James, Most safety standards have requirements for ground bond testing based on the current available in the hazard. I've never seen requirements specifying the type of washer other than it cannot have compressible material in the stack up, as polymers or fiber washers.
Back in the day, I learned my earthing (EU) or grounding (US) for high power equipment from a German expert at LGA Landesgewerbeanstalt Bayern in Nürnberg and the guidance I received was to use star washers on plain metal surfaces; not to cut through paint as many believe, but to dig into the metal parts to provide an oxygen free connection. Yes, initial conductivity for a steel star washer is not great, but the EU Liability Directive would indicate that the connection needs to be reliable for up to 10 years. For a normally very low current (mA) ground to launch into service at a moment's notice, and safely carry away a few hundred amps, is sometimes a challenge if the long term environment is in the least bit corrosive. Notably, my mentor also allowed serrated lock washers. Best, Doug Douglas E Powell Laporte, Colorado USA LinkedIn <https://www.linkedin.com/in/coloradocomplianceguy/> (UTC -07:00) Mountain Time (US-MST) On Tue, Feb 15, 2022 at 8:34 AM James Pawson (U3C) < ja...@unit3compliance.co.uk> wrote: > Hello all, > > > > I’ve given myself a regular internet headache trying to understand the > relative merits of spring vs star washers for use on an earth stud for > protective earthing purposes. > > > > What is the conventional wisdom and justification? I know I can trust you > folks to be above a simple “we’ve always done it this way” > > > > Can anyone point me towards any citable references or standards covering > this subject? > > > > I promise I will write a blog post to pull the information together for > future confused generations. > > > > Thanks and all the best, > > James > > > > > > James Pawson > > The EMC Problem Solver > > > > *Unit 3 Compliance Ltd* > > *EMC : Environmental & Vibration : Electrical Safety : CE & UKCA : > Consultancy* > > > > www.unit3compliance.co.uk | ja...@unit3compliance.co.uk > > +44(0)1274 911747 | +44(0)7811 139957 > > 2 Wellington Business Park, New Lane, Bradford, BD4 8AL > > Registered in England and Wales # 10574298 > > > > > > > > > ------------------------------ > [image: AVG logo] <https://www.avg.com/internet-security> > > This email has been checked for viruses by AVG antivirus software. > www.avg.com <https://www.avg.com/internet-security> > > <#m_848691752694288160_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> > - > ---------------------------------------------------------------- > > This message is from the IEEE Product Safety Engineering Society emc-pstc > discussion list. To post a message to the list, send your e-mail to < > emc-p...@ieee.org> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > > Attachments are not permitted but the IEEE PSES Online Communities site at > http://product-compliance.oc.ieee.org/ can be used for graphics (in > well-used formats), large files, etc. > > Website: http://www.ieee-pses.org/ > Instructions: http://www.ieee-pses.org/list.html (including how to > unsubscribe) <http://www.ieee-pses.org/list.html> > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > Scott Douglas <sdoug...@ieee.org> > Mike Cantwell <mcantw...@ieee.org> > > For policy questions, send mail to: > Jim Bacher <j.bac...@ieee.org> > David Heald <dhe...@gmail.com> > - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
