You are here

Blast Booth Noise Reduction - An OSHA Compliance Issue


OBJECTIVE: To reduce employee exposure to hazardous noise during Blast Cleaning Room (BCR) and Blast Cabinets (BC) abrasive media blasting operations to or below OSHA 8-Hour Time Weighted Average without increasing ergonomic stress on the operator. DESCRIPTION: Currently Air Logistics Complexes and many other DOD maintenance, repair, and overhaul organizations use compressed air abrasive media blasting to remove materials from surfaces and prepare surfaces to receive coatings. These operations are conducted in blast cleaning rooms, and blast cabinets. During these operations operators are exposed to compressed air blast nozzle volumes of 99dBA-110dBA to as high as 132dBA. Which resulted in the 2011 OSHA Citation 1, Item 1: Employees were subjected to sound levels exceeding those listed in Table F-16 of Subpart G of 29CFR 1910.95 and feasible administrative or engineering controls were not utilized to reduce sound levels. Blast cleaning rooms (BCR"s) and blast cabinets (BC"s) range in size from a large breadbox to enclosures large enough to fit entire aircraft or ground equipment. BC"s are somewhat small and are operated through gloved ports in the side of the cabinet. BCR"s can be the size of a hangar and are operated by an operator(s) inside the BCR. Both BC and BCR operators can be subjected to compressed air blast nozzle noise exceeding 132dBA. BCR"s blast operations are performed using one or more dual-action, 1.25 in. diameter X .25 in. wall, high pressure (100psi) compressed air hoses that release compressed air only or compressed air with abrasive media at the flip of a switch. These hoses provide the air used to; blast (blow-down) the metal surfaces with abrasive media and to blow-off the dust and debris with compressed air. In addition to the noise hazard, employees performing abrasive media blasting operations experience ergonomic stress resulting from the size, weight and stiffness of the compressed air hose. Employees working in blast areas using thicker walled hoses experience higher stress and fatigue and report a higher number of stress related injuries. Therefore, systems engineered noise abatement/exterior operator solutions must not increase operator ergonomic/musculoskeletal stressors above current levels. Currently, employee exposure to blast booth noise is being monitored by industrial hygienist and all operators are enrolled in the Hearing Conservation Program. Bio-Environmental controls include utilizing 20+dB NRR ear muffs over 20+db NRR ear plugs and time-limited work periods in some blast areas. The attenuation provided by PPE (ear plugs and muffs) is generally insufficient to provide the Air Force standard dose of 85 dBA equivalent continuous level for 8 hours. Many processes include daily time limits as low as 30 minutes per worker total exposure per day to keep noise dose under 100%. This topic solicits an R & D engineered solution(s) that will provide manned hearing safe and/or automated BC and BCR environments that meet or exceed current production rates, does not induce any additional ergonomic stress on the operator(s) and meets or exceeds OSHA"s 8-Hour TWA for noise. PHASE I: Establish feasibility of and development path to BOTH, engineered 90dBA manned, AND unmanned pneumatic abrasive blast coating removal operations in currnet BCR and BC work areas using media such as steel peen, walnut shell, CO2, starch, garnet and Quick Strip. PHASE II: Phase II Design, develop and test a prototype of the system/strategies developed in Phase I in a relevant operational environment AND Provide an engineering development plan sufficient to demonstrate the ability to provide a viable pilot manufacturing line. PHASE III: DEMONSTRATE the technology in an OPERATIONAL environment and Provide fully coordinated transition plan which addresses all technical readiness & manufacturing readiness necessary to transition from engineering development to commercial products for government and non-government customers. REFERENCES: 1. OSHA Standard 29 CFR 1910.95, Occupational Noise Exposure. 2. Performance Specification, Blast Cleaning Room MIL-PRF-32037. 3. Military Specification, Plastic Media, For Removal of Organic Coatings MIL-P-85891A.
US Flag An Official Website of the United States Government