Answer SSEP Question 27
Q27.
With regard to new sulphur cap of 0.5% w.e.f. 1st Jan.2020, list the
challenges likely to be faced onboard. What are the options in case a
vessel is unable to get compliant fuel.Answer: Fuel storage and stability Issues
Storage issues:
- As ECA regions operate with 0.1% and the rest of the regions will operate with 0.5% fuel, hence ships will need at least 2 different storage tanks. Also, the need for proper transfer & purification is a challenge without contamination is grim.
Fuel stability issues:
- Bulk fuel stored for long periods can become unstable . The asphaltene content can precipitate out of solution causing the formation of sludge. This has the potential to block filters and pipes, leaving tanks with a un-pump-able residue.
- Compatibility problems occur when heavy fuel oils with a high asphaltene content are mixed with lighter fractions with 'a Predominance of aliphatic hydrocarbons. The mixing can cause precipitation of the asphaltenes. lt occurs when fuel.oil suppliers blend in order to reduce final fuel oil viscosity, specific gravity; or other fuel property.
Viscosity based issues:
The viscosity of low Sulfur fuel oil is extremely low compared to the viscosity of heavy fuel oil and marine diesel oil (Min 1.5 CST at 40°C in DMA grade of ISO 8217) As a result the following issues are likely to occur;
- Internal leakage in FO pump
- Increase in flowability Of fuel from the fuel injection nozzle.
- Engine acceleration issues.
- Malfunctioning of fuel sliding valves
- Leakages throughout the system through gaskets and o-rings
Lubricity related issues:
Since the lubricity of fuel oil depends on the viscosity, the lubricity of low-sulfur fuel oil is low Consequently, abnormal wear is likely to occur in the sliding/contact parts of pumps, etc.
- One of the main concerns is the pump where the plunger gets stuck or seized during critical times leaving the engine restriction or unavailability.
- Transfer pump issues, gears and other parts wear our easily.
Acidity related issues:
- The sulfur content in fuel oil chinges to acid salt because of combustion, but most of it becomes sulfur dioxide ($\displaystyle \mathrm{SO_2}$ ) while a part of it gets converted to anhydrous sulfurous oxide ($\displaystyle \mathrm{SO_3}$ ). Anhydrous sulfurous oxide reacts with water ln scavenging air or water generated during combustion to form sulfuric acid with the reduction in sulfur content, the amount of sulfuric acid generated also reduces.
- When cylinder oil with high alkali base number for heavy fuel oil in diesel engines is used continuously, deposits may be formed, and abnormal wear of the cylinder liner may occur.
Flash point related issues:
- Fire hazard increases because the flash point of low-sulfur fuel oil, such as gas oil, is low
- The use of fuel oil with flash point below 60° C is prohibited according to the SOLAS Convention (Regulation 42.11 of II-1).
- On the other hand, the lowest flash point of gas oil of DMX grade defined in ISO 8217 is 43°C; the introduction by mistake of gas oil with such low flash point into ships is a cause for concern.
Compatibility of cylinder oils with fuel oil:
- It is common to use high alkali base number cylinder oil (BN 70-80) for heavy fuel oil (sulphur content 1.5% or more), but engine and oil manufacturers are recommending the use of low alkali base number cylinder oil for low-sulfur oil (sulphur content below 1 .5%).
- As measures for low-sulfur fuel oil, it is important to monitor the exhaust gas temperature to check abnormalities of rings/liners, and to carefully check the condition of the rings during the maintenance and inspection.
- Any sign of abnormality is detected, the most realistic response that can be taken is to adopt the necessary measures after discussion with the engine manufacturer.
Ignition delay and defective combustion:
- The viscosity and residual carbon low-sulfur fuel oil in recent years are generally low, There is a high probability that clarified Oil (CLO) with high aromatics is used as cutter stock in the manufacturing stages of such fuel oil. Fuel oil with high aromatics tends to become ignitable, combustible, and also defective; Such fuel oil generally hinders combustion because of the abnormal wear it causes in rings/liners
- When a sign of abnormility is detected (rise in exhaust temperature, etc.), the following methods may be consideted as immediate measures on board the ship:
- Reduce engine output.
- Reduce cylinder cooling water temperature
- Tentatively increase the cylinder oil quantity
- Raise the scavenging air temperature
- Advance fuel injection timing.
- Enhance fuel cleaning.
- Mix with normal fuel.
- Add combustion accelerating agents.
What are the options in case a vessel is unable to get compliant fuel?
