UTJECAJ TVRDOĆE STIJENE NA USITNJAVANJE HIDRAULIČNIM ČEKIĆEM I NA DROBLJENJE U ČELJUSNOJ DROBILICI

The physical and mechanical characteristics of intact rocks depend on the way of their formation, sustained deformations and the process of wearing a specific rock has been exposed to. These characteristics have a rather high influence on the technological process of extraction and dressing of mineral raw materials. However, the mechanical characteristics of rocks due to use of explosives for their extraction in the open pit have a more significant impact. The rock blocks extracted by blasting which are larger than the opening of the primary crusher are usually fragmented by hydraulic hammer. The paper presents the results of the testing of impact of rock hardness on fragmentation of rocks by means of hydraulic hammer and during crushing in jaw crusher. The testing was carried out on the rock samples from five quarries. According to the obtained results the hardness has a considerably larger impact on the fragmentation energy by hydraulic hammer than on the crushing energy in jaw crusher.Fizičko-mehaničke značajke intaktne stijene ovise o načinu postanka, pretrpjelim deformacijama i procesu trošenja kojima je pojedina stijena bila izložena. Ove značajke imaju velik utjecaj na tehnološki proces dobivanja i oplemenjivanja mineralnih sirovina. Međutim, puno veći utjecaj imaju izmjenjena fizičko-mehanička svojstva stijena uslijed upotrebe eksploziva za njihovo otkopavanje pri površinskoj eksploataciji. Blokovi stijena dobiveni miniranjem koji su veći od ulaznog otvora primarne drobilice obično se usitnjavaju hidrauličnim čekićem. U radu su prikazani rezultati ispitivanja utjecaja tvrdoće stijena na usitnjavanje stijena hidrauličnim čekićem i tijekom drobljenja u čeljusnoj drobilici. Ispitivanje je provedeno na uzorcima stijena iz pet kamenoloma. Rezultati su pokazali da tvrdoća ima znatno veći utjecaj na energiju usitnjavanja hidrauličnim čekićem nego na energiju za drobljenje u čeljusnoj drobilici

CONSTRUCTION AND TESTING OF THE MEASUREMENT SYSTEM FOR EXCAVATOR PRODUCTIVITY

Hidraulični bager jedan je od najčešće korištenih strojeva u rudarstvu, graditeljstvu i geotehnici. Kao takav korisnicima predstavlja i važnu stavku u troškovima goriva i održavanja. Detaljna mjerenja učinka ovoga stroja izvode se u svrhu poboljšanja efikasnosti odnosno uštede. Mjerni sustav s takvom svrhom može biti složen i skup, tražiti specijalnu opremu proizvođača stroja te ne postoji kao gotovo rješenje koje bi omogućavalo praćenje radnih parametara poput trajektorije lopate, sila i energije kopanja, visine radnoga čela i sl. Iz toga razloga osmišljen je i testiran sustav za praćenje radnih parametara i učinka bagera. Sustav se sastoji od triju pretvornika linearnoga pomaka i triju pretvornika tlaka, za mjerenje produljenja i tlakova hidrauličnih cilindara, te jednoga žiroskopa za mjerenje kuta zakretanja bagera. Pretvornici su spojeni na jedinicu za prikupljanje podataka, opremljenu SD karticom i 12-bitnim AD pretvaračem. Jedinica je bazirana na Atmega328 mikrokontroleru, što omogućava primjenu Arduino sučelja za programiranje i razvijenih biblioteka koda. Mjerni sustav testiran je laboratorijski radi određivanja točnosti, rezolucije i moguće brzine uzorkovanja podataka. Tlakovi mogu biti mjereni u rasponu 0 bar – 500 bar s točnošću od 0,026 % MO i rezolucijom 0,15 bar. Izvlačenje cilindra može biti mjereno u rasponu 0 mm – 2300 mm, s točnošću od 0,087 % MO i rezolucijom 0,58 mm. Točnost mjerenja kuta zakretanja iznosi 1,2° po okretu ili 0,33 % MO. Testirana brzina uzorkovanja iznosi 39 Hz – 588 Hz, ovisno o programskome kodu.hydraulic excavator is one of the most used machines in mining, construction and geotechnics. Monitoring its productivity can provide benefits such as savings in fuel consumption and maintenance, cost optimization of working parameters and a higher working efficiency. A measurement system for such a purpose can be complex and expensive, as it requires special equipment from the manufacturer and does not exist as an out of the box solution that would measure working parameters such as bucket trajectory, digging energy, digging force, etc. A measuring system was designed to monitor productivity and gather working parameters. It consists of three pressure transmitters for measuring cylinder pressures, three draw wire sensors for cylinder elongations, one inertial measurement unit for the measurement of swing angle and one logger unit for data acquisition and storage. The logger unit, equipped with an SD card module and 12-bit AD converter, is based on Atmega328 microcontroller, which allows for the usage of Arduino IDE and already developed libraries. The system was tested in a laboratory to determine its accuracy, resolution and usable sample rate. Cylinder pressure can be measured in the range of 0-500 bar with an excellent accuracy of 0.026 % FSO and 0.15 bar resolution. Cylinder elongation can be measured in the range 0-2300 mm with an accuracy of 0.087 % FSO and 0.58 mm resolution. Swing angle measurement accuracy is 1.2° per circle or 0.33 % FSO. The usable sample rate of the system is found to be 39 Hz-588 Hz, depending on the logger executing code

