Double Retired wrote:
Could signage have been a problem?
After I had heart surgery they warned me MRIs could be a problem. But much later I was walking by a door to the MRI area that was usually closed with a big MRI-warning sign.
I was looking for someone in that part of the hospital and noticed that the door that was normally closed was open, had no warning sign, and had no one attending it. So I went through the door to see if there was someone. (There was no sign telling me to stay out! I assume the MRI machine must be off.)
Well, I was barely through the doorway and a nurse tackled me an pushed me back out.
It could have been part of the problem. The warning signs for the MRI machine are required by law to be posted outside the door. (We had to put the same warning signs on the NMR room doors.) Likely the guy just did not read the signs and went into the room. If he had a pacemaker installed, the magnetic pulse would have stopped it and killed him right there.
The electromagnets used in NMR/MRI instruments have a pull zone. One can picture a sphere of several feet around the instrument than has the force vectors of the magnet. This sphere does not stop when it hits a wall or floor. On a liquid He cooled NMR instrument, the sphere is roughly around six feet of distance. For MRI machines the distance is usually greater due to the increased power of the magnet involved. It can take up the entire room of the instrument. Anything that comes into contact with that sphere is under the influence of the magnet. The force becomes stronger the closer the item gets to the instrument.
One might assume that the magnet would be off if the power is cut to the instrument, but that is a wrong assumption. The magnet is always "on" as long as it is cooled to liquid He temperatures. The electrons in the central core wires are free flowing at that temperature, as it is a superconducting medium.
I have several stories about students (and professors) not being very smart around the NMR that I managed for several years. One research group attempted to connect an electric water bath near the outlet where the controls were for the instrument. I permanently kicked them out of the instrument room for this incident. The chemistry professor involved could not get his mind around the fact that you cannot put an electrical motor near the magnetic pull zone, let alone one with water around the main electric cables. The cart that they were using was also not made of non-magnetic stainless steel. It could have easily destroyed the instrument. They lost card and key access to the room. I was so pissed off from that incident that I installed multiple video camaras down the hallway leading to the NMR room just to watch for them. There were multiple camaras installed in the instrument room already. The NMR instrument would cost more than a million dollars to replace. I really hated working around such dumb people for so long.
Then there were the construction workers who wanted to install a gas valve in the ceiling above the instrument. Someone in administration decided that they needed to do an improvement to the room in case of a He purge. They were going to put a ladder right above the instrument and use electric power tools to do the installation. They thought that they could drill the holes into concrete right above the instrument. I would not let them get anywhere near the instrument, so they left. Their supervisor got an earful from me on that one. The administrator was fired from the university shortly after.
I could go on and on and on...