Over the past 15 years, Direct Pipe technology has steadily established itself in the world of piping.In its early days, it was used to safely cross rivers.As the technique has developed and its popularity has grown with customers and contractors, the range of applications for Direct Pipe has been steadily expanding in recent years.Today, with a track record of over 165 successful crossovers and 90 kilometers of pipeline installed, Direct Pipe is increasingly being used for submarine outfalls.The following article presents an overview of the Direct Pipe process, some of its general advantages, as well as some lesser known ones, and recent advances such as Direct Pipe's small diameter and hard rock capabilities.Main advantages of Direct PipeIn the context of climate change, sustainability becomes the focus of planners, operators and contractors.This not only affects the pipeline industry, but also power grid companies, which face the same challenges on their power grid tracks.A recent study for a possible pipeline project, including a land crossing and an underwater outfall each 1,000 meters long, has analyzed the environmental impact of Direct Pipe.Almost all the environmental aspects compared in the study show that Direct Pipe is positioned ahead of horizontal directional drilling (HDD).The range of environmental aspects analyzed includes fuel consumption and emissions, water and bentonite consumption, withdrawal of drilling fluids and excavation materials, footprint of the work and discharge of fluids at the outlet to the marine environment.CO2 emissions are worth mentioning, motivated by relatively low energy requirements and, as a consequence, also fuel consumption.Considering installed power for equipment, Direct Pipe showed in analysis that it only required half the resources of a horizontal directional drilling (HDD).Based on a number of equally applied assumptions and simplifications, the results showed that Direct Pipe fuel consumption was reduced by approximately 50%.Since CO2 emissions are directly related to fuel consumption (burning 1 liter of diesel produces around 2.65 kg of CO2), the CO2 footprint for Direct Pipe was at least half that of the of an HDD (for platforms powered by diesel engines).In addition, the sound pressure level (SPL) of Direct Pipe was 40-45% lower compared to diesel HDD, while the sound power level (SWL) was 70-80% lower.In terms of 'noise', understood as the sensations perceived by the human ear, HDD would have a perception of 1.3-1.5 times higher than Direct Pipe.Also, noise emissions at the outlet end are practically non-existent, since hardly any operation is needed at the outlet end of Direct Pipe, except to recover the MTBM.Other aspects, such as the discharge of drilling fluids into the ocean (at the outlet or during drilling work) are almost nil in the case of Direct Pipe.For outfalls, drilling fluid discharge at the outlet was reduced by 90-97% compared to HDD.Every pipe that goes through the water sooner or later will sink.However, in recent years the number of submarine outfalls has increased due to the growing need for energy supply of the population.More and more water desalination plants and offshore wind plants are appearing all over the world.Similarly, awareness of sustainability and the environment is also increasing.Traditional installation techniques such as dredging, trenching, or directional drilling are becoming less attractive for well-known reasons.Public opinion and pressure on project owners are pushing stakeholders to consider low-impact alternatives.Direct Pipe adds an innovative variant to the range of trenchless technologies available for shore approaches.Export cables for the Beatrice offshore wind farm, ScotlandThe first approach to shore took place in 2017 in Scotland, where the Beatrice Offshore Wind Farm was connected to the onshore substation.With Direct Pipe, even in North Sea weather conditions, two 48” inshore cable ducts with a length of 440 m could be installed.The main reason Direct Pipe was chosen was to reduce the impact on the protected flora and fauna in the coastal zone, as well as the requirements of the wind farm operators to install the cables with as little coating as possible, so that ensures efficient heat transfer to seawater.After each run, the MTBM was recovered from the seabed in one piece.With the help of a remote controlled disconnection and retrieval module, it was separated from the pipe.The MTBM was properly sealed to protect it from water infiltration, while the pipeline was flooded in a controlled manner.The South Texas-Tuxpan gas pipeline connects the coasts of Texas (USA) and Mexico through the Gulf of Mexico.For the installation of this gas pipeline, three outfalls were made: two with Direct Pipe and one with piping.Direct Pipe's first landfall was completed in late 2017 in Brownsville, Texas.The 42-inch, 1,500-meter-long pipe set a distance record up to that date.In Tamiahua, Mexico, after another 700 meters, another MTBM reached its final position in July 2018, completing the project's second outfall.Record length