Leap in quality for TRM cast-iron pipes thanks to innovative coating technology

Autor: Roland Gruber , 14.10.2019

Tiroler Rohre GmbH, which is a traditional manufacturer of ductile cast-iron pipes from Tyrol, consistently relies on innovation and further development. Over a period of two years, ...

... the TRM research department worked alongside an Austrian ­cement manufacturer to produce a new type of fibre cement mortar for the outside coating of the pipes. Since the autumn of last year, two machines have been set up at the plant in Hall to enable the pipes to be wrapped with the new type of fibre ­cement mortar in an almost fully automatic fashion. The first pipes coated in this way are now being produced. Thanks to the new type of outer sheath, the pipe system offers not only a maximum level of chemical and mechanical protection, but also offers tangible economic benefits.

The fact that Tiroler Rohre GmbH has been able to maintain its high level of quality for more than 70 years is down not least to its consistent drive to champion innovation. In the past, the engineers at this traditional company have constantly managed to develop “their” product further and deliver new innovations to the market. Courage and a willingness to innovate have made TRM’s ductile cast-iron pipe what it is today: a pipe system that sets the benchmark when it comes to resilience, durability and economic efficiency. The most recent product of in-house development work is called “ZMU-Austria”: It represents a self-developed cement mortar coating which is applied to the pipe using an extrusion method. “We devoted around two years of development work to this project, which was only possible thanks to the excellent cooperation with our long-standing cement technology partner. The objective here was to develop a cement mortar which on the one hand offers a maximum level of outer protection for the pipe and on the other hand is easy to apply in production. We managed to do this,” says engineer Christian Auer, Head of Quality Management at Tiroler Rohre GmbH, with great satisfaction.

ADHESION WITHOUT GLUE
Another challenge in developing the new cement mortar was to create the perfect adhesive strength for the material on the cast-iron pipe. “It was very important for us to make the cement capable of adhering without using any adhesion promoters at all. First of all, an adhesive means the additional use of a chemical substance, and second the application of the adhesive in production means an additional stage in the process, and third it was also key to avoid excessive adhesion on the pipe because it also needs to be capable of being cut at the construction site and it must also be possible for the coating to be stripped away,” explains Christian Auer, referring to the specific roughness of the zinc surface on the pipes which is applied beforehand and which fundamentally provides a good foundation for the adhesion of the cement. The fact that the new pipes with the ZMU-Austria coating are produced without any adhesion promoter at all has so far proved to be a unique selling point in the market. In production, the special cement mortar is extruded onto the pipe via a mesh bandage and smoothed at the same time. This production step is performed automatically. For this purpose, special machines were purchased last autumn and, in close collaboration between TRM and the Austrian machine manufacturer, they were adapted to suit the requirements of the production process. “Once we have eradicated the initial ‘teething problems’, production will be able to commence in the coming days,” says Christian Auer.

COMPLEX STRUCTURE – SOLID PROTECTION
If you look at the structure of the ductile cast-iron pipe with the new ZMU-Austria, you can talk about three layers surrounding the pipe. It is clad on the inside with a cementation comprising Portland, blast-furnace, alumina or plastic-modified cement. On the outside, the first layer comprises a fine zinc coating in a thickness of 200 g/m². The outermost protective layer is then the novel fibre cement coating, which is 5 mm thick. The spigot end and socket remain free of cement mortar and are instead provided with the tried-and-tested PUR or epoxy coating. “For the connection areas, we recommend using special rubber or shrink-on collars for fitting so that the whole pipeline boasts optimum protection,” explains Christof Mairinger, BA, MBA, marketing manager at TRM. It is obvious that theydid not want to limit one of the great strengths of the ductile cast-iron pipe – namely its flexibility – as a result of the cement coating. Depending on their diameter, the pipes still have a flexible ductility of 3 to 5 per cent even in the ZMU-Austria version.

CHEMICAL RESISTANCE
Another important property that is key for the new fibre cement mortar is its chemical resistance. Specifically, it involves a high alkaline composition which prevents any corrosion beyond a pH of 10. “The fibre cement mortar which we have developed also demonstrates very high sulphate resistance. This means that the new pipe system offers maximum protection in highly aggressive, contaminated and sulphate-containing soils,” explains Christof Mairinger. Thanks to its harmless electrochemical properties, the ZMU-Austria pipe can also be used within the sphere of stray currents. The marketing manager also points out a special property on the outermost surface of the cement shell: “As a result of the carbonation on contact with the surrounding environment, the cement hardens further on the surface and forms a sealed, resistant and water-repellent layer.”

MECHANICAL PROTECTION
But the pipe’s most obvious attribute is its mechanical protection. The 5 mm thick fibre cement mortar layer ensures that the pipe is not damaged during storage, transportation and of course also when being installed. The latter also plays a particular role when the pipe is installed without a trench as ultimately large loads occur on the pipe as it is being pulled into place. The ZMU surface protects against any damage.
The multi-talented ZMU-Austria product is just made for use in alpine and high alpine terrain. Thanks to the great mechanical robustness, almost any excavated material can be used for backfilling, with rock inlays up to 100 mm in size being permitted. Christof Mairinger says: “The benefit of being able to use this pipe ideally in alpine terrain is down to the fact that no additional bedding or backfill material is required. In addition, there are also no costs for disposing of the excavated material that is produced because it can be reused. The economic benefit is obvious. But in this context the ecological benefit should also not go unmentioned: The repatriation of the original excavated material preserves the natural structure of the soil at the site. This is a point which repeatedly comes up with questions relevant to the environment.” Its outstanding suitability for use in alpine pipeline construction makes the ZMU-Austria the pipe of choice when it comes to penstocks for hydropower plants, but also for artificial snow-making facilities.

