ISO 540:2008 pdf download – Hard coal and coke – Determination of ash fusibility
8 Calibration check
Check the pyrometer regularly under routine test conditions by observation of the melting point of gold (5.3) and, if possible, the melting point of palladium (5.5). Test the reducing atmosphere by observing the melting point of nickel (5.4). If the observed melting points for gold or palladium differ by more than 10 °C from the melting points given in 5.3 and 5.5, readjust or recalibrate. NOTE 1 An alternative to the observations of the melting points of gold and palladium is to check the pyrometer using a thermocouple certified by a recognized reference laboratory or with a calibration that is traceable back to a standard reference laboratory. If the observed melting point for nickel differs by more than 10 °C from the melting point given in 5.4, it can be due to oxidation of nickel caused by an insufficiently reducing atmosphere. Examine the apparatus for Ieakages, control the flow rate and the quality of the gases, and recheck the melting point of nickel. NOTE 2 The correct melting point of nickel is not a guarantee that the composition of the reducing atmosphere is correct, as the fusibility is not likely to be affected until the deviations are considerable.
9 Preparation of the test piece
Prepare the ash according to the method specified in ISO 1171. Ensure that the incineration is complete. Grind the ash in an agate mortar (6.6) until the maximum particle size is less than 0,075 mm. To maximize the number of particles in the peak of the pyramid, grinding to less than 0,063 mm is recommended. Moisten a sufficient quantity of the prepared ash with demineralized water or, if necessary, with an adhesive dextrin solution (5.1), and make the mixture into a paste. To facilitate the removal of the test piece, the mould (6.3) may first be coated with a thin layer of petroleum jelly (5.2). Fill the mould uniformly and completely with the prepared paste of ash so that the edges and tip of the specimen are sharp. Allow the test piece to visually dry before attempting to remove it from the mould. If the ash paste dries too quickly, it is acceptable to moisten it slightly with additional water or solution. After removal, mount the specimen onto its support (6.4), using a thin layer of paste of the prepared ash to effect adhesion, taking care not to damage the tip or edges. The specimen(s) should be examined with the optical instrument (6.8) and those that do not have sharp edges and tips should be discarded. Allow the test piece to dry, and remove any organic matter by heating the test piece slowly up to a temperature of about 815 °C. If preferred, this preliminary heating may be performed in the furnace (6.1) used for the test.
10 Procedure
Transfer the test piece on its support (6.4) to the furnace (6.1), and adjust the composition and flow rate of the atmosphere, taking into account the warning in 7.1. To minimize the risk of explosion when a reducing atmosphere is used, purge the furnace with carbon dioxide before admitting hydrogen. The specimen shall be positioned on the tile so that, when inserted into the furnace, its vertical face is parallel to the longitudinal axis of the inspection opening. Further, the specimen shall be placed as close as possible to the end of the thermocouple sheath. Ensure that the thermocouple is in the correct position.