Here's a more or less 'modern' version of a pressure jet burner, cover off. Exactly the same functions as the 'Ray', except all the parts are crammed into the smallest possible space to make maintenance a nightmare. [Just like under the hood of your car!]. This one happens to be running on vegetable oil, hence the fryer at rear heating the oil to get the viscosity and flash point closer to diesel oil's.
https://www.electrical-contractor.net/PC/AB_CIMG0741.JPG The main safety feature in pressure jet burners is a photoresistance coupled with the controller. At 'call for heat', the photoresist circuit will not allow the oil solenoid to open if it 'sees' light or IR, for that indicates that the boiler/furnace is already on fire! Assuming it's not, the controller instigates ignition, and the photoresistance must now see light/IR within about 15 seconds, or it shuts down the burn. It monitors that burn throughout ensuring flame outs dont cause a hazard. This is to prevent the firebox filling with diesel, all primed to burn your house down next time ignition succeeds! Finally at 'call end' the controller resets, awaiting next call.
Older controllers are just a series of relays and timers arranged to a safe sequence, modern ones may be solid state.
If a burn sequence fails, it's usual for the controller to 'lock-out' and await a manual reset. [I should add that there are other sequences in the controller, such as pre-heat nozzle, spark on/off, motor on/off etc.]
Aussie, what you saw was probably a wick type burner. These only ran on kerosene [paraffin to us limeys!], a lighter fraction which is re-processed to remove low flash-point fractions [petrols]. This fuel was first used earlier last century as lamp oil. The wick burners are very efficient, hence the blue flame, but obviously need more care to keep the wicks in good trim. When I was a kid smaller units ran in folks houses exhausting fumes into the rooms. Deodorised kero was often used, [Pink Dont Stink, Esso Blee-Dooler, ]
I have lately noticed these in-room blue flame heaters on sale here in France. And they do stink!
As to bursting into flame, that is thankfully a rare event, but it does happen. A guy up the road from here lost his home in an oil boiler fire. The burner malfunctioned and pumped diesel into the fire. The granite walls melted!
