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On-Board Testing to Mitigate Cold Corrosion Damage

BACKGROUND

The International Maritime Organization’s (IMO) Marine Environment Protection Committee (MEPC 70) will lower the maximum allowable sulfur content from 3.50% to 0.50% effective January 1, 2020. For ship owners choosing to switch from High Sulfur Fuel Oil (HSFO) to Low Sulfur Fuel Oil (LSFO), it will be critical to have accurate sulfur levels of loaded fuel before leaving port to ensure regulatory compliance.

The shipping industry is facing many challenges with increasing fuel costs and more stringent regulations. Many ship operators are planning to utilize slow steaming to help mitigate these challenges. Oceangoing vessels were designed to operate at 27 knots, but operators are learning that if they reduce speed to 18 knots it enables them to utilize their entire fleet as well as save money on fuel costs.


CHALLENGE

The disadvantages of slow steaming are the harsh side effects of cold corrosion on engines. Cold corrosion occurs when the pressure in the engine cylinder increases and reduced temperatures create conditions below the acceptable dew point, allowing water to condense on cylinder liner walls. That condensate combines with sulfur and forms sulfuric acid – corroding the liner surface and creating excessive wear of the liner material. This corroded liner is continually scraped against by the piston, resulting in the formation of iron compounds which can then be measured in the lubrication oil. Replacing a cylinder engine can cost over $100k. Having the ability to test for both iron and sulfur on-board and quickly will be crucial to prevent costly engine damage.


SOLUTION

Petra MAXTM, a multi-elemental analyzer by XOS, is an ideal solution for shipboard analysis of critical elements in marine fuel to ensure compliance with existing ECA sulfur requirements and 2020 regulations, as well as elemental analysis for cold corrosion mitigation. The analyzer is compact, robust, and easy for non-technical operators to use. Analysis is as simple as pouring a few mL of fuel into a disposable plastic cup, sealing with a plastic film, closing the lid on the analyzer and pressing “Measure”. The instrument complies with the same ISO 8217 approved methods that are used by fuel laboratories and refineries.


EXPERIMENT

To assess the measurement capabilities of Petra MAX in relation to iron, sulfur, and other elements of interest, two commercially available samples of residual oil were analyzed. The first sample contained lower concentrations of various elements including sulfur (S), iron (Fe), nickel (Ni), vanadium (V), and calcium (Ca), while the second sample contained higher concentrations of all elements except iron.

Each sample was measured in 10 separate aliquots for 300 seconds. To prepare the measurement, the sample was swirled for 5 seconds then pipetted into a standard XRF cup that was cleaned with canned air. Each XRF cup was filled to roughly ¾ full and then sealed with a sheet of Etnom® film. Once each sample was ready for measurement, the sample cups were vented using a push pin and placed into the analyzer’s measurement chamber.


RESULTS

Residual fuels, while not often useful in commercial settings, are utilized in vessels and large ships for power. When measuring these samples, we were able to capture concentrations for sulfur, iron, nickel, and vanadium. As noted in Tables 1 and 2, we found high concentrations of sulfur and low concentrations of iron. Across both sets of sample data, a low relative standard deviation is shown which showcases a high degree of precision.




Table 1: Lower Concentration Residual Oil
Sample-Run S (ppm) Ca (ppm) V (ppm) Ni (ppm) Fe (ppm)
S/V in Res. Oil-1 773.30 10.84 54.01 1.38 12.27
S/V in Res. Oil-2 899.30 10.32 51.83 1.42 12.16
S/V in Res. Oil-3  906.70 10.02 51.47 1.35 12.44
S/V in Res. Oil-4 900.90  9.98 51.30 1.42 13.40
S/V in Res. Oil-5 898.60  9.91  51.68 1.38 12.26
S/V in Res. Oil-6  914.30  9.86 52.48  1.41  12.76
S/V in Res. Oil-7 909.80 10.21 50.75 1.45 12.31
S/V in Res. Oil-8 906.50 9.93 51.05 1.39 12.46
S/V in Res. Oil-9 917.30 10.17 51.22 1.42 12.66
S/V in Res. Oil-10 881.10 9.73 51.13 1.38 12.47
Average 890.78 10.10 51.69 1.40 12.52
Standard Deviation 42.49 0.32 0.95 0.03 0.36
RSD 4.77 3.12 1.83 2.08 2.88

Table 2: Higher Concentration Residual Oil
Sample-Run S (wt%) Ca (ppm) V (ppm) Ni (ppm) Fe (ppm)
Elements in Res. Oil-1 0.47 37.34 339.20 2.08 8.56
Elements in Res. Oil-2 0.47 36.92 336.90 2.13 8.46
Elements in Res. Oil-3 0.46 36.64 335.50 2.10 8.69
Elements in Res. Oil-4 0.45 38.19 345.10 2.10 8.76
Elements in Res. Oil-5 0.47 36.89 338.40 2.05 8.45
Elements in Res. Oil-6 0.47 36.39 333.30 2.09 8.60
Elements in Res. Oil-7 0.47 36.88 334.20 2.15 9.13
Elements in Res. Oil-8 0.48 37.20 342.00 2.11 9.52
Elements in Res. Oil-9 0.48 37.48 338.20 2.18 9.67
Elements in Res. Oil-10 0.47 38.53 342.70 2.12 9.93
Average 0.47 37.25 338.55 2.11 8.98
Standard Deviation 0.01 0.67 3.82 0.04 0.55
RSD 1.88 1.81 1.13 1.74 6.10

Footnote: In addition to these elements, Petra MAX can measure other elements of interest including zinc and phosphorus.

CONCLUSION

Ship owners can mitigate the risk of cold corrosion damage on their engine cylinders by implementing an onboard elemental analysis solution. Petra MAX is an ideal solution for this application, in addition to rapid and precise sulfur testing with a limit of detection as low as 0.0006% - well below the new regulatory limits. Achieve elemental analysis with the push of a button, results within 5 minutes, and portability for onboard testing.


Petra MAX

Powered by HDXRF, Petra MAX utilizes XOS patented doubly curved crystal optics coupled with a high-performance silicon drift detector and an intense monochromatic excitation beam. This industry leading technology reduces background noise and increases signal-to-noise output, enabling low detection limits and high precision. Petra MAX offers low-level detection of iron, saving the marine industry money on engine replacement and lube oil costs.

The test methods and specifications approved for marine fuel are controlled by ISO 8217. Sulfur measurement methods compliant with the specification include ISO 8754, ASTM D4294, and IP 336. These methods all use a technology called X-ray Fluorescence (XRF) that is widely used by refiners and fuel laboratories around the world for sulfur analysis. While it can seem intimidating to use laboratory equipment for those that don’t use it routinely, XRF technology has been selected by non-technical users for field applications like port customs inspection and environmental hazard investigation because it is simple to use and provides results in just minutes.

Petra MAX

Author: Sarah Chiasson, Senior Marine & Transportation BDM

Author: Joseph Iaia, Petroleum Product Manager