Skip to main content

Novel drilling system for cost effective extraction of the 30 million tons of ornamental stone blocks in Europe with lower environmental impact.

Final Report Summary - STREAM (Novel drilling system for cost effective extraction of the 30 million tons of ornamental stone blocks in Europe with lower environmental impact)

The aim of the STREAM project was to develop an innovative diamond-like carbon (DLC) coating technology by plasma assisted chemical vapour (PACVD) technique, so as to design, fabricate and test a new down-the-hole (DTH) water hammer of small dimensions for mining and quarry applications.

The PACVD technique was firstly modelled using a pilot scale plant, in order to optimise the deposition process and improve the coating quality. In addition, a semi-empirical control system of the plant was defined. Further tests enabled to examine alternative base materials and define optimal solutions, while improving the pre-coating and thermal treatment of the elements of the water powered drilling hammer. It appeared that DLC coating provided good corrosion resistance, high wear resistance and low friction. Moreover, excellent adhesion properties of the coating layer and low presence of cracks were confirmed.

The developed technology was applied to STREAM prototype components after completion of the experimental evaluation stage. Furthermore, an industrial scale plant was constructed and two DTH hammers of different external diameters were designed, based on the analysis and improvement of an existing water top hammer. The prototypes were applied and evaluated in varying field conditions. Finally, a prototype with smaller external diameter was fully designed and mathematically simulated so as to verify the correctness of the mechanical design and to calculate expected performances. The potential for exploitation was apparent in the mining sector, as well as in civil engineering applications, such as tunnels' drilling, which represented a significant secondary market.

The project activities were organised in nine distinct, yet interrelated, work packages, with the following tasks:

1. Production of the analysis tool, which was software aiming to support end users in estimating the critical parameters of manufacturing mechanical components using the STREAM coating process. The software was evaluated and reviewed throughout the project elaboration and was available in the project web portal.
2. Identification of target requirements and specifications, which involved extensive review of available drilling technologies, equipments and methods. The design of the drilling machines' valve was crucial for the determination of the most promising design prerequisites. Moreover, the specific requirements for piston and cylinder base material, heat treatments and coating were defined.
3. Selection and testing of the utilised materials and technologies. The surface treatments of the cylinder were finalised as a hybrid method consisting of two diffusion treatment processes, namely vacuum carburising process and gas nitriding. Conclusions on the selections were derived based on simulation and laboratory experiments.
4. Development of the laboratory scale plant, which was suitable for coating the sliding surface. The process allowed for evaluation, optimisation and tuning of the proposed method. The WP success motivated the design of an industrial DLC plant, which was not included in the initial scope of works.
5. PACVD process optimisation so as to achieve the target performance and attributes of the final products. The process control was acquired by numerous tests which enabled prediction of the temperature profile versus time as well as of the adjustable parameters of the fitting curve.
6. Design and manufacturing of the drilling demonstrators, which involved implementation of the STREAM system according to the requirements defined in preceding WPs. The prototypes were conceptualised and simulated prior to being fabricated and applied in the field.
7. Testing and system performance demonstration, through specific trials which enabled evaluation of the optimised demonstrators' characteristics. The design success was verified through a series of experimental drills, with alternative stones, drilling angles and site conditions. The low friction coefficient prolonged the equipment working life and reduced energy dissipation, while the system performance was in many cases superior to that of commercial alternatives.
8. Activities related to the innovations' industrial and commercial exploitation. The potential for patenting the system was investigated and a marketing strategy was defined. Furthermore, a knowledge dissemination plan was applied.
9. Project management, which guaranteed optimal exploitation of resources and effective transfer of information and expertise throughout the project elaboration, allowing for its successful and timely completion.