Horizontal directional drilling represents a milestone in pipeline construction. Schenk AG from Heldswil (CH) has been using this technology since 1989 to cross under rivers, railway tracks, roads and other obstacles in an efficient manner.
Piles of soil on grassy areas are a clear sign that moles have been digging nearby – but drilling by Schenk AG, who specialise in the controlled horizontal drilling process, leaves no lasting traces. With around 20 drilling rigs with diameters ranging from 10 to 180 cm, the company can cut an elegant path through the soil. Distances of up to 2 km can be covered with the largest machine. Following meticulous planning, the determined drilling parameters are implemented by experienced drilling teams.
The first step is to drill a pilot hole from the launch pit. For this, a steerable drill head is driven into the soil or rock by means of a continuously extendable drill rod. The drill operator in the rig can use a guidance system to precisely steer the drill head. At the same time, a bentonite drilling mud is pumped through the drill rod, which removes the soil mechanically and hydraulically. The excavated material is pumped back into the launch pit, where the drilling mud is cleaned up and reused. In order to achieve the required bore diameter, the bore is enlarged and cleared in the second step. A reamer is mounted on the drill rod for this purpose. This is rotated back through the ground to the drilling and boring machine. In the third and final step, a protective pipe or product pipes, such as cast iron water pipes, with a total weight of up to 200 tonnes are pulled into the bore.
The hydraulic system of the drilling machine is the heart of the machine. With precise control of pressure and volume flow, it delivers power to units such as the plunger pump for conveying bentonite and excavated material. The drill drive has the greatest requirement in terms of hydraulic power. In addition, all control and driving functions form part of the system. Hydraulic oil plays a key role in the transmission of power, lubrication and the cooling of components. Not only long-lasting performance is required – a wide operating temperature range is essential for year-round use. In summer, temperature peaks of up to 100 °C can occur, which have to be dissipated through optimum thermal conductivity in the cooling system. Schenk AG has achieved outstanding long-term results in various drilling rigs with ECOSYNT HEES 46. The key selling points of the zinc-free long-life hydraulic fluid are its high wear protection, excellent shear stability and very good material compatibility. ECOSYNT HEES 46 is also easily biodegradable in accordance with OECD 301B.
When working in soil and rock, often close to water, it makes sense to use EAL (environmentally acceptable lubricants). “This is not just because it is increasingly stipulated by the client; it also provides added safety and peace of mind. And it makes sense from a business point of view too,” confirms Beni Schenk (owner). Contamination of groundwater and soil is an expensive risk that needs to be minimised. The machine is equipped throughout with the easily biodegradable ECOGREASE B300 and the threads of the drill rods are lubricated with ECOPASTE HT 400. Solid lubricants in the special release paste protect the threads and prevent the highly loaded surfaces from fusing together. Even after dirt and moisture have infiltrated, the drill rods can be easily loosened from each other and work interruptions caused by jammed screw connections are a thing of the past.
The application advantages achieved by the heat transfer fluid used are significant. Firstly, the lubricating effect of the non-toxic and easily biodegradable 1,2-propylene glycol in ANTIFREEZE P4.4 RTU reduced wear on the multiple rubber pistons of the high-pressure pump for bentonite supply by 50 %. This is equivalent to doubling the service life. Secondly, in winter the biodegradability in accordance with OECD 301B contributes to improved sustainability when rinsing the drilling rig and the drill head at the end of the working day. The cold protection also prevents the dreaded freezing of the plunger pump and piping on the drilling rig.
By specialising in the HDD (Horizontal Directional Drilling) drilling process, Schenk AG and its more than 100 employees in Switzerland and across Europe contribute to the efficient creation of infrastructure: excavation and demolition work is eliminated, construction times are shortened, land is protected and the impact on public life remains minimal.
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