1,721,038 research outputs found
Development of a framework to assist with risk mitigation in a procurement environment
Get PDFThesis (M.B.A.)--North-West University, Potchefstroom Campus, 2008.Master
Six Sigma : a framework for successful implementation in South African firms
Get PDFThesis (M.B.A.)--North-West University, Vaal Triangle Campus, 2009.There can be little doubt that Six Sigma is far more than just another novelty concept; in fact, it can be considered as a proven quality philosophy and if applied correctly, ensures a competitive advantage. A rapidly increasing number of firms, from all industries and of all sizes, are now reporting significant savings or returns on their program and training investments, because of the implementation of Six Sigma.
This paper investigates the origin, definition, financial benefits and challenges of Six Sigma and its implementation. Certain critical success factors determine the successful implementation of Six Sigma in any firm. Many firms have reported significant benefits as a result of Six Sigma project implementation, though not all are yet success stories. This paper reviews the literature related to the critical success factors for the effective implementation of Six Sigma. This research will provide the useful information for firms, which are willing to implement Six Sigma and help firms avoid the risks during the process of Six Sigma implementation. The primary objective of this exploratory research is to identify the critical success factors required for the successful implementation of Six Sigma. Then, based on the critical success factors identified in literature and the survey, the purpose is to develop and propose an applicable framework for firms to successfully implement Six Sigma. The research is explorative of nature and a survey research design was used with a questionnaire as data-gathering instrument.
Descriptive statistics (e.g. means and standard deviations) were used to analyse the data. The results confirmed that the most critical success factors for successful Six Sigma implementation include management commitment, change management, effective communication and alignment. The proposed framework presents six interlinking components of Six Sigma which is dependent on these four critical success factors. Limitations in the research are identified and recommendations for future research are made.Master
Respiratory exposure during the additive manufacturing of sand casting moulds
Get PDFMSc (Occupational Hygiene), North-West University, Potchefstroom Campus, 2017.Background: During additive manufacturing (AM) of sand casting moulds, potential dust species of unknown particle size or mineral composition, and hazardous chemical substances (HCS’s) such as silica (crystalline), volatile organic compounds (VOC’s) and polycyclic aromatic hydrocarbons (PAH’s) are liberated/released during the pre-processing, processing and post-processing phases of manufacture. Aims and Objectives: Bulk sand samples were collected from two research facilities (Facility A and Facility B) in South Africa to determine particle size fractions and mineral composition. Respiratory exposure monitoring of HCS’s was conducted. Methods: Physicochemical characterisation of new, used and mixed bulk sand samples through particle size distribution (PSD) analysis, scanning electron microscopy (SEM) analysis and X-Ray diffraction (XRD) was conducted to determine particle sizes and their mineral composition. Area and personal respiratory exposure monitoring of particles not otherwise classified (PNOC), crystalline silica (quartz), PAH’s and VOC’s was conducted for the duration of each process to determine concentration levels for comparison with national legislation. Results and discussion: For new sand, a mean particle size of 137.49 μm at Facility A and 282.70 μm at Facility B was found, indicating that both Facilities had particle sizes larger than the inhalable size fraction. However, 10% of particles at Facility A were smaller than 75.35 μm, indicating the presence of inhalable particles. The SEM imaging supported the abovementioned particle size findings, with particle sizes > 100 μm. XRD analysis indicated that sand at Facility A had a majority percentage of mullite present while sand at Facility B comprised of 100% crystalline silica (quartz). Respirable PNOC exposure was lower than the national occupational exposure limits (OEL) at both facilities. Respirable silica (quartz) time-weighted average (TWA) exposure at Facility B indicated a 0.06 mg/m3 and 0.05 mg/m3 for two operators respectively, which is below the South African OEL-CL of 0.1 mg/m3 but at a concentration warranting further action. The only PAH compound present at either Facility was naphthalene, but with a TWA far below its OEL. Exposure to seven VOC’s (acetone, pentane, hexane, benzene, toluene, cyclohexane and naphthas) indicated TWA’s below their respective OEL’s at both facilities. Conclusions: This is the first study of its kind to assess the physicochemical characteristics and the respiratory exposure to HCS’s during the AM of sand casting moulds. This study is of imperative value, especially as the results have indicated exposure to respirable fractions of crystalline silica (quartz) at one Facility as well as low concentrations of naphthalene and other VOC’s, indicating the need for biological monitoring. This study opens the doors to research other facets of exposure, such as assessing the inhalable and thoracic exposure and assessing furfuryl alcohol exposure. Keywords: Silica, particle size fractions, occupational exposure, polycyclic aromatic hydrocarbons, volatile organic compounds, health effects, additive manufacturing
Agtergrond: Tydens dunlaagvervaardiging (DV) van sandgietsels word potensiële stof spesies van onbekende partikel groottes of mineraalsamestelling, en gevaarlike chemiese substanse (GCS’s) soos kristallyne silika, polisikliese aromatiese koolwaterstowwe (PAK) en vlugtige organiese verbindings (VOV) bevry/vrygestel tydens die voor-verwerking, verwerking en na-verwerking fases van vervaardiging. Doelwitte: Grootmaat sandmonsters is versamel van twee navorsingsfasiliteite (Fasiliteit A en Fasiliteit B) in Suid-Afrika om partikel groottes en mineraalsamestelling te bepaal. Respiratoriese blootstellingsmonitering van GCS is uitgevoer. Metodes: Fisies-chemiese karakterisering van nuwe, gebruikte en gemengde grootmaat sandmonsters deur partikel grootte verspreiding (PGV) analise, skandeerelektronmikroskopie (SEM) analise en X-straaldiffraksie (XSD) is uitgevoer om partikel groottes en hul mineraal samestelling te bepaal. Area en persoonlike respiratoriese blootstellingsmonitering van partikels nie andersins klassifiseerbaar (PBAK), kristallyne silika (kwarts), PAK en VOV, is uitgevoer vir die duur van elke proses om konsentrasie vlakke te bepaal vir 'n vergelyking met die nasionale wetgewing. Resultate en bespreking: Vir nuwe sand, is 'n gemiddelde partikel grootte van 137.49 μm by Fasiliteit A en 282.70 μm by Fasiliteit B gevind, wat aandui dat beide fasiliteite partikel groottes groter as die inasembare grootte fraksie gehad het. Tien persent van die partikels by Fasiliteit A was egter kleiner as 75.35 μm, wat dui op die teenwoordigheid van inasembare partikels. Die SEM beelde ondersteun die bogenoemde partikelgrootte bevindings, met partikel groottes > 100 μm. XSD ontleding het aangedui dat sand by Fasiliteit A 'n meerderheid persentasie van “mullite” bevat het terwyl sand by Fasiliteit B uit 100% kristallyne silika (kwarts) bestaan het. Respireerbare PBAK blootstelling was laer as die nasionale beroepsblootstelling drempel (BBD) by beide fasiliteite. Tyd beswaarde gemiddeld (TBG) van respireerbare silika (kwarts) blootstelling by Fasiliteit B was 0.06 mg/m3 en 0.05 mg/m3 onderskuidelik vir twee operateurs, wat laer is as die Suid-Afrikaanse BBD van 0.1 mg/m3, maar by 'n konsentrasie wat verdere aksie regverdig. Die enigste PAK teenwoordig by enige van die Fasiliteite was naftaleen, maar met 'n TBG ver onder sy BBD. Blootstelling aan seve VOV (asetoon, pentaan, heksaan, benseen, tolueen, sikloheksaan en nafta) het aangedui dat die TBG onder hul onderskeie BBD was by beide fasiliteite. Gevolgtrekkings: Dit is die eerste studie van sy soort wat die fisies-chemiese eienskappe en die respiratoriese blootstelling aan GCS’s gedurende die DV van sandgietsels evalueer. Hierdie studie is van imperatiewe waarde, veral omdat die een Fasiliteit se resultate die teenwoordigheid van respireerbare deeltjies van kristallyne silika (kwarts) asook lae konsentrasies van naftaleen en ander VOV’s getoon het, dui dit op die noodsaaklikheid vir biologiese monitering. Hierdie studie maak die deure oop om ander fasette van blootstelling, soos die assessering van die inasembare en torakale blootstelling en die assessering van furfural alkohol blootstelling.Master
