There are a large number of problems with aluminosilicate refractory fibres for the main boiler hearth of ships: the refractory fibre surface coating is all chapped, the refractory fibres near the air vent bricks and at the bottom of the boiler hearth side walls are peeling off severely, some boiler hearth refractory bricks have collapsed in small areas, the metal anchorages have melted and eroded, almost every furnace has been partially repaired several times during the minor repair period, and more than half of the ships have carried out at least one The refractory material of the main boiler was completely renewed. Typical appearance of failure of refractory fibre materials after a period of use.
After a period of operation, the main boiler refractory fibre material was sampled from several ships and furnaces and found that the fibre mats were heavily chalked. Samples were taken from 1 to 4 mm on the surface to study the crystalline changes and to carry out a comparative microscopic analysis.
Through the above analysis, the failure mechanism of refractory fibre materials for boilers can be summarised as follows:

(1) The long-term safe use temperature of aluminosilicate refractory fibres is 1000°C, and the maximum use temperature is 1100°C. But in the actual working environment of the boiler in the ship, the working temperature of aluminosilicate refractory fiber is 1100℃, and the working temperature exceeds 980℃ when the aluminosilicate refractory fiber will precipitate mullite crystals, mullite grain growth, which leads to fiber necking fracture, fiber pulverization, and fiber shedding.

(2)The outer layer of refractory fibre felt is 2~5mm thick refractory coating layer, due to the refractory coating compared to the internal refractory fibre felt, the specific gravity is larger, the thermal conductivity is larger, thus the line shrinkage rate is smaller when heated, thus the thermal stress is larger at the bonding surface area, under the effect of thermal shock or mechanical vibration, the refractory coating and refractory fibre felt is very easy to crack, peel off.

(3) Refractory fiber mat strength is very low, room temperature compressive strength is only 0.3 ~ 0.5MPa, high temperature compressive strength (1100 ℃) only 0.06MPa, high temperature fiber pulverization, the strength will be even lower. It can be imagined that the existing refractory material with such a low strength, simply can not be used in the harsh environment of the ship boiler long-term stable, reliable work.

In addition to the above reasons, the impurities in the heavy oil formed by the combustion of the smoke, ash on the failure of refractory fibres also played a role in accelerating.