Page 73 - QRedition5.0 062021

Quality Requirements Edition 5.0 European Enamel Association

B. Enamelling

Test method Requirement Remarks Frequency
3.5 visual assessment external: fundamental defects may not occur fundamental defects are flake off, chip 100 %
internal: in consultation off, copper heads, fish scales, pull off, bur-
ning through as described in NEN 2711
4.3 thickness enamel coating 120 - 400 μm 2 % in production
4.9 impact resistance at 20 N no damages > 2.0 mm diameter after 24 hours on test sheets may be conform when taking into production new recipe,

to EN ISO 28764 but at least 1 x a year
4.10 adherence min. 2 on test sheets may be conform in production 1 x a day
to EN ISO 28764
2
4.13 defects external < 25 / m per individual sheet according to defects in the form of cracks 2 %
method B; average < 10 / m with respect to sheets are not permitted
2
forming part of a heat exchanger bloc. Internal method and
quality requirement to be discussed in consultation with
principal and enameller, depending on application
flatness requirement after the enamelling if required in consultation between if required in consultation between
enameller and customer enameller and customer
2
4.35 boiling sulphuric acid max. 3.0 g/m Test specimens shall be prepared in 1 x per 10 tons enamel
accordance with EN ISO 28764 and shall
be pre-treated and enamelled under the
same circumstances as the production
of the heat exchanger parts. They shall
have an enamel layer of 150 μm ± 20 μm.
4.40 thermal shock resistance 5 x 350 °C on test sheets may be conform to ISO when taking into production new enamel
2723, the resistance is tested on sheets recipe, but at least 1 x a year
of 100 mm x 100 mm with an enamel
coating thickness of 150 + 20 μm.
The sheets are cooled down in water of

20 ± 2 °C.

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