Exposure of workers to nickel, copper and lead in a base metal recovery plant and laboratory
Get PDFThesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2011Objectives: The objectives of this study were to establish the extent of dermal and respiratory exposure at selected locations at a South African platinum mine. The study included exposure to lead oxide fumes in an assay laboratory, nickel sulfate powder at a nickel sulfate crystallizer circuit and packing site and metallic copper dust whilst executing copper stripping. Methods: In an availability study, the dermal metal exposures were measured before, during and at the end of shifts. Dermal exposure samples were taken with GhostwipesTM from the dominant hand, wrist and forehead. Wipes were analyzed using Inductively Coupled Plasma-Atomic Emission
Spectroscopy (ICP-AES). Wipe samples were taken from surfaces in the workplace and analyzed according to NIOSH 9102, using ICP-AES. Personal and static inhalable dust samples were taken and the dust samples were analyzed according to NIOSH 7300, using ICP-AES. A validated questionnaire was used to evaluate self reported dermatological complaints of the workers at the fire assay laboratory and base metal recovery plant. Results: 100% of the nickel respiratory exposures and 36.8% of the lead respiratory exposures were above the occupational exposure limits (OEL). Copper respiratory exposure was present but less
significant with a geometric mean of 0.071 mg m-3. All of the dermal lead measurements and the majority of the nickel and copper dermal measurements were below the limit of detection. Nickel surface contamination was the most significant and ranged between 8.430 μg cm-2 and 387.488 μg cm-2. Only 30% of the copper surface sample results were below the detection limit with a maximum surface sample of 14.41 μg cm-2. Lead surface contamination was low with 90% of the samples below the limit of detection. All of the workers at the nickel crystallizer circuit and packing site had a Dalgard score above 1.3 and therefore are at a higher risk of developing a skin disease.
None of the workers at the copper stripping site had a significant Dalgard score and only one worker at the fire assay laboratory had a score above 1.3 and therefore is at a higher risk of developing a skin disease. Conclusions: Recommendations were made to lower the exposure to inhalable lead and nickel. The low lead dermal measurements may be due to adequate personal protective equipment usage and hygiene practices. Although the ethnicity of the workers may be the reason for the low incidence of
dermatological complaints, the Dalgard score indicated that five workers are at risk of developing skin diseases.Master
Recommendation of a classification system and occupational exposure limits for chemical carcinogens
Get PDFMSc (Occupational Hygiene), North-West University, Potchefstroom Campus, 2016Introduction: An increased number of occupational cancers reported annually can be attributed to workers being exposed to hazardous chemical substances (HCSs) in their workplace. Carcinogen classification systems such as the International Agency for Research on Cancer (IARC), the American Conference of Governmental Industrial Hygienists (ACGIH), Environmental Protection Agency (EPA), National Toxicology Programme (NTP) and the European Union (EU) help to identify the carcinogenic risk associated with certain HCSs with the help of data collected from scientific research programmes. Incorporation of such a system into South African legislation may reduce the number of occupational cancers developed by the South African workforce. Aim and objectives: The Aims and objectives are as follows: (1) to evaluate existing carcinogen classification systems of developed countries in order to establish which system or combination of systems is the best option to use for establishing a carcinogen classification system to be recommended for incorporation into South African occupational health legislation; (2) To identify hazardous chemical substances (HCSs) listed in the carcinogen classification systems of developed countries and to compare them with the HCSs listed in the Regulations for Hazardous Chemical Substances (RHCS) and the Mine Health and Safety Regulations (MHSR) that should be classified as carcinogenic; and (3) to compare the occupational exposure limits (OELs) of above mentioned carcinogens as listed by developed countries or organisations with the OELs listed in the RHCS and the MHSR.