URBAN APPLICATIONS
However, the extreme resilience and the high level of durability are not only regarded as noticeably desirable benefits when constructing pipelines in alpine territory. “There is one thing you should bear in mind here: It is of course relevant whether clearances are required in a forested area when the pipeline needs to be replaced after just 20 years or maybe not until as many as 100 years have elapsed. However, the question is an even more delicate one in heavily developed urban areas. You just have to envision the fact that simple plastic pipes in urban areas frequently need to be replaced after fewer than 20 years – with all the consequences this entails for traffic and the whole infrastructure. This is why the durability provided by the TRM pipe also plays an important role in this area,” argues Christof Mairinger. In urban areas, another very sensible possible application for the new pipes might present itself in the near future: Under the specialist term “sponge city”, design engineer Christoph Bennerscheidt, Managing Director of the European Association for Ductile Iron Pipe Systems, has developed a solution model for cooling in increasingly hotter urban centres. “To cool the city centres of the future in a natural way, the desire is increasingly to rely on green areas where trees will be planted. The roots of the trees need to be provided with sufficient space in a coarse-grained substrate so that the areas can absorb increasing amounts of water, which incidentally will also deliver beneficial effects in coping with the increasingly heavier rainfall events that are occurring. The only drainage pipes that can be used here are of course those that are 100 per cent root-resistant – such as our new ZMU-Austria pipe,” says engineer Carina Kirchmair from TRM’s applications engineering department. A pilot project of this type is set to be launched very soon in a major city in Austria.

ECOLOGICAL FOOTPRINT IMPROVED
With all innovations at TRM, the questions of sustainability and the ecological footprint play a leading role. According to the marketing manager, this is a central concern of the management. It is no wonder then that the new ZMU-Austria pipe also sets the benchmark in this regard. “For our ductile cast-iron pipes, we generally only ever used recycled material that we obtain from the immediate vicinity. Another factor is that, thanks to our photovoltaic installation with a collector surface area of 9,000 m², the largest roof-top installation in Tyrol, we use the energy that is generated ourselves and thus make a substantial contribution to conserving the environment. In addition, any by-products that are produced are utilised: The best example of this is our waste heat, which is fed into the Hall district heating system. The ecological footprint of the ZMU pipe has of course been significantly minimised by the fact that the pipe no longer needs to be delivered to an external source for the coating to be applied. This is now all done by us at the factory.”

SOLUTIONS TO PRACTICAL QUESTIONS
This enables the traditional company to respond with even greater speed and flexibility to customer enquiries. Although TRM has a very well-stocked warehouse, in practice it is very often necessary to deal with special requests quickly. “The two new coating facilities enable us to wrap the pipes in their coating within a few days. In theory, we can also recoat pipes that have already been coated on request,” explains Christian Auer. Christof Mairinger refers in this context to the great importance of the in-house applications engineering department, which repeatedly responds to practical requests and thus promotes the further development of the product. “Our great strength is our close links with the customer. Our sales representatives are engineers who can support the customer with advice and practical assistance. Their feedback frequently provides vital inspiration for developing the pipes further. Our research department is therefore also consistently supported by the management in its drive for innovation.”

ALL DIMENSIONS AVAILABLE
The most recent result of this research and development work is thus the new type of ZMU-Austria pipe which, thanks to its resilience, is suitable for use in both pressurised and unpressurised areas. All the relevant certificates and approvals are also provided. “We did not invent the ZMU pipe, but we have almost perfected it,” reckons Christof Mairinger with a degree of pride. Today the factory in Hall has two coating facilities, one for the dimensions DN300 – DN1000 and another for DN80 – DN600. By the middle of this year, all sizes of pipe within this range will be available with ZMU-Austria. What is also new is the improvement in traceability and process data recording. Today every single pipe that leaves the factory in Hall boasts its own QR code which enables it to be identified automatically. This ensures seamless documentation and traceability that provides information about when and in which series the pipe was produced. The ZMU-Austria pipe from Tiroler Rohre GmbH represents another milestone in the technical development of the cast-iron pipe in Austria.

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In the case of installation without a trench, it is advisable to use a special sheet-metal cone to provide additional protection for the couplings.

photo credits: TRM

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ZMU-Austria pipes can of course be secured just as easily using the tried-and-tested locking segments. The spigot end and coupling area remain free of the cement sheath.

photo credits: TRM

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Together with a partner from the Austrian cement industry, TRM has developed an innovative fibre cement coating. The Tyrolean company is thus once again setting the standard when it comes to resilience and durability.

photo credits: TRM

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The roughness on the galvanised outer surface means that the new type of cement adheres very well to the pipe.

photo credits: TRM

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The fibre cement sheath is applied in a thickness of 5 mm fully automatically using an extrusion method.

photo credits: TRM

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Two winding machines, which were adapted in recent weeks so that they are best suited to the production processes, are capable of coating pipes from DN80 to DN1000.

photo credits: TRM

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For the application of the TRM tapping clamp, the cement mortar layer is partially removed.

photo credits: TRM

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After it has been cut, the cement mortar layer can simply be removed with a hammer and a chisel.

photo credits: TRM

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The high mechanical load capacity means that no special bedding material is required, and the excavated material can generally be used as backfill.

photo credits: TRM