BS EN 14866:2005 – Vitreous and porcelain enamels — Regenerative, enamelled and packed panels for air-gas and gas-gas heat exchangers — Specifications

6.3 Thermal shock resistance
Test specimens for the determination of thermal shock resistance shall be prepared in accordance with ISO 2723 and shall be pre-treated and enamelled under the same circumstances as the production of the heat exchanger.
They shall have an enamel layer thickness of 150 µm ± 20 µm. The thermal shock resistance shall be determined on at least three test pieces in accordance with Annex A at a test temperature of 350 °C. After testing five times at the test temperature, the test specimens shall show no damage.
The test shall be carried out on every 5 t of enamel frit. 6.4 Fundamental defects A 1 00 % visual examination of the enamelled surface shall be carried out for fundamental defects.
The enamelled surface shall be free of fundamental defects such as blisters, burn-off, chipping, copper heads, cracking, crazing, fish scales, spalling and tearing (see Clause 3).
The enamelled surface shall be visually examined from a minimum distance of 1 ,5 m, in either natural light or artificial daylight D65 in accordance with EN ISO 1 05-J03.
NOTE Fire tool marks may be accepted.
6.5 Open defects Open defects down to the basis metal shall be detected in accordance with EN ISO 8289:2001 , method B. In a random check of 1 0 pairs of panels out of a production of 1 0 000 pair of panels, the average number of open defects shall be as given in Table 2.
This sampling is sufficiently representative of the production whenever the results are within the specified norm. If the results differ from the specified norm then the sampling can be extended to between 2 and 5 per thousand.
Alternatively, if the production process demands the number of defects on pairs of heat exchanger panels may be determined by checking 1 % of production on a 2 h cycle. 6.6 Edge covering of gas-gas heaters If required by the customers the edge covering of the panels of gas-gas heaters shall be determined in accordance with EN 1 4863. The mean shall be agreed between the customer and supplier at the time of ordering.
6.7 Boiling sulphuric acid resistance Test specimens for the determination of acid resistance shall be prepared in accordance with ISO 2723, and shall be pre-treated and enamelled under the same circumstances as the production of the heat exchanger.
They shall have an enamel layer thickness of 150 µm ± 20 µm. When determined in accordance with EN 1 4483-2:2004, Clause 1 1, the enamel coating shall have a maximum mass loss as given in Table 3. The test shall be carried out on every 5 t of enamel frit
BS EN 14866:2005 – Vitreous and porcelain enamels — Regenerative, enamelled and packed panels for air-gas and gas-gas heat exchangers — Specifications