It is reported that pulp and paper mills use many specialty chemical additives in the process of creating the paper products we use every day. These chemicals control undesirable conditions such as foam, the growth of biocidal slimes, the pitch introduced by some wood species, and sticky substances from recycled cardboard.

Left untreated, these conditions can produce defects in the finished product as well as increasing energy costs and forcing mill operators to use more chemicals such as bleach. Other specialty chemicals are added to treat mill water both before and after its use in paper making, thereby reducing corrosion in boilers and preventing scale build up on heat transfer surfaces.

Mills have many feed systems that deliver these chemicals in precise quantities at strategic stages for wet-end management and water treatment. The feed systems must resist aggressive chemical components such as solvents, acids and bases, and corrosive biocides, as well as provide years of maintenance-free, round-the-clock service and ensure the safety of mill workers.

The report said that Buckman Canada, in Vaudreuil-Dorion, Quebec, and its suppliers have built and shipped some 1,000 feed delivery systems in the past 10 years. Most are made of nickel containing S30400 and S31600, though sometimes S31603 is selected for its resistance to particularly corrosive chemicals.

Materials such as ABS plastic, brass, rubber, aluminum and fiberglass reinforced plastic provide satisfactory resistance against some chemicals. However, certain other chemicals will swell, cloud, soften, harden, corrode or completely destroy these materials.

Mr Peter Campisi who runs Buckman’s equipment department said that Buckman prefers S30400 and S31600 because they are compatible with most of the company’s products and because using them simplifies both design and inventory management. He added that “These two stainless steel types cover most of our requirements.”

Mr Campisi said that “Ideally we would hope to never have to repair or replace equipment but adds that a service life of five years is likely in most cases, owing to the effects of the chemicals used, frequency of usage and various environmental factors. We try to get as close to zero maintenance as possible, which usually means spending more money up-front. In the long term, this trade off is worth it, which is why we mostly use S31600 as a standard, even when we could use less expensive alternatives.”

For the mills, another advantage is that corrosion-resistant stainless steel construction is less prone to leaks which gives workers improved safety conditions while reducing chemical loss to the environment.