Category A - waters are defined as “narrow rivers and canals where the depth of water is generally less than 1.5 meters”.
Category B - “wider rivers and canals where the depth of water is generally 1.5 meters or more and where the significant wave height could not be expected to exceed 0.6 meters at any time”.
Category C - “tidal rivers and estuaries and large, deep lakes and lochs where the significant wave height could not be expected to exceed 1.2 meters at any time”.
Category D - “tidal rivers and estuaries where the significant wave height could not be expected to exceed 2.0 meters at any time”.
Under the consultation process, the UK Government was advised and accepted that, for the purposes of UK interpretation and enacting the European Directive (through the SI), the new fuel standards regulations should adopt a consistent definition of “to sea” with the Merchant Shipping regulations that govern air emissions from ships.
Under this sensible move, the new fuel standards apply to provision of fuel for Inland Waterway Vessels and Recreational Craft which do not normally operate to sea but are operating on canals, on Category C lakes and lochs (within the definitions at the SI referring to wave heights on such lakes and lochs) and other rivers and waters within Categories A and B. In effect, this means that the regulations apply to inland waterways vessels and Recreational Craft that normally operate on non-tidal rivers and other waters.
PITFALLS AND HOW TO AVOID THEM
PROBLEMS IN STORAGE AND DISTRIBUTION
The storage of fuel containing bio-diesel requires additional precautions and management. These considerations apply equally to both bulk storage at the point of supply, during handling and transit and also within a vessel’s own fuel storage tanks.
WATER AND MICROBIOLOGICAL CONTAMINATION
All gas oil or Diesel fuel in storage tanks contains or gains a degree of water content, either as free water, where it separates out and lies below the fuel or as absorbed water, where droplets of water of microscopic size remain suspended in the fuel. Usually, such absorbed water content is a very small proportion and standards exist to control this at the point of sale. Once in the storage tank or vessel, water can arise from a number of sources, which can be controlled by good housekeeping and system management. However, changes in ambient temperature can cause condensation in the upper parts of fuel tanks, thereby increasing the absorbed or free water content. As a consequence, operators most often fill tanks, prior to vessel lay-up over winter, to reduce the volume and area where condensation can occur.
However, quite apart from the effects of water, operators should be aware that long-term storage may cause the fuel’s properties to deteriorate. Much Diesel fuel is now a blend of straight-run distillate and product cracked by catalytic processes. Many operators have found that the longer fuel having a significant content of cracked, as opposed to straight run distillate, is stored, the likelihood is increased of it absorbing water, becoming unstable and losing its specified properties.
It should be noted that bio-diesel of FAME type has the scope for
accumulating a considerably higher water content than fossil diesel fuel, whether straight-run or cracked. This is because its chemical make- up is very different from mineral distillate fuels and is much more hygroscopic – it literally draws moisture in from surrounding air more readily than distillate fuels.
After a period of time, any significant water content may collect at the bottom of a storage tank (diesel has a lighter Specific Gravity than water and therefore floats) and should normally be drained off at regular intervals. However, lower levels of water content may also remain in suspension in the fuel, as tiny droplets incapable of separating out. This condition is known to exist within bio-diesel mix fuels.
While it is a known fact and many engineers have experience that certain micro- organisms can thrive in fuel tanks and bilge areas of vessels, sea-going ships usually have the equipment, personnel and procedures to ensure that this is rarely a serious problem. Due to the need for food and oxygen, micro-bacterial contamination (MBC) tends to be most prevalent at the fuel/water interface. It is acknowledged that bio-diesel has a much greater propensity to support the development of MBC than fossil diesel fuel, being fundamentally a vegetable substance, having a lower Sulphur content (a poison), a potentially higher water content and therefore being a more suitable food source for the microbes.
COLD FILTER PLUGGING POINT AND OTHER FACTORS
Diesel fuel that is blended with bio-diesel content naturally has a higher Cold Filter Plug Point (CFPP) than fossil diesel fuel, which means it may stop flowing (known as waxing) in cold weather at a higher temperature. It is also known that such blends may have poorer longterm oxidation stability. Advice has been received that storage time should be minimised, in order to prevent any such precipitated
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