Flexible hose dust extraction question.

[Cabinetman]

So I picked up a D/X mobile unit and it works just great for what I will use it for - single mc at a time, it came with a flexible hose that has a copper multi strand wire running through it fastened to the tin duct connectors. Fairly obviously the wire has to be long enough for when the hose is stretched and this means that when it isn’t the wire flaps about inside and is causing blockages with planer shavings.
Now I have never earthed my flexible hoses in the past and I’ve never had a problem with explosions lol, am I being Blasé ?
Are you meant to expose the wire in the construction of the hose where it touches the tin duct ends? But then the wire is insulated from the dust in the hose. Confused.
What do you all do? Earthing wire or not, anyone ever had a problem without?
Ian

 

[AJB Temple]

No idea. But I would be interested in the answers.

 

[Mike]

What do you all do? Earthing wire or not, anyone ever had a problem without?

There are no earthing connections on any of my dust extraction ducting and no adverse reactions. The H&S fanatics will paint a gloomy image of doom and destruction of static-induced fires and explosions if you don't earth the non-conductive ducting. The paranoia appears to come from large volume (high flow with lots of dust) operations, which do not translate accurately to hobbyist workshop operations.

When the earthing (grounding) subject comes up on other discussion boards, no one is able to provide a single example of a hobbyist workshop experiencing a fire or explosion due to static discharge in a dust extraction system. My system is a mix of 120mm metal ducting with 120mm and 100mm flexible hose at the machine connection. The metal ducting is not earthed and is attached to the ceiling of my shop with insulated brackets. After nearly seven years of use, the dust flowing through the ducting has had ample opportunity to send me to the afterlife, but the proper conditions do not exist in my shop.

For comparison, the business in Mannheim where I purchased most of my shop equipment closed its doors a few years ago. I helped the owner dismantle the large dust and chip extraction system, which used 800mm metal ducting for the main lines, 500mm ducting for the branch lines, and a combination of 200mm and 300mm ducting to the machines. Connections to the machines were with the flexible hose. As with my system, the ducting was not earthed and the suspension clamps were insulated. In over 45 years of operation with very large shop machines, there were no fires, explosions, or static discharge.

Eventually, I will replace the main distribution of 120mm metal duct with 150mm non-conductive storm drain pipe, and will correct errors I made during the initial design and installation (two 90-degree bends near the cyclone inlet). Four years ago, I helped a friend in Stuttgart install his dust extraction system using the same Barnado blower I have and the 150mm drain pipe. The only earthing in the system is the electrical connection to the motor chassis through the power cable.

 

[Cabinetman]

Thanks for that Mike, that’s a comprehensive and reassuring answer.
My old extraction system was bought second hand it’s a 3 pot 3 phase beast but only 400 mm at the thick end, we suspended it from the ceiling using webbing straps and it always worked well, the main ducting was all steel pipes and connected direct to the body of the mc but then the flex end hoses weren’t grounded.
Ian