# Investigation of Inner Lining Loss and Correlation with Steel Structure Quality in Rotary Kilns
## 1 Introduction  
Laser scanning has become a common surveying technology over the past 30 years and is used for a variety of purposes. In engineering practice, it is used, for example, to determine volumes, measure deformations, and compare the state of an object over time based on a measured point cloud [1; 2; 3]. A rotary kiln is a large cylindrical industrial furnace that is used for drying, calcination, and chemical reactions, among other applications. Typically, it consists of a steel shell lined with refractory materials to withstand extreme temperatures [4; 5; 6; 7]. Slowly and continuously rotating rotary kilns allow materials to be processed or heated as they move along the length of the kiln [8]. In industries such as cement production, lime production, and chemical processing, they are commonly used for clinker production, mineral roasting, and waste incineration. Figure 1 shows a measured rotary kiln with a terrestrial laser scanner. A rotary kiln usually has a cylindrical shell, a riding ring, pads for the riding ring, thrust rollers, support rollers, and a method for turning the ring [9; 10]. The scheme is shown in Figure 2 inside the shell. There is often a refractory lining that protects the shell from the high temperatures created by the operation of the kiln [11; 12; 13; 14; 15; 16]. Depending on what the rotating kiln is used for, it may also have other parts, such as a cooler or a preheater. Rotary kiln shape features  
Shape: the shape of the kiln as a whole, including any changes from a perfect cylinder. Size: the length and width of the kiln, as well as the depth. * Symmetry: the degree to which the kiln is symmetric, including any differences from perfect symmetry. * Wear and tear: the amount of wear and tear on the surface of the kiln, including any places where there is a lot of damage or wear. * Ovality: the extent to which the cross-section of the kiln is circular or elliptical. * Displacement: the amount that the kiln moves or shifts. * Twist: the amount that the shaft of the kiln is turned. * Deformations: any changes to the surface of the kiln. The cylindrical shell of a rotary kiln can be made of a number of different materials depending on what it will be used for and how it will be run. Carbon steel, stainless steel, refractory bricks, and cast refractory are all products that are often used. The focus is on the cylindrical shell of the rotary furnace and its geometric features such as the diameters of the parts that are welded together and how oval or round they are [17; 18; 19; 20; 21; 22]. The deformation of the rotary kiln shell can cause a number of problems, such as the uneven wear of the refractory lining, bigger mechanical stress on the shell and support rollers, and a decline in the kiln's efficiency and ability to make things. Deformation can also cause the kiln to be out of place, which wastes energy and reduces the quality of the products. So, keeping an eye out and figuring out how the rotary kiln shell is changing is important to ensure that the kiln works well and lasts a long time [23]. Rotary kiln controls  
* Checking the refractory lining for damage or wear that could cause the shell to overheat and change shape. * Check for the wear or misalignment of the ring and support wheels, which can cause the shell to load and change shape. Figure 1: Exterior of the rotary kiln. Figure 2: Rotary kiln scheme. Check for wear or damage to the thrust rollers and thrust bearings, which can cause axial thrust loads that can cause the shell to bend. * Making sure the drive system is aligned and working right, which can affect how the shell is loaded and where it is placed. * Checking the shell for signs of cracks, deformation, or other damage, and fixing or replacing it as needed. * Keep an eye on the kiln's temperature and other conditions and make changes as needed to prevent damage to the shell. There are several ways to measure the ovality of a rotary oven. The shelltester is a tool used to measure how oval rotary kiln shells are.