online condition monitoring of bearings for improved reliability in packaging materials industry

The production processes in the packaging materials industry has to be very efficient and cost-effective. These processes usually take place under extreme conditions and high speeds that requires a high level of reliability and efficiency. Rollers including their supporting bearings and motors are the most common components of production machines in the packaging materials industry. Bearing faults, which often occur gradually, represent one of the foremost causes of failures in the industry. Therefore it is very important to take care of bearings during maintenance and detect their faults in an early stage in order to assure safe and efficient operation. We present a new automated technique for early fault detection and diagnosis in rolling-element bearings based on vibration signal analysis. After normalization and the wavelet transform of vibration signals, the standard deviation as a measure of average energy level and the logarithmic energy entropy as a measure of the degree of order/disorder are extracted in a few sub-bands of interest as representative features. Then the feature space dimension is optimally reduced to two using scatter matrices. In the reduced two-dimensional feature space the fault detection is performed by a quadratic classifier and the fault diagnosis by another two quadratic classifiers. Accuracy of the new technique was tested on the ball bearing data recorded at the Case Western Reserve University Bearing Data Center. In total four classes of the vibrations signals were studied, i.e. normal, with the fault of inner race, outer race and balls operation. An overall accuracy of 100% was achieved. The new technique can be used to increase reliability and efficiency by preventing unexpected faulty operation of machinery bearings

Synthesis of tetraalkyl thiuram disulfides using different oxidants in recycling solvent mixture

A new optimized laboratory synthesis of tetraalkylthiuram disulfides, starting from dialkyl amines and carbon disulfide in presence of three oxidants (hydrogen peroxide, potassium peroxodisulfate and sodium hypochlorite) and appropriate reaction media (two mixtures of isopropyl alcohol-water used in two consecutive syntheses) was presented in this work. The first synthesis was performed in a recycled azeotropic mixture of isopropyl alcohol-water 87.7%-12.3%, and second in a filtrate obtained after first synthesis, which was a mixture of isopropyl alcohol-water 70.4%-29.6%. After the second synthesis and filtration, recycled azeotropic mixture isopropyl alcohol-water 87.7%-12.3% was regenerated from the filtrate by rectification. Considering this, the technology for beneficial use of recycling isopropyl alcohol-water mixture as a reaction medium for tetraalkylthiuram disulfides synthesis was developed. This concept could contribute to extraordinary economical benefit of implemented optimal laboratory synthesis at semi-industrial level. High yields of tetraalkylthiuram disulfides were obtained at both laboratory and semi-industrial level. Structure and purity of synthesized compounds were confirmed by elemental analysis, as well as FTIR, 1H- and 13C-NMR, and MS spectral data.U ovom radu je prikazan nov optimizovani laboratorijski postupak sinteza tetraalkiltiuramdisulfida, polazeći od dialkilamina i ugljendisulfida u prisustvu oksidacionih sredstava (vodonik-peroksid, kalijum-peroksodisulfat i natrijum-hipohlorit), u odgovarajućem reakcionom medijumu: dve smeše izopropil alkohol-voda korišćene u dve uzastopne sinteze. Prva sinteza se izvodi u reciklovanoj azeotropskoj smeši izopropil-alkohola-voda sastava 87,7%-12,3%. Izvršena je optimizacija postupka u odnosu na molarni odnos reaktanata i koncetraciju proizvoda u suspenziji. Filtrat, dobijen nakon filtriranja suspenzije tetraalkiltiuram-disulfida iz prve sinteze, koji sadrži smešu izopropil alkohol-voda 70,4%-29,6%, uspešno je korišćen za naredne sinteze tetraalkiltiuram-disulfida. Nakon druge sinteze, filtracijom suspenzije, dobija se filtrat kao smeša izopropil-alkohol-voda 57,0%-43,0%, koji se regeneriše rektifikacijom pri čemu se dobija azeotropska smeša sastava izopropil alkohol-voda 87,7%-12,3%. Primenom navedenog postupka osvojena je tehnologija koja uključuje proces reciklovanja smeše reakcionog medijuma izopropil alkohol-voda za sintezu tetraalkiltiuram-disulfida. Takav koncept doprinosi izvanrednoj ekonomičnosti implementiranog optimalnog laboratorijkog postupka sinteze na poluindustrijski nivo. Visoki prinosi tetraalkiltiuram-disulfida su dobijeni sintezama na laboratorijskom nivou, kao i primenom na poluindustrijskom nivou proizvodnje. Struktura i čistoća sintetisanih jedinjenja: tetrametiltiuram-disulfid (TMTD), tetraetiltiuram-disulfid (TETD), tetrapropiltiuram-disulfid (TPTD), tetraizopropiltiuram-disulfid (TiPTD), tetrabutiltiuramdisulfid (TBTD), tetraizobutiltiuram-disulfid (TiBTD), su potvrđene FTIR, 1H- i 13C-NMR spektroskopijom, MS spektrometrijom i elementalnom analizom. PR Projekat Ministarstva nauke Republike Srbije, br. 172013

Online Condition Monitoring of Bearings to Support Total Productive Maintenance in the Packaging Materials Industry

The packaging materials industry has already recognized the importance of Total Productive Maintenance as a system of proactive techniques for improving equipment reliability. Bearing faults, which often occur gradually, represent one of the foremost causes of failures in the industry. Therefore, detection of their faults in an early stage is quite important to assure reliable and efficient operation. We present a new automated technique for early fault detection and diagnosis in rolling-element bearings based on vibration signal analysis. Following the wavelet decomposition of vibration signals into a few sub-bands of interest, the standard deviation of obtained wavelet coefficients is extracted as a representative feature. Then, the feature space dimension is optimally reduced to two using scatter matrices. In the reduced two-dimensional feature space the fault detection and diagnosis is carried out by quadratic classifiers. Accuracy of the technique has been tested on four classes of the recorded vibrations signals, i.e., normal, with the fault of inner race, outer race, and ball operation. The overall accuracy of 98.9% has been achieved. The new technique can be used to support maintenance decision-making processes and, thus, to increase reliability and efficiency in the industry by preventing unexpected faulty operation of bearings

Structural Properties of the Multiwall Carbon Nanotubes/Poly(Methyl Methacrylate) Nanocomposites: Effect of the Multiwall Carbon Nanotubes Covalent Functionalization

The structural characteristics of polymer nanocomposites with functionalized multiwall carbon nanotubes (MWCNTs) in poly(methyl methacrylate) matrix have been studied in relation to nanofiller loading and surface functionality. Different functional groups have been covalently attached on the MWCNTs sidewalls in order to induce interfacial interactions at nanofiller/polymer interface, which resulted in an improved nanomechanical features. Structural properties of nanocomposites, studied with XRD and Raman analysis, indicated the most pronounced decrease in a degree of amorphousness for samples containing 0.5 and 1 wt% of MWCNTs functionalized with dapsone (dapson-MWCNT) and diethyl malonate (dem-MWCNT). SEM and TEM micrographs confirmed improved dispersibility of the MWCNTs modified with aromatic structure of dapsone inside PMMA matrix. A significant increase in a glass transition temperature of over 60 degrees C has been found for the 1 wt% dapson-MWCNT nanocomposite. Additional modification of dapson-MWCNT by further increasing aromaticity and voluminosity of attached moiety (fid-MWCNT), showed 30 degrees C increases in a glass transition temperature at 4 wt% of nanofiller loading, which is similar to shift of 37 degrees C with loading of MWCNTs modified with ester terminal group. A maximum increase of 56% of reduced modulus and 86% of hardness was obtained for 1 wt% loading of dapson-MWCNT nanofiller