14 causes of boiler explosion

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The boiler tube explosion refers to the combined impact of water wall tubes, convection tubes, and economizer tubes in the heat exchange surface of the boiler operating under the combined action of various factors such as overheating, erosion and corrosion, pipe bursting and water leakage, leading to the boiler unable to operate normally. Over many years of theoretical and practical accumulation, it has been found that the bursting of boiler tubes is mainly due to 14 causes.

1. High water hardness

The main reason leading to this situation is that some boiler water is drawn from underground, with high hardness up to 5mmol/L, belonging to hard water, and high sulfur content, high iron content, once the water is not treated properly, it is easy to cause pipe bursting, and the boiler has to stop for repair, which greatly affects production and life.

2. Decrease in mechanical efficiency at welds

In the production, installation, and maintenance process, the pipes of the boiler will have stress and decrease in mechanical efficiency at the welds, and the pipes will burst at the main parts of this stress concentration and mechanical decrease, which will also cause the boiler to be damaged and difficult to supply production needs.

3. Pipe blockage

Impurities falling into the pipes during the installation or maintenance of the boiler cause blockages in the pipes, causing poor water circulation or complete destruction.

4. Poor water circulation

The branched and folded water pipes make the water circulation in poor condition.

5. Low boiler water level

If the boiler water level is too low during operation, there will also be poor water circulation, and after such a situation, the local temperature of the pipe will be too high, deforming until it bursts.

6. Pipe overheating

In the design and installation of oil boilers, gas boilers, or coal-fired boilers, due to the improper adjustment of the nozzle angle, some boiler chains will also be overheated.

7. Sudden expansion

Incorrect operation of fire lifting and shutting down the furnace causes cold air to blow the boiler tubes, and the rapid or frequent expansion and contraction of the tubes due to thermal expansion and contraction, leading to harmful stresses.

8. Damaged thermal insulation wall

Smoke pipes and fireproof walls of the combustion chamber are damaged, causing short circuits of exhaust gases, causing local overheating of the boiler tube and combustion of the boiler tube.

9. Low exhaust gas or feed water temperature

Explosions due to pipe corrosion and aging of equipment. Often occur in economizer tubes on the rear heating surface. The reason is that the exhaust gas temperature is too low or the feed water temperature is too low.

10. Deposits on heat exchange tube bundles

The local smoke velocity is too fast, when installing and overhauling the surface heating pipe, the height of the heating surface pipe and the distance between the heating surface pipe and the furnace wall do not meet the design requirements, and a local exhaust gas passage is formed between rows of pipes and rows of pipes or between rows of pipes and furnace walls, or local pipes cause the heating surface pipe to accumulate ash and build a bridge, making the local smoke velocity too high and thus increasing the corrosion and overheating of the pipe in this section.

11. Air leakage at connection points

Due to careless construction, the connection points of the furnace wall are not strictly sealed according to construction requirements, so air leaks create vortices, and this condition will also cause part of the pipe to be too hot, or the heating system is uneven, and air leaks also increase the exhaust gas velocity behind it, posing a danger to the warm heating surface of the furnace tail.

12. Working temperature too high

Operating at high temperatures of pipes is also an important reason for boiler explosions, due to the reduced mechanical properties of pipes under overheated conditions and the plastic deformation of pipes under the pressure, meaning crack and even rupture.

13. Frequent changes in operating modes

The influence of the operating environment can also cause boiler tube bursts, such as frequent start-up and shut-down of boilers, heavy load changes, incorrect adjustment of flame centers, the impact of the first and second air washing of water wall tubes, and rapid cooling of boilers, all leaving potential dangers for boiler explosions.

14. Untreated feed water

Corrosion of carbon dioxide or oxygen in the network of pipes of the boiler heating system, or condensation network of water vapor pipes, and when oxygen and carbon dioxide are stored in the boiler feed water system at the same time, the corrosion of the steel network of the heating system pipes will be more serious, and carbon dioxide will make the feed water acidic and destroy the protective membrane of the pipes, and with the increase in oxygen content, the carbon steel equipment and pipe network of the heating system will appear larger or smaller loess state, speeding up the occurrence of corrosion, and the result is the color of groundwater or condensate is yellow, red and even soy sauce color, with a large iron ion content, and the steel pipe is perforated. Water and steam pipes are usually corroded, perforated, and leaking. This is also the reason why the service life of some new carbon steel boiler pipes is only 4-5 years, meaning the condensing pipes need to be replaced every 4-5 years.

The iron content of the boiler feed water exceeds the standard, which will not only cause the "red water" phenomenon of the boiler water but also cause corrosion under iron oxide sediment. Moreover, it will lead to the rapid formation of scale in the boiler, the thermal conductivity of iron oxide sediment is very poor, the heat transfer efficiency of the iron oxide sediment layer is very different from the heat transfer efficiency of the boiler tube, seriously hindering heat transfer, making the local temperature of the heat transfer surface too high, thus reducing the metal strength, posing a danger to the safety of the boiler, and causing deformation of the boiler tube leading to tube rupture.