CrVI ) Hexavalent Chromium (Cr( Exposures in Electric Power Generation
Arlen W Siert, PhD, CIH, CSP, CHMM Xcel Energy Stephen C Woods, MS, CIH Xcel Energy Kenneth D Blehm,, PhD, CIH Colorado State University Darrell L Dechant,, PhD, CIH, Esq Sabre Technical Services
Scope of Cr VI Exposure Assessment Study 10-year study (1996-2006) 13 power plants in 2 states Colorado: 7 coal fired, 3 gas-fired Texas: 2 coal-fired, 1 gas-fired
Scope of Cr VI Exposure Assessment Study Total 201 air samples / 182 8hr TWAs Welding & Thermal Cutting 156 air samples / 148 8hr TWAs Fly Ash Cleaning 33 air samples / 22 8hr TWAs Chromate Paint Abrasive Removal 10 8hr TWAs Boiler Refractory Installation 2 8hr TWAs Analysis: Wisconsin Occupational Health Lab using OSHA ID-215
Welding & Thermal Cutting Processes Thermal (flame) spraying Shielded metal arc welding (SMAW) Flux-cored arc welding (FCAW) Gas tungsten arc welding (GTAW) Air carbon arc cutting (ACAC) Plasma arc cutting (PAC)
Chromium Steels High Alloy Stainless Base Metals 304 SS 347 SS 321 SS 316 SS Cr% 18 18 18 17 Consumables Hardfacing 309 SS 308 SS 347 SS 316 SS INCONEL82 Cr% 27, 40 23 20 18 17 20 Medium Alloy T-91 9 9015 9 Low Alloy T-22 T-11 2¼ 1¼ 9018 8018 2¼ 1¼
Sampling Inside the Hood Omega 25 mm 0.8 µm PVC pre-weighed filter
Thermal (Flame) Spraying hydro runners with 13% Cr
Thermal (Flame) Spraying Hydro runners 13% Cr SMAW Hardfacing 27-40% Cr Measures 8hrTWA µg/m3 Measures 8hrTWA µg/m3 Samples (n) 5 Samples (n) 7 High 102 High 220 High / PEL 20.4 High / PEL 44 High air concentration 490 High air concentration 621 Median 50.1 Median 207 % n > PEL 5 µg/m 3 % n > former 52 µg/m 3 PEL 100 % n > PEL 5 µg/m 3 50 % n > former 52 µg/m 3 PEL 100 86
SMAW Hardfacing 27% Cr in coal mill
Cr VI high air concentration without LEV = 621 µg/m 3 with LEV = 231 µg/m 3
SMAW Hardfacing 30% Cr coal mill discharge valve AC 120 µg/m3 8hr TWA 46.8 µg/m3
FCAW 17% Cr in ash hopper
FCAW 17% Cr in boiler wet bottom
Flux-Cored Arc Welding High Alloy Shielded Metal Arc Welding High Alloy Measures 8hrTWA µg/m3 Measures 8hrTWA µg/m3 Samples (n) 9 Samples (n) 41 High 19 High 220 High / PEL 3.8 High / PEL 44 High air concentration 19 High air concentration 621 GM / AM 3.2 / 6.5 GM / AM 4.1 / 24.3 % n > PEL 5 µg/m 3 % n > former 52 µg/m 3 PEL 44.4 % n > PEL 5 µg/m 3 0 % n > former 52 µg/m 3 PEL 39 19.5
Shielded Metal Arc Welding Medium Alloy Gas Tungsten Arc Welding High Alloy Measures 8hrTWA µg/m3 Measures 8hrTWA µg/m3 Samples (n) 6 Samples (n) 21 High 15.6 High 1.1 High / PEL 3.2 High / PEL 0.2 High air concentration 16.3 High air concentration GM / AM 3.2 / 6.5 GM / AM 0.2 / 0.3 2.8 % n > PEL 5 µg/m 3 % n < AL 2.5 µg/m 3 17 % n > PEL 5 µg/m 3 67 % n < AL 2.5 µg/m 3 0 100%
GTAW INCONEL 23% Cr turbine blades
Cr VI Grinding stainless steel hydro runner 23% Cr AC 1.3 µg/m 3 + AC ND < 0.93 µg/m 3 =8hr TWA 0.89 VI AC
Grinding on ash-coated boiler tubes Cr VI air concentration [AC] 0.47 µg/m 3 Cr VI [AC] 0.21 µg/m 3
ACAC 17% Cr in ash hopper Cr VI AC 170 µg/m3 8hr TWA 43.6 µg/m3 AC 34xPEL
PAC 23% Cr in plant Cr VI AC 245 µg/m3 8hr TWA 20.4 µg/m3 AC 49xPEL
Air Carbon Arc Cutting High Alloy Plasma Arc Cutting High Alloy Measures 8hrTWA µg/m 3 Measures 8hrTWA µg/m 3 Samples (n) 10 Samples (n) 6 High 48.2 High 20.4 High / PEL 9.6 High / PEL 4.1 High air concentration 170 High air concentration 245 GM / AM 17.9 / 26.9 GM/AM 4.6 / 7.6 % n > PEL 5 µg/m 3 % n > former 52 µg/m 3 PEL 80 % n > PEL 5 µg/m 3 0 % n > former 52 µg/m 3 PEL 50 0
