The Comparative Analysis of the Design of Shredder Hammer Tips and Bars in Sugar Milling Applications

Di Mauro, Matthew N. (2022) The Comparative Analysis of the Design of Shredder Hammer Tips and Bars in Sugar Milling Applications. [USQ Project]

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In Australian raw sugar factories, sugarcane preparation is completed with the use of a hammer mill, specifically a heavy-duty shredder. The disintegration of the arrangement of cane billets permits subsequent milling processes to better separate dissolved sucrose using mechanical preparation, crushing/squeezing and cleansing techniques. Aiming to achieve better preparation ultimately leads to increased sugar extractions (also measured as Pol % bagasse), and minimal amounts of moistures in the beginning products of bagasse. Historically, existing heavy-duty shredders have indicated higher cane preparation levels; however, they require greater power/energy usages. Therefore incurring higher capital, maintenance and production expenditures. This dissertation reports on two separate investigations to improve shredder units used in Australia to extract raw sugar from cane billets.

The first component of this study resulted in two factory trials, completed for three weekly increments, held at a milling factory in North Queensland. These factory trials were completed during the 2021 production season, with the aim to assess the outcome of the design of the shredder-hammer tip on shredder performance. The two shredder tip designs trialled were the conventional wedge tip (Tip Type 1) and alternative flat tip (Tip Type 2). The key objective of this element of study was to determine which tip type performs better under a wide array of different shredder performance measures. These include first-stage pressures, first and final mill extractions, POC’s, rotor and turbine speeds and HP steam expenditures. Results that were extracted from these trials were implemented into previous mathematical models to assess power & energy efficiencies and experimental data relevance to theoretical models. During these trials only, the conventional wedge tips (Tip Type 1) performed the best.

The second element of this study resulted in a concept design for shredder hammer bars, aimed to improve the overall operational lifespans, whilst also reducing the bars and hammers likelihood to failure. Within this investigation, there were key elements involving material selection, contact and component compatibility analysis, Finite Element Analysis (FEA) and component failure studies to assess the conditions of both the shredder bar and hammer.

During the methodology phase of this report, the Property Parameter material selection criterion was selected to assess which of the seven materials, identified, would be optimal for the shredder applications in sugar milling. Concluded during this investigation was that Grade 630 (17-4PH) martensitic stainless steel is the preferred material.

By applying the properties of both the hammer, having a material characterisation of 30CrMo, and the previously specified bar, it resulted in the optimal clearance between both components of 1.3mm. This ultimately resulted in a contact pressure, between the hammer and bar, of 241.6MPa. A Factor of Safety rate of two was applied to determine applicability of the bar and hammer in its worst scenario. The property recommendations from the material specifications were suitably met.

Employing results of contact pressures and rotational forces into FEA simulations resulted in a maximum deformation of 3.4 × 10−2mm, maximum Von Mises stress of 472.9MPa and maximum principle strain of 2.7 × 10−3 , which is well below the maximum property specifications. The Figures (39), (40) and (41) represent these FEA simulations, respectively, in Section (4.6). The maximum applied stress/strain values were observed to be located approximately every four intermediate discs as well as both ends of the shredder bar at the chamfer points. This demonstrates that the maximum deformation occurred equally, through the middle point of the hammer’s location on the bar.

During the component failure facet of the study, it concluded with the axial load subcase generation of a fillet stress concentration factor of 4.5, which occurs approximately 0.85mm from each end of the shredder bar where

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Item Type: USQ Project
Item Status: Live Archive
Faculty/School / Institute/Centre: Current – Faculty of Health, Engineering and Sciences - School of Engineering (1 Jan 2022 -)
Supervisors: Lobsey, Craig
Qualification: Bachelor of Engineering (Honours) (Mechanical Engineering)
Date Deposited: 20 Jun 2023 01:46
Last Modified: 20 Jun 2023 01:46
Uncontrolled Keywords: sugar mill; ham mill; shredder; mechanical preparation

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