I’m watching this arborist on YouTube and they have a truck with a bucket on an arm so they can reach heights without climbing. On/after a rainy day the bucket will accumulate water and they mentioned they can’t drill a hole to drain because it will compromise the grounding.
My understanding of grounding/electricity doesn’t explain this. Can someone help me understand why this would make a difference?
Edit: I get it, I/he should have said “electrical isolation” instead of “grounding”. Either way, a hole allowing a stream of dirty water seems to be the answer here. Thanks 🙂
In: Physics
Drilling a hole will add an exit point for electricity. Without the hole, electrical charges will have to follow the bucket, then the arm and end with the truck, thus further from the person in the bucket.
That claim makes no sense. More likely the bucket is fiberglass, or some other composite, and adding any holes would compromise it’s structure.
If anything electrical, the worker would be safer NOT grounded, and maybe a hole would compromise ground isolation.
It is entirely possible this person does not understand how grounding works and is talking out their ass.
I’d need more details on the construction of their bucket and how it’s grounded. Assuming there’s some kind of earthing cable running up the armature into the floor of their bucket, then yes, just drilling a large hole through the plate (and into the cables) could create an issue. That area they damaged would have different resistance, under load it could heat up and melt.
That said, an engineer with details of their bucket could design a proper drainage system. Even if you can’t drill a hole, you can use a subfloor, pump, and siphon to move water out of the bucket.
I think they are normally insulated instead of grounded. If they were grounded then it would give high voltage a path to arc through the boom arm to the ground.
I’m still not sure why a small hole would be a problem though. They might just refuse to certify the machine if there’s any damage to the bucket liner.
The bucket is made of a non-conductive material to prevent the operator from coming into contact with live electrical components. This insulation helps protect operator from electrical shocks or electrocution when working near power lines.
Water dripping out of a hole in the bucket would estabish an electrical pathway to where the operator is standing.
The purpose of the solid bucket is to maintain electrical isolation, not grounding. People just confuses the two.
It is probably more that this specific bucket is constructed in a way that they can’t add drainage holes, rather than that it’s a general rule.
A hole in a truck bucket voids its insulation rating. Period.
Water with any impurities in it (which includes ALL water you would find out in nature) is a pretty good conductor of electricity.
Furthermore, elevated buckets like those used by arborists get sawdust fines and other types of grime in them all the time. When it rains, you get a mix of particularly dirty water at the bottom of the bucket. If there were a drain hole, you get a path for nicely conductive water from the earth to the feet of the folk in the bucket. These folk are reaching up and out with tools in their hands that can contact energized wire. Zap.
Elevation equipment must be regularly inspected and certified to ensure they are still safe to be allowed near live lines.
To address water accumulation, some store their trucks with the buckets spun upside down. Others, like my company, use big ‘shower caps’ over the top of the buckets to keep them dry between uses.
I’m an arborist who formerly did line-clearance work. The reason is mostly because any crack or hole in the fiberglass is a place for conductive debris/water/material to accumulate, which defeats the purpose of having a non-conductive bucket. It is also a structural compromise that can lead to equipment failure.
Your question states “maintain grounding”. It is to avoid grounding.
There are two buckets in a proper setup. A fiberglass outer shell and a plastic liner internally that can be removed for cleaning. Usually the arm (boom) of the buckets have fiberglass sections as well. When being tested,, the entire contraption is tested after cleaning and often waxing the booms. The hydraulic systems operating the bucket/boom are specifically non-conductive as are the hoses being used. There have been tragic accidents where a mechanic has inadvertently used a steel reinforced hose.
Pure water does not conduct, but dirty water is a great conductor and the environments the crews work in are often filthy. Once the bucket/liner/boom are all wet, the opportunity for tracking goes up. A hole in the bucket provides that path.
Bear in mind that the insulation in the bucket is to isolate the worker in the bucket, but the truck frames themselves are solidly grounded to the system neutral. There have been occasions where an ungrounded truck became hot from an undetected contact with the line. With it sitting on rubber tires, no one knew until the first poor slob that went over to open a bin, get a tool, and was electrocuted from frame to ground. If a system neutral can’t be obtained, the truck needs a barrier around it.
So isolation isn’t just for the guy in the bucket. It protects the ground crew too.
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