Paper 360
An old and popular advert promoting efficient, reliable, and user-friendly household equipment ended with the vigorous claim “Facts, not just words.” The underpinning message being the guarantee of “actual results, not only promises.” Studying the list of Toscotec’s TT Headboxes—32 units since 2020, of which 23 in operations and nine undergoing manufacturing—provides a reminded of that popular ad.
Over the last 16 years, Toscotec has sold over 130 TT Headboxes to be installed on tissue machines; 32 have been in the last three years. The majority of these units were part of complete tissue line orders (23 units), some were part of major rebuilds (four units), and the rest (five units) were sold as replacements of existing headboxes. The latter replaced headboxes manufactured by other machinery suppliers with the aim of improving paper quality and production performance. Since headboxes are normally sold with the complete tissue machine, the fact that paper producers are willing to replace only the headbox testifies to its importance, as it affects the machine’s production both in terms of paper quality and energy performance.
Toscotec’s TT Headboxes sold since 2020 vary in size, characteristics, and performance:
- 15 TT Headboxes have a pond width lower than 3,000 mm, while 17 units are between 3,000 and 5,800 mm.
- The majority are designed for high speed machines (up to 2,200 m/min).
- 5 TT Headboxes are equipped with paper profile dilution control (connected to QCS), while 5 units are designed for its future installation.
- 21 units are single-layer TT Headboxes and 11 are multi-layer units.
- 26 TT Headboxes are installed on crescent former machines and 6 units on twin wire former machines.
- 3 TT Headboxes are installed on TAD machines and the rest on DCT machines.
Toscotec’s headboxes produce high quality products—from facial and low basis weight toilet tissue (below 12 gsm) to towel tissue (up to 32-35 gsm)—processing different furnishes, including virgin fibers, deinked pulp, and 100 percent wastepaper.
All TT Headboxes feature high flexibility in terms of:
- flow out of the headbox and into the forming section through precise slice opening control
- jet landing on the first dewatering part of the former.
To ensure a proper and uniform feed, they are equipped with best-in-class instrumentation for the control of process parameters such as pressure, temperature, and consistency.
ACTUAL RESULTS: SUPERIOR PERFORMANCE
After a short period of optimization and fine-tuning following start-up, all TT Headboxes met the guaranteed figures and customer requirements, as high quality formation was always reached on all applications and on all grades. In several cases, the headboxes have set a new benchmark for paper formation, which was subsequently adopted in other mills of the same group, and on various occasions also led to repeat orders.
TT Headboxes, those without dilution control and only the basic configuration of the slice lip controlled with manually operated micro jacks or micrometric screws, have always met bone dry profile guarantees within 1.5 percent of mean bone dry value when averaged over the control window corresponding to the adjusting spindle spacing.
For TT Headboxes equipped with automatic cross direction (CD) dilution system, the main operating parameters are:
- dilution flow accounting for 7 to 10 percent of the flow out of slice
- pressure ratio (pressure in dilution header divided by pressure in headbox header) normally in the range of 1.3-1.4
- standard control window of 82 mm
- bone dry profile 2 sigma values below 0.8-0.9 percent (ratio of bone dry 2 sigma CD gsm/average bone dry gsm∗100) for all products
The accomplished 2 sigma figures are based on the control window of the profiling system. Even when all scanner readings are used to calculate the 2 sigma figures, the variability never exceeds 1.5 percent of the average bone dry value.
Why is bone dry profile uniformity so important? Because after paper formation is completed, it is a crucial property as it normally translates into:
- better control of the Yankee coating
- avoiding over-drying to compensate for lack of moisture profile uniformity with significant energy saving in the Yankee and hood area
- better moisture profile at the pope reel
- better runnability in the converting
- fewer complaints from final customers
TT HEADBOX: A SUCCESSFUL TECHNOLOGY
Optimal headbox performance and high quality paper production require an optimized control of stock injection and a proper selection/operation of the equipment in the approach system. A good control of the water recovery circuit is also key for smooth, clean, and efficient operation of the headbox, especially for furnishes such as wastepaper and deinked pulp.
Toscotec has developed a deep knowledge of the approach system design and best practices to avoid process disturbances, which could affect TT Headbox’s operations, enhancing both Machine Direction (MD) and CD profile control. As a result, it offers all the necessary support for the control of the complete process both upstream and downstream of TT Headbox.
The success of TT Headboxes derives from:
- extensive experience and deep product knowledge
- effective and precise manufacturing specifications
- optimal quality control of the final product
- stricter and more accurate quality control procedures of sub-suppliers
Based on the increasing knowledge of the product, Toscotec has developed standard headbox specifications which are then applied and customized for each customer based on the specific need in terms of flow, control capacity, and geometry of the application.
Besides quality and profile control results, the TT Headbox is close to 100 percent free of internal build-up issues or the need for special cleaning requirements.
