[ RadSafe ] Fw: [OEM] TIG Welding and Titanium face implants

[Gary Masters]

I am no expert on this topic.

A bit of Google searching revealed a text _Exploiting advances
in arc welding technology_ and a table of contents listing
"Microwave powered plasma for welding and cutting" under the
heading "Process developments - TIG welding".  This can be seen
at http://www.woodheadpublishing.com/en/book.aspx?bookID=105.
It appeared I'd have to pay $270 to learn anything further in
this vane.

All of the TIG welding I've had experience with -- several years
ago -- was as Richard describes below.

It seems to me that if TIG welding created appreciable microwave
radiation there would be OSHA, or other regulating body,
requirements to protect the operator.  I am not aware of any
requirement to protect the operator from anything other than
the heat, UV, and visible light emissions.

This could be easily and definitively resolved if someone
were to measure the microwave field strength in the vicinity
of the operator's head with an active arc.  It would be
more interesting to use an RF spectrum analyzer in the same
circumstances and look at the emitted RF spectrum.  If anyone
does this be sure to establish the noise floor first (roughly
analogous to doing a background count).

Gary Masters

On Sat Jan 14, 2006 at 07:53:29 -0500, Richard L. Hess wrote:
> Please do not rely on what I am about to say as 
> this is just some preliminary thoughts for 
> further research. I am a broadcast engineer not a CHP nor MD.
> 
> It appears that the bulk of TIG welding is done 
> with mains-operated AC arcs. There appears to be 
> benefits to using AC over DC in the welding process.
> 
> http://www.twi.co.uk/j32k/protected/band_3/ksgbm001.html
> 
> Indicates that the HF energy introduced into the 
> arc for starting the arc (and perhaps for 
> stabilization during the process). One reference 
> indicates that this is 50,000 Hz and above. 0.05 
> MHz. A microwave oven operates at about 2,450 MHz 
> (near the 802.11 b/g spectrum-joy). 
> http://www.ccohs.ca/oshanswers/phys_agents/microwave_ovens.html
> 
> I don't see a lot of energy being available for facial heating.
> 
> The biggest risk I see is aiming a lot of energy 
> in the direction of the person's face when that 
> energy would be of such a frequency as to 
> resonate with the metal implants.  In that case 
> there could be heating of the implants. Let's 
> assume the implants are less than six inches long 
> and little power will be transferred to them if 
> they are less than 1/8 of a wavelength (both 
> conservative numbers driving the frequency 
> lower). So what is the frequency of to be 
> conservative again a 2 m wave in space? It's about 150 MHz.
> 
> Would we expect to see substantial energy at 150 
> MHz from this arc plus the HF ignitor? I could 
> find any spectrum plots, but my first guess would be no.
> 
> Now there may be other techniques that I am not 
> aware of using microwave energy to heat the 
> metal, but TIG looks like a conventional arc with 
> a shielding gas and a non-sacrificial tungsten electrode.
> 
> More research required. Hope this out-loud 
> thinking was at least slightly helpful.
> 
> Cheers,
> 
> Richard
> 
{SNIP}