The query I'd like to put to the readers of this list is not exactly 
EMC related, but is close enough that I hope you'll forgive me 
asking.

Can anyone give me an idea of the voltages likely to be induced 
in the unprotected input wiring of a process plant control system, 
when welding is carried out nearby?  Or point me to a resource 
that may give me some help?

The welding cables will be close (within a metre of the inputs to 
the control system, perhaps even touching the control system 
metal case).  The welding transformer will be tens of metres 
away.  The process plant control  system is an old logic design 
based around 4000 series CMOS.

The control system will not be energised when the welding is 
going on, so my main worry is induced voltages/currents blowing 
up the CMOS.  Should I worry, or sleep happy?

All advice gratefully received (except if someone tells me to throw 
away the control system and get something better protected, as 
that's not an option...)

Regards,   Mark
--
Mark Hone

  Wellman CJB Limited               Email: [email protected]
  Airport Service Road              Tel: +44 (0)2392 629239 (Direct)
  Portsmouth, Hampshire             Tel: +44 (0)2392 664911
  PO3 5PG, ENGLAND                  Fax: +44 (0)2392 697864

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