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Christian Weinberger, Schlüsselbauer Technology GmbH & Co KG,

Austria

As part of this long term-oriented, strategicplanning, it was decided to commencemanufacture of concrete pipes at the com-pany Amiantit domiciled in the Sultanate ofOman in addition to the already estab-lished pipe construction products after theban on asbestos fibre cement pipes.Concrete pressure pipes will be manufac-tured first and foremost, in addition to con-ventional concrete pre-cast componentssuch as reinforced concrete pipes and box- culverts. Compared to steel pipes, forexample, concrete pressure pipes are char-acterised by reduced material costs withsimultaneously higher corrosion resistance.In addition, tight joints are simpler to attainwith concrete pressure pipes. With theanalysis and determination of the productconcept and the specification of the neces-sary manufacturing technology an interna-

tional team of advisors was commissionedunder the leadership of Mr. John Munro,owner of Munro Ltd. headquartered inOntario, Canada. Established productsand available procedures were examinedon a global scale in order to ultimately beable to make a certain awarding decision.After the recommendation for selection ofequipping companies which would facili-tate the most cost-effective manufacture inaccordance with the specific requirements,the experts at Munro are continuing toassist the manufacturer in the commission-ing of the extensive manufacturing technol-ogy and the commencement of production.

The segment of concrete pre-cast compo-nent manufacture is new for the manufac-turer. To date, they have longstanding expe-rience with the materials PVC, PE and GRPand the now prohibited asbestos fibrecement pipes. In the newly established com-pany Amiantit Oman Concrete ProductsLLC concrete pipes are now produced for

Start of manufacture of PCCPs (Pre-stressed Concrete Cylinder Pipes) for long-term water supplies in the Gulf of Oman

Schluesselbauer Technology GmbH&CoKG, 4673 Gaspoltshofen, Austria

Future-oriented water management is one of the most strategically significant economic issues in the Gulf state of Oman. It includes, on theone hand, the creation of infrastructure for overcoming a few concentrated intense rain events. The growing requirements with regard to thedaily mobility of people and commodities do not permit public life to come to a standstill several times a year as a result of heavy rainfall.On the other hand, in a country which is extremely exposed to the elements with growing conurbations such as Oman, providing reliabledrinking water supplies constitutes a financially, technically and also politically demanding task. The cost-effectiveness of concrete pressurepipes for drinking water transportation compared, for example, to steel or cast-iron pipes was crucial for making an investment in the com-pletely new manufacture of concrete pressure pipes prepared in an exemplary manner, as well as a legislative act. In addition to conven-tional concrete pipes for surface water management, concrete pressure pipes will now also be manufactured in a new factory with an oper-ating pressure of up to 25 bar for future drinking water projects.

Amiantit Oman, founded in 1974, is one of the largest manufacturing companies of the Gulf state.

In addition to concrete pressure pipes, reinforcedconcrete pipes of nominal widths DN300 toDN1800 and concrete jacking pipes are manufactured.

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gravity sewers in a first stage in the nominalwidths DN 300 to DN 1800 and box - cul-verts of 2000 x 1500 mm to 2500 x 2500mm. The box - culverts and the large DN1200 to DN 1800 mm pipes are manufac-tured on a Schluesselbauer Exact XL verti-cal dry casting machine, the smaller pipedimensions are manufactured on a packer-head machine. This subdivision into twomanufacturing processes is justified by thefact that this machine type was needed forthe inner lining of steel cylinders for the pro-duction of concrete pressure pipes – thesubsequently described second stage in the

set-up of concrete pipe manufacture. In thepast, related manufacturing procedureswere analysed to develop a concept for themanufacture of concrete pressure pipes.The multitude of methods such as one-, two-or three-layer manufacturing procedures,

ring and/or longitudinal pre-stressing, steelpipe connections with a rolling or slidingrubber connection and the resulting differ-ent product characteristics led to the deci-sionmakers establishing a team of advisorsunder the coordination of a successful man-

For the manufacture of the sheet steel core used for the impermeabili-ty of the concrete pressure pipe, a cylinder is automatically weldedand cut to length and tested according to the pipe construction length.

