Examples | Cyclones and risers | Carbon electrodes | Slates | Pre-cast refractory blocks | Cast-iron products for the mining industry | Accessories for the aluminum industry cast-houses
Cyclones and risers
Use of SonicByteTM for verifying the quality of the refractory castable lining of cyclones and risers used by refineries
Refractory lining degradation on firing
The refractory lining of cyclones and risers is generally made of a refractory castable. After forming and curing at room temperature, the lining is subjected to a first firing causing water loss from the castable and then its sintering. These lead to dimensional changes of the lining that may cause microcracking and delamination. The later is especially more favored by a stiffer shell design and/or anchorage system which offer restriction to the castable dimensional changes.
Refractory lining quality control
After curing and/or firing, three complementary refractory lining quality control methods should be used:
Visual inspection
This method allows the detection and the localisation of longitudinal and radial cracks present on the inside surface of cylindrical linings. This method does not allow the detection of internal defects, such as delamination cracks.
Hammer test
This method allows the detection and the localisation of internal cracks close to the inside surface of the lining, including delamination cracks. This method does not allow the detection of deep cracks.
Acoustic resonance - SonicByteTM
While several frequencies treatment methods can be used by SonicByteTM, the acoustic signature is the most liable and accurate technique for deep delamination cracks detection in monolithic refractory linings. This technique is based on the amplitude distribution measurement of the fundamental and harmonic frequencies generated by the lining, after the later had been submitted to soft mechanical impacts at the proper locations.
The lowest collected resonance frequency is used by SonicByteTM to determine the modulus of elasticity of the refractory lining, after eliminating the effect of the metallic shell by means of a mathematical method. The relative amplitude of the highest collected resonance frequency is used as an indicator for the presence of delamination cracks into the lining. High relative amplitude ensures the absence of such cracks since the later act as a filter that prevents the propagation of high frequency acoustic waves. The modulus of elasticity of the lining is finally used to quantify, on an absolute basis, its quality irrespectively of its size, shape and geometry.
Refractory lining inspection results
The refractory linings, before and after firing, of several cyclones and risers were submitted to the above three complementary quality control methods.
The fired lining of one of the inspected risers showed delamination cracks, both by hammer testing and with SonicByteTM. The presence of these cracks close to the lining surface was confirmed by visual inspection of core drilled samples. For all other inspected units, SonicByteTM showed that the quality of their refractory lining was varying between 69 and 97%, based on their modulus of elasticity compare to that of samples prepared in laboratory, according to the ASTM standard procedure, from the same castable. From these samples, a 45% decrease of the castable's modulus of elasticity after firing was detected by the SonicByteTM.
