling with a high chrome andnickelcontentandarelativelysignificantmolybdenumcontent.Thepackingringfortransferringthejackingforceismadefromparticleboard and is prefitted to the coupling. A pre-stressing ring is fitted ateachspigotend.Theseringsprovideadditionalprotectionduringtransport and in case of relatively poorly controlled steering motionsduringjacking.Atthesametime,thishasincreasedthepermissiblejacking forces.11AssembliesTheseshallremainwatertightwhentestedatinternalorexternalpressures of 5 kPa (0,05 bar) and 50 kPa (0,5 bar). The joint under suchinternal or external pressure must not show any visible leakage whenfurther be subjected to:Angular deflection (after 5 mm draw)The joints are tested in accordance with EN 295, which means that theyareguaranteedtobeleak-tightat0.5bar,includingtheangulardeflectionsandradialloadsspecifiedinthestandard.Theyarealsotested in accordance with ZPWN 295(1) and ATV A142, with guaran-teedleak-tightnessat2.4bar.Leak-tightnessisalsotestedatanexternalpressureof6bar,whichprovidesahighlevelofsecurityagainst penetration of soil slurries and bentonite.Nominal size Deflection per meter (DN) of deflected pipe length DN 800 20> DN 800 10StructuraldesignSteinzeug | Keramo advises on the loads and stresses that occur duringand after pipe installation by jacking. Specific advice is given as to thepipecapabilityregardingallfactors.Thecalculationsaredoneinaccordance with the ATV guideline A161.Precisely what stresses will in fact be inflicted relies on the expertise ofthe contractor. These stresses can depend on the soil type, and also ona series of additional factors that determine the friction on the boringshield and on the pipe body.When jacking the results of the static calculations must be respected.Additional guidelines for the correct execution of jacking work can befound in:-the European standard EN 12889 with the criteria for pre-investiga-tions,designandexecution,andadescriptionofteststobecon-ducted after insertion,-guidelines from the administration granting the commission,-instructions from the designer or the engineering consultancy,-manuals and recommendations from the manufacturer.TrenchlessconstructionDifferentmethodscanbeusedfortheconstructionofundergroundsewers.Steinzeug|Keramopublishesabrochurewiththeprincipalcharacteristics and dimensions of the various types of jacking pipes invitrified clay. This free brochure is available on request. We also offer achecklist in order to make sure that you will not forget anything.02-008-0308Keramo Steinzeug N.V.Paalsteenstraat 36 . B-3500 HasseltTelephone +32 11 21 02 32Telefax +32 11 21 09 44E-Mail:info@keramo-steinzeug.beInternet:www.steinzeug-keramo.comSTEINZEUGAbwassersystemeGmbHAlfred-Nobel-Str. 17 . D-50226 FrechenTelephone +49 22 34 5 07-0Telefax +49 22 34 5 07-2 07E-Mail:info@steinzeug.comInternet:www.steinzeug-keramo.com