In real estate, the prevailing adage is “location, location, location.” At North Pacific Paper Corp (NORPAC), a joint international venture between Japan’s Nippon Paper Industries and Weyerhaeuser, that adage also holds true.
The location in question had to do with the dye system NORPAC was using in its Longview, WA facility, where the company has been producing newsprint and high-bright uncoated mechanical paper for newspapers, commercial printers, book printers, and magazine publishers for 30 years. According to Brian Dalgardno, who oversees some of the chemical programs on the NORPAC machines, the dye control system was simply located too far from injection point and measurement point.
“We have historically experienced precipitation problems when making down the dye,” he said. “The types of dye we have always used, which are basic dyes, tend to precipitate out in the water phase and form a gummy deposit that clogs up the lines.” With color quality standards as high as NORPAC’s, clogged lines in the dye system were intolerable. “We just felt there was a pressing need to shorten the distance between the dye system and the end product for a number of technical reasons,” recalled Dalgardno.
While other papermakers might have been willing to deal with the problem, NORPAC has established a reputation for not being content with the status quo. Founded in 1976, the company produced 220,000 tons of newsprint in 1979. Today, NORPAC’s three machines can manufacture more than 720,000 tons annually, making it the largest newsprint facility in North America.
Purchasing a New System
Thus, five years ago, when the opportunity to improve the quality of its operation -- and its product -- presented itself, NORPAC management decided to purchase a completely new dye system. After an exhaustive search, the company purchased a system equipped with six 520 Series dye pumps from Watson-Marlow Bredel, manufacturer of peristaltic pumps.
“We are using the 520 Series pumps to meter in dye for tinting control of our white papers,” said Dalgardno, who handles quality development as well as financial, cost and runability issues for the company.
The pumps play an integral role in the system’s overall performance. For Dalgardno and NORPAC, the most critical factor was flow -- both high and low. The original pumps NORPAC was using failed to achieve adequate turndown rates from the high flow level required by some dye grades to the very low flow level required by other grades.
“We needed a pump capable of quickly adjusting from a fairly high level of flow to almost zero. We used to dilute our dyes to ratios ranging from 20:1 to 100:1, depending on the dye. Ultimately, we were looking at a much wider range of turndown,” said Dalgardno. “We were convinced that the Watson-Marlow Bredel pumps, integral to the dye system, would fit those requirements.”
NORPAC installed the 520 peristaltic metering pumps, which use microprocessor-controlled brushless dc drive technology to deliver an unparalleled flow turndown over a million to one, a maximum flow of 55 GPH, ± 0.1 rpm precise speed controllability, and digital/analog auto control capability.
Adopting Direct Injection
Dalgardno admitted that he was looking at alternatives to the Watson-Marlow Bredel pumps, but all had their shortcomings. “We looked at one brand considered the ‘standard’ for low dilution, but they were pretty unreasonably priced,” he said. “Also, that brand actually offered less turndown than the peristaltic technology from Watson-Marlow Bredel.”
The Watson-Marlow Bredel 520 peristaltic pumps originally installed by NORPAC were rated to 30 psi, and although Dalgardno was satisfied with the turndown performance, he needed to turn the pressure up in order to further improve his process.
“With the new system, we still needed to dilute the dye and had many problems. In the older dye system, we had larger lines, so the deposits just built up over a longer period of time before we’d have to steam out the lines to remove the deposits,” said Dalgardno. “As a result, we decided that we would rather inject the dye directly into our process without going through the current delivery skid system. With this system, we wanted the neat dye to travel all the way from the injection point to an instantaneous dilution stage just before injection to minimize precipitation issues.”
For direct injection, some of the dyes required as much as 50 psi of process pressure. Watson-Marlow Bredel engineers had just the right pump for the job -- their new 520REH high pressure peristaltic pumphead. The 520REH, capable of 100 psi continuous duty injection, was perfect for NORPAC’s application and allowed NORPAC to achieve the flow rate, high turndown, and direct injection pressure they needed for process optimization.
“Considering the critical shade grades we were moving to, in order to get better shade control we had to go down to very low flows, particularly on red dye -- as low as 3 milliliters per minute,” said Dalgardno. “With such a huge turndown, the system of direct injection with the 520 pumps worked much better for this application. Plus, the final dilution pressure and flow was high enough to keep the diluted dye lines pretty well scoured out.
“We pump the dye from the dye tote, through a filter and into the 520 pump, then pass it through 3/8-inch Teflon lines to a final metal injection header that has a 30 psi governed water source,” Dalgardno added. “Twenty-five gallons per minute of water mix with the dyes in a 1 ft line that is directly injected into the suction of our headbox supply pump. Basically, we’re injecting the dye directly into the process -- from tote, to filter, to pump, to the process, to the final dilution water site, then to the paper machine headbox.”
Pumps Aid Successful Implementation
NORPAC is now using six Watson-Marlow Bredel 520 pumps for the neat dyes along with two more for some other additives; four more are currently on order. In fact, the pumps are being used for some other low-flow chemical systems, such as optical brightener control and some polymer additions.
The 520 Series peristaltic pump is extremely well-suited for neat dye and chemical applications like these throughout the pulp and paper industry. Watson-Marlow Bredel pumps keep fluid contained within the tube at all times, never allowing the often abrasive or caustic process fluid to come into contact with the pump mechanism, ensuring gentle, low shear handling. After the fluid is drawn into a pump, it is trapped between two rollers and finally expelled from the pump.
The complete closure of the tube, which is squeezed between the roller and the track, gives the pump its extremely accurate positive displacement action, preventing backflow and eliminating the need for check-valves, which can often corrode, stick, or clog. The elastomer tubing resists abrasive wear, providing predictable and low pump lifecycle costs, as the inexpensive tube is the only part that will need replacing. The pump’s operation is uncomplicated yet remarkably effective. And maintenance of the pumps is an extremely simple procedure.
“There haven’t been any maintenance issues to date with the motors,” Dalgardno said. “With the tubes, we perform maintenance every 10 weeks by rotating the tube on the lower pressure tubing by half a revolution. With the higher pressure tubing, the different tube design requires that we remove and replace it. But that’s a quick, 30-second process: we simply close the plastic valve, remove the tube, and put the new tube on the nipple that ties into the valve.”
The high-pressure tubing Dalgardno refers to is Watson-Marlow’s patented LoadSure® tube elements, which guarantee correct loading every time, as well as easy one-step maintenance -- a pump rebuild is achieved by simply switching the tube element.
Overall, the entire dye system project and peristaltic pump technology from Watson-Marlow Bredel helped NORPAC realize an 80% return on investment. The savings in maintenance time and productivity losses that NORPAC was experiencing with diluted dye systems -- not to mention the cost of maintaining corroding system versus all plastic -- have allowed NORPAC to uphold its reputation as a company that goes above and beyond.
You might say that the Watson-Marlow Bredel pumps were put into a high-pressure situation -- and responded beautifully.