DEPENDENCY OF SPECIFIC ENERGY OF ROCK CUTTING ON SPECIFIC DRILLING ENERGY

Specifična energija veličina je koja povezuje radne veličine stroja sa značajkama stijene u kojoj stroj radi, a jednaka je ukupnome radu potrebnom za razrušavanje jediničnoga volumena stijene. Pretpostavlja se da kod strojeva koji imaju istu ili sličnu mehaniku razrušavanja stijena, a koji se koriste za različite namjene (npr. rezanje i bušenje stijena), po stoji znatna zavisnost između specifičnih energija. Prilikom eksploatacije arhitektonsko-građevnoga kamena često se koristi lančana sjekačica i rotacijska bušilica, tj. strojevi koji služe za rezanje, odnosno bušenje stijene, a čija je mehanika razrušavanja vrlo slična. Radi određivanja zavisnosti specifične energije rezanja stijena o specifičnoj energiji bušenja provedena su preliminarna laboratorijska ispitivanja na uređaju za pravolinijsko rezanje stijena i laboratorijskoj bušilici kojima je simulirano rezanje stijena lančanom sjekačicom, tj. bušenje stijena rotacijskim bušenjem. Analizom mjernih rezultata dobivene su smjernice za nastavak laboratorijskih ispitivanja odnosno provedbu terenskih ispitivanja.Specific energy is the measure which connects the operating parameters of the machine with the characteristics of the rock in which the machine works and is equal to the total work required to break a unit volume of the rock. It is assumed that in machines with the same or similar rock breaking mechanics used for different purposes (e.g. cutting and drilling of rocks), there is a significant dependence on their specific energy values. In the exploitation of dimension stone a chain saw and a rotary drill are often used, i.e. the machines for rock cutting or rock drilling whereas their mechanics of rock breaking is very similar. In order to determine dependence of the specific energy of rock cutting on the specific drilling energy, preliminary laboratory tests were carried out on a linear cutting machine and a laboratory drill with simulated cutting of rocks with a chain saw, and drilling by rotary drilling. The analysis of the measurement results has provided the guidelines for the continuation of laboratory testing, i.e. field testing

IMPACT OF ROCK HARDNESS ON FRAGMENTATION BY HYDRAULIC HAMMER AND CRUSHING IN JAW CRUSHER

The physical and mechanical characteristics of intact rocks depend on the way of their formation, sustained deformations and the process of wearing a specific rock has been exposed to. These characteristics have a rather high influence on the technological process of extraction and dressing of mineral raw materials. However, the mechanical characteristics of rocks due to use of explosives for their extraction in the open pit have a more significant impact. The rock blocks extracted by blasting which are larger than the opening of the primary crusher are usually fragmented by hydraulic hammer. The paper presents the results of the testing of impact of rock hardness on fragmentation of rocks by means of hydraulic hammer and during crushing in jaw crusher. The testing was carried out on the rock samples from five quarries. According to the obtained results the hardness has a considerably larger impact on the fragmentation energy by hydraulic hammer than on the crushing energy in jaw crusher