The sheet steel cylinder is automatically placed on a joint and concreted after the equipping of the mould for the manufacture of the internal lining of earth-moist concrete.

The steel wire required for pre-stressing is alsobrought to the plant in coils where it is pro ces - sed with a wrapping speed of up to 6 m/s.

The pre-stressing machine developed by Schluesselbauer works at a wrapping speed of up to 6 m/s.

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ufacturer of concrete pressure pipes. Afterclarification of pipe construction require-ments in the Sultanate of Oman and com-parison with available manufacturing meth-ods, a two-layer concreted pipe with asheet steel core and ring pre-stressing rein-forcement to be provided with an outer pro-tective layer created from shot - crete wasselected. The pressure pipes will be manu-factured in the nominal diameters DN 600,800, 1000, 1200 and 1400mm in accor-dance with the AWWA C301 and C303standards.

The machines for the manufacture of thesteel cylinders, steel end rings and the wirepre-stressing needed to be designed withappropriate flexibility. And the entire han-dling also needed to be conceived in anappropriately flexible manner in order to

be able to execute all critical manipulationtasks in a fully automated manner and withthe least expense for conversion works.

Concrete pressure pipes have proven them-selves in their use in drinking water pipesfor decades. An inspection of a pressurepipe test stretch in Baden-Württemberg,Germany with a total of four different typesof DN600 concrete pressure pipes at apressure of 10 bar showed that the pipeswere in an impeccable state after continu-ous operation over several decades. Thistest stretch was constructed in 1954 to1956 in a geodetically highly stressed sec-tion of piping in order to acquire insights forthe subsequent construction of a long-dis-tance water pipeline. Over half a centurylater this pipe would now be utilised forenergy generation due to its gradient and

the pressure would be increased to up to13 bar. Four types of pressure pipe avail-able at the time were originally installed.Three of the pipes affected by the intendedchange in use were tested at a test pressureof 14 bar. After the first positive insight thatthe pipes were still in a very good opera-tional state came the second positiveinsight. The tested pipes also easily with-stood the increased pressure. Due to theseinsights, it can also easily be stated in rela-tion to the concrete pressure pipe principlein the 21st century too to thus create struc-tures with a lifespan of over hundred years.

It is primarily the manufacturing technologyof the concrete pressure pipe principlewhich has changed fundamentally since thepreviously described project. Individualworking steps were modernised, the entire

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In accordance with the necessary operating pressure of the concrete pressure pipes, wire thickness, pre-stressing and the pitch of the wrapping are determined.

In the final manufacturing step, an externalprotective layer is applied to the pipe withspun concrete.

Concrete pressure pipes can be manufactured with different joinings.In the specific project, joints and spigot ends are moulded with steelend rings.

The high degree of automation of the entire plant makes a consider-able contribution to the protection of workers and products. Thus, cycle times can be optimised and the reject rate minimised.

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production process intensely automatedand individual pipe components can nowbe manufactured and processed morequickly and precisely. The integration of thepre-stressing in particular frequently consti-tuted a bottleneck process in series manu-facture in the past. With a processing speedof 6 m/s the pre-stressed wire is now inte-grated so rapidly with state-of-the-art tech-nology that upstream and downstreamprocesses are no longer delayed as aresult. However, the basic concept of pres-sure pipe manufacture has remained almostthe same and encompasses three funda-mental areas: steel cylinder manufacture,wire pre-stressing and coating in concrete.Added to this in modern concrete pressurepipe manufacture is the manipulation orhandling of individual components, semi-fin-ished components and finally the end prod-uct.

In steel cylinder manufacture, solid steelend rings which will subsequently form thejoints of the finished pipes must be manu-factured on the one hand. Hot rolled steelprofiles are bent into rings, welded andstretched for this purpose. The steel cylin-ders of the pipes are welded from sheetsteel in different wall thicknesses by a fullyautomatic helicoidal welding machinedependent on the operating pressure of thepipes.

