Refractory castables are usually composed of aggregates of different particle sizes, fine powders and binders. When left standing, the aggregates may sink and the slurry may float due to density differences (stratification). Through uniform vibration energy, the particles are redistributed to maintain a uniform mixture of aggregates and matrix. After avoiding stratification, the overall performance of the material is more uniform and it is not easy to crack due to thermal expansion differences at high temperatures.
There are three most common types of vibrators:
1.Insertable vibrator (internal vibrator).
When the vibrating rod is working, the rod is inserted into the refractory castable, and the vibrator moves in the material to compact the material. The material is liquefied and bubbles are discharged through high-frequency vibration (usually 10,000 to 15,000 times/minute). It is suitable for thick-walled structures (such as industrial furnace linings, large-volume castables) or parts with complex shapes. It has a large vibration depth and good compaction effect. However, it is necessary to pour in layers to avoid excessive vibration causing aggregate sinking and slurry floating (layering phenomenon).
2.Flat plate vibrator.
The vibrator contacts the surface of the material when vibrating, and moves the vibrator in the plane to compact the material. The vibration motor is fixed on a metal plate. The plate contacts the surface of the refractory castable and transmits vibration to compact the surface material. It is suitable for large-area flat construction (such as the ground and the bottom of the furnace). It is easy to operate and suitable for thin-layer construction. However, the compaction depth is limited (usually <200mm), and layered operation is required.
3. The wall-attached vibrator is installed on the mold without contact with the material. The material is compacted by the vibration of the mold. The vibration motor is fixed on the outside of the template or mold. The vibration is indirectly transmitted to the castable through the template (the frequency is about 3000~9000 times/minute). Thin-walled structures (such as pipe linings, narrow spaces) or areas where vibration cannot be directly inserted. Avoid direct contact with the castable and protect the surface of the material. However, the template must have sufficient rigidity, and the vibration effect is affected by the template fixing method.
So how to choose a vibrator in actual construction?
For thick walls > 300mm, choose an inserted vibrator; for thin walls, choose an attached or flat plate type. For large-area flat construction, a flat plate vibrator can be used in conjunction with an inserted vibrator. Correctly selecting the type and parameters of the vibrator can significantly improve the construction quality of refractory castables and avoid defects such as cracking and peeling.