Irena M. Hlaváčová

High-energy liquid jet technology - risk assessment in practice.

ObjectivesThe contribution deals with a risk assessment in practical applications of the high-energy liquid jet technology from the point of view of the risk identification, estimation and evaluation.Materials and MethodsDifferences between three different types of workplaces are highlighted and analysed — the indoor, the outdoor and the research ones. Theoretical analyses are supported by particular application of the method for the risk assessment in the Laboratory of Liquid Jets at the VŠB — Technical University of Ostrava. This laboratory is primarily oriented to research. Nevertheless, the conclusions can be used also for predominantly commercial workplaces.ResultsSome new considerations and evaluations concerning health and safety are presented.ConclusionsFailure Mode and Effect Analysis (FMEA) procedures were applied and their limitations in risk assessment of water jet-based technologies are explained.

Testing of the High-Velocity Water Jetting on Concrete Samples Inside the Overpressure Vessel

The concrete samples with various erosion states were disintegrated inside the overpressure vessel using high-velocity water jet. Their erosion states were prepared by application of several laboratory techniques simulating the concrete aging under the natural conditions due to the real applications in practice. The influence of the erosion state on the disintegration rate was tested and the surface topography was studied both prior the application of water jet and post it. The water jet was applied in the overpressure vessel used for simulation of pressures equivalent to the submersion to several depths under the water level. Usual experimental scale responsive to the national practical application range was from the depth of submersion close to the water level up to the depth about 100 meters with the 20 meters step. Nevertheless, the data were obtained for overpressures equivalent to the submersion levels up to 140 meters enlarging so the range of results useful for regression analysis of the physical trend. Several samples were tested even in overpressures simulating depth of submersion equal to 160 meters and more. Few samples of special decorative concretes were also studied and special techniques of their working up were prepared and tested. All results are discussed regarding their application in practice and further development of special routings.Copyright

Investigation of Samples From the High-Velocity Water Jet Driven Micro/Nano Particle Collider

The power of the high-velocity waterjets has been utilized for intentional disintegration of material particles, namely minerals. Firstly, the garnet particles were tested and studied being used usually as the most common abrasive additives for waterjets improving their cutting abilities. Later on, other mineral particles have been investigated because there are some practical applications of them. Primarily, the product generated inside the mixing chamber and the focusing tube has been studied. Subsequently, the special colliding chamber has been designed and produced enabling the collision of the two opposite moving waterjets containing material particles. This device was named “Water Jet Driven Particle Collider”, shortly WJDPC. The product created in the collision of the opposite moving particle containing waterjets has particle sizes covering partially both the nano-scale and the micro-scale. The investigation of parameters influencing the amount of particles with sizes in respective dimension scales is the topic of the contribution. Some samples of special materials were studied and tested. The discussion of the results of the computational modeling of the suction process and its influence on the final product is included. All results are discussed regarding their application in practice and further development of special routings for material particle preparation.Copyright