Methods: A carcinogen classification system was identified by making use of set criteria points. Thereafter, the HCSs that were considered human carcinogens were identified in the RHCS and the MHSR using the selected carcinogen classification’s notations. The OELs listed in the RHCS and MHSR for these HCSs were then compared to the OELs listed for the same HCS’s OELs within ten developed countries/jurisdictions with the help of the geometric means method. In addition the interval method was used for the comparison of the number of MHSR OELs that are similar, lower or higher than that of the RHCS. Results: The carcinogen classification system with the highest score was the IARC. Therefore, this study used the HCSs classified as human carcinogens by the IARC. The RHCS contains two tables that list OELs for HCSs namely Table I and Table II. The total number of HCSs listed in the RHCS (Table I = 22 HCS and Table II = 55 HCS) was 77. It was found that the country/jurisdiction with the lowest geometric mean when Tables I and II were combined was Finland with a geometric mean of 0.300. It was found that there is no statistical significant difference (p = 0.138) between the geometric means of the RHCS’s Table I and II. The database for the MHSR only contained 76 substances listed as carcinogenic by the IARC. Finland also had the lowest geometric mean with a value of 0.475. Since the geometric mean for Finland in both the analysis for the RHCS and MHSR was far below 1, it indicated that the OELs contained in this list was the lowest of all the developed countries included in this study. When the interval method was used to determine the number of MHSR OELs for carcinogens that are similar, lower or higher than the RHCS OELs it was found that 64.5% of the RHCS OELs are similar to the MHSR and 34.2% of the MHSR OELs were lower than the RHCS OELs. Conclusion: The carcinogen classification reasonably practicable for use within South African occupational health legislation is the IARC’s carcinogen classification, which classified a total of 481 substances of which the RHCS contained 77 substances and the MHSR contained 76 substances classified as carcinogenic to humans (Group 1, Group 2A and Group 2B). It was found that South African OELs are at a higher level than the OELs listed by some developed countries. The geometric mean values calculated for most developed countries were below 1 with the exception of OSHA in the RHCS. In the MHSR it was found that OSHA, Australia and the United Kingdom had a geometric mean >1. When the RHCS’s OELs were compared to the MHSR a geometric mean of 0.651 was calculated that confirmed the overall level at which OELs of the MHSR are set were at a lower level. Using the lowest available OEL from all countries/jurisdictions will provide protection to the workforce in South Africa against the development of occupational cancer.Master
Electrophysiological effects of fractions isolated from the venom of Parabuthus granulatus on calcium channels in cardiac myocytes
Get PDFThesis (M.Sc. (Physiology))--North-West University, Potchefstroom Campus, 2005.Scorpion toxins specific for Na+ and K+ channels, have been studied extensively but relatively little has been done on Ca2+ channel toxins. Toxins in the venom of only two South African scorpions P. transvaalicus and P. granulatus have been found to interact with Ca2+ channels. Kurtoxin isolated from the venom of P. transvaalicus inhibits the T and L-type neuronal Ca2+
channels, whereas KLI and KLII (Kurtoxin-like peptide I and II), isolated from P. granulatus,
inhibits T-type Ca2+ channel activity in mouse male germ cells. In this study the effects of fractions isolated from the venom of P. granularus on Cca2+ channels in rat ventricular myocytes were investigated by means of the whole-cell patch clamp technique. Fractions of P. granulatus crude venom were isolated with Sephadex G50 columns (fraction I-IV). Fraction III (PgIII) showed a voltage dependent increase of the inward Ca2+ current and influenced the channel kinetics by shifting the voltage dependence of activation towards more
hyperpolarizing membrane potentials and decreased the rate of inactivation and deactivation. The time of the current to reach peak was also delayed. PgIII was further separated by HPLC in an attempt to identify the subfraction/s responsible for the agonistic effect. Subfraction I had an agonistic effect similar to PgIII, whereas subfraction II and III, decreased the Ca2+
current. The observed agonistic effect has not been described in the literature. The
identification of new peptide structures with unique functions are important in the field of
toxin research. Peptides that target Ca2+ channels can be valuable tools to characterize Ca2+ channels. Ca2+ channels in the heart are implicated in a number of pathological disorders like angina, ischemia, some arrhythmias and hypertension.Master
Comparison of airborne particulate exposure in two platinum refining process areas