in New ZealandIn 2018 a new length record was achieved, with 1,930 meters near Auckland, New Zealand.The Army Bay Wastewater Treatment Plant required the installation of a 48” replacement pipe on the peninsula on which it sits.However, the current Direct Pipe distance record has been set in 2020 at a 48” outfall for the Warkworth & Snells Algies Wastewater Treatment Plant.Most of the 2,021 meters of distance is over land, with only a quarter under the South Pacific.The most remarkable thing is that only one Pipe Thruster was used.Soil conditions ranged from clay to shale to sandstone, requiring only a change of cutting tools.Figure 3: TBM Direct Pipe in the starter shaft, ready to run two kilometers in New Zealand.Traditionally, Direct Pipe was used to safely cross rivers and other obstacles.In 2015, two relevant 48” crossings were made in Texas, USA. The shortest was also the first to break the 1,000-meter barrier in the United States, including a three-dimensional alignment;this figure was surpassed only a few weeks later by a second installation of 1,230 m.Safe crossing under leveesSomething worth noting is that both crossings passed under a series of levees overseen by the US Army Corps of Engineers (USACE).The low pressure of the drill hole obtained thanks to Direct Pipe had drawn the attention of the authorities, who requested the complete supervision of the process.The successful completion of the crossings and the result of drilling supervision met everyone's expectations.A couple of years later, the National Energy Board of Canada (NEB) also recognized the advantages of Direct Pipe in a difficult 48” crossing in Alberta.Small Diameter Direct PipeIn Poland, Direct Pipe's first small diameter system to use injection pump technology has recently managed to cross two rivers.An AVNS600 has completed two 28” sections for the Poland-Lithuania Gas Interconnector.The first crossing of 340 meters was completed thanks to the installation of a single prefabricated pipe, while the second crossing of 884 meters was divided into two sections of pipe.Anticipated soil conditions at both crossings included sand, silt, clay, some peat, and pebbles.However, the first crossing ground conditions encountered were very different and changed shortly after launch to heavy gravel and some rocks for the rest of the run.In any case, this prototype demonstrated what until then had been considered impossible: small-diameter installation with an AVN slurry microtunneling machine is possible even over long distances.Traditionally, small diameters were limited by centrifugal pumps, too wide to fit inside the pipe.The new undersized injection pump concept, AVNS range, can be installed within diameters as small as 20”.Distances up to 1,500 meters (depending on soil conditions and depth) are possible with a single discharge pump.For Direct Pipe, this opens up the range available to install pipe diameters from 24 to 60”.Direct Pipe in hard rockAlong with the small diameter AVNS series, Herrenknecht has also developed a hard rock AVNS series for traditional microtunneling and incorporated it into the AVNS concept for Direct Pipe, being compatible with conditions up to 150-200 Mpa.This new AVNS rock series defines a purpose built line of MTBMs with features like stronger main bearings that allow for better penetration, performance and RPM.The cut-off wheels are equipped with TCI Tricone Bits or cut-off wheels with laminated teeth.The high degree of wear resistance allows greater distances to be covered with a smaller diameter than ever before.They have already proven their ability to work in conditions where the main underground formations are gravel or rock.The new AVNS concept together with the injection pump and the AVNS series for rocks represents a milestone for microtunneling and Direct Pipe, pushing the limits and making longer runs possible with smaller diameters.Future advances in guidance technology by VMT (Herrenknecht Group) are expected to make these systems even more reliable, simple and versatile.Although Direct Pipe has already taken its place in land crossings and submarine outfalls thanks to its advantages over trenchless technologies, its great benefits in terms of sustainability and environmental impact are becoming increasingly important.In the future, fuel consumption, CO2 footprint and other aspects are expected to be key elements in decision-making.Subscribe to our Newsletter - See exampleI authorize the sending of newsletters and personalized informative notices from interempresas.netI authorize the sending of communications from third parties via interempresas.netI have read and accept the Legal Notice and the Data Protection PolicyTanker E.Li.TLMycsa, Mulder and Co., SLTen Alonso y Cía, SL MariniTechnique and Mach.of quarries“We are facing the best generation of entrepreneurs in history”“I am going to work for Maqel, for JLG and for our sector the best I know how”"The entire congress is structured around a fundamental idea: achieve sustainable development for the sector"© 2019 - Interempresas Media, SLU - Nova Àgora Group