Business Situation:
The board and packaging segment has been exposed to a number of changes in market dynamics that have forced them to respond quickly in order to remain competitive. Costs for fiber, energy, maintenance, environmental compliance and additives have continued to rise, which has put increased pressure on margins and the return delivered to stakeholders.
There continue to be capacity additions in emerging markets that have introduced new production into global markets with machines that are the biggest and most efficient in the world. The increased competition from plastic has also been of concern. The implications of these market dynamics for the board and packaging producers have included an increasing need to perform efficiently.
In this case study, the papermill was struggling to consistently meet its 28-day target for press fabric life. Runnability became worse near the end of the fabric run, as the fabric filled and Uhle box vacuum levels climbed. Runnability issues manifested themselves as reduced machine speed, more frequent batch-down fabric cleaning, and premature maintenance shuts where the fabrics were changed.
In the dryer section, fabric cleaning was often skipped due to lack of time, given all of the other maintenance tasks. This led to an excessively dirty dryer fabric and moisture profile issues resulting in inefficient dryer performance. The papermill was interested in taking the next step in terms of a superior fabric conditioning program.
| Grade: | Corrugating Medium |
|---|---|
| Speed: | 520-640 mpm (1700-2100 fpm) |
| Production: | 900 TPD |
| Furnish: | 63% NSSC / 37% recycle fiber |
Analysis of Business Situation:
Key Business Drivers - On-Machine Efficiency (OME)
- Increased press fabric life; extended run time between shuts
- Improved dryer performance; reduced steam demand; increased machine speed
- Reduced sheet defects and Breaks
Challenge
- Achieve improvements on existing program considered successful
Opportunity
- Extend fabric life
- improve sheet moisture profiles
- increasing on-machine efficiency
Program Design:
Mechanical – HelioJET® water conditioning and delivery equipment is used to combine steam and water in a highly efficient (98%+) process to deliver 150?F (66?C), 250 psi (17 bar) water to the press and dryer fabrics of two machines. Internal brush showers are also provided, which can be rotated to dislodge any buildup within the showers during predefined purge cycles.
The entire cleaning process is managed using a Programmable Logic Controller (PLC) that allows for fine tuning the application as needed to match the level of contamination and to do so in an easy and safe manner.
Operational – Press fabric conditioning is performed continuously. High temperature water is fed to the press fabrics continuously during production through fan showers providing full fabric coverage continuously. Once per shift, the fabrics are treated in batch-on-the-fly mode. Batch-down cleaning is available, but typically only performed during process upsets or during maintenance shutdowns.
Dryer fabrics are cleaned during each maintenance shut. They are cleaned as the dryers are cooling and the process is completed before the maintenance crews are allowed on the machine. The HelioJET® equipment is properly interlocked with the paper machine to prevent premature cleaning while the paper is on the machine, and Standard Operating Procedures are clearly defined and followed during each conditioning process.
Press Felt Cleaning – a solventized alkaline cleaner designed specifically for the challenging conditions created by the HelioJET® unit, is fed during production in batch on-the-fly mode. The product is fed once per shift to eliminate stickies and alkaline soluble contaminants. Acidic product is fed during production in batch-on-the-fly mode. This product is fed once per shift as well to eliminate scale buildup in the fabrics.
Dyer Fabric conditioning – a solventized alkaline product is fed at a heavier dosage and applied using the HelioJET® conditioned water. The product is allowed to soak before rinsing with the HelioJET® conditioned water until all of the foam is completely removed. An anti-scale product is also fed to the suction side of the HelioJET® unit, to prevent scale buildup in the unit and showers during water rinsing. This is critical as scaling can be significant at HelioJET® operating temperatures.
Key Performance Indicators:
- Press fabric life – target 35+ days from current 28 days
- Improved runnability from improved dryer performance
- Machine speed increase and/or steam usage decrease
- Improve sheet moisture profile
- Reduce downtime for cleaning dryer fabrics
Program Results
The press fabric conditioning program successfully met the primary goal of the program - to extend press fabric life by 7 days.
With the new solution, the papermill’s current fabric life is now 35 days, a 25% improvement. Extrapolated over two machines, this saved the papermill over $500,000 per year from reduced downtime by allowing the papermill to extend their shutdown schedule.
Furthermore, the machines ran better over the entire life of the fabrics, maintaining relatively low Uhle box vacuum for the entire 35 days. This translated to additional increases in OME since the machine went down less often due to sheet breaks and for batch-down fabric cleaning.
Upon completion of the dryer fabric cleaning cycle, the fabrics are "as clean as the papermill has ever seen," according to the papermill superintendent. The papermill now cleans the dryer fabrics on every shut since they can clean while the dryer is still hot before the maintenance crews are allowed on the machine anyway.
Previously, the papermill often ran out of time during shuts and skipped cleaning the dryer fabrics, choosing instead to absorb the on machine efficiency hit from higher steam usage and/or reduced machine speed due to dirty dryer fabrics.
Furthermore, the papermill now has the capability of cleaning the dryer fabrics during short shuts, such as sheet breaks. The fabrics can be cleaned in 30 minutes or less, without cooling the dryer cans, thereby keeping the dryer fabrics performing with high efficiency.
The dryer fabric conditioning program has extended dryer fabric life by up to 100% due to more frequent and improved cleaning over the lifetime of the fabric. Dryer fabric lives of easily over a year have been demonstrated, something the papermill has never accomplished in the past.
The papermill estimates that steam usage has decreased significantly since the start-up of the solution. After cleaning the dryer fabrics, the moisture profile, which runs 1.5 - 2.25 on a dirty dryer fabric, is improved to 0.75 - 1.5.
Conservative estimates indicate that it takes up to 5 days for a clean dryer fabric to become contaminated to the point that the moisture profile reaches the range of 1.5 - 2.25. Based on the papermill’s actual steam usage and cost, savings of $45,000 per year have been gained by the papermill.
However, if the papermill translates the dryer capacity into increased machine speed for both machines, the papermill could recognize over 2,600 additional tons and nearly $800,000 in incremental revenue from added production.
Maintaining the Value
The success of the fabric conditioning program utilizing the HelioJET® technology is remarkable, because the previous press fabric conditioning program was already considered to be best practice.
Combining operational expertise with the HelioJET® technology delivered results far in excess of a chemical only program. This highlights the competitive advantage delivered with mechanical-operational chemical approach to fabric performance optimization.
Conclusion
With the addition of the HelioJET® delivery system, a complete solution that addressed all of the mechanical, operational, and chemical aspects of conditioning paper machine fabrics. The papermill has extended its regular maintenance shutdown schedule by one week and runnability is improved over the entire run period.
The total estimated gains from increased production exceed 3600 TPY and $1.6MM per year in incremental revenue. The papermill now boasts the highest OME of any papermill in its organization and which rivals that of the best in the industry.
The solution addresses all three critical factors relevant to removing contamination from machine fabrics – temperature, pressure, and chemical solubility. No other solution in the industry is able to deliver this level of performance.