Online monitoring of gas jet wiping in hot dip coating lines
Gas jet wiping is a key operation in hot dip coating, which determinates the homogeneity of the coated product properties and its performance. To improve this wiping complementary tasks were carried out in the project. The first task consisted of the online monitoring of the dimensional parameters of the wiping nozzles for which three sensors were developed: - the first follows the movements of the jets with high precision, leading to the improvement of production by the continuous correction of the jets' position; - the second measures the lips' gap and has demonstrated a negligible influence of thermal effect and pressure variation on the gap and so on the Zinc coating; it was used to check the wipers' design; - the third measures wiping nozzles' shape measurement; this was successfully tested in laboratory. The second task consisted of the development of a 3D model to describe the strip formation between air knives versus the intermesh of the immersed roll taking into account a cooling thermal gradient and a tension differential. All the studies were done with two different configurations (3 and 2 rolls) and with 460° C rheology. Injected stress, sink roll diameter and tension were some of the parameters studied. The 2D model results are lower than the 3D model ones, due to physical constraints. Even if the model results were not very close to the experimental ones, the final conclusion is that the model explains in a qualitative mode the crossbow even if it has still to be improved. The third task was to design a virtual sensor using local models to provide an accurate estimation of the Zn coating thickness in a hot dip galvanising line from indirect measurements such as line speed, distance from air knives to the pot and to the strip, etc. After various iterations, an MLP-NARX model (a non-linear extension of the auto-regressive moving average linear model using multi-layer perceptron) was tried.
Bibliographic Reference: EUR 23192 EN (2008), 117 pp. Euro: 20
Availability: Katalogue Number: KI-NA-23192-EN-S The paper version can be ordered online at: http://bookshop.europa.eu
ISBN: ISBN: 978-92-79-08107-1
Record Number: 201010068 / Last updated on: 2010-01-22
Original language: en
Available languages: en