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equipment for hot-dip galvanising lines
FOEN® wiping equipment has been continuously improved to meet the growing expectations of the strip coating and automotive industries. More than 130 lines have been equipped worldwide, with many orders received from customers who already had a FOEN® air knife system working on one of their existing lines. Process and product developments are described.
用骄傲造句G
alvanid steel strip is accounting for an ever- increasing proportion of strip production due to its superior corrosion resistance properties. A schematic of a typical galvanising line is shown in Figure 1. An important feature of such a line is the ability to adjust zinc thickness according to customer demand. FOEN® air knife wiping equipment is able to accurately adjust the zinc coating weight by blowing air or nitrogen at the strip at a specific pressure to remove excess zinc. The design features are such that a s
uperior uniform coating weight distribution is achieved without edge build-up.
The equipment compris a three-roll guiding system above the molten metal pot which assures the fixed vertical pass-up line of the strip between the air knives above the pot (e Figure 2). Figure 3 shows the galvanid strip after passing the air knife. An asmbled air knife in the workshop prior to shipment is shown in Figures 4 and 5. During operation, the correcting roll can be moved by remote control to and from the strip to flatten the strip crossbow, enabling production of a flat strip in the wiping area.
The controlled air or nitrogen is blown through a gap along the whole strip width to adjust the amount of molten zinc on the strip by wiping off its excess. The zinc layer weight depends mainly on the air knife pressure, air knife distance to the strip and air knife height.
Authors: Pascal Fontaine, Holger Behrens and Catherine Mintmans Fontaine Engineering and SMS Siemag
r Fig 1 T ypical strip galvanising line (source: SMS Siemag)青豆怎么做好吃
NEW RELIABLE UPGRADE OPTIONS
Incread quality requirements of the automotive industry as well as environmental requests have led both to major improvements in all parts of the existing air knife and the development of new devices that achieve the tightest tolerances, as illustrated below:
小米路由器3Dynamic electro-magnetic coating optimir (DEMCO®) In conventional hot-dip galvanising lines, undesired strip movements can lead to uneven strip coating and under- or over-coating. The reduction of strip vibration in the process ction enables significant improvements in coating quality. FOEN® has developed a strip correction system that is characterid by its compact size, high force application and very fast control times. The stabilising effect on the strip is achieved through inductive measurement of the strip position and control of magnetic forces across the strip width. Depending on the width, three or five pairs of coils are in u where only the central one is fixed; the other pairs moving synchronously.
The effect of a DEMCO® strip stabilir with five coils is shown in Figure 6 which shows the measurement of the strip motion above the actuators, the activity of the coil pairs and of the coating weight when the strip stabilir is switched on and off. The upper graph indicates the strip
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up to 55% of nitrogen or air consumption, depending on the relative strip width compared with non-closable air knives. Customers report that top dross can be reduced by 40-60% when using this device due to reduced air turbulences on the zinc surface.
Model bad controller (MBC) A new mathematical feed forward model to optimi coating weight control has been developed. Numerous interfaces to well-known suppliers give it the advantage of a completely free lection of coating weight gauges (hardware). Furthermore, the time the operator needed to control the air knives is reduced to a minimum. The model works in such a way that the air knife height, air knife pressure and air knife distance to strip are adjusted immediately after any changes in ttings.position by eddy current nsors. The middle graph shows the resulting stabilir currents as measured at the off side, centre and drive side of the strip. The lower graph indicates the top and bottom coating weight in g/m 2.Lar controlled distance to strip FOEN® developed the first lar distance control about 15 years ago. It was ud at TKS Duisburg to control the air knife distance to the strip (automatic skewing position). Today, more advanced lar technolo
gy allows a very accurate and fast respon measurement unavailable years ago. Extensive tests have shown that this lar is able to operate in tough environments and has an automatic crossbow control of the strip while moving through the air knives when developed a new touchless positioning mechanism for the edge coating control device. It allows accurate positioning of the baffles relative to the strip to define the position of the baffles without using the rolls, which were formerly in contact with the strip. This helps to achieve even better coating on the edges of the strip.
红茶有什么作用The latest nsor technology is ud to fulfil the requirements for accurate positioning. For safety reasons the rolls remain in place on many lines (but without touching the strip) and are only ud to protect the hardware of the edge coating control device.
Variable nozzle gap width adjustment When running strip of differing widths gas flow must be cut off where there is no strip prent otherwi gas is wasted. The system is fully automated with complete hardware including stepper drives and side closure devices.
According to production experience it is possible to save
r Fig 3 Galvanid strip after passing the air knife
waitting
r Fig 2 3D drawing of the complete wiping equipment r Fig 4 Asmbled air knife in workshop prior to despatch
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New air knife lifting device The traditional air knife lifting device with one jack has been replaced with a more rigid construction, consisting of two screw jacks combined with linear bearings on both sides. Both lifting devices (operator side and drive side) are equipped with electrical drives replacing the old design with the connection shaft between the lifting devices. The synchronous movement of the jack motors is cured via a PLC.
The benefit of the new type of lifting device is to enable a free view of the wiping process when watching the production from the side of the air knives. A camera can also be installed.
New ceramic sleeve design for sink roll A newly developed FOEN® ceramic almost doubles the lifetime of the ceramic sleeves. It therefore also reduces shutdown time for maintenance. On one European customer’s galvanising line, the new ceramic is replaced after a total operation time of more than one year with campaigns of about 30 days each.
The target for this new development was to increa the lifetime of the ceramic sleeves and operation time as well as reducing the wear on the end caps. This was achieved.
RETROFITTING EQUIPMENT
only intermittently, this period of low activity can be ud to upgrade the equipment and train operators, which would be much more difficult once production returns to normal levels. As an incentive, FOEN® offers packages combining profit-making upgrades and training of operational staff in order to run the equipment with first-class performance. Long-term payment conditions may also be agreed for the packages so that savings in energy and/or zinc and higher output quality ensure an immediate return on investment. MS
Pascal Fontaine is General Manager and Catherine Mintmans is Assistant to the General Manager at Fontaine Engineering und Maschinen GmbH,
Langenfeld, Germany. Holger Behrens is with R & D Strip Processing Lines, SMS Siemag.
大白鲨怎么画CONTACT: pascal.fontaine@foen-gmbh.de
陶谢r Fig 5 DEMCO ® mounted on the air knife in the workshop东莞松山湖花海
r Fig 6 Effect of DEMCO ® strip stabilir in operation
