Recently, CIMAC published a detailed guidance for fuel suppliers and shippers as presented by suppliers, shippers, industry stalwarts and regulatory bodies. Today, we are highlighting a part of that 64 page, which specifically shows what and how fuel suppliers need to do it.
What should suppliers do?
A fuel supplier needs to have in place a robust and applied QMS which addresses all of the factors that affect the quality or characteristics/properties of the fuel which is to be supplied, and the ability to meet the ordered specification, by:
- controlling the quality of the individual blend stocks used to produce the fuel;
- avoiding the entry of extraneous, potentially harmful, materials within the supplier’s (or
upstream) storage, handling and delivery systems; - ensuring that the correct blending procedures are applied so that a homogeneous fuel is
delivered.
How To Blend Stocks
The actual physical supplier of a consignment of fuel may be a refinery operator supplying fuel based on blend stocks received directly from its own refineries. In other instances, the blend stocks used will have been traded, potentially a number of times, by brokers between the various sources and the final supplier; this may have involved the splitting and mixing of different consignments along the way.
Irrespective of the particular supply chain, it will become increasingly important for these operations to be documented so that both the final supplier and the shipowner/operator understand the characteristics of the fuel.
How To Keep Away from Extraneous Materials
The effective application of a robust QMS by fuel oil suppliers will minimize the risk of undesirable material entering the fuel or its constituent components. Such material could be extraneous to the fuel product, e.g. water (covered by ISO 8217:2017; includes fresh/brackish/saline—together with the risk that it may encourage proliferation of bacteria in the interphase between fuel and water), dust, maintenance materials or corrosion debris.
Alternatively, such undesirable material could be other fuel/hydrocarbon products, e.g. line residues, washings, or materials remaining in shore tanks or barges (including ‘unpumpables’).
In some instances, this extraneous material has been found to contain waste chemicals and other such material for which marine fuels are occasionally seen by some as a convenient disposal route.
The addition of used lubricating oil (ULO) as a fuel blend component from both shipboard and land-based sources can also provide a route for waste materials to enter the fuel pool, and can add undesirable contaminants from anti-wear additives containing zinc, calcium and phosphorous.
The blending process
Regardless of where the blending takes place, the supplier’s intent should be to make the best use of the available component products to maintain the quality characteristics.
However, since a residual fuel needs to be blended to achieve the required viscosity and density, with attention also being paid to achieving the required sulphur content limit (all other residual fuel characteristics will usually be what is normally expected, being that they are mostly interrelated), there will inevitably be some compromises.
For example, such blending may, on occasion, result in the delivery of a fuel which has a much lower viscosity than the specification ordered. This situation is likely to exacerbated for many types of fuel with the introduction of the post-2020 sulphur limit of 0.50% m/m.
When sulphur content is used as a defined ‘not to be exceeded’ blend target, other parameters such as viscosity and density may vary extensively compared to that in
an unconstrained sulphur regime.
For blending to be undertaken correctly in the first instance there needs to be accurate data (e.g. on viscosity and density, together with sulphur if that is a factor) in respect of the blend components to be used.
Secondly, the blend proportions determined from those data need to be calculated correctly and then established, after which they should be uniformly maintained. Blending should, in principle, only take place on shore in order to ensure that the end product is homogeneous.
Variable in-line blending during delivery, where ratios of components are continuously adjusted to meet blend targets, can result in the delivery of a non-homogeneous
product—an issue that may not be detected from the continuous drip samples taken over the whole of the bunkering period.
This may have potentially serious consequences for the end user, particularly where the fuel is loaded in series into a number of different tanks, and should, therefore, be avoided.
As bunker barges and similar vessels will be used within bunker supply chains, any blending that is carried out on board should be in compliance with SOLAS Chapter VI,
Regulation 5.2.
It is the duty of the fuel supplier in producing the blended fuel to be delivered, or indeed of any other party upstream from that point, to ensure that all component blend stocks, including cutter stocks, that are to be mixed are mutually compatible and will not result in asphaltene precipitation.
Furthermore, it is imperative that the various components are sufficiently well mixed to ensure that the fuel will not tend to settle out to its original components over time—a
process known as stratification; again, this is an issue that would not normally be detected from continuous drip sample testing.
To ensure that the product conforms to relevant specifications and statutory limits, the final blend should always be tested against the relevant standards, and the test results documented. Once a bunker blend has been produced and tested, appropriate storage and product handling, both inshore tanks and on-board cargo and bunker supply tankers, should be adopted to maintain product integrity
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Source: CIMAC