If installed with Scrubber or any other approved technology such as washing the high sulphur fuel with water to remove Sulphur then the ship can be run on HSFO. Another option available is to use MDO meeting the Sulphur requirements. MDO is available in most of the global ports.
Storage issues:
- As ECA regions operate with 0.1% and the rest of the regions will operate with 0.5% fuel, hence ships will need at least 2 different storage tanks. Also, the need for proper transfer & purification is a challenge without contamination is grim.
Fuel stability issues:
- Bulk fuel stored for long periods can become unstable . The asphaltene content can precipitate out of solution causing the formation of sludge. This has the potential to block filters and pipes, leaving tanks with a un-pump-able residue.
- Compatibility problems occur when heavy fuel oils with a high asphaltene content are mixed with lighter fractions with 'a Predominance of aliphatic hydrocarbons. The mixing can cause precipitation of the asphaltenes. lt occurs when fuel.oil suppliers blend in order to reduce final fuel oil viscosity, specific gravity; or other fuel property.
Viscosity based issues:
The viscosity of low Sulfur fuel oil is extremely low compared to the viscosity of heavy fuel oil and marine diesel oil (Min 1.5 CST at 40°C in DMA grade of ISO 8217) As a result the following issues are likely to occur;
- Internal leakage in FO pump
- Increase in flowability Of fuel from the fuel injection nozzle.
- Engine acceleration issues.
- Malfunctioning of fuel sliding valves
- Leakages throughout the system through gaskets and o-rings
Lubricity related issues:
Since the lubricity of fuel oil depends on the viscosity, the lubricity of low-sulfur fuel oil is low Consequently, abnormal wear is likely to occur in the sliding/contact parts of pumps, etc.
- One of the main concerns is the pump where the plunger gets stuck or seized during critical times leaving the engine restriction or unavailability.
- Transfer pump issues, gears and other parts wear our easily.
Acidity related issues:
- The sulfur content in fuel oil chinges to acid salt because of combustion, but most of it becomes sulfur dioxide ($\displaystyle \mathrm{SO_2}$ ) while a part of it gets converted to anhydrous sulfurous oxide ($\displaystyle \mathrm{SO_3}$ ). Anhydrous sulfurous oxide reacts with water ln scavenging air or water generated during combustion to form sulfuric acid with the reduction in sulfur content, the amount of sulfuric acid generated also reduces.
- When cylinder oil with high alkali base number for heavy fuel oil in diesel engines is used continuously, deposits may be formed, and abnormal wear of the cylinder liner may occur.
Flash point related issues:
- Fire hazard increases because the flash point of low-sulfur fuel oil, such as gas oil, is low
- The use of fuel oil with flash point below 60° C is prohibited according to the SOLAS Convention (Regulation 42.11 of II-1).
- On the other hand, the lowest flash point of gas oil of DMX grade defined in ISO 8217 is 43°C; the introduction by mistake of gas oil with such low flash point into ships is a cause for concern.
Compatibility of cylinder oils with fuel oil:
- It is common to use high alkali base number cylinder oil (BN 70-80) for heavy fuel oil (sulphur content 1.5% or more), but engine and oil manufacturers are recommending the use of low alkali base number cylinder oil for low-sulfur oil (sulphur content below 1 .5%).
- As measures for low-sulfur fuel oil, it is important to monitor the exhaust gas temperature to check abnormalities of rings/liners, and to carefully check the condition of the rings during the maintenance and inspection.
- Any sign of abnormality is detected, the most realistic response that can be taken is to adopt the necessary measures after discussion with the engine manufacturer.
Ignition delay and defective combustion:
- The viscosity and residual carbon low-sulfur fuel oil in recent years are generally low, There is a high probability that clarified Oil (CLO) with high aromatics is used as cutter stock in the manufacturing stages of such fuel oil. Fuel oil with high aromatics tends to become ignitable, combustible, and also defective; Such fuel oil generally hinders combustion because of the abnormal wear it causes in rings/liners
- When a sign of abnormility is detected (rise in exhaust temperature, etc.), the following methods may be consideted as immediate measures on board the ship:
- Reduce engine output.
- Reduce cylinder cooling water temperature
- Tentatively increase the cylinder oil quantity
- Raise the scavenging air temperature
- Advance fuel injection timing.
- Enhance fuel cleaning.
- Mix with normal fuel.
- Add combustion accelerating agents.
What are the options in case a vessel is unable to get compliant fuel?
If installed with Scrubber or any other approved technology such as washing the high sulphur fuel with water to remove Sulphur then the ship can be run on HSFO. Another option available is to use MDO meeting the Sulphur requirements. MDO is available in most of the global ports.
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