The pulp & paper industry has seen tough times, but the business will still be around for many decades; the product is too much in demand. Those involved in valves for this industry need to understand how the processes work.
Perhaps no manufactured product plays a more significant role in everyday human activity than paper and paper products. Paper provides the means for recording, storing and disseminating most of today’s information. Even though people have extolled the coming of the paperless society, it has not yet arrived. Humans still print e-mails and other correspondence and information they get from the paperless communication channels of the computer and the Internet. And beyond that, paper is the most widely used wrapping and packaging material as well as a critical component today in everyday life. From drywall to napkins to office supplies, paper is used for many purposes, and that situation won’t change for a long, long time.
The uses and applications of paper and paper products are truly vast, and new specialty products are constantly under development. At the same time, the industry itself faces a vast array of inroads and competition from other sectors, most notably plastics and electronic media. To remain competitive in existing markets and, at the same time, be receptive to new opportunities, the paper industry today is adopting new technologies and methodologies.
Some time back, on a tour of the pulp and paper mills in Finland with a number of North American pulp and paper people, one customer expressed amazement at the investment in new machinery and processes the Finnish companies had recently completed. This customer referred many times to the return on investment in North American pulp and paper mills, which he said was less than 3%. Why would anyone spend money for a 3% return, he questioned, when you could keep your money in the bank and get a better return. This is one of the reasons there has been very little investment in North American pulp and paper mills in recent times. The other two are stringent requirements from the Environmental Protection Agency and a buildup of stock of finished goods.
This means most growth opportunities in pulp and paper are outside North America. And the areas where companies are making money are regions nearer to the major renewable resource that runs this market—trees.
Globally, pulp and paper companies are still merging, buying and selling mills in an attempt to get the right mix to make a profit. This trend will probably continue until there is less paper in storerooms and/or more demand for different types of products.
Several years ago, the buzz word used most often in the industry was “Process Variability,” which meant using better process control to improve quality at the same time you use fewer raw materials and get higher production rates.
Another trend many mills adopted is “Life Cycle” analysis where a mill looks at a product to see if it can be repaired as opposed to being replaced and how many times it can be repaired to increase its life cycle. To accomplish this requires strong cooperation between the maintenance group and the procurement group to determine the best percentage cost balance of a new valve versus repair of a product. Is it 50% cost of new or upwards of 80% cost of new?
It also takes recognizing the value of a quality product in the first place. Quality means repair less often and often means less expense for that repair. The trend for some time has been toward mills repairing valves more frequently, leading more mills toward metal-seated ball and butterfly valves, which have a higher initial cost but longer life cycle. Also, some mills that traditionally used soft seats have moved to more rugged metal seats in many applications—not only for longer life but also because of higher pressure and temperatures in certain applications.
Beyond the usual maintenance, repair and operations issues in the paper industry are challenging applications where a valve in a mill is subjected to slurries, scaling, high velocities, high or low cycling, or where special attention is needed from the maintenance group.
Valves are often chosen by a mill based on how they can handle these challenges. In high-scaling applications, where the media sticks to the surface of the valve, for example, most plants will consider a ball valve first. This is because these valves offer full flow characteristics. Ball valves also rotate 90 degrees, and with the proper scraper seats, the media that has scaled can be wiped off the ball so the ball is clean before it gets seated. In some multi-turn valves, the scaling could sit in the bottom of the pipeline, and the valve blade cannot get through the scale to seat the valve. Cycling the valve or even partial stroking the valve can alleviate the scale buildup. As an example, green liquor (which we discuss later in this article) is a high-scaling media that can stick to the sides of pipe causing a 6-inch pipe to have a 1-inch hole because of the severity of the scaling. In cases where the scaling is extreme, cycling the valve on a weekly basis is recommended to scrape the media off the ball face.
In high-cycling applications, care must be given to packing of the valve. For example, on the echo filters in the recaustisizing area, the filters separate the impurities in white liquor. In this area, a large-diameter valve may cycle every hour because the white liquor and lime mud that are the media in this area are abrasive so that, not only do the seats get worn, but the packing tends toward wear. For this reason, a double-packed valve with live-loading is often recommended. The bottom line in any of the liquor applications, however (mills deal with green, white, black, orange, red and brown liquors), is that high-quality valves are needed and the supplier of those valves should have expertise in this specific application.