Vapourshield Plus
Elmelin Solutions for the Metal
melting Industry
Why Vapourshield ?
Many foundries would like to save
money by making use of some
galvanized scrap in their melts.
They are often prevented from
doing this by the possibility that
zinc vapour could condense onto
the induction coil, causing interturn shorting. Other metals such as
lead, tin and cadmium can cause
similar problems.
About Vapourshield
Vapourshield has been developed for
customers who have already
encountered problems caused by metal
vapour deposition and also for
customers who would like to increase
the galvanised content of their scrap.
The Type 2 version is particularly
designed for use in mains and medium
frequency induction furnaces, where
appropriate. With respect to suitability,
reference should be made to the
relevant Vapour shield Suitability
Guides, prior to use.
The Plus
Three additional enhancements.
1. Metal Penetration Alarm.
Vapourshield plus, with its stainless steel core, can be attached to the earth-leakage system of an induction furnace.
Were the melt to penetrate the crucible and come in contact with the earthed Vapour shield core, an alarm can be
triggered and the furnace made to shut down. In this way a major Health and Safety gain can be achieved.
2. Metal Penetration Barrier.
Depending on the temperature of the melt, Vapourshield Plus can be an effective, if temporary, barrier to metal
penetration to the coil grout and beyond to the coil. In this way Vapour shield may be able to prevent catastrophic
damage to the coil from occurring.
3. Improved Push-out Characteristics.
One of the many benefits of using mica based slip-plane materials in the lining of coreless induction furnaces, is the
improved push-out performance that they provide. It has been shown that the addition of the internal stainless
steel layer within Vapour shield Plus, has significantly added to the performance of our standard slip-plane
materials, in this regard.
Versuchsbericht / Test report
Vapourshield test October 2011.doc 9 -rc
ABP Induction Systems GmbH, Kanalstr. 25, D-44147 Dortmund, http://www.abpinduction.com
Von/From ABP/DA1 Robin Chakrabarti
Telefon/Phone + 49 231 997 2278
Fax 2431
An/To G. Ulrich
1/11
Datum/Date 2011-11-11
Firma / Company
Schütte, Meyer & Co. Gusstechnik GmbH
Teilnehmer / Participants
Stephen Weiss (Elmelin),
Andrejs Umbrasko, Stefan Martini, Robin Chakrabarti
(ABP)
Besuchsdatum / Visiting Date
12. – 13.10.2011
Melting equipment:
FS10 (1t) / 750kW / 500Hz / IGBT
Test aim:
To establish, to what extent, the
electromagnetic field of a medium
frequency induction furnace, would
couple with the stainless steel foil of
the Elmelin Vapourshield material.
Vapourshield is a laminate of flexible
phlogopite mica paper and stainless
steel foil. It is designed to prevent the
carbon and metal vapours, which are
generated by the melt, from
condensing onto the induction coils of
the furnace.
Test set-up:
The old crucible is pushed out.
2 lengths of Vapourshield (1150mm long x 960mm wide),
are sufficient to cover the furnace wall.
In total, approx. 2m² of. The Vapourshield was installed, with
50mm of overlap
Avoiding an electrical circuit.
For this trial, an additional strip of conventional mica foil
was inserted between the 2 sheets of Vapourshield, at the
overlap points, to rule out any possibility of an electrical
circuit being formed.
The upper ends of the Vapourshield foil were slit, to permit
the foil to be easily formed over the top lip of the furnace.
The slits in the spout area extend lower down into (the
magnetic field of) the furnace.
Where possible, slits should not extend into the vertical wall
area of the furnace, because of their potential to create
local hot-spots, and gaps in the vapour barrier.
Temperature monitoring.
Two prefabricated thermocouple panels were installed – one
at the point of overlap, and the other in the middle of a
sheet.
Each panel contained 3 thermocouples which were set at
different heights.
The thermocouples were attached to temperature displays.
The furnace, which was empty and had not been given its
refractory lining, was then switched on and allowed to run
at full power.
The maximum temperature recorded on the upper
thermocouple was approx. 330°C, in the middle it was100°C
and at the bottom it was 200°C.
These maximum measurements were obtained at the
overlap points, where there is a double thickness of foil and
2 vertical edges.
The middles of the sheets were much cooler – at typically
approx. 100°C
The furnace control panel, when running at full power.
The maximum voltage that could be obtained with an empty
furnace, was approximately 2,210V at 409 Hz and 273kW.
Red glowing spots, at the end of the slits in the
Vapourshield, in the spout area.
These result from the intrusion of the slits into an area of
dense electromagnetic field, caused by the current path.
(see note on P. 3)
In order to supplement the temperature readings from the
six thermocouples, the Vapourshield was painted matt
black, so that measurements could be taken with a thermal
imaging camera
General view of the temperature distribution of a full sheet
of Vapourshield, with the furnace running at full power.
The electrical power readings taken on the Control
Panel of the furnace, were checked and confirmed
by measurements taken at the rectifier input.
Cutting away the slit material, in the area of the spout,
prevented the formation of a glowing hot spot - see also
photos pages 3 & 4.
In theory, larger sheets should get hotter than smaller
sheets.
Tests were carried out on 140mm, 280mm and 400mm wide
strips of Vapourshield, in order to confirm this.
Temperature distribution of a 140mm wide layer.
Temperature distribution of a 280mm wide layer .
Temperature distribution of a 400mm wide layer.
Overall it was concluded that the best in service results, would be
achieved using full width Vaporshield sheets.
Results:
When the furnace was running at full power, the induced power in the approximate 2m² of installed
Vapourshield foil, was 8kW or 2.93% of the total. (Dr. Umbrasko had predicted this result, from his theoretical
calculations.) This means that the Vapourshield was absorbing about 4kW/m² of induced power.
The vertical edges of the foil tended to generate the hottest spots, because of the dense electromagnetic
fields caused by the current paths.
The vertical edges of the wider sheets of Vapourshield, tended to be hotter than those of the narrower
sheets.
Generally, it can be said, that this 2 day trial has demonstrated that the installation of Vapourshield foil, in
middle frequency crucible induction furnaces, should not adversely affect the performance of the furnace or
its lining.
For this always to be the case, the parameters of every furnace where Vapourshield is going to be installed,
(power, frequency, size etc.) and the precise method of installation, should be discussed with Elmelin, prior to
its use.
This was a very demanding trial for Vapourshield, because in service, the foil would be covered by a massive
refractory lining on one side, and on the other side would be the water cooled coil grout. These two factors
would substantially dissipate any local hot spots in the low mass foil.