At Amiantit Oman Concrete Products LLCsheet steel of the wall thicknesses 1.5 to 6.5mm can be processed to approximately 6m long cylinders. The maximum weight ofthe steel coil to be processed is 20 t. After

being cut to length, the steel end rings arewelded onto the steel cylinders. The imper-meability of all steel cylinders is then testedcompletely. A water pressure test takingplace over a period of several minutes at atest pressure of 4 bar recognises the slight-est leakages which can be repaired if nec-essary in a user-friendly manner directly atthe testing facility. In contrast to oldmachines, it is no longer necessary toremove the steel cylinders from the test sta-tion. After the quality test has been success-fully completed, the cylinder is ready forinternal lining with concrete.

The concrete encasement of pressure pipescan be conceived in just as diverse a man-ner as the types of concrete pressure pipes.Either earth-moist concrete or cast concretecan be used for the simple concrete liningof Lined Cylinder Pipes (LCP). For multipleconcrete coating - internally and externally– such as necessary for EmbeddedCylinder Pipes (ECP) – both concreteencasement procedures can be combinedor the entire pipe is manufactured with castconcrete.

An external protective layer, known as coat-ing, is typically applied with shot - crete. Inspecific cases, it was initially decided dueto the required pipe nominal widths and thedesired greater productivity only to manu-facture Lined Cylinder Pipes and to useearth-moist concrete for the internal liningof the steel cylinders. After the hardening ofthe internal lining in curing chambers theconcrete steel cylinders are ready for appli-cation of the pre-stressed winding wire.

A high-speed pre-stressing machine asthe core element of efficient concretepressure pipe manufacture

A wire pre-stressing machine developed bySchluesselbauer, the technology partner ofAmiantit Oman Concrete Products LLC, nowprovides the concrete steel cylinders withwire radial pre-stressing externally, after acement-water based primer has beenapplied to the cylinder. The pre-stressingforce possible for this type of machine ismore than double the pre-stressing force of20 kN currently required in this factory. Forthe manufacturer this means flexibility incase projects with increased requirementsare operated in future. Furthermore,increased requirements can also be fulfilledby multiple wrapping with prestressingwire. However, this pre-stressing machine ispredominantly characterised by its process-ing speed. Up to 6 m of pre-stressing wire iswrapped on the concrete lined steel cylin-der per second in a defined pitch.

In addition to these three core elements ofconcrete pressure pipe manufacture, thisnew factory is predominantly characterisedby its high degree of process automation.There is not currently an acute shortage ofworkforce on site. In the efficient manufac-ture of concrete pressure pipes in particular,the use of manual activities must bereduced to those areas in which, on the onehand, people are guaranteed not to beplaced in danger and in which, on theother hand, even the high-quality productscannot be impaired by human error. A riskfactor for workers compared to convention-

Steel cylinders lined with concrete generallyharden in kilns in one day. Completion thenfollows with application of the pre-tensionedwire and the external coating.

A range of fully automated manipulators move the semi-finished concrete pressure pipesthrough the production plant. The picture illustrates an insight into the concrete lining of theconcrete pressure pipe.

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al manufacturing companies results fromthe dimensions and masses which aremoved here. Even the semi-finished compo-nents such as steel cylinders or concretesteel cylinders demonstrate considerablemasses and in this case a constructionlength of approximately 6 m which canonly be safely manoeuvred by machines.Intelligent automation must contribute hereto the fact that industrial safety is not calledinto question in any phase by partially orfully automated handling and damage tothe product is prevented.

