True story time.
And one reason why elf and safety regs exist.
The first thing you need to know is that in a ship engine room, even with the main engines shut down, there are many sources of noise, you could be inside a tank with a lump hammer and those outside the tank would not necessarily know you are there...
So, these big engines, often opposed piston 2 strokes, often with electrically driven scavenger / blowers, you get periodic maintenance.
In some cases maintenance means opening the blast doors and crawling inside the manifold to access the rings through the ports for cleaning and maintenance, or sometime piston crowns through the ports.
Regs state two people, one stays outside, you stay on an orange safety line, one outside never leaves his station, not even for a piss, while you are inside, anyway, elf and safety regs weren't followed, guy crawls inside to do his maintenance job.
They reckon the ship rolled a little at her moorings, maybe bunkering, maybe a gust of wind, and event, the blast door that should have been dogged back swings shut and a couple of the dogs drop into place.
Some hours later a different fitter on the next shift notices some of the dogs undone, tuts to himself, and dogs them all down tight.
An hour later the main engines fire up, the poor bastard still inside the manifold starts getting flashed with cylinder temperature exhaust gas, which in the case of a big engine just working up is 150 to 170 celcius, not a quick death or a pretty one.
Many hours later the crew realise one is missing, many hours after this they have eliminated MOB etc and determined that the last anyone knew old freddie was going to clear out the rings and ports, they have sea room so engines are shut down, this time two people, one goes in and finds and retrieves the flame grilled body.
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More lister centric.
I used to have a set of pictures, a guy walked past a running 6/1, somehow a loose fold of overalls got caught in the keyway at the end of the crank, within the next second it has grabbed him, literally spun him around vertically off his feet and slammed him head first into the ground, luckily for him this was an earth flower bed and not the concrete driveway the lister was sat on, at which point the extra torque required to fling him around again fell below the point at which his old cotton overalls and working jeans would tear, so in the next second he is up under the crank getting abraded by the flywheel (luckily he had gloves for that) and the torque is trying to wrap him around the crank, overalls tear, jeans tear, even his underpants are ripped off his body.
30 seconds after this the pictures are taken, you can already see the massive bruises coming up on his legs and hips and buttocks.
I would never ever wear anything except old cotton overalls and work clothes, modern synthetic overalls are just unwrapped synthetic rope, more than strong enough to tear you in half.
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when I was a lad I put a 1.5" whitworth spanner (a big spanner) on top of a running stationary engine, just for a minute, while tapping up some mounts, it vibrated off and into the flywheel.
luckily for me I dropped a nut at that exact moment and bent down to pick it up, I felt something go past my head and simultaneously heard a clang.
the spanner, which weighed about 4 lb, went through the space where my head was at flywheel rim speed, basically 50 mph, which for you ballistics guys is a 4lb slug moving at about 75 feet per second (old rule of thumb, 1 mph = 1.5 fps) which is in bullet, say hello to watermelon, territory.
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My dad, a fucking world class engineer who forgot more than I well ever know and who spent his life around big machinery as well as small, lost half of his index finger on his right hand, not on a fucking great machine, but on a car battery powered atco electric cylinder lawnmower, which jammed on a twig, which he pulled out without first isolating the battery.
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there are very few machines so small and so weedy that they cannot maim or kill you, but when you start going bigger they can maim and kill you in all sorts of interesting and new ways, simply because of the kinetic and potential energies at play.