The refractory material is the most fragile of the boiler. Break or fracture easily. An exchange or repair is quite expensive and is carried in addition a long period of time where you can't count on the boiler.

The designs of boilers old used refractory material (cement or bricks, refractory bricks) to isolate those areas in which the flame or combustion gases could enter in contact with the steel that had no water to cool it on the other side.

In boilers of smoke tubes ancient, the most common use of the refractory material was in the return chamber gas (turnaround chamber) and in the doors where it was used in large quantities and complex geometries that made him very fragile. Especially a section of a refractory material used to separate the gas from the second and third step, commonly called “altar or frame refractory” (refractory bridge) .

The designs of modern boilers minimize the use of refractory material since it will increase the reliability and efficiency and reduces the maintenance required.

A boiler with horizontal smoke tubes moderna 80 HP or greater, it does not require a frame refractory as their diversion chamber gas is made of steel. This camera is water-cooled and is referred to as Wet-Back (Return wet) (See technical guide: WET BACK) and neither does it require a refractory material in front and rear doors as they are replaced with mineral wool and stainless steel sheet.

To ensure the reliability and low maintenance cost, all boilers, horizontal smoke tubes of Powermaster 80 HP or greater, equipped with a Wet-Back and not using a refractory material in their front doors or rear. The only refractory material they contain, is located in the register goes-a man of Wet-Back and at the nozzle refractory burner.