Overhead Cranes Inspection Peculiarities & Real Use Cases
To date, the issues of safe operation and examination of industrial safety of lifting equipment is absolutely vital since it falls in the focus of many supervisory authorities. One of the components of the examination of lifting devices is a significant technical diagnosis of overhead cranes to identify hazardous operational defects. In this article, prepared in close collaboration with GMH Company, Granada Material Handling, specialised in overhead cranes and gantry hoist production and maintenance and being one of the UK industry leaders, we consider the experience of the application of acoustic emission control method for diagnosing metalwork lifting structures.
From the experience of operating gantry cranes it is known that the a result of the impact of various adverse factors forms dangerous fatigue failures. The identification of such defects in the course of the examination of cranes traditional methods of control over existing methods is extremely problematic, especially in remote or hard to reach areas. On this basis, to identify hazardous operational defects and reliable assessment of the technical condition of the crane, the companies may want to make use of the acoustic emission method. This method makes it possible to record wave elastic stresses arising from internal local dynamic restructuring of the material structure. These processes are accompanied by the accumulation of structural damage, the formation and growth of cracks that eventually lead to a limiting conditions and structural failures.
The article presents the experience in technical diagnosis using acoustic emission method of metal structures of gantry crane KKS-10 with carrying capacity of 10 tons. The purpose of monitoring is to identify AE developing and prone to the development of defects which appear during load changes, as well as determining their location and assess their risks.
The monitoring was carried out for the following parts of the crane: the transit horizontal truss and supporting mechanism for the four pillars. The acoustic emission transducers (RT) for metal structures where installed; the linear location enabled a 100% control of the transit horizontal truss structure, including welded joints. Control of the pillars, given the complexity of the geometry of the structure, carried out with the installation on each leg at least eight sensors. This scheme was chosen from the need to minimise the effects of false AE signals occurring at joints for supports and bracing elements supports.
Furthermore, to increase the pillars reliability control results a combined location-based linear and triangular diagrams were utilised. Before performing AE control channels AE equipment was calibrated according to Su-Nielsen scheme. Calibration was carried out to test the sensitivity of the channels, as well as to determine the velocity of propagation of elastic waves in the test object. AE control of diagnosed object was held in the low frequency range. Selecting the frequency band of the filter due to the need for sustainable registration AE sources away from the receiving transducer in a selected map location. Loading object control was carried out through lifting and holding the rated load in working conditions within 5-12 tons.