Posted by Ron Laden on 19/12/2019 12:57:35:
Posted by Michael Gilligan on 19/12/2019 09:18:43:
Quite simply, Ron … Mains voltage hurts if you touch it.
One thing can lead to another, and nasty accidents occur with machine tools.
Many light units are not earthed [or reliably earthed], which increases the risk.
Industrial machines have long been required to use ‘safety low voltage’ in their lighting, and I consider it a wise precaution.
MichaelG.
I thought that the reason though I dont know I fully agree with it, at least not with a good installation, …
It's amps that stamps and volts that jolts. Anything that encourages current to flow through the human body is best avoided. For example, ordinary power sockets and switches are forbidden in bathrooms because wet contact greatly increases current flow. What's acceptable in the rest of a house isn't safe in bathrooms.
Lathes and milling machines create a bathroom-like electrical hazard. Large metal tools are always carefully earthed to reduce the risk of electrocution should it develop an internal fault. However, an earthed object with a large surface area itself becomes dangerous in the event of an external problem, such as a faulty mains lamp. Putting the palm of one hand on a lathe bed whilst touching a live lamp with other is apt to be fatal. While earthing generally makes electricity safer there are plenty of exceptions!
The easiest way to make machine mounted lamps safe is to power them with low voltage via a transformer. Even if they go wrong the low voltage and transformer inhibit the amount of current that can flow through the body.
Dave