Page 119 - QRedition5.0 062021

Quality Requirements Edition 5.0 European Enamel Association

8.6.6. Admissible differences of application thickness on corrugated and undulated Consideration

pairs of sheet steel panels for heat exchanger The mean out of the 36 measurements on points No. 1 and 2 of the corrugated panel must
be < 250 μm. A peak thickness on these points of < 300 μm is permissible, but only one

Purpose and scope measurement, out of the 36, may be 20% above the maximum value. The average thick-

Enamelled heat exchanger panels are exposed to mechanical and chemical demand. In ness on the 18 measuring points No. 3 of the undulated panel must be < 200 μm. The
both cases, the application thickness of the protecting enamel layer is of decisive maximum thickness is < 250 μm, merely one measurement can be as high as 300 μm. With
importance. Due to the nature of these parts, an absolutely even application is not the exception of edges and suspension holes, the application thickness should nowhere
fall below 80 μm.
possible. Hence, this specification sheet tries to plot the requirements for admissible
tolerances. On the edge area the entire thickness of the panel may measure 750 μm + thickness of
the sheet.

Test method
Use a thickness measuring instrument of an accuracy of 0.01 mm. Measurements are to

be carried out from point A to I on the front and reverse side of the panel, according to the
sketch represented at the bottom. The test points are situated about 50 mm off the edge.

The measuring points on the corrugated panel are marked with No. 1 and 2, on the
undulated panel with No. 3. Per pair of panels (one corrugated and one undulated) 54
measurements (36+18) result from this test.

Illustration: Optical layer distribution on undulated sheet steel (enlargement 6 : 1)

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