Cr VI Welding 8-Hour 8 TWA Exposures new vs previous OSHA PEL Cr Steels Cr VI Overexposures by Process (5 µg/m 3 vs 52 µg/m 3 ) Alloy Cr% SMAW FCAW GTAW High Cr/Ni 17-40 most 17-23 N: 40 New: 40% > PEL 23% > AL N: 9 New: 33% > PEL 11% > AL N: 21 New: 0%>AL Old: 15% > PEL 15% > AL Old: 0% > PEL Old: 0%>AL Medium Cr/Mo 9 N: 6 New: 17% > PEL 17% > AL Old: 0% > PEL Not used Not used Low Cr/Mo 1¼ 2¼ N: 12 New: 0% > AL Old: 0% > PEL ------------ N: 5 New: 0%>AL Old: 0%>PEL
Cr VI Thermal Cutting 8-Hour 8 TWA Exposures new vs previous OSHA PEL Cr Steels Cr VI Overexposures by Process (5 µg/m 3 vs 52 µg/m 3 ) Alloy Cr% ACAC PAC OAC High Cr/Ni 17-23 N: 9 New: 78% > PEL 11% > AL Old: 0% > PEL N: 6 New: 50% > PEL 17% > AL Old: 0% > PEL Not used 100% of air concentrations [AC] > New PEL 50%[AC]>NewPEL 22%[AC]>Old PEL 17%[AC]>Old PEL Low Cr/Mo 1¼ 2¼ N: 3 New: 33% > PEL Old: 0% > PEL N: 1 New: 0% > AL Old: 0% > PEL N: 4 New:0% >AL Old:0%>PEL
Welding & Thermal Cutting Processes Thermal (flame) spraying Shielded metal arc welding (SMAW) Flux-cored arc welding (FCAW) Gas tungsten arc welding (GTAW) Air carbon arc cutting (ACAC) Plasma arc cutting (PAC)
Thermal Cutting/Welding on Chromate-Painted Steel 3 Projects Air carbon arc cutting on boiler casing outdoors # air concentration samples # 8hr TWAs % Cr in paint range average 10 6 0.07-0.8 0.54 12 12 0.015-0.024 0.06 Welding on coal dumper spur rails indoors # air concentration samples # 8hr TWAs % Cr in paint range average 6 6 0.07-2.7 0.58 High Cr VI air concentration µg/m 3 0.67 0.22 High Cr VI air concentration µg/m 3 0.6
CrVI in Fly Ash Exposures Highest dust exposure processes monitored Baghouse bag changing Shoveling Vacuuming Air lancing Exposures differed by coal type higher in subbitumious coal ash lower in bituminous coal ash
Baghouse bag changing
Fly Ash shoveling in boiler during vacuuming
Air lancing fly ash at the top of a baghouse compartment
Abrasive Chromate Paint Removal 5 Projects Project # 8hr TWAs Needlegunning on coal feeders Needlegunning on generator Needlegunning on boiler fan Grinding on coal mill Needlegunning on boiler casing % Cr in paint range average 4 0.077-0.49 0.13 2 0.015-0.024 0.79 1 0.021 1 0.017-0.090 0.068 2 0.16 High Cr VI air concentration µg/m 3 0.69 0.15 0.19 0.11 ND<0.88
Grinding on a coal mill: shrouded grinder/attached HEPA vacuum
Needlegunning a generator: shrouded grinder/hepa vacuum
Needlegunning on coal feeders 25% lead in paint Lead air concentrations > PEL Potential for CrVI VI overexposure
Refractory Mixing Castable refractory contains low levels of Cr an air sample each of mixing and gunniting indicated levels < AL Cr VI
Gunniting castable refractory in boiler wet bottom
Conclusions on impact of OSHA Cr VI standard Welding & thermal cutting Largest impact by far Most under OSHA Cr VI Construction Std New requirements - Exposure assessment - Training - Medical surveillance - Respiratory protection - Medicals - Fit tests - Training
Impacts of OSHA Cr VI Standard Fly ash cleaning Second largest impact Under OSHA Cr VI General Industry Std New requirements Exposure assessment Training Medical surveillance Hygiene facilities Housekeeping
Impacts of OSHA Cr VI Standard Abrasive paint removal OSHA Cr Cr VI Exposure assessment Training Medical surveillance Construction Std Refractory probably exempt confirm exposures < 0.5 µg/m 3 with more samples