ISO 6249:2021 pdf download – Petroleum products -Determination of thermal oxidation stability of gas turbine fuels.
6.2 Heater tube deposit rating apparatus, either of the tube raters (see fi.21 to f2A) shall be used
for evaluating heater tubes.
6.2.1 Visual tube rater (VTR). the tube rater described in AnnexE.
6.2.2 Interferometric tube rater (ITR), the tube rater described in AniiexC.
6,2.3 Ellipsometric tube rater (ETR), the tube rater described in AnnvxD.
6,2.4 Multi-wavelength ellipsometnc tube rater (MWETR), the tuberator described in AnnexE.
6.2.5 Nylon brush, to clean the heater tube section with no worn bristles.
NOTE Once the bristles of the brush wear down, they cannot effectively remove deposits/residue from the inner walls of the heater tube section.
7 Samples and sampling procedures
Unless otherwise specified, the samples shall be taken using the procedures specified in ISO 3170 or
ISO 3171. with the following additional requirements:
a) Containers shall be in line with ASTM 04306.
b) Prior to sampling, all containers and their closures shall be rinsed at least three times with the fuel being sampled.
c) Samples shall be tested as soon as possible after sampling.
Test method results are known to be sensitive to trace contamination during the sampling operation and from sample containers. New (previously unused) containers are recommended, but when used containers are the only ones available, they should be thoroughly rinsed with tn-solvent (52). followed by cleaning solvent (13) and dried with a stream olair.
8 Preparation of apparatus
8.1 Cleaning and assembly of heater test section
8,1.1 Clean the inside surface of the heater test section to remove all deposits using a nylon brush
(625) saturated with tn solvent (12).
8.1.2 Check the heater tube to be used In the test for surface defects and straightness using the following procedure.
Inspect the heater tube between 5 mm and 55 mm above the bottom shoulder using the light box (U21).
If a defect (e.g. scratch, dull or unpolished area) is seen, establish its size. If it is equal to or larger than 2,5 mmd, discard the tube.
Discard the tube. if the defect is smaller but is still visible in laboratory light.
8.2 Cleaning and assembly of the remainder of the test components
8.2.1 Perform the steps gwen in .Z.Z to .LfI in consecutive order, prior to running a subsequent test.
NOTE It Is assumed that the apparatus has been disassembled Ironi any previous tests (see the appropriale operating manual tar assembly/disassembly details).
8.2.2 Inspect and, using the cleaning solvent (S.3), clean components that contact the test sample. Replace any seals that are faulty or suspect, especially the lip seal on the piston, and the 0-rings on the reservoir cover, lines and pre-uilter cover.
8.2.3 Refer to the equipment manual supplied by the manufacturer for specific cleaning procedure.
8.2.4 Install the prepared heater section (see l.1.3).
8.2.5 Assemble pre-lilter with new element and install.
8.2.6 Check the thermocouple to ensure that it is in the correct reference position arid lower it into the standard operating position (see 1025).
NOTE Failure to insert the thermocouple can cause over heating of the heater test section and result in damage to the equipment.
9 Calibration and standardization
9.1 Perform checks of key components at the frequencies indicated in 92 to 9.6 (see Annex A for details).
9.2 Thermocouples, calibrate a newly installed thermocouple (see A.9) and periodically thereafter after a maximum of 50 tests, or at least every 6 months.
9.3 Differential-pressure cell, standardize once a year or when installing a new cell (see A.).
9.4 Aeration dryer, check at least monthly and change if the colour indicates absorption of water (see SA) or as recommended by equipment manufacturer for replacement.
9.5 Metering pump, perform two checks of flow rate during each test in accordance with 10.4.5 and 1flii
9.6 Filter by-pass valve (if applicable), check after a maximum of 50 tests, or at least every 6 months (see Au).
10 Procedure
10.1 PreparatIon of fuel test sample
10.1.1 Filter minimum 600 ml of the test fuel, at a temperature between 15 °C and 32 °C through a single layer of filter paper (5.5) into the reservoir. Aerate the filtered fuel for 6 mm through the sparger (52) at an air flow rate of 1,5 I/mm.
10.1.2 Maintain temperature of sample between 15 C and 32 °C during aeration. Put reservoir containing sample into a hot or cold water bath to change temperature, if necessary.