What are the causes of flame-out of gas-fired or oil-fired boiler?

1) The causes of flame-out of gas-fired boiler:

Flame-out caused by the sudden increase of fuel gas pressure; fuel gas supply failure caused by magnetic valve’s malfunction; great changes of fuel gas composition and excessive moisture content of fuel gas; low temperature of furnace caused by excessive pressure, air leak or excessive air due to the malfunction of forced draft fan or induced draft fan.

2) The causes of flame-out of oil-fired boiler:

Malfunction of oil pump; suction tube coming out of the oil level; blocking of oil filter or fuel feed pipe; oil supply failure caused by magnetic valve’s malfunction or operator’s mistake; oil with water when heated by steam in the pass; oil with water due to the wrong position of suction tube; inappropriate combination of oil and water (water floats on oil); oil with water due to the blocking of drain-pipe of oil tank.