It's poorly explained in the game, but you can increase the amount of machine health by researching "Improvements". One also has to keep track of the machine strength which is only visible in the bottom right corner when hovering over the machine. It will deteriorate over time, and at some points the machines will have to be replaced.
Those damned earthquakes destroying different equipment (usually the slack tongue slicer) annoy me, but it’s all good fun though.
I tried to play the reboot, but I prefer Theme Hospital.
On the mend.mid is my favourite piece of music from the series.