Research on Interdependence between Specific Rock Cutting Energy and Specific Drilling Energy

A method based on extensive laboratory and field measurements was developed to determine the dependence of specific rock cutting energy (SEc) on specific drilling energy (SEd) for machines with different operating and design characteristics and similar breaking mechanics. Laboratory measurements were performed on a linear rock cutting device and a laboratory drill, using a measurement system to measure electrical power and cutting forces using force/torque transducers. Field power consumption measurements were performed on a chainsaw cutting machine and a hydraulic rotary drill under real working conditions in the dimension stone quarries. The analysis of the measured results confirmed the strong dependence of the specific rock cutting energy on the specific drilling energy and confirmed that laboratory devices can be used to simulate actual rock cutting and drilling process. In addition, the results are applicable in the dimension stone exploration and exploitation phase in order to assess and reduce energy consumption by optimizing the operating parameters of the chain cutter and/or the hydraulic rotary drill

DEPENDENCY OF SPECIFIC ENERGY OF ROCK CUTTING ON SPECIFIC DRILLING ENERGY

Specific energy is the measure which connects the operating parameters of the machine with the characteristics of the rock in which the machine works and is equal to the total work required to break a unit volume of the rock. It is assumed that in machines with the same or similar rock breaking mechanics used for different purposes (e.g. cutting and drilling of rocks), there is a significant dependence on their specific energy values. In the exploitation of dimension stone a chain saw and a rotary drill are often used, i.e. the machines for rock cutting or rock drilling whereas their mechanics of rock breaking is very similar. In order to determine dependence of the specific energy of rock cutting on the specific drilling energy, preliminary laboratory tests were carried out on a linear cutting machine and a laboratory drill with simulated cutting of rocks with a chain saw, and drilling by rotary drilling. The analysis of the measurement results has provided the guidelines for the continuation of laboratory testing, i.e. field testing

Development of a Reference Device for the Calibration of Optical One-Shot Time-Interval Measurements

This paper presents the development of a device that creates two or more light pulses with a precision time delay in a range from microseconds to several seconds and for the purpose of the calibration of velocity of detonation (VOD) measurement instruments. The device was assembled, programmed, and tested for functionality. Measurements were conducted using a reference counter. First, a precision OCXO (oven-controlled crystal oscillator) was used as a clock source. For verification of programmed subroutines, a counter oscillator output port was used as a source of clock signal for the microcontroller. This enabled the cancellation of possible oscillator errors. The signal had to be converted from an AC sine signal to a signal with positive values only using a clamper circuit. By the proposed solution, a calculable standard of time delay between two light pulses was achieved. According to the obtained results, this device can be used to calibrate field measurement devices for VOD measurements in explosives or some other use where the measurement device records the time interval between multiple light pulses. This enables more confidence in measurement results, faster recognition of instrument drift and increases the quality of measurement

Detecting atypical values and their influence on blast-induced seismic measurement results

Blasting is an essential part of any mining or civil engineering project along with all the benefits that it brings, such as cost and time effectiveness, and safety. Still, there are a few downsides to blasting. Ground oscillation velocity as the most significant impact of blasting has been studied broadly. However, not all measured values should be used for PPV (peak particle velocity) predictor or model development. If a false measured value is included in the model or predictor development, it will provide erroneous results that can lead to the damage of the surrounding structures or an increase in the cost of blasting works. There is no clearly defined procedure for separating atypical values (outliers) within blast-induced seismic-effects measurement data. This paper recommends how to properly validate vibration velocity data by detecting and excluding atypical values and how it influences blast-induced seismic measurement results

Detecting atypical values and their influence on blast-induced seismic measurement results

Blasting is an essential part of any mining or civil engineering project along with all the benefits that it brings, such as cost and time effectiveness, and safety. Still, there are a few downsides to blasting. Ground oscillation velocity as the most significant impact of blasting has been studied broadly. However, not all measured values should be used for PPV (peak particle velocity) predictor or model development. If a false measured value is included in the model or predictor development, it will provide erroneous results that can lead to the damage of the surrounding structures or an increase in the cost of blasting works. There is no clearly defined procedure for separating atypical values (outliers) within blast-induced seismic-effects measurement data. This paper recommends how to properly validate vibration velocity data by detecting and excluding atypical values and how it influences blast-induced seismic measurement results