Static electricity or equipment in need of repair?

Question

Hi!
I work on a transport team for a hospital. My job is to go out to surrounding hospitals and retrieve newly born infants that are ill and need speciality care.

The equipment we use is contained on a metal framed cart. We have an isolette to place the baby in, a transport monitor, and a transport ventilator. The vent does not require electricity to run. The isolette and monitor each have internal batteries to sustain them when we are on a trip.

The question/problem I have is that frequently we get shocked when we are pushing the cart. It doesn't matter if we are rolling on carpet or other flooring. It has shocked me rolling across concrete. I don't mean just a little shock either- sometimes it is really a lot. It also does it repeatedly. You get shocked, take a step or two, change hands on the cart and get shocked again- just as hard.

I just read the article by Mr. Static "Charging by Walking" and if I understood it correctly, it is possible to have static charge just by taking one step.

So, is it just static electricity shocking the crap out of me- repeatedly, or is there a potential electrical proble with our equipment that needs to be looked at?

It has only happened once, but one time when it shocked me I didn't let go- I intentially held on- I could feel what felt like a light electric current pulsing for several seconds. I have not had that happen again.

Everyone I work with thinks I am wrong for thinking it is anything more than static electricity. I think Biomed needs to check out our equipment.

What do you think?
Thanks! MO

Answer 1

I'm glad you said what do you THINK, because I don't know.

If it were a normal electrical shock, you would have had to complete a circuit from your hands to whatever you touch on the machine, to a power supply of some sort in the machine, to the other side of the power supply, through one or more wheels to a conducting walking surface, through your shoes to your body...I think it unlikely. Also I expect that the battery voltages are too low for you to feel them through this path.

It acts like static electricity, but you say it can happen after taking just a step or two. What are the chances you have an unintentional static generator in the wheeled unit? This could be any rotating part, like a fan or pump. My main concern would be the possible effect on an infant, particularly the type you describe. Something pretty active, though to recharge in just a few steps.

Fastening a chain or flexible wire to a conducting surface on the cart, long enough to drag on the walking surface, would minimize stati voltage build-up.

Answer 2

An electrically isolated cart should not deliver continous current. OK maybe if you walked it past a radar installation you might get induced currents but not in a hospital.
I would concentrate on discharging the cart before you touch it. To do this hold a metal object like your keys and then touch the key to the cart. If there is static then you will get a spark from the keys to the cart but as long as you are holding the keys firmly then you won't even feel it. This is because the static is dissipated over a bigger area of skin instead of one point.

Answer 3

I don’t know about spontaneous ignition of fuel vapor, personally I think that’s more of an urban myth than a real danger, but every fueling operation I’ve worked around grounded the vehicles and fuel trucks, so what do I know LOL Static electricity is dangerous to electronics, now that I know for a fact. I’ve fired more than one piece of computer hardware because I was too lazy to ground properly. -edit- Oh yeah, I just remembered a situation where static electricity can be dangerous to human life. Helicopter blades produce a lot of static so don’t grab the cargo rope from a hovering H-46 without the using the grounded grabber thing!

Answer 4

A simple check will tell you if it is static or not. Ground the cart to the floor by letting a piece of metal, (blade of a screwdriver, piece of copper wire, even a metal spoon etc) make a path for the static charge to dissipate from the cart. Just let it touch the floor beneath the cart as you are pushing it around. If it is static, that should solve your problem.

Answer 5

I'd get the equipment looked at. Doesn't sound to me like the discharge of static electricity; especially the incident you describe when the electricity seemed to pulse for a few seconds.

Answer 6

Insulate the place where you put your hands with adesive tape for electrical insulation and everything will be OK.It is static electricity from the wheels in contact with the surface or from your plastic equipment without cotton.