For years, severe abrasive wear present in sugar mills have resulted in costly repairs and lengthy maintenance standstills. Two areas where this is particularly apparent are; Shredder grates (the metal casing used around the rotating hammers which crush the cane) and on the Elevator Rake Pads, which are highlighted later on in this article. A specialized material Ferobide, already widely used in agricultural machinery (including on sugar cane harvesters), has been showing some astonishing results in these applications and a promising solution to abrasive wear in these areas.
Ferobide is a durable tungsten carbide composite material, which combines high levels of wear resistance and toughness with the ease and reliability of a weldable material. It’s hardened steel matrix efficiently binds together hard tungsten carbide particles, which give the material unique properties and allow it to stand out as possibly the world’s hardest weldable material.
When replacing hard facing welds on the steel frame of shredder grates in an Australian sugar mill, Ferobide achieved a 60% cost saving. These areas are subject to such extreme wear and corrosion, that the hard facing applied to protect them often completely disappears before the end of the processing season. This results in damage to the metal structure it is supposed to protect. When Ferobide strips were welded on the same areas and examined after 1 season, remarkably they showed hardly any signs of wear. They provided full protection to the metal and helped to avoid costly maintenance downtime.
This lifting lug also proves problematic to maintenance engineers. Even when hard-faced, it completely wears away during a season which leads to the requirement of at least half a day of extra labour when dismounting the grate.
When 6mm thick Ferobide strips were welded to the lifting lug instead, it could still be used at the end of the season to quickly dismount the grate without the need of any additional standstill.
A second area of application where Ferobide is showing great promise is on guide pads used on elevator rakes. The pads constantly slide against steel guide plates during the transport of the sugar cane from the shredder to the extraction station. This causes high levels of abrasion and the guides currently require changing 2/3 times per year depending on the output at a particular mill. As well as the replacement parts constituting an extra cost to the mill, lengthy maintenance operations are required mid-season. By simply replacing lining the rake pads with 4mm thick Ferobide pads, it is highly likely the pads and the guides will last a whole season, avoiding costly maintenance standstills.
Tenmat (the manufacturer of Ferobide) have carried out an in-house simulation of this application to demonstrate the potential benefits of using Ferobide to protect both the steel guides and the rake pads. A hardened steel pad (representing the rake pad on the elevator guide) was slid along a longer steel strip with 10mpa of pressure applied to the pad. The wear this caused on both the pad and the steel was then recorded in mm per km. The test was then repeated. However during this second test, a small Ferobide tile was welded to the metal pad .
The results of this test were remarkable. Not only did the Ferobide protected pad last approximately 700 times longer than the standard hardened pad, it also caused the steel counterforce against which it was sliding to wear 19 times less.
The explanation for this is that the fine tungsten carbide grains present in Ferobide (which typically exhibit a hardness of 1500 Vickers ), protected the pad, whilst the use of Ferobide reduced friction levels between the 2 steel parts as they slid against one another. It is expected that once this test is replicated on a Elevator rake , the use of Ferobide will allow the rake pads and the steel guides to achieve a full season of service without requiring maintenance.