Get PDFThesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2011.The aims and objectives: The aims and objectives of this study were to characterize and compare the airborne particulate matter in the tankhouse and crusher areas of a base metal refinery sampled with two separate methods, in terms of mass concentration, nickel content, and particle size distribution. Methods: Area sampling was conducted in the two areas. Two methods were applied to collect particulate samples. The first is a multi–stage virtual impactor, the Respicon, which was used to determine the three critical particle fractions (inhalable, thoracic and respirable). The NIOSH 7300 method determined the particle concentration and nickel percentage present in each fraction. Using formulas provided by the manufacturers two additional particle–size fractions (extra–thoracic and trachea–bronchial) could be calculated. The second was based on the standard NIOSH 0500 method, which determined particle size distribution depicted as cumulative percentages. The samples were analyzed using laser scattering instrumentation. Results: In the tankhouse the highest level of exposure was to particles bigger than 10 um, with the highest nickel percentage also falling into this range. However, high nickel percentages were present in all three cut–off sizes (4 um, 10 um and > 10 um). The particle concentration for the crusher area was the highest for particulates bigger than 10 um, with the highest nickel percentage present in this fraction. After comparing the tankhouse and crusher areas, it is clear that the particle concentration is much higher in the crusher area according to all sampling methods used. The nickel content present in the analysis of these areas is of great concern. Conclusion: With the knowledge obtained through this research one hopes to establish a basis for particle size sampling in the platinum mining industry. This may lead to the development of health based OEL's and reflect a more accurate evaluation of workers particulate exposure. This information will give a greater understanding of health risks workers are exposed to.Master
Dermal and respiratory exposure to nickel in a packaging section of a base metal refinery
Get PDFMSc (Occupational Hygiene), North-West University, Potchefstroom Campus, 2014Nickel is one of the most commonly known sensitisers and has been classified by the International Agency for Research on Cancer (IARC) as a possible carcinogen to humans (group 2B). Workers at a South African base metal refinery packaging area are potentially exposed to many hazardous chemicals that include nickel. Aims and Objectives: The aim and objectives of this study were to assess dermal and respiratory exposure of workers exposed to nickel in a packaging section at a South African base metal refinery and to assess the change in skin barrier function during a work shift by measuring percentage change in trans epidermal water loss (TEWL), skin hydration and skin surface pH. Skin health was established with a skin questionnaire. Surfaces that workers may come into contact with were also assessed.
Method: Respiratory and dermal exposure assessment was done concurrently. Respiratory exposure was assessed and analysed by using the National Institute for Occupational Safety and Health (NIOSH) method 7300. The Institute of Occupational Medicine (IOM) inhalable aerosol sampler was used for personal air sampling. The TEWL index, skin hydration and skin surface pH of the index finger, palm, forearm and forehead were measured before and at the end of the shift with a Derma Measurement Unit, EDS 12 and Skin-pH-Meter® pH 905. These measurements were reported as percentage change in skin barrier function during the shift. Dermal exposure samples were collected with Ghostwipes™ from the index finger and palm of the dominant hand before, during and at the end of the shift, while samples from the forearm and forehead were only collected before and after the shift. Surface sampling was collected and all wipes were analysed for nickel according the NIOSH method 9102, using inductively coupled plasma-atomic emission spectrometry. Results: Respiratory exposure for the whole group of workers in a packaging section was well below the eight hour Time Weighted Average (TWA) respiratory Occupational Exposure Limit (OEL) of 0.5 mg m-3 for nickel. Dermal nickel loading was detected for all the job categories on all the anatomical areas even before the shift had commenced. During the shift more nickel was detected on the index finger and palm of the hand. Levels on the forearm and forehead were much lower in comparison with the index finger and the palm of the hand. Workplace surfaces, which workers may come into contact with on a daily basis, were also contaminated with nickel. Forklift drivers showed high exposure on the index finger and palm of their hands, and this can be attributed to them not wearing any gloves for hand protection. An increase in percentage change for TEWL was seen for most of the job categories on all anatomical areas measured during the shift. Percentage change in skin surface pH and skin hydration varied among job categories.
