Paper Technology International 2020 - Journal - Page 96

PAPERTECHNOLOGYINTERNATIONAL
Toscotec launches new TT Headbox-SL generation design for paper and board
Luca Ghelli - Toscotec R&D Director
INTRODUCTION:
Considered the very demanding operating conditions of headboxes, and in order to guarantee high quality and uniform profiles,
Toscotec has developed a strict design and quality control protocol especially devised for headbox manufacturing.
This protocol involves raw materials tracing, manufacturing
control of single parts, and final pre-assembly in the workshop with
the objective of certifying the following features of the final headbox
assembly:
•
Lip opening uniformity (at different slice openings and during
slice movement)
•
Surface integrity, planarity, and roughness
•
Sharp lip edges integrity and linearity
•
Stability under operating conditions (pressure test)
•
Material quality
Toscotec has installed more than 100 TT Headbox on tissue and
paper and board machines. Based on its vast experience in design
and operation, Toscotec has recently introduced the new generation
design of TT Headbox-SL for paper and board application by
benefiting from the experience of its headboxes for tissue machines.
Considering their high performances, tissue production is very
demanding due to the following features:
•
•
•
High speed required at the jet (up to 2200 m/min) with
corresponding high structural strength required due to high
internal pressure. This pressure poses the challenge of
reducing headbox deformation or allowing manifestation of
inherent minor manufacturing issues.
High flow due to typical low consistencies used in tissue
machines (up to 0,15%) with corresponding large size
headboxes to fit into a typical gap forming geometry.
Most tissue market headboxes manufactured are prepared
for the installation of a dilution control system in order to
ensure very precise paper profile control on a very low basis
weight (11-12 gsm).
TT Headbox-SL for paper and board: key technical features
Toscotec’s TT Headbox-SL has a robust structure to
withstand internal pressure and large machine width, and a compact
design for easy installation both on new machines and on rebuilds.
The internal components are designed to guarantee good
fiber distribution across the machine width and good fiber mixing
before jet delivery to the forming section (both on Fourdrinier or gap
former).
The special design of the tube bank’s tubes ensures an
optimal uniformity in cross direction and good preparation of the
fiber slurry before the converging zone with minimal head losses.
After the tube bank, a series of lamellas (blades) are
installed to maintain a high level of microturbulence for optimal fiber
mixing just before leaving the headbox making it optimized for the
final jet delivery out of the lip.
On both sides of the tube bank structure, specially designed
valves control the flow at the extreme edges of the headbox, in order
to ensure a uniform fiber orientation on the entire width up to the
edges.
A comprehensive system of mechanical jacks and electrical
motor reducers allows operators to have full control of the top
slice to adjust jet thickness across the lip and the jet landing
(impingement) according to production needs.
Figure 1: Toscotec’s TT Headbox-SL.
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