Assessment of suspended dust from pipe rattling operations

摘要

Six types of aerosol samplers were evaluated experimentally in a test chamberwith polydisperse fly ash. The Andersen sampler overestimates the mass of smallparticles due to particle bounce between stages and therefore provides a conservativeestimate of respirable particulate mass and thoracic particulate mass. The TSP samplerprovides an unbiased estimate of total particulate mass. TSP/CCM provides noinformation below ESD 2 ????m and therefore underestimates respirable particulate mass.The PM10 sampler provides a reasonable estimate of the thoracic particulate fraction.The RespiCon sampler provides an unbiased estimate of respirable, thoracic, andinhalable fractions. DustTrak and SidePak monitors provide relative particleconcentrations instead of absolute concentrations because it could not be calibrated forabsolute particle concentrations with varying particle shape, composition, and density.Six sampler technologies were used to evaluate airborne dust concentrationsreleased from oilfield pipe rattling operations. The task sampled was the removal ofscale deposited on the inner wall of the pipe before it was removed from service in aproducing well. The measured mass concentrations of the aerosol samplers show that a Gaussianplume model is applicable to the data of pipe rattling operations for finding anattainment area. It is estimated that workers who remain within 1 m of the machinecenterline and directly downwind have an 8-hour TWA exposure opportunity of (13.3 ????9.7) mg/m3 for the Mud Lake pipe scale and (11.4 ???? 9.7) mg/m3 for the Lake Sand pipescale at 95 % confidence. At distances more than 4 m downwind from the machinecenterline, dust concentrations are below the TWA-TLV of 10 mg/m3 for the worker inboth scales. At positions crosswind or upwind from the machine centerline there is nomeasurable exposure. Available data suggest that the attainment area for the publicstarts at about 9 m downwind from the machine centerline in both scales, as 24 houraverage concentrations at these distances are smaller than the 0.15 mg/m3, the NAAQSfor unrestricted public access. The PSD of the suspended plume is dominated byparticles smaller than ESD 50 ????m.