The plasma jet: industrial hygiene aspects and a survey of current United States practices for employee protection.
Abstract The plasma torch, because it concentrates large amounts of thermal energy in a small volume, has become increasingly popular in industry. During the past fifteen years, the plasma torch has developed into an important industrial tool, and it has been used for metal cutting and welding fabricating operations that would not be possible otherwise. However, along with technological advances, the plasma torch has presented new problems to the industrial hygiene field. It is the purpose of this paper to discuss these problems and the extent of industrial hygienist's awareness of them. A brief outline of the theory of the plasma torch and the history and scope of its industrial usage is also presented.
A Preliminary Study of Some Health Hazards in the Plasma Jet Process
A brief technical description is given of the plasma jet process, and reference is made to its likely practical applications in industry. An opportunity has been taken during experiments with a prototype plasma jet to assess some of the health hazards which might arise from these industrial applications and to indicate the type of precautions which should be observed in practice. Measurements and analysis of the noise emitted during the operation of a jet showed that the sound intensities ranged from 79·5 to 90·5 dB (re 0·0002 dynes/cm.2) per octave band between 300 and 10,000 cycles/second. Three male volunteers exposed to the noise for a period of one hour were subsequently found to have a mean temporary threshold shift of 19 dB at 4,000 cycles/second. Air sampling and analysis for ozone and nitrogen dioxide in the near vicinity of the jet gave a negative result for the former substance but demonstrated that the latter contaminant was present in concentrations ranging from 0·1 to 9·6 p.p.m.
Finite Difference Modeling on the Temperature Field of Substrate in Friction Surfacing
Friction surfacing is an advanced process of great potential, especially in the field of repair and reclamation of worn and damaged components. As a kind of thermal processing technology, the temperature profile and changes of the substrate in friction surfacing are important factors to get coatings of high quality. In this paper, the temperature field of the substrate during the process is simulated by finite difference method. The results are consistent with experiments, reappearing the temperature change of the substrate during friction surfacing, allowing further study on figuration and quality of coatings.