BS EN ISO 7526 pdf free download

BS EN ISO 7526-2020 pdf free download.Ferronickels – Determination of sulfur content – Infrared absorption method after induction furnace com bustion.
6.1.3 Maintain a glass-wool filter (5A) between the furnace chamber and the analyser and change as necessary. The furnace chamber, pedestal post and filter trap should be cleaned frequently to remove oxide residues.
6.1.4 The manufacturer may ,‘eornmend setting the programming unit to give a pre-burn period before oxygen enters the furnace chamber. The test portion should be at a red heat during the pre-burri period. When oxygen is introduced for the combustion stage. the temperature increases substantially.
6.1.5 The temperature reached during combustion depends on the furnace, and the type and quantity of metal in the crucible. A high temperature (>1 700 °C) is maintained after the test portion is fused so that the sulfur dioxide can be completely removed from the furnace to the infrared analyser.
6.1.6 The flow rate of oxygen can vary from one instrument to another but is usually about 2,0 1/mm during the combustion period.
6.1.7 After the equipment has been idle for a few hours or after cleaning the furnace chamber or filters, the instrument should be stabilized as described in 1.
NOTE Features of commercial equipment are given In AnnexA.
6.2 Ceramic crucibles and lids.
Ceramic crucibles, containing the sample and any additions that can be necessary, are required for the combustion. They shall be of precise dimensions for the system and fit the supporting pedestal post so that the test portion in the crucible is positioned correctly within the induction coil for heating.
Typical dimensions of combustion crucibles are: a height of 25 mm, an external diameter of 25 mm. an internal diameter of 20 mm, a wall thickness of 2,5 mm, and a thickness of base of 8 mm. The dimension of the hole of the lid should be larger than 10 mm.
Crucibles and lids shall be as specified by the manufacturer of the instrumentation used and shall be capable of withstanding combustion in an induction furnace without evolving sulfur-containing chemicals so that achieving and maintaining blank values within specification is possible.
In order to remove any sulfur contamination, pre-ignite the crucibles in air or oxygen in a furnace for not less than 1 h at 1 100 °C and store in a desiccator or a closed container. A resistance furnace with a combustion tube through which a flow of oxygen passes may also be used.
Crucible lids, used to help retain the solid oxidation products in the hot zone of the induction coil, shall be pre-ignited in a similar manner.
6.3 Crucible tongs, capable of handling recommended crucibles (ff2).
7 Sampling and sample preparation
7.1 Sampling and sample preparation shall be carried out by normal agreed procedures or, in cases of dispute, by appropriate national standards.
7.2 The laboratory sample is normally in the form of a powder, granules, millings or drillings and no further preparation of the sample is necessary.
7.3 II it is suspected that the laboratory sample is contaminated with oil or grease from the milling or drilling process, it shall be cleaned by washing with high purity acetone and drying in air.
7.4 If the laboratory sample contains particles or pieces of widely varying sizes, the test portion should be obtained by riffling.
8 Procedure
WARNING — The risks related to combustion analysis are mainly burns in pre-igniting the ceramic crucibles and in the fusions. Use crucible tongs at all times and appropriate containers for the used crucibles. Normal precautions for handling oxygen cylinders shall be taken. Oxygen from the combustion process shall be removed effectively from the apparatus since a high concentration of oxygen in a confined space can present a fire hazard.
8.1 Preparing and stabilizing the instrument
8.1.1 Assemble the apparatus and prepare it for operation according to the manufacturer’s instructions. Test the furnace and analyser to ensure the absence of leaks.
8.1.2 Condition an(1 stabilize the equipment by combusting several samples, similar to those to be analysed, using appropriate fluxes and accelerators, before attempting to calibrate the system or determine the blank.
NOTE It is not necessary to use pre-ignited crucibles.
8.1.3 Allow the instrument to cycle several times with oxygen flowing and adjust the zero of the instrument.
8.2 Blank test and zero adjustment
8.2.1 Sulfur contents S 0,05 %
For each instrument range, transfer the selected mass ot flux to the nearest 0,005 g, into a preignited crucible (6.2). add the selected mass of a CRM (5.6) having a very low sulfur content, and then cover it with the selected mass of accelerator (5j3).
The type and mass of the flux and accelerator used in the blank test should accord with those used for the determinations (details as in 4J). Record the mass of the CRM. Place the crucible and contents on the furnace pedestal and operate the furnace in accordance with the manufacturer’s instructions. Repeat the determination three more times. Average the results.
Subtract the sulfur content of the CRM from the average to determine the blank value. If the blank is greater than 0,001 % (mass fraction) and the related standard deviation is greater than 0,000 2 % (mass fraction), find the cause of the problem, fix it and repeat the experiment.
Record the average blank value into the analyser in accordance with the manufacturer’s instructions. NOTE 1 The reading obtained corresponds to the blank due to the crucible, flux and accelerator.
lithe analyser does not have automatic blank correction, the blank value should be subtracted from the total result prior to any calculation.
NOTE 2 An alternative procedure is to record the reading of the blank test and make the correction using a calibration graph.
8.2.2 Sulfur contents> 0,05 %
It is preferable not to carry out a blank correction. However, a check of the blank level shall be done. The value shall remain below 0,000 5 % (mass fraction).
8.3 Calibration
8.3.1 Select a set of steel and/or ferronickel CRMs (56) for calibration and verification which, at a minimum, fall at the bottom, top, and quartile points of each operational operating range.BS EN ISO 7526 pdf download.