Machine shop equipment interference

EMI

by AgentX86 - 2020-09-14 13:32:56

Who, exactly, ans told you this?  Just how big are these machines?   Why do you need an ICD?

The chances that what you've been told is true is very small.  "They" would have a point if you were working on turbines in a 1000MW power plant or even arc welding.  How big are these chucks?

There are essentially two problems with interference and pacemakers. First is a DC magnetic source, like a scrap metal crane or being very close to rare-earth magnets.  The issue here is closing the magnetic safety switch in the pacemaker. This switch is used to "safe" the pacemaker, essentially shutting it down and putting it into a safe, constant rate, dumb state.  While this isn't desireable, it's certainly not life-threatening.

The larger issue is in rotating magnetic fields, like your magnetic chuck.  It matters how big it is (and your underlying condition).  The real issue is that the rotating magnetic field will induce a current in your leads, causing the pacemaker to "oversense".  This causes the PM to think there is (senses) a heartbeat when there isn't.  It won't, then, supply the trigger for the heartbeat.  If you're pacemaker dependent, this is a problem because there may not be any beat.  Not good. 

If you're not dependent, your heart will go on as if you didn't have a pacemaker.  While this isn't good, and could cause trouble, it's probably not life-threatening.  If it were bad, you'd most likely feel it and have a chance to stop what you were doing.  Your magnetic chuck will likely cause a rotating magnetic field but it should be contained within the chuck.  Emphasis on "should".

There is no reasonable sheilding that would matter in the above cases.  Magnetic fields will penetrate a lot of iron/steel, more than you're going to carry around.  Copper won't do anything.

You should talk to your EP about this situation. Your employer may get freaked and you may need the help of your EP to calm your employer's HR department.

In *theory* a Mu-metal shield might help

by crustyg - 2020-09-14 17:38:14

Let's assume that the moving magnetic fields are enough to cause problems.  There is an alloy that could, in theory, help, Mu-metal.  Back in the day when oscilloscopes were built around cathode-ray tubes, they all had a shield around the tube to reduce distortion of the beam(s) by external magnetic fields (transformers, large currents, bench PSUs, etc.).  This shield was really quite effective at diverting the lines of magnetic force into the Mu-metal and avoiding it affecting the electron beam.

Whether anyone actually makes a mu-metal shield that you could slip into a pocket over your heart is a different matter.  But the science is there.

Mu-metal

by AgentX86 - 2020-09-14 18:11:01

True enough but you still couldn't carry that much. Its permeability is a few tens of times that of iron but it's still heavy, like iron (which it mostly is). Such a shield would have to enclose the body to be effective.  It doesn't stop magnetic fields, it "conducts" them around the interrior of the shape.  ...and if you remember, those oscilloscopes were on the heavy side.  There was also a calibration for the Northern and Southern hemispheres because they weren't perfect shields. If this were an easy problem, mu metal (or Permalloy) would cover the PM's guts, where it would take much less of it.

You could wear a superconducting T-shirt, too, but that would have its own set of problems. ;-)

Wasn't thinking...

by AgentX86 - 2020-09-14 19:07:35

The issue is the leads not the pacer itself.  Wrapping the pacer in Mu-metal wouldn't help at all.  The whole system, pacer and leads, would have to be in one continuous Mu-metal shield.  That's next to impossible.  Undersea communications cables used to be wrapped in Mu-metal but that's a little easier.  ...and the weight is an edvantage.

Bad information repeated over and over

by Theknotguy - 2020-09-15 16:54:55

One of the things that is hardest for a new person with a pacemaker/ICD is trying to determine which is absolute garbage (otherwise known as BS) and which is good information.  There is a lot of bad information out there that gets repeated over and over.  Things that may have been true twenty or more years ago isn't necessarily true today - and may not be true next week.  

It also happens to us who have had our pacemakers/ICDs for a while too.  I was volunteering at the hospital where I got my pacemaker.  Was talking to a rehab lady and she was telling me there was a life time limit of  lifting 57 pounds on the pacemaker side of the body.  I was having a hard time trying not to start screaming at her as I regularly move 4x8 sheets of melamine at 55 pounds per sheet.  I'm moving more that her weight limit and the only person who told me it was a problem was the rehab lady.  I literally walked down three floors and got into a conversation with a security guy who broke a lead on his pacemaker bench pressing 300 pounds.  He said he knew he was pushing the envelope and wasn't surprised he broke a lead.  Up to the 300 pounds he was getting along fine.  So, as I said, a lot of bad information gets repeated over and over.  Because of possible legal action, the medical companies err on the side of caution.  

