Discussion on The Breakage And Repair of Extrusion Roller

Jan. 29, 2023

Roller press is the most critical mechanical equipment in cement industry, mainly used for extrusion and crushing of raw material and clinker, with low energy consumption, high output and low noise. However, cement machinery roller press also has a lot of difficult problems to be solved, and the most critical problem is the wear and damage of the roller face. According to the actual investigation, after the installation of the roller press, generally use half a year roller surface pattern is nearly worn out, if the material quality is a little poor or the material contains more foreign matter, even two months of continuous use broken can not continue to use. Therefore, to reduce the breakage of roller press roll surface, as well as the correct repair after the breakage, is a problem we must solve.


1. Reasons for breakage of roller face of roller press


Passivated Extrusion Roller

1.1 Mechanism of broken roller surface of cement machinery roller press


The roller press is to squeeze the material passed in the middle gap by two rollers with the same speed and relative movement, so that the granular material becomes flat and crack-filled cake under high pressure, which is ready for the next step of material grinding. From the working principle of roller press, it can be seen that the material is subject to squeezing pressure and friction when passing through the two roller surfaces, which is typical of high stress abrasive wear. The material is subject to pressure and elastic and plastic deformation when passing through the roller surfaces, and the material exerts cyclic tensile stress on the roller surfaces, and with the continuous high speed and long time work of the roller press, when the repeated action of the cyclic load exceeds the fatigue strength of the roller material, it will make the roller Fine cracks appear on the surface, and when the roller with cracks on the surface continues to work, the cracks further deepen and expand, thus leading to the fracture and spalling of the roller surface.


1.2 The main reason of roller surface breakage


(1) The material of roller surface is poor. At present, the roller surface material of roller press on the market is generally poor, resulting in fast wear and short service life of roller surface.


(2) The material is poor in ease of grinding. The higher the temperature or too much over-burned material, yellow heart material and flying sand material in the ingredients, the worse the ease of grinding and the more wear on the roller face.


(3) The particle size of the incoming material is large. The raw material of roller press comes from the crusher in the previous process. The larger the particle size of the crushed material is, the greater the damage to the roller surface, so the particle size of the material entering the roller press needs to be strictly controlled.


(4) The material contains metal foreign matter. The metal in the material is not removed, which will cause bruising and damage to the material of the roller press.


2. Roll surface repair method

Passivated Extrusion Roller

The roller surface damage of roller press is divided into normal wear damage, transitional use wear damage, surface spalling damage, long time overload operation damage, damage caused by the performance of the roller body and damage caused by the entry of metal foreign bodies. According to the downtime, it can be divided into on-site temporary repair, on-site downtime overhaul and restoration overhaul.


2.1 On-site temporary repair


On-site temporary repair refers to the on-site temporary welding and overhaul for the small local damage or small area spalling of the roll surface caused by the entry of foreign objects or other reasons without affecting the production. On-site temporary repair only needs to clean up the damaged part and the small part around, then according to the degree of damage or spalling, different welding wires or wire combinations are used for overlay welding to quickly repair the broken roller surface and avoid the broken part of the roller surface from bursting inside and around to extend one step.


The welding process of temporary repair on site is simple, with fewer process measures, not restricted by conditions, and can be carried out in almost any situation, and the repair is better in use.


2.2 On-site shutdown overhaul


On-site shutdown overhaul refers to the case where the cement roller press has been working for too long, causing extensive damage and requiring a complete overhaul, without dismantling the roller body of the roller press, and directly cleaning the damaged layer of the roller surface thoroughly, then after a certain degree of preheating of the roller body, an automatic or semi-automatic welding machine is used to carry out a complete repair of the roller surface. This repair method can be used for normal wear damage, transitional use wear damage and long time overload operation damage of roller presses, etc. It is a more convenient emergency repair method because there is no spare roller body to replace or time is short to replace the roller body. The welding process of onsite shutdown overhaul is relatively simple compared with restoration overhaul, there is no need to heat treat the roll body as a whole, only need to preheat the roll body for a period of time, then it can be welded, and the welding pattern requirement is not high.


However, since there is no heat treatment to eliminate the welding stress and working fatigue stress of the roll body, the repair life is shorter than that of the restoration overhaul, and the use effect and efficiency are relatively poor.


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