The main risk factor for the material is thehuman being. With every working step, thevalue of the pipe workpiece increases untilit is ready for installation. Schluesselbauerhas taken fully into consideration therequirements of the manufacturer in thisregard with an intelligent configuration ofindividual processes and a series of auto-matic handling systems. The indoor over-head crane is used with special load liftingmembers for handling the raw materialsand steel cylinders. The worker still has highlevels of autonomy here. The equipping ofthe mould for the lining of the steel cylinderswith concrete, the offbear of the mould andthe placement of the lined steel cylinderinto and removal from storage in the curingchambers are also performed with theremote controlled overhead crane. In orderthat the subsequent working steps are alsofully automated and human error can bealmost completely eliminated, a number offully automated manipulators have beeninstalled. They place the lined steel cylin-ders in the correct position for wrappingwith prestressing wire, move the semi-fin-ished pipe on to external coating – andthen to handover to the Transexact roboticcrane. This transports the completed con-crete pressure pipe to the final curing cham-bers and then to the transfer belt for dis-patch to the external storage area.Furthermore, the automatic crane closes andopens the covers of the curing chambers.

In addition to the technology partnerSchluesselbauer which, as well as the com-plete handling equipment, was also respon-sible for the helicoidal welding machine forthe steel cylinder manufacture and testing,for the pre-stressed wire wrapping and thecoating and for the production plant for themanufacture of large pipes and box cul-verts, a series of further reputable plantmanufacturers were involved in this project.Thus, for example, Putzmeister supplied aconcrete pump for the production of indi-vidual custom built wetcast precast struc-tures or components produced in seriessuch as road barriers. The machines for the

manufacture of the cage reinforcement forconventional concrete pipes were commis-sioned at MBK Maschinenbau and theentire concrete batching and conveyingtechnology was supplied by Skako. In addi-tion to the bucket conveyors, a total of threemixers each with a volume of 2.5 m³ werecommissioned which supply the entire con-crete required at all production machines.For the optimum utilisation of the spaciousmanufacturing halls, Demag installed aseries of indoor overhead cranes with liftingcapacities from 5 to 50 t.

A summary could give the impression thatthe high degree of automation in producthandling was solely based on the outlinedsafety aspects and not on cost pressure,especially with regard to staffing. In thisregard it must be specified that a staff short-age is not anticipated in the foreseeablefuture, first and foremost due to the highnumber of available migrant workers inOman. Such manufacture would be undercost pressure nevertheless if damage con-stantly arose to semi-finished products orend products due to manual interventionsand human error. A rejected pipe woulddestroy an irrevocable income stream andwould also incur costs for professionalreprocessing. Sufficient attention was alsopaid to this aspect in this automation con-cept. The result is a production facility forlined concrete pressure pipes which is glo b-ally unique in the implemented form and inits efficiency.

Amiantit Oman was founded in 1974 andnow numbers among the largest manufac-turing companies of the country with abroad range of products. Amiantit Omanemploys approximately 90 staff, roughly80 of whom work at Amiantit OmanConcrete Products LLC. The company harksback to a joint venture of the largest indus-trial groups in the Sultanate of Oman, theOmzest group, the Suhail Bahwan Groupand the Saud Bahwan Group. Over 75companies are integrated into the OmzestGroup currently in full or part possession,approximately two thirds of the turnover isgenerated in manufacturing companies.The Suhail Bahwan Group comprises morethan 40 companies and in the SaudBahwan Group among others products ofnumerous reputable vehicle manufacturerssuch as Ford, Toyota or MAN are market-ed. In addition to the Amiantit Oman pro -duct range, which is primarily focused onthe construction sector, the most diverse ofservices can be found in the group of com-panies as a whole. Consequently, almostthe entire population of the country is inte-grated into the value-added process. �

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FURTHER INFORMATION

SCHLÜSSELBAUER TECHNOLOGY GmbH & Co KGHörbach 44673 Gaspoltshofen, AustriaT +43 7735 7144 0F +43 7735 7144 56sbm@sbm.atwww.sbm.atwww.perfectsystem.eu

The Schluesselbauer Transexact automaticcrane transports the finished products intothe hardening chambers and then to thedelivery conveyor belt. It also operates thechamber covers.

ENGL

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