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The failure analysis of the drilling rig hoisting steel wire rope

Peterka Pavel, Krešák Jozef, Vojtko Marek, Halek Branislav, Heinz David

Eksploatacja i Niezawodność

2020

Vol. 22, no. 4

667--675

Drilling rigs belong to the lowest-safety level of hoisting rope systems. The valid regulation for drilling permits the usage of steel ropes on condition that their permanent safety does not decrease under the value 2.5. Considerable dynamic and cyclic stresses, abrasion and corrosive environment generated during the operation cause rapid fatigue and rope damage. The stress of the rope in operation leads to the specific precautions ensuring the safety rope work. The specific precautions include monitoring of the rope tractive work measured in tonne-kilometres (ton-kilometres services). The working part of the hoisting ropes of the drilling rigs - after the stated number of tonne kilometres was worked off - is slipped and a regular non-destructive rope test (NDT) is recommended. Rope under sizing, failing in rope slipping program and non- implementation of NDT controls led to the situations endangering the drilling crew safety. After the critical situations the operator decided to perform the analysis of the condition of all ropes.

3D printed Polylactid Acid based porous scaffold for bone tissue engineering: an in vitro study

Bodnárová Simona, Gromošová Sylvia, Hudák Radovan, Rosocha Ján, Živčák Jozef, Plšíková Jana, Vojtko Marek, Tóth Teodor, Harvanová Denisa, Ižariková Gabriela, Danišovič Ľuboš

Acta of Bioengineering and Biomechanics

2019

Vol. 21, no. 4

101--110

The objective of this study was to fabricate PLA-based porous scaffold by 3D printing technology and to evaluate their cytotoxicity and biocompatibility under in vitro conditions in respect to bone tissue engineering. Material and methods: Pure PLA in filamentous form was processed via 3D printing technology of fused filament fabrication into porous scaffolds. The structure and porosity of scaffolds were measured by metrotomography. PLA scaffolds were pre-treated by human serum, foetal bovine serum and complete cell culture medium to enhance bio-attractivity of the scaffold’s surface for the adherence of the cells. Cells were enzymatically isolated from the periosteum of the proximal tibia and then expanded in monolayer. Periosteum-derived osteoprogenitors (PDOs) were seeded on the pre-treated PLA scaffolds and subsequent cell proliferation was measured by commercially available cell proliferation assay. Adherence of PDOs on the PLA scaffold was confirmed by scanning electron microscopy (SEM). Results: Prepared scaffolds had well-defined structure and were characterized by uniform distribution of pores. They were non-toxic and biocompatible with PDOs, however, PLA scaffold with the periosteum-derived progenitor cells was significantly better in the group of scaffolds pre-treated with normal human serum. Conclusions: The obtained PLA porous scaffolds favored attachment of periosteum derived progenitors and proliferation, furthermore, cells penetrated into the scaffold through the interstitial pores which was meaningful for cytocompatibility evaluation.

Experience of the Crane Steel Wire Ropes Non-Destructive Tests

Peterka Pavel, Krešák Jozef, Vojtko Marek

Advances in Science and Technology. Research Journal

2018

Vol. 12, no 4

157--163

The non-destructive tests (NDT) of the steel wire ropes put on the crane pulley blocks comprise more than a half of our NDT services. The intensive utilization of cranes often leads to critical situations endangering health and safety at work. The operators are forced to provide safety use of the cranes due to new cranes constructions, new construction of the block pulley and put on the new steel wire rope constructions. The NDT tests of the crane steel wire ropes are coordinate by the Standard ISO 4309. We have experienced only the crane steel wire ropes with an individual wire rope core during our NDT tests so far. The visual NDT test usually used is ineffective to the steel wire ropes with this construction. Based on our previous experience it can be confirmed that surface ruptures are produced after the disintegration of wires inside of a rope; it often leads to the rope abruption during its operation. The reduction of the pulley block dimensions often leads to the problem of the multi-axis rope bending. This kind of the rope line in the pulley block causes the increase of the fretting fatigue of the wires and the rope strands. The same type of the stress is created when the dead ends of the rope are badly constructed.