Bonding Wire Question

Ever see the aftermath of an internal exposition in ductwork?

It's one hell of a mess to sort out. I've worked with pulverised coal it's frightening when it goes bang.

The straps are to stop static build up between sections.

Just as a follow on to above:

Someone had the brilliant idea of vacuuming coal spillage. Great idea, but they didn't use conductive hose. It didn't explode, just caught fire.

The numerous points of contact between bolt and flange, nuts etc, over time will oxidize and become low grade semiconductor junctions here and there. Stray RF fields will get rectified and create random noise. If there is a welded continuous path between the metals, this will be prevented. The actual nuts themselves will still do this, but this will not be a problem compared to metals doors and runs of pipe.

People who make RF shielded rooms know all about 'debuzzing' of these rooms - any bits of metal not well connected.

Hi hien,

Most or usually bonding wire made into flexible, therefore any movement on your pipe will not cause loose on grounding and delivered 100% continuity.

Cheers mate.

Roman

To guarantee the correct flow of current you use bonding jumpers on flanges, remember that the bolts under tension will have slightly differing electrical conductivity, plus you will have gaskets as well as myabe insulated washers. So to avoid all the issues, you use bonding jumpers, safer and guaranteed

If a star washer is placed between the underside of the head of the bolt and the flange, and another between the underside of the head of the nut and the other flange, then a bonding wire is unnecessary.

partially true, a star washer under the correct tension will bite through insulating oxides - at first-, but as time goes by, thermal cycles, humidity, condensations cause this formerly gas tight connection to inexorably corrode and degrade, in time becoming a resistive connection, or worse, a rectifying one.

Where RF noise is not a problem, who cares, but for shielded rooms, bond everything

..........which will be fine for preventing the build-up of static electricity on the pipeline, which is where the technique is often used.

British Standard 7671 requires equipotential bonding for non-double-insulated equipment via the incoming power cable or via a supplementary earth wire.