Ceramic coating technology significantly enhances production efficiency: A case study from a mill in Central China

Solving customer challenges

The main equipment of the paper machine in this mill is sourced from domestic suppliers. It primarily produces corrugated base paper, with a basis weight ranging from 60–100g/m² and operates at a machine speed of 850m/min. However, during actual production, the equipment has encountered the following issues:

1. Frequent web breaks, severely impacting production efficiency.
2. Accumulation of stickies on the center roll surface, leading to a reduced doctor blade lifespan and necessitating frequent blade changes replacements.
3. The average grinding cycle of the original rubber-covered center roll is less than one year, resulting in increased maintenance costs and downtime.

Valmet has proposed a state-of-the-art solution to address the issues faced by the customer: upgrading the center roll from a rubber cover to Valmet’s exclusive ceramic cover for press rolls. This advanced ceramic coating Press Roll Cover PD-W offers superior release performance and enhanced wear resistance, effectively reducing surface contamination on the center roll and extending the doctor blade lifespan. Valmet is also providing start-up and regular follow-up services to ensure the equipment operates stably post-modification, achieving optimal production results.

Good cooperation with Valmet experts at the customer mill.

Results speak for themselves

Significant improvements were achieved following the upgrade by Valmet. The center roll release line stability increased, leading to a substantial reduction in web breaks. Especially web breaks decreased by 40 percent, resulting in a marked improvement in production efficiency.

The doctor blade lifespan was also significantly extended. Before the upgrade, it was required to change doctor blade even every five days. After upgrade lifespan was extended up to eight days, considerably reducing maintenance costs. The center roll maintenance also became more convenient. Unlike the original rubber cover, which needed grinding at least once a year, the ceramic cover only requires a regular inspection of its surface roughness. This eliminates the need for off-machine grinding, further reducing downtime and maintenance costs.

Valmet ceramic cover in operation

In today’s increasingly competitive market, the importance of product quality and performance is universally recognized. To develop process and product quality customer chose Valmet’s ceramic roll cover. The exceptional performance of Valmet’s Press Roll Cover PD-W ceramic roll covers earned the customer’s trust, leading to prompt additional orders.

“One of the key reasons we continue to choose Valmet ceramics is the notable improvement in production efficiency. For example, we’ve seen a reduction in the number of web breaks in our press section of nearly 40 percent. When producing low-weight paper grades, the center roll’s stable release performance ensures better machine speed and output. The consumption of the center roll’s doctor blades has also decreased, reducing our operating costs. The in-machine time of Valmet’s ceramic covers has been significantly extended, leading to substantial savings in transportation and grinding costs across the base. Furthermore, the reduction in the number of roll changes across multiple lines reduce our maintenance team’s workload, reducing the potential safety risks associated with roll changes.” Qiu Dingtao, Head of Production Technology department

“A significant industry trend is the replacement of rubber center roll covers with ceramic ones in three nip center roll presses. However, during implementation, it’s crucial to consider the potential impacts of changes in material and diameter. In addition to cover products, Valmet offers a comprehensive range of solutions to enhance the performance of center rolls, including crowning checks, roll shell inspections and repairs, doctor adjustments, start-up services, and expert support. Valmet also boasts a vast network of domestic and international experts who are always ready to assist customers in resolving production issues.” Wang Changhong, Product and mechanical design manager, Valmet

This upgrade project showcases Valmet’s professional expertise and innovative prowess in paper machine upgrades. The introduction of ceramic cover technology has significantly enhanced the mill’s production efficiency and stability while reducing maintenance costs and downtime. This advance provides robust support for the paper industry’s ongoing development.

Text: Changhong Wang