Cylinder is the substrate of the kiln. Cylinder should have sufficient stiffness and strength to keep the axis straightness and roundness of cross section in the installation and operation, which is related to lengthen the life of the rotary kiln’s lining bricks, reduce running resistance and power consumption, non-uniformity wear and mechanical accidents, thus ensuring long-term safe and efficient operation, which is crucial. The rotary kiln’s cylinder should be designed according to the requirements.
The cylinder’s radial stiffness is mainly the ability to resist deformation in the huge cross-section transverse shear force. Transportation, installation, bricklaying process also has certain requirements for the stiffness. The radial deformation on each point on the cylinder during operation has some change. Excessive radial deformation will inevitably lead to internal lining brick loose, affecting service life. To explore the cylinder radial deformation rule, the special cylinder derformeter should be used to measure radial deformation. The study shows that radial deformation of the cylinder at the fulcrum is the maximum, then decreases at the span, the attenuation rate increases and accelerate with thickness of the cylinder and the diameter of the wallpaper. The strength problem of cylinder showed that the cylinder could have cracks under load, especially in the vicinity of the rolling ring. The stress measurement made by Tangshan Cement Machinery Design and Research Institute, Hubei Institute of Architecture showed that the cylinder’s value could reach to several hundred kg / cm ² when large stress value is in the cylinder. Tangential stress ratio is larger than the axial stress. Under the welding joint between load stress and the inevitable stress, cracks might exist.
Guaranteeing and maintaining the cylinder axis’ straightness is manufacturing, installation, adaption and maintenance work tasks. Even if the installation is very accurate, after a period of operation, the foundation’s uneven subsidence also occur, prop shaft tile, roller, rolling ring’s inside and outside circle’ abrasion, large temperature changes may cause the central location of the cylinder at each fulcrum changing. It must be based on the operation of the kiln to make inspection and the correction of the axis. The kiln cylinder is made from the steel plate, the materials’ temperature in the kiln is up to 1450 ℃, so the interior of the cylinder is lined with refractory materials. In operation, the cylinder is in a high temperature 250-400 ℃ for a long time, withstanding refractory bricks, materials and the weight of heavy loads. In order to make long-term operation of the rotary kiln, the cylinder should have sufficient strength and rigidity to maintain the straightness of axis.
At present, the domestic kiln cylinder’s diameter is generally φ3-φ6.4m. Usually the diameter D≤φ4 kiln material should not be less than Q235B, for D> φ4m kiln, the material should not be less than the specified Q235C.
The relevant provisions of the cylinder stitching: 1) General section width should be between 1.8-2.5m, 2) high-temperature section, cold section, and other small pieces of gear section section generally should not be less than 1m, 3) In the same span, the width of 1.5m should not be more than one, and arranged in the middle of the span.
Cylinder’s welding requirements; 1) The cylinders’ circumferential welding should not pass the discharging hole and inlet hole, the distance between holes and welding should not less than 100mm. 2) Small section should be rolled by the whole plate as far as possible, when short section need to align plates along the ring, each short section’s longitudinal welding should not be more than two strips. Cylinders’ adjacent segments’ longitudinal welding must be staggered over 45, the shortest aglin plate should not less than 1/4 of the circumference. Meanwhile, longitudinal sealing could not pass through a variety of openings. With a short section for tire pad, longitudinal welding must be arranged in the middle of the two pads, which should not overlap with each other.
