Keeping a paper mill operational

Jon Lawson

De-barkers process high volumes of material, creating an extremely abrasive environment, but an innovative lining can help keep things running

Used to strip the bark from logs, de-barkers are among the most robust pieces of machinery operating within industry, facilitating high-volume processing at an early stage within the paper-making process.

Handling several logs at any one time, the de-barking process begins with a wet drum phase, where the logs enter a cycle with water, designed to loosen and soften the surrounding bark.

Subsequently, a dry drum cycle exfoliates the bark, separating the materials for further treatment. Altogether, this method creates an incredibly abrasive environment, progressively wearing the machine’s components.

A Polish paper mill operated by Stora Enso was suffering from this exact problem, as the hardened steel protection plates were wearing away at a rate of 2-3mm per year. With each block of wood averaging 170kg in weight, these significant static and dynamic stresses were severely abrading the equipment. Stora Enso required a solution to prolong the life of the equipment; however, if the problem was not resolved during the planned maintenance period, then the customer could risk a stoppage to the plant and costly downtime.

As an existing customer, the mill contacted Belzona’s Polish distributor, Belse, for further advice on the situation.

Having completed a range of applications for the mill previously, the team specified an abrasion-resistant solution that, crucially, could be cold-applied within the designated maintenance period. In addition, Belse had carried out an identical application for a de-barker the previous year.

This had been a big success, particularly in terms of the longevity within a severely abrasive environment; therefore, the mill chose the Belzona solution to complete the repairs and lining of the de-barker.

Upon selection, the work was performed by eight technicians over the course of six days, including full surface preparation of both the wet and dry drum by grit-blasting.

Initially, the steel drums were coated using Belzona 1321 (Ceramic S-Metal), a ceramic filled epoxy coating, designed to combat highly erosive environments.

Additionally, a protective barrier of Belzona 1811 (Ceramic Carbide) was applied. Incorporating abrasion-resistant ceramic aggregates, this system was chosen to provide the de-barker with long-term wear and abrasion resistant characteristics, alleviating the issues it faced.

The sheer size of the application required large product quantities, including 5000kg of Belzona 1811 and 360kg of Belzona 1321. Due to the scale of the de-barker, which measured 10m in length and 3.9m in diameter, the paper mill was impressed that the application was completed within the designated timeframe so quickly and effectively. Moreover, the customer was pleased to hear how other de-barker applications carried out by Belse had faired since their installation. This further reinforced the long-term, cost-effective nature of the project versus traditional repairs or replacement.

Such a big application serves to indicate the potential in other paper mills, as well as throughout the pulp and paper industry. This solution is suited for many kinds of wood processing, paper or pulp plants, that have a de-barker drum suffering from a similar amount of abrasion and wear.

Thomas Belli is with Belzona

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