Analysis of barometric pressure temperature and air density on flow rate of gravimetric dust sampling pumps and silica dust monitoring at a South African gold mine

Abstract

The eagerness to overcome workforce health crises in the mining industry continues to be a challenge, undermining health system transformation globally and more specifically in South Africa. Despite policy implementation and interventions towards health system improvements in South Africa’s mining sector, literature does not provide a detailed narrative on accurate analysis and calibration, when barometric pressure, temperature and air density variations occur, during crystalline silica dustmonitoring processes. Incorrect reporting of crystalline silica concentrations may therefore be a contributing factor in unceasing new cases of silicosis and other silica dust related health issues. This study aimed to determine the impact of barometric pressure, air density and temperature on the concentration of respirable dust samples, using personal gravimetric dust sampling instrument. The study further sought to establish the impact these environmental variables may contribute and whether this can be quantified and applied on measurements taken to correct historical measurement results. The following objectives were used to: • Determine the impact of barometric pressure, air density and temperature on the flow rate of various gravimetric dust sampling pumps. • Determine the impact of barometric pressure, air density and temperature on the concentration of respirable dust samples, using dust sampling instruments. • Establish the impact of the environmental variables that may contribute to the differences in the results obtained. • Establish whether the GilAir Plus and Tuff pumps do maintain a constant flow rate at various barometric pressure levels. • Analyse gravimetric data to determine the percentage error, if correction factor needs to be applied. • Analyse the particulate matter collected on the filter media to determine the type and particle sizes of the particulate. When a personal airborne silica dust sampler is used underground, it is subjected to extreme ambient thermal conditions, such as barometric pressure, air density changes, and temperature variations due to changes in the geothermal gradient and the increase in virgin rock temperature. However, these changes are not accounted for, neither are they considered when sampling strategies are employed. The current industry sampling methodologies are applied in a manner that assumes that the airborne particulate sampling device, set at certain flow rate under certain conditions of barometric pressure, air temperature and density on surface, will maintain that flow rate when subjected to different ambient environmental conditions underground. The study found that barometric pressure, air density and temperature changes do affect the GilAir Plus and Tuff gravimetric dust pump’s flow rate and therefore underground conditions need to be considered when gravimetric sampling is conducted. The ability of an individual pump to adjust its flow rate as it encounters variations in barometric pressure, temperature and density is dependent on its age, amongst other factors. The GilAir-3 pumps were the only pumps that indicated an increase in flow rate as barometric pressure increased, unlike the GilAir Plus and Tuff pumps. The implications hereof are that the GilAir Plus and Tuff pumps overcompensate for the changes in environmental conditions. The Tuff and GilAir plus, although at first glance seem to be exaggerating the exposure levels, should they be used as instruments of choice for monitoring dust exposures in industry, it could mean that the results obtained, may demand stricter dust control measures be implemented. Instruments of high accuracy in determining worker exposure to quartz are required. This remains that the primary reason for conducting measurements is not merely for compliance, but rather to improve dust control strategies.