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Vormann • 150 years of drilling experience
150 years of drilling experience


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Direct flushing procedure

Normally, rotation drillings are sunk applying the direct drilling procedure at least for smaller diameters of up to approximately 300 mm. For this purpose, pumps will press the flush water through the drill pipes bringing the cuttings stripped off by the boring tool in the annulus between drill string and wall to light.

For the purposes of this process, it is of decisive importance that an equivalent relation of pump performance and drill progress is maintained. With too high a pressure, jointed zones may be clogged caused by the supersaturated rinse liquid already during the drilling phase leading to congestions above the drill collars; the boring tool will really be rotating in its own drilling mud.
At any time, the rising speed of the flushing liquid should be such that a continuous transport of the cuttings is made possible.

Frequently, drillings made using the direct flush drilling procedure serve for exploration processes and they are expected to provide information on the profitability of a main bore.
For the drilling procedure, the coordination of all components must be effected by an experienced person in order to avoid the mixing of cuttings within the flushing flow. This is the only way that a precise sample examination can take place over several days.

Air-lift procedure 

We dig large diameter conveyor wells almost always using the air-lift procedure. Unlike the direct flushing method, the flushing flow is exactly the other way round (reverse circulation). Air is pressed into the drill pipes by a high pressure compressor thus creating a vacuum within the entire drill string.

The cuttings are sucked in by the boring tool, brought to light within the drill string and guided towards the slurry tanks. Thus, the special benefit of this method is almost explained by itself: through direct suction at the bottom of the bore hole, jointed zones are kept free to the greatest possible extent while the high rising speed ensures clean and unmixed cuttings and a precise soil examination over several days. However, this method requires high driving powers and reserves of energy due to the largely dimensioned tools.

In this connection, the size and the weight of the drill collars and guide rods play an important role. They should be dimensioned so that the drill string counteracts deviations caused by rock layers using the counter action at the pull down. Thus, larger deviations from the vertical and resulting tensions within the filter line can be avoided. 



Other procedures:

Pneumatic drilling


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