VPS Technical Focus: ‘Difficult’ to determine parameter limit for bunker contaminants

VPS Technical Focus: ‘Difficult’ to determine parameter limit for bunker contaminants


Dr Malcolm Cooper, the Group Managing Director of marine fuel testing and inspection agency Veritas Petroleum Services (VPS) explains to Manifold Times readers why it is impractical to set limits for substances found in contaminated marine fuel:

VPS created marine fuel testing in 1981 and remains by far the largest bunker fuel testing company today, with close to 50% of the testing market. It is this experience and our extensive database of more than 1 million samples that enables us to determine the likely impact of specific contaminants. This enables VPS to both detect bunker fuel contaminants and then understand the impact of burning these fuels.

When it comes to organic contamination, a huge variety of substances can be found in bunker fuel. VPS has over the years identified many different substances that are not usually found in bunker fuels including alkene, aldehydes, alcohols, chlorinated hydrocarbons, esters, heterocyclic compounds, ketones, fatty acids, phenolic compounds, styrenes and others.

Some of these have only small effects on the combustion of the fuel, but a number of these substances are harmful to fuel combustion and can cause major engine problems such as those seen in the recent cases in Houston, Panama and Singapore.

The key to understanding the impact of bunker fuel organic contaminants is to first detect them using Gas Chromatography – Mass Spectrometry (GCMS) and then determine whether their presence causes engine problems. This is done by tracking bunker fuel burnt in many different vessels to corroborate data.

The types of operational issues that arise from burning bunker fuels containing organic contaminants include pumps seizing and sticking, heavy sludging at separators and purifiers, filter and purifying problems, filter clogging, sticky hard film stopping the valve rods right through to worn out fuel pumps and complete mechanical failure.

It is difficult to determine a limit for organic contaminants as there are no accepted industry standards or limits for these types of contaminants. Furthermore, there are a wide variety of shipboard conditions experienced by the fuel, both in terms of fuel storage and handling on board the vessel and in terms of the combustion conditions that may arise in different types of vessels whereby different injection equipment, different materials (alloys) and different engine temperatures will have an influence on how certain contaminants may react.

Indeed, even sister vessels may have different on-board fuel treatment systems (e.g. separators, heaters, etc.) with the effect that one vessel may burn a contaminated fuel okay, but another may suffer problems.

As such, it is not possible to be prescriptive as the impact of fuel contamination may be different on different vessels. However, vessel and crew need to optimise running of the fuel treatment plant and engines to minimise adverse effects of these contaminants. Some best practices that can be followed by ship operators are as follows:
  • There should be no mixing of fuels in storage tanks and kept to a minimum during change over.
  • The start, stop & change over procedures during arrival, departure and maneuvering are to be followed as recommended by makers.
  • Engine functions should be tested at regular intervals when waiting for berthing. Occasional running on gas oil to clean deposit build up during sea passage should be initiated.
  •  Engine manufacturer recommendation and on-site survey will be essential in such damage case investigation.

In VPS we deal with each case individually and advise our clients on a bespoke basis accordingly. Our technical advisors are able to make use of our extensive database of case histories to advice how best to deal with organic contaminants.

Related: Marine fuel quality: Where do we go from here?
Related: VPS Technical Focus: To GCMS, or not to GCMS – why does results take so much time?
Related: VPS Technical Focus: ASTM test method for contaminated bunkers ‘limited’



Photo credit: Manifold Times
Published: 23 November, 2018

 

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