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Keyhole Technology: All-Round solution for house connections

The keyhole technology is used specifically for repairing lines, new installations and renewing house connections. The keyhole is a small circular head access hole with a diameter of 650 mm; all drilling and repair jobs can be carried out through this little hole. It is the counterpart of a significantly larger rectangular head access hole.

The advantages of the keyhole are obvious: minimally invasive intrusion with minimil excation by a suction excavator, thus little time and effort is needed for reinstatement. The road surface, opened up with a core drill unit, is sealed again with the bore core after the work is done. The bore core forms a solid bond with the road surface and guarantees stable endurance, even if the traffic volume is continuously heavy.





Keyhole Jobsite in Wilhelmstal / Germany
 
In the Alte Schulstraße in Wilhelmstal, 25 upper parts of house connection valve gates needed replacement. A low-priced solution which would go easy on the surface of the road and could be finished in the shortest possible time was exactly what the customer was looking for. This was a case for the keyhole technology! 
 
The parts were replaced in co-operation with the fittings manufacturer EWE, Braunschweig and the water supplier Frankenwald-Gruppe from Steinberg. The construction company Anton Eidloth GmbH, also from Steinberg, carried out the project as a demonstration jobsite, supported by TRACTO-TECHNIK, Lennestadt and TUR Suction Excavator Services, Niederau.
 
The fittings manufacturer EWE had already performed his own part of development for the keyhole technology, collecting valuable experience along the way. It is now possible to install or repair the fittings from the surface without having to work in the keyhole itself, a job which would hardly be possible, anyway, because of the small diameter. 
 
TRACTO-TECHNIK has developed a special core drill for drilling out the asphalt core to establish a keyhole. The core drill does not need a separate drive, it is powered by the auxiliary drive of the suction excavator. After the asphalt core has been drilled out, the suction excavator starts its work, removing the soil from the keyhole down to line level in a line-friendly, efficient and quick way. Even larger rock pieces are gathered that way. With this individual project, it took an average of 45 minutes for the keyhole drill and the suction excavator to establish each keyhole. 
 
As soon as the fittings are replaced, the keyhole is filled up with fine sand, crushed rock and single-grain filler in layers which are finally compacted. The asphalt core, drilled out beforehand, is replaced precisely in height and position and cemented in place with a special mortar. Then the flat joint area is grouted with cold bitumen. Asphalting is not required. This mode of action is road-friendly because the surface is not burdened by great tension after the circular asphalt core has been replaced. In the medium to long term, crack growth and scar formation as well as subsidence are prevented. 
 
As this jobsite demonstrates, the return on investment is due to saving time and resources and optimised  working processes. Establishing the keyholes and replacing the fittings can be staggered. While one keyhole is prepared with the core drill and suction excavator, the fittings can be replaced in another. The advantage of this alternating work method is of growing importance for projects with a multitude of replacements in a single street of houses, a residential area or a complete small town.
 
All-Round Character of the Keyhole Technology 
 
The keyhole technology is not restricted to the replacement of fittings, however; the separation of house connections, repair of valve gates or renewal of joints all belong to the jobs which can be performed with special tools in the non-accessible head holes. Cornerstone for an essential expansion possibility of the keyhole technology is a drill rig designed by TRACTO-TECHNIK at the suggestion of Gas de France. This drill rig, named GRUNDOPIT K, is custom-made for the keyhole and can be installed inside. It enables the new installation of pipes with diameters up to 63 mm and lengths up to app. 30 metres for gas, water and telecommunication connections.
 
Another development for the renewal of house connection lines is the GRUNDOTUGGER. From out of the keyhole, the old house connection lines are broken up per cable winch with a bursting facility, comparable with the pipe bursting method, and a new pipe is pulled in.
 
The keyhole technology features the triple benefit - repair, new installation and renewal of house connections. This all-round technology has attracted the attention of professional circles. This fact was confirmed at the BAUMA this year, where it was greatly acclaimed by the visitors, and by an accompanying survey and documentation carried out by the E.ON New Build & Technology, Gelsenkirchen. 
 

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