For the crack phenomenon of boiler, we must first find the reason, to solve the problem. This article will explain to you the causes of cracks after the light insulation castable refractory building furnace:
1. The "gray-water ratio" of castable refractories has not been reasonably controlled in the mixing process:
After the product is formed, the internal porosity of the material is high, the strength of the material is reduced, and the natural solidification time is too long, extending the health time. Add too little water, the material circulation is not good, the vibration is not dense, easy to leave pores, caves, etc., the strength will be greatly reduced.
2. Poor control of mixing time and vibration time of castable refractories:
The mixing time is too short, the material is not mixed evenly, not dense, and the strength is reduced. The product pouring should use tamper to carry out stratification. The shaking time is too long, and the material is easy to stratify. Fine powder floats on the surface and the stone sinks to the bottom, causing the material to reduce strength and easy to fall off. The product should be used up within 30 minutes of mixing and should be poured into the specified thickness and height at one time. Commodity construction needs to be carried out in the environment above 5℃, because the temperature is too low, the material is not easy to dry solid, even if dry solid, is false condensation phenomenon, the commodity should be poured continuously into the first layer of the commodity before drying solid, should cast two layers of material. If the construction clearance exceeds its initial setting, it should be treated according to the requirements of settlement joints.
3. Poor control of departure time of castable refractories:
Mold the product before hardening. Should be in the strength of the commodity to ensure that its edge and Angle will not be destroyed by mold, it can be disassembled. Before cleaning the mold, the bearing template should reach 70% strength on the product. In order to promote the mold, before casting, all the mold casting surface should be coated with a layer of oil.
4. No reasonable control of health time of castable refractories:
After the completion of the boiler, there should be sufficient natural drying period, so that most of the water in the fire layer can be separated, to avoid a large amount of water in the oven can not be discharged in time, so that the refractory layer split and fall off. Before oven, the product has the corresponding natural strength (adequate health period) to proceed. The principle of oven is "moderate length should not be short, moderate slow speed should not be fast". According to the preset oven curve, the heating speed should be uniform and stable, and the temperature control time and temperature should be well controlled, so that the temperature fluctuation should not exceed ±20℃ of castable refractories. Avoid temperature rise too fast, can not discharge water in time, break the anti-wear layer; Secondly, it can prevent the temperature field in the fire resistant layer is too large and produce huge thermal stress, so that the fire protection layer crack, expansion and fall off.
