DEFECTS DURING THE OPERATION OF DRILLING TOOLS AND MACHINES IN MINING

Journal of science. Lyon №70/2025 24 TECHNICAL SCIENCES DEFECTS DURING THE OPERATION OF DRILLING TOOLS AND MACHINES IN MINING Velev S., Ph.D, ., Bulgarian Academy of Sciences Institute of metal science, equipment and technologies "Akad. A. Balevski” with hydroaerodynamic center 67 Shipchenski prohod , 1574 Sofia, Bulgaria Kalchevska K. Ph.D., Assoc.Prof., Bulgarian Academy of Sciences Institute of metal science, equipment and technologies "Akad. A. Balevski” with hydroaerodynamic center 67 Shipchenski prohod , 1574 Sofia, Bulgaria https://doi.org/10.5281/zenodo.17256217 Abstract Non-destructive methods for examination and control of parts and assemblies of structures allow determining the probable causes of boils and fractures after unacceptable loads. Some of the evaluations made in the Laboratory of "Destructive Control" at the Institute of metal science, equipment and technologies with hydroaerodynamic center. Keywords: non-destructive testing,visual examination methods, radiographic test method, capillary method. 1. Introduction State authorities in the country such as Regional Departments of the Ministry of Interior and Investigation Department at the relevant departments provide us with material evidence from materials and assemblies that have led to industrial accidents or accidents after improper use of metal equipment. Details of a vertical drilling hammer type Hammer and a piston from a drilling machine of brand FlexiROC D50 have been followed. The tests were performed at the Laboratory of non-destructive testing in IMSETHAC-BASLicense I-5454 registration number 6130 for using of ionizing ray sources for scientific and economic pur 2. Test methods Visual control – tests are according to standards [1].Rent-rate and penetrating liquid testing according to standards [4],[5] ,[6],[7]. Non-destructive control with radiation methods and with roentgen defectoscope of type 200/5 model MXR-200. Technical parameters: spot focus 2,45x2,80 mm; anode current 5 mA; tension 180 kV at measured equivalent dose 0,210 mSv with tapping ± 0,8 %. Work conditions and reading of the roentgenograms are conformity with Standards BDS EN ISO [1, 3]. Calibration and certification -in accordance with - Industrial X-ray system MXR 200 ( No 201017) Certificate of calibration №553-Ro/22.05.2020; Negatiscope KL-1500 (No 151) Certificate of calibration №462-HC/21.06.2018; Radiographic technology B; film system C4, film D7. Capillary control was performed according to standards [4], [5], [6], [7] . Equipment uset : Caliper № 187, Certificate of calibration № 187-ID/03.12.21; Lux meter MS6610 : № MBFG077505, Certificate of calibration № 35-OI/11.03.2022г.; Set penetrants: DIFFU-TERM 890, 871 ,860 , Certificate of 07.11.2022. 3. Product 1.Metal materials and forging. Test to clarify the reasons for breaking a hydraulic hammer workpiece plunger with No FUROKAWA. Details of a geological exploration company – piston fig.1a and fig b position №8 on structural documentation – from broken hydraulic hammer FUROKAWA. The specimen is of steel type 40Ch2N2MA. DIN analogue 1.6565 40NiCrMo 6; Analogue: Japanese brand JAPAN JIS No G 4103 steel grade SNCM8 type. Journal of science. Lyon №70/2025 25 Fig.1 a Broken piston Fig.1 b Documentation of the piston position No.8 The rolled steel of the above-mentioned material is 160mm and within the limit of 100÷400 mm is with subsequent heat treatment of the forgings – tempering 850 oC in oil and annealing at 610 0C, which allows a workpiece made with additional machining to be loaded to an impact of 5120 J energy according to the BDS EN 10002-1:2000 documentation. Fig.2 X-ray photo Fig.3 X-ray photo Journal of science. Lyon №70/2025 26 Fig.4 Analysis with penetrating fluids of workpiece 1.а 1-cluster of pores in the fracture region and an incipient crack about 35 mm long 2-cracks min 15 pieces with lengths between 1.5 and 12 mm 3-single pores between 0.5 and 2 mm 4-pores and a crack measuring about 9 mm After the radiographic control according to the current standards BDS EN ISO [1] and [3] Figs.2 and 3 show the found inadmissible gaps A>10%. 3.2 Product - FlexiROC D50 Vertical reach (mm) Feed swing angles - standard feed Fig.5 Fig.6 Capillary NDT. It was found in compliance with standards [3,[4],[5] and [6]. Pores /Fig.4 / with a length of more than 0.5 mm and cracks /Fig.6/ with a length of 2.2 mm, 3 mm and a main crack with a length of 4÷5 mm were found. Journal of science. Lyon №70/2025 27 Fig.7 Permissible flange defects after repeated loading of the working tool Fig.8-broken teeth on a working flange Fig.9 drawing of a restored part 4.Conclusion The detail of the FUROKAWA FXJ 275 hydraulic hammer was broken due to the large number of cracks inside the forging, as well as pores and cracks at two diametrically opposite ends that led to a highway crack. Established defect A>10% Non-linear indication Ф>0.5mmCP3, LP7 Linear indication L 2÷12 mm-CP8,AP8 In the second detail – part of an elliptical element with screw M6 clearly distinguish two zones: brittle and plastic. The area occupied as a result of the brittle destruction of the element is twice as large as the plastic zone. The registered cracks inside the forging, as well as pores (in blue) at the two diametrically opposite ends, clearly show the dividing line of destruction. The demolition area clearly indicates that the load is above the allowable. Unfortunately, the element was part of the equipment for climbers and shearing the stem of the bolt could have caused the climber to slight. The manufacturer provides instructions on the permissible defects after multi-cycle loading /Fig.7/. Fig. 8 shows the part after use in normal operation, without overload in operation. The defects - broken teeth on the flange - are visible. It was necessary to manufacture the part Fig./9/ with the material selected after analysis and the necessary heat treatment. References: 1. Test method: BS EN 13018:2016 Non-destructive testing. 2. Visual testing. General principles Released: 2016-02-29; BS EN 13927:2003 Non-destructive testing. Visual testing. Equipment, 2003; Journal of science. Lyon №70/2025 28 3. BS ISO 5579:2013 Non-destructive testing — Radiographic testing of metallic materials using film and Xor gamma rays — Basic rules; 4. ISO 3452-1:2013 Non-destructive testing — Penetrant testing — Part 1: General principles; ISO3452-2:2013(en) Non-destructive testing — Penetrant testing — Part 2: Testing of penetrant materials; 5. BS EN 10228-2:2016 Non-destructive testing of steel forgings. Penetrant testing; 6. ISO 23277:2015 Non-destructive testing of welds — Penetrant testingAcceptance levels; 7. ISO 10675-1:2016 Non-destructive testing of welds — Acceptance levels for radiographic testing — Part 1: Steel, nickel, titanium and their alloys; EN ISO 17637:2016 Non-destructive testing of welds - Visual testing of fusion-welded joints; EN 1371-2:2015 Liquid penetrant testing - Part 2: Investment castings.