Conclusion: The research addressed the problem statement, with the stated objectives. It was hypothesised that workers at a packaging section of a base metal refinery are exposed to quantifiable levels of nickel through the dermal exposure route. The hypothesis was accepted and control measures together with future studies were recommended. The results confirmed that all workers at a base metal refinery are exposed to quantifiable levels of nickel through the dermal exposure route. Dermal exposure was evident on all anatomical areas for all job categories before the shift had commenced. Personal protective equipment was provided to all employees, but forklift drivers did not wear gloves when operating the forklift. Respirable exposure to nickel was below the OEL. Changes in TEWL and to a lesser extent skin hydration, suggest a deterioration in skin barrier function during the shift. Forklift drivers as well as plate washers may be the highest risk job categories in developing allergic contact dermatitis. Several measures to lower respiratory and dermal exposure to nickel are also recommended.Master
Assessment of the occupational exposure to cobalt at a base metal refinery
Get PDFMSc (Occupational Hygiene), North-West University, Potchefstroom Campus, 2016Objectives: The objectives for this study were (i) to assess the respiratory exposure of base metal refinery workers to cobalt sulphate; (ii) to assess the dermal exposure of these workers to cobalt sulphate; (iii) to assess the skin barrier function by means of TEWL, skin hydration and skin surface pH; (iv) to assess workers’ urine cobalt concentration by means of biological monitoring and; (v) to determine the contribution of each exposure route to the total urine content. Methods: The study was conducted at a base metal refinery where workers stationed in a Cobalt plant (20 workers) and Packaging plant (5 workers) are potentially exposed to soluble cobalt sulphate through respiratory and dermal exposure routes. Evaluation of the respiratory exposure was quantified using the Institute of Occupational Medicine (IOM) aerosol sampler. Evaluation of the dermal exposure included quantification of the cobalt deposition on the skin using Ghostwipes™ as a removal method, while TEWL, skin hydration and pH measurements were used to determine the change in skin barrier function. Dermal measurements were done on four different anatomical areas (forearm, wrist, palm of hand and back of hand) before, during and after the working shift. Evaluation of the cobalt content in the urine of employees was included to evaluate the exposure through all exposure routes (respiratory and dermal).
Results and Discussion: Occupational exposure to cobalt at a base metal refinery was detected through the respiratory and dermal routes of exposure. High inhalable airborne exposures above the Occupational Exposure Limit - Time Weighted Average (OEL-TWA) were noted for several workers in both the Cobalt and Packaging plant of the base metal refinery. Respirable fractions only contributed a small fraction of the total airborne exposure to cobalt. Detectable levels of cobalt were found on the skin of exposed workers in both the Cobalt and Packaging plant with geometric means ranging between 0.104 μg/cm2 on the back of hand and 77.600 μg/cm2 on the wrist. The majority of measurements indicated an increase in TEWL percentage changes from the beginning to the end of the shift, with a decrease being reported in all skin hydration measurements, and pH indicating high variability between the Cobalt and Packaging plant. Biological monitoring data indicated baseline urine levels above the Biological Exposure Index (BEI) of 15 μg Co/g Creatinine in five out of the 12 workers in the Cobalt plant. The mean urine cobalt concentration in Cobalt plant workers decreased slightly from a baseline measurement of 17.83 μg Co/g Creatinine to 12.37 μg Co/g Creatinine on day 5. Workers’ urine levels in the Packaging plant however indicated cobalt concentrations of approximately three times lower than the recommended BEI, with levels ranging between a baseline measurement of 2.5 μg Co/g Creatinine and 6.6 μg Co/g Creatinine on day 5. Pair wise correlations indicated significant strong positive correlations between dermal exposure and biological monitoring (change in urine cobalt concentration between Day 3 and the Baseline) in the Cobalt plant and the Cobalt and Packaging plants combined. Conclusion: Refinery workers are exposed to cobalt sulphate (liquid solution and cobalt sulphate crystals) through the respiratory and dermal routes of exposure in both the Cobalt and Packaging plant of the base metal refinery, of which only dermal exposure significantly correlated with the total urine content of the workers. Changes in the skin barrier function also indicated that the skin integrity was compromised.Master
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