Blast Cabinet Static Electricity
Blast Cabinet Static Electricity
(OP)
I learned from experience that grit blast cabinets will build up a static electricity charge and the operator can receive mild shocks. So, when I put a blast cabinet in my hobby shop I made sure it was grounded. I would still get a little shock once in a while. In the past week, I have been blasting two motorcycle fenders (steel)and got an occasional shock on my hands through the rubber gloves that protrude into the cabinet. Yesterday I got quite a few and not just in the hands. I started wondering what was suddenly different. I thought about my shoes of the day--a ratty old pair of Reboks. On the previous days I wore an old pair of Iron Age steel tow safety shoes. Nothing special--black leather slip-ons with a rubber sole. On a hunch, I switched shoes and the static shocks ceased. Anyone got a clue on why switching shoes ended the static shocks?





RE: Blast Cabinet Static Electricity
RE: Blast Cabinet Static Electricity
Your shoes must be fairly good insulators. If you have a resistive path to earth, even one in GΩ, then the static charge will generally bleed away to earth. Chances are your other shoes have a slightly lower resistance to earth and were preventing the charge buildup. Dirt, sweat and damp lend themselves to making a conductive path, plus some rubber materials are inherently static dissipative.
You can try a drain earth on the blast nozzle itself connected back to the machine frame. A length of single-core flexible cable will be more than adequate if you ty-rap / zip-tie it to the blast hose to keep it out of the way.
RE: Blast Cabinet Static Electricity
If grounding the blast nozzle doesn't do the trick, you could try some sort of bonding conductor between say, your ankle and ground - but use something like a rare earth magnet that will easily pull loose to form the actual connection point between your ankle and the conductor so you're not mechanically tethered to the machine - just in case of a fire or something like that.
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
RE: Blast Cabinet Static Electricity
The cabinet is grounded. You are not.
Another possible solution may be one of the conductive wrist bands that are used for work on static sensitive electronic equipment.
They are fastened with Velcro I believe.
I encountered a similar situation working under 500,000 Volt transmission lines. Capacitive shocks rather than static, but when a large group of electrons abruptly enter or leave the body, both effects feel the same. We were a long way from town and we improvised with stranded #14 bare copper wire around one wrist and connected to the objects that were charging up and zapping us. (WE did not have a "Quick Release".)
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Blast Cabinet Static Electricity
http://www.kobakant.at/DIY/?p=70
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Blast Cabinet Static Electricity
RE: Blast Cabinet Static Electricity
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
RE: Blast Cabinet Static Electricity
RE: Blast Cabinet Static Electricity
I bought the appropriate safety codes. The code required the flooring resistance, as determined by a specified test method, to be in a range that was high enough to prevent touch potential shocks but low enough to discharge static sparks.
As an aside, the hospital has an interesting history.
It was established by two Baha'i families as a faith based project. They operated the hospital for a number of years as an unprofitable, for profit enterprise.
It was a small but steady drain on the families finances.
Then hurricane Mitch hit Honduras. It was little know outside of the affected areas that Cuba sent a medical support team to aid in the relief efforts.
It was a well planned team;
Five doctors of different specialities, all of which useful in disaster relief.
Also five support staff. A lab technician, a radiologist, and some nurses.
About this time the Baha'i families were asking the Honduras Government to take over the running and support of their hospital.
Cuba agreed to send part of their medical team to the hospital and the Cubans took over manning the Hospital for a time.
Link
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Blast Cabinet Static Electricity
Dan - Owner
http://www.Hi-TecDesigns.com
RE: Blast Cabinet Static Electricity
RE: Blast Cabinet Static Electricity
Dan - Owner
http://www.Hi-TecDesigns.com
RE: Blast Cabinet Static Electricity
Here is an article I found discussing this issue you may find helpful,
http://www.clemcoindustries.com/news_detail.php?id...
MikeL.
RE: Blast Cabinet Static Electricity