BS ISO 349:2020 pdf free.Hard coal- Audibert-Arnu dilatometer test.
BS ISO 349 Electric furnace, example shown in Figure B.5, consisting of a block of metal resistant to oxidation and of sufficiently high melting point. A suggested material is aluminium bronze. The metal block is pierced by at least two holes of 15 mm diameter by 350 mm deep to take the dilatometer tubes and one hole 320 mm deep to take a temperature-measuring device, which intends to keep the thermojunction of the thermocouple in the middle position of the inserted coal pencil with 60 mm. The block is heated by a metallic winding, suitably insulated. Control gear permits the use of any selected rate of heating up to 5 °C/min over a temperature range of 300 °C to 550 °C. The furnace shall be constructed so that the temperature conditions are uniform in the dilatometer tubes placed in their normal position in each hole. To verify this, heat the furnace at a rate of 5。C/min. When the temperature reaches about 450 °C, make an exploration of the lower 180 mm of a dilatometer tube placed in the furnace, by comparing the readings on the normal temperature-measuring device and a thermometric probe placed in the tube. The difference between the probe temperatures and the mean temperature shown by the normal temperature-measuring device shall be less than +2 °C in the lower 120 mm, +5 °C from 120 to 180 mm. This verification is not to be confused with the later calibration of the temperature-measuring device; it is intended to measure only the temperature variation along the tube.In order to inspect the wear of the tube and piston after a hundred determinations have been carried out in one tube, compare the results of the next four determinations using that tube with those obtained in a new tube. This comparison will thus be made successively on four coals.As certain types of hard coal are very susceptible to oxidation, it is necessary to minimize the contact with air after reducing the gross sample. BS ISO 349 pdf download.