The optimised maintenance of vertical roller mills (VRMs) using hardfacing technology does not consist solely in refurbishing the surface by means of welding to the original profile. To achieve an efficient solution for improvement and reliability of components, an assessment of these components and a methodical evaluation through an engineering approach and auditing system is necessary, says wear protection and welding consumables specialist Welding Alloys South Africa (WASA).

Before selecting a hardfacing solution, an analysis of the operating conditions must be conducted. Points to be considered include:

• The base material of the grinding components and their age;
• The type of mill and the year of its construction;
• The type of material being ground and the fineness required;
• The feedstock particle size;
• The design capacity of the mill;
• The current performance of the mill;
• The current electricity consumption of the mill;
• Whether watering has taken place or not during the grinding;
• The incoming volume of air;
• The average temperature of the mill chamber; and
• The component wear assessment and weight loss in gram per ton of product ground.

WASA has developed a support service to reduce running costs of VRMs. This service consists of gathering valuable operational data from the mill and the identification of the correct hardfacing consumable and equipment and technology to deposit these consumables in the correct configuration and quality to ensure the most effective wear solution.

In addition, the company’s Smart Welding Concept includes the management of wear profiles which can further improve the maintenance methodology of VRMs by preventing the component profiles from deteriorating owing to aggravated wear.

As the grinding components reach a certain threshold, excessive wear causes a decrease in milling efficiency which, in return, requires excessive regrinding and causes an increase in electricity consumption, compared with when the mill was running at optimum performance.

Therefore, WASA aims to increase the time components spend in the optimal operating range to maintain the best mill performance and reduce excessive electricity consumption. During WASA’s mill assessment and optimisation programme, the company addresses these two aspects in the most cost-effective manner possible, ensuring the best mill performance at a reduced operating cost.