MEASUREMENT & TESTING
27
Figure 5 shows test reports, generated by the automated analyser, of residual fuels samples and corresponding total sediment value. To evaluate a level of conformity in spot rating, the test was performed in parallel with several ST10 instruments (due to the space limitations of this article only 2 spots are shown).
The spots of samples T3 and T6 were rated 4 and 5 accordingly. These fuels reported as unstable by D4740 have been confirmed by ISO10307-2 as having significant level of sediments. The sample T6-1 generated a warning by spot test with rating 3. In this case the verification by onshore testing reported a low level of sediment, and the fuel can be considered as stable. Thus, additional laboratory tests help to clarify borderline cases.
More comprehensive stability assessment can be performed in an onshore laboratory by evaluating asphaltenes stability and solvency power of the fuel or fuels blend by, for example, S-value analysis described in ASTM D7157. This test method determines stability reserve, i.e. the ability of the fuel to keep the asphaltenes in colloidal suspension .
Figure 4. Example of the ST10 database
Performed by the SV10 analyser, manufactured by AD Systems, France, the test procedure is fully automated and involves the dilution of fuel samples by the addition of an aromatic solvent (toluene) followed by titration with a paraffinic solvent (heptane). Asphaltene precipitation is detected by an optical detector monitoring a change in the light transmission properties of the solution. To calculate fuel stability parameters, 3 samples with different dilution ratio are tested and the regression line is plotted. The automatic SV10 analyser can run all 3 samples simultaneously in parallel, thus saving time. The S-value, Sa and So calculated values reported by the analyser will help better evaluate the stability and optimise blending operations.
Figure 6 displays the corresponding reports on D4740 and D7157 tests of residual fuel samples performed by the automated analyser for ST10 (spot test) and SV10 (S-value).
Figure 6 displays the corresponding reports on D4740 and D7157 tests of residual fuel samples performed by the automated analyser for ST10 (spot test) and SV10 (S-value).
ISO10307 Total Sediment = 0 (wt%)
Figure 6-1. Stable fuel sample ISO10307 Total Sediment = 0 (wt%)
The spot is rated 1 and the S-value analysis has shown no floculation, confirming a stable distillate fuel containing no asphaltenes.
ISO10307 Total Sediment = 0,01 (wt%) Figure 6-2. Unstable fuel.
The spot test rated 5 of this HFO sample demonstrates that being thermally stressed this fuel makes asphaltenes precipitate. The S-value test confirms the low capacity of this fuel (S value 1.5) to keep the asphaltenes in a colloidal dispersion ( Sa value < 0.8) and, thus, has low stability reserve.
Conclusion
ISO10307 Total Sediment = 0.12 (wt%) ISO10307 Total Sediment = 0.4 (wt%)
The automated D4740 ST10 tester provides vessel operators with a quick and reliable enough determination of the compatibility of onboard fuels without the worry of a potential errors caused by an inexperienced ship’s crew. As a result, the apparatus can be used anywhere by untrained personnel wherever and whenever a power source is available.
A video of ST10 in operation is available:
https://www.youtube.com/Kl7trsQYCsU
Routinely used by numerous customers, the ST10’s proven high level of reliability and precision is helping ships operator in this challenging time.
In cases when a spot result requires validation, the stability and compatibility of fuel can be future evaluated in onsite laboratory using Total Sediment ISO 10307-2, Asphaltene Intrinsic Stability (S-value) by ASTM D7157 or other test methods.
ISO10307 Total Sediment = 0.4 (wt%) Figure 5 : Examples of the test reports by the automated analyzer and corresponding sediment level.
However, it needs to be noted, that while it remains a valid and easy test undertaken onboard, the ASTM D4740 spot test can return ‘false positives’ when testing waxy/paraffinic nature fuels.
Typically containing very low asphaltenes content, such fuels may form an inner ring due to wax separation and not asphaltenes precipitation.
If a spot result requires validation, the stability and compatibility of fuel can be future tested in an onsite laboratory using robust tests such as the Total Sediment test by ISO 10307-2 [3] or Asphaltene Stability test, for example, Intrinsic Stability of Asphaltene (S-value) by ASTM D7157 [4].
References:
[1] ASTM D4740 “Standard Test Method for Cleanliness and Compatibility of Residual Fuels by Spot Test”
[2] CIMAC Guideline Marine fuel handling in connection to stability and compatibility. (2019)
[3] ISO 10307-2 “Petroleum products — Total sediment in residual fuel oils — Part 2: Determination using standard procedures for ageing”
[4] ASTM D7157 “Standard Test Method for Determination of Intrinsic Stability of Asphaltene-Containing Residues, Heavy Fuel Oils, and Crude Oils (n-Heptane Phase Separation; Optical Detection)”
Author Contact Details Igor Borissov, AD Systems • Saint-André-sur-Orne, 14320, France • Email:
iborissov@adsystems-sa.com • Web:
www.adsystems-sa.com
ANNUAL BUYERS’ GUIDE 2022
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80
