# Vibration Diagnosis of Sand Units in a Stone Crusher Plant: An On-Site Field Test
## 1 Introduction  
Natural sand has been formed through the normal erosion process of exposed rocks. Sands of various configurations, different sizes, and different non-rock inclusions of organic material are lined on the beach or with rivers or lake shores. Therefore, sand can be easily found in our surrounding natural environment, such as rivers and seas. Over the past decades, humans have been required large amounts of sand for social overhead capital (SOC) facilities and infrastructure, including large-scale construction of buildings, roads, bridges, airports, and harbors. However, as most natural sand is obtained from rivers and seas, its availability in the natural environment is limited. Moreover, indiscriminate collection of sand from rivers causes flooding and destruction of the natural environment such as river ecosystems, leading to various social issues. In the case of sand collected from the sea, it must proceed by removing the salt and undergoing a drying process. Therefore, a method for manufacturing artificial sand using a stone or rock grinding mechanism is used as a solution to prevent environmental destruction and sand depletion problems caused by massive natural sand production. In contrast, artificial sand is essentially manufactured or processed to have appropriate particle sizesrequired for the intended utilization. Most studies related to artificial sand in civil engineering have focused on the comparison of strength property between natural sand-based concrete and artificial sand-based concrete [1; 2; 3; 4; 5; 6; 7]. In addition, several works on the equipment design and analysis have been reported to enhance the production efficiency of an artificial sand manufacturing facility [8; 9; 10; 11]. A few works on the vibration problem of artificial sand manufacturing facilities have been introduced by carrying out transverse and longitudinal oscillation analysis of screen units [12; 13]. Recently, in order to improve the screening efficiency of the vibration screen and make the vibration process smoother, a new type MR damper was proposed and evaluated at a laboratory level [14]. Furthermore, shape memory alloy (SMA) is applied to the screen unit to properly achieve a sufficient spring constant by controlling the operating temperature [15]. The rock (or stone) breaking and crushing process plays an important role in minimizing the particle size of stone or rock for various construction activities, such as building bridges or infrastructure. They can be obtained in large quantities from artificial sand production plant facilities such as jaw crushers, vibration screen units and sand units. In the manufacturing process of an artificial sand, relatively large stones or rocks are first crushed, then screened, washed, and fine-sized [16; 17; 18; 19; 20; 21]. An artificial sand production system consists of large motors with high power output and jaw crusher or impact crusher to break rocks or large stones. In addition, a hopper and cone crusher are required to break large stones into small sized stones or gravels. Then, the gravel and sand which are respectively transferred to the vibrating screen unit and sand unit are sorted by particle size by a washing and screening process. Subsequently, the fine sand is moved to a designated storage place Thus, the artificial sand production from crushed stones or rocks requires various types of equipment related to the full manufacturing processes. These facilities are large and hence inevitably have a significant impact, generating a high level of vibration and noise. Therefore, an artificial sand manufacturing plant should be built on large plains or mountain entrances which are far from densely populated residential areas and industrial complexes. Otherwise, if an artificial sand plant is located close to a densely populated area such as a residential complex or an industrial complex, then there will exist significant noise and vibration issues when the artificial sand manufacturing facilities are operating in such sites.