Health Safety and Environmental Concerns

There are some health, safety, and environmental concerns associated with thermal spray coating processes, as with most industrial processes. In general they are similar to those associated with welding processes. Obviously, all plant or laboratory, local, state, and federal government directives should be followed. None of the thermal spray processes should be attempted without proper training of all of the personnel involved and careful consideration of any hazards associated with the particular materials being used to prepare for or produce the coating. Proper care and maintenance of the equipment, including all gas and electric lines, will greatly reduce any hazards. In addition, design and procedure reviews for safety by qualified engineers are advisable. These should include the ancillary processes of surface preparation, part handling, and finishing as well as the coating process itself.

Dust and Fumes. All thermal spray processes produce dust and fumes, so operators must be protected and the dust and fumes collected. When possible, the coating process should be conducted in a cubicle equipped with ventilation and dust collection equipment and with the operators outside. Each thermal spray process has its own airflow requirement to provide adequate ventilation, and the equipment manufacturer should be able to provide guidelines. Nonetheless, dust monitors should be periodically used to ensure that the ventilation system is working properly. If the operators must be in the cubicle or the coating must be done in the open, the operators should wear respirators. It is no longer considered adequate to rely only on air flow away from the operator to provide adequate protection. The type of respirator used depends on the material being deposited. The effluent from the dust collection system should be periodically monitored to ensure compliance with all regulations.

Noise generated by thermal spray processes ranges from about 80 dB for some of the flame spray processes to over 120 dB for some of the HVOF processes, over 140 dB for some plasma spray processes, and to over 150 dB for the detonation gun processes. Individual ear protection is adequate for the former, but the latter must be operated in sound-reducing cubicles. Sound levels at the operator's position should be measured and compliance with all regulations ensured. In addition, all personnel in the vicinity of the spray operation should have their hearing checked periodically.

Light Radiation. The spectrum of light emitted by the thermal spray devices ranges from the far infrared to extreme ultraviolet. Adequate eye and skin protection must be used. Shade 5 lenses may be sufficient for some flame spray processes, but shade 12 is required for plasma spray and electric (wire) arc. Fire-retardant, closely woven fabrics should be worn to protect the skin from burns. Burns can be caused by heated particles bouncing from the substrate, hot gases, or light. Ultraviolet radiation will burn exposed skin and penetrate loosely woven fabrics, causing burns similar to a severe sunburn in minutes.

0 0

Post a comment