The recently concluded MEPC74 meeting held in London last month put forward some valuable guidelines regarding fuel and machinery problems which are of paramount importance to shipowners and operators as they prepare for the big switch to scrubbers and low sulfur fuel. Here’s an excerpt from that Guidelines as made public by IMO on their website.
Machinery Should Be Capable
The experiences and lessons learned from the transition to the 0.10% m/m SOX-ECA
limit indicated that current ship machinery operations should be sufficiently capable of
addressing the concerns regarding combustion of the new 0.50% m/m limit fuel oils.
Currently most of the marine diesel engines and boilers on ships operating outside
Emission Control Areas (ECAs) are optimized to operate on heavy fuel oil. From 2020 ships
are required to use fuel oils with a sulphur content of 0.50% m/m or lower, unless fitted with an approved equivalent means of compliance.
Distillate fuels use guidelines
- Low Viscosity Means Added Caution:A major challenge with distillate fuels is low viscosity. Low viscosity may cause internal leakages in diesel engines, boilers and pumps. Internal leakages in fuel injection system may result in reduced fuel pressure to the engine, which may have consequences for the engine performance (e.g. starting of the engine). Equipment makers recommendations should be taken into account, and adequate testing, maintenance and possible installation of coolers, etc., may be performed.
- Considering Plugging Points: Cold Filter Plugging Points (CFPP) and Cloud Points (CP), as well as the Pour Point (PP) for distillate fuels, need to be considered in light of the ship’s intended operating area and ambient temperatures.
Why these are of concern?
- These issues are critical concerns as they can result in the formation and accumulation of wax sediment, which can cause costly and avoidable maintenance. In the worst-case scenario, sediment can cause engine fuel starvation and power loss.
- ISO 8217:20173 limits the cold flow properties of fuel through setting a limit on the PP. However, given that wax crystals form at temperatures above the PP, fuels that meet the specification in terms of PP can still be challenging to operations in colder operating regions, as the wax particles can rapidly block filters, potentially plugging them completely.
- For cold weather, additional cold flow properties, CFPP and CP, should be reported by the supplier when the receiving ship has ordered distillate fuel for cold weather operations, a requirement that is specified in ISO 8217:20173
- Since the residual fuels are usually heated and distillate fuels are not heated, particular attention needs to be given to the cold flow properties of distillates. Cold flow property challenges can be managed by heating the fuel. CIMAC has issued “01 2015 CIMAC Guideline Cold flow properties of marine fuel oils”.
- Fuel temperature should be kept approximately 10°C above the PP in order to avoid
any risk of solidification, however this may not reduce the risk of filter blocking in case of high CFPP and CP.
- It is good practice to review the possibilities of heating arrangements for distillate fuels
on board. This is usually very limited, as it is not standard practice to have heating
arrangements in distillate storage, settling or service tanks. Transfer arrangements may be adapted to pass through a residual fuel oil heat exchanger should the need arise.
- The latest edition of the ISO standard is recommended.
- Knowing the fuel properties before bunkering will assist in taking the necessary
precautions where and when necessary. If the ship is heading towards colder climates and the cold flow properties are inferior, the fuel may be:
either used before entering cold regions, used with suitable heating arrangement, as mentioned above.
- If the approach of applying heat is being followed it should be ensured that the fuel is
not overheated resulting in the viscosity dropping below the minimum recommendation of 2 CST at any point in the fuel system, including the engine inlet. In order to reduce this risk, heating should be limited to max 40°C.
Distillate fuel with FAME content usage guidelines
Increased demand for Distillate fuels may result in more land based products making
their way into the marine supply pool, some of these fuels (e.g. biodiesel) may contain Fatty Acid Methyl Ester (FAME).
There are various technical challenges associated with use of fuel having FAME
content, e.g. potential oxidation of biodiesel, its biodegradable nature etc. with adverse
implications, limitations in storage life etc. It also needs to be tested for stability.
The ISO 8217:20173 standard includes a maximum FAME content of 7.0% by volume
for DFA/DFZ/DFB fuel oil grades since some ports may offer automotive diesel fuel as the only fuel available, which contains FAME and could violate the fuel flashpoint requirements
addressed in SOLAS chapter II-2. The maximum 7.0% (v/v) has been chosen as this aligns
with the concentrations allowed in some of the countries applying environmental regulations.
Manufacturers of engines and equipment like oily water separators, overboard
discharge monitors, filters, coalescers etc. need to be consulted to confirm the ability of
engines and equipment to handle biodiesel blends of up to B7 (i.e. 7.0% v/v).
3.2.5 It is recommended to avoid using such biodiesel blend fuels for lifeboat engines,
emergency generators, fire pumps, etc. where it is stored in isolated individual unit fuel tanks and subjected to conditions for accelerated degradation.
CIMAC has provided a Guideline for Shipowners and Operators on Managing
Distillate Fuels up to 7.0% v/v Fame (Biodiesel).
Residual fuel use guidelines
- Stability and compatibility: It is essential to distinguish between “Fuel stability” within a single batch of fuel and “Fuel compatibility” between different fuel batches.
Regarding stability: the fuel shall be stable and homogeneous at delivery and it is the
responsibility of the fuel oil blenders and suppliers to ensure this.
A wide range of blends of refined products will be used to make the new 0.50%
sulphur fuels, and the stability and compatibility of the blends will be an important concern for shipowners/operators. Unstable fuels can separate on their own and incompatible ones can do so when mixed in a single bunker tank, forming sludge that can block filters and ultimately ause engine failures. It is recommended that ships have a commingling procedure. The procedure should primarily aim to ensure new bunkers are loaded into empty tanks to the extent possible. In the event that a ship finds itself possibly having to commingle a new bunker with bunkers already on board, then it is important that the ship determines the compatibility between the two said bunkers before comingling. The reference test method shall be the total potential sediment test in accordance with ISO 10307-2:2009.
- Catalytic fines (cat fines): Cat fines are a by-product of refining and consist of small particles of metal that are deliberately introduced as catalysts to “crack” the fuel oil. Unless reduced by purification, cat fines will become embedded in engine parts and cause serious and rapid engine damage. Reference should be made to engine manufacturer’s guidance with respect to managing cat fines.
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Source: IMO MEPC74