If you look around the forum you'll find a couple of posts where I was running a larger DeWalt 110 volt power drill.  Got tired of using my arms and started using my shoulder.  Consequently my pacemaker was lying on top of a running 110 volt power drill  No problems.  I finally figured out after I had drilled about a hundred holes that my pacemaker was lying on top of a running drill.  However, no side effects, not dizzy, no problems. So when they tell you that you can't run a grinder because of the magnetic chucks, I'm trying to figure out how big the chucks are and how close you'll be to them.  I doubt, seriously, that you'll be hugging the magnetic chucks, so I don't see where you'll be close enough to them to have a problem.  

My pacemaker was within a foot of one of those rare earth magnets.  This is the kind you have to use some kind of pry bar to separate the magnets.  A very concentrated field, but also concentrated in a small area.  I won't be so stupid as to put the magnet directly over my pacemaker, but there was no effect when I walked by it and the pacemaker was within a foot of it.  

We've also seen people on the forum who have been told not to use a riding lawn mower.  Supposedly the magnetic field put out by the gasoline engine will interfere with the pacemaker.  I haven't had any problems with that type of power equipment and I have yet to see anyone on the forum saying they've had a problem. 

Doctor's aren't too much help either.  Once they get out of their area of expertise, it's like talking to an African witch doctor.  Chanting, using rattles, and spoken curses come into play.  I'm still trying to figure out how people who are so smart in one area can be so dumb in another.  Consequently since they don't understand electricity and magnetic fields they err on the side of caution - probably thinking of how much their liability insurance costs - and they'll just repeat bad information rather than tell you there won't be a problem.  Frustration is a word that doesn't adequately cover my feelings about it.  

I don't know if your EP will sign off.  Don't know if your HR department or you legal department will look the other way and give you an OK.  Are you working in a union shop?  Personally I don't feel you'll have any problems but I don't know if you'll get others to go along with it even if you do use a testimony from us on the forum.  I just wish you the best of luck and hope things work out.  

EMI

by AgentX86 - 2020-09-15 23:39:22

I'm the one who was told in no uncertain terms that I was not to use a riding lawnmower (tractor, actually).  It had nothing to do with the gasoline engine, rather sitting on the alternator.  He had no problem with a weed whacker, chainsaw, or whatever.  The problem is not the gasoline engine but sitting on the alternator.  I was also warned about working under the hood of a car.  Note that I'm pacemaker dependent and may not live through a period of oversensing.  Most others wouldn't have the same result.

As I said, magnets would just set the pacemaker to its default setting.  It would change things but nothing dangerous.  The magnetic sensor is there for the express purpose of disabling enhanced pacemaker feature during medical procedure.  It's not there to harm.

Sorry, but I listen to my EP (and cardiologist).  I tend to do that with people who have saved my life (I do with those who say they'll kill me  too but that's for another forum).

Machine shop equipment interference

by jlmac64 - 2020-11-12 17:19:25

I am not pace reliant, but have an EF of 28%. My EP has told me to stay away from the grinders, although I believe he's speaking from a liability standpoint and not technical knowledge. The stationary magnetic chucks are 6" x 18" and the variable rate chucks are 12"x24" and three phase. I also use a Blanchard grinder that has a 36" dia variable rate chuck that is also very powerful. 
   An engineer from the Chuck manufacturer suggested that I likely wouldn't be able to be within arm's reach of them, but couldn't say definitively without knowing the exact application and that information is over my head. I can stay at least 2 ft away from motor windings on just about everything else in the shop. My only other question is about the wire EDM machines. I have been in other shops that had warning signage for pacemakers, but nothing about distances. 
   I'm currently waiting on my employer to make a decision on having a site evaluation done for EMI/EMF(non union shop). Health comes first, but it is a high paying job and I would really like to know where I stand.