Chemistry sets sail for success

The marine fuels market is on the brink of a major global upheaval – and chemical testing is at the vanguard of ensuring the World’s merchant fleet keeps on sailing…

The decision by the International Maritime Organisation (IMO) to reduce the worldwide cap on vessel sulphur emissions from 3.5% to 0.5% come January 2020 will prompt the development of special fuel formulations.

In all likelihood these new low sulphur fuels will initially be more expensive than heavy fuel oil (HFO), the longstanding mainstay of the global marine freight market – an unwelcome burden during a prolonged period of depressed freight rates.

This economic backdrop, when combined with costly and complex fuel changes, will see many container vessel operators chasing the cheapest possible bunker fuel options. However, ongoing ‘grey practices’ by some fuel vendors, and the prospect of compatibility and stability issues for the new fuel grades, mean that it will be more important than ever for vessel operators to get their fuel purchases properly and quickly tested.

Compatibility issues and the presence of catalytic fines – harmful metallic production residues – are likely to generate the most headlines in the run-up to the 2020 change but the damaging and costly issue of water contamination must not be overlooked. The problem of unscrupulous fuel resellers bulking out bunker deliveries with water, above the permitted limit stipulated by ISO 8217:2012, is not new. However, at a time of squeezed sea freight margins it is essential that vessel operators get the fuel they pay for. In addition, excess water can trigger costly and time consuming handling and maintenance issues.

Cost implications

A 0.5% water level – which is the allowable upper limit of the ISO specification – amounts to 5 metric tonnes in a 1,000 metric tonne bunker delivery. At a cost of around £450 per metric tonne, this is the equivalent of £2,300. Water removal can also lead to additional disposal costs, plus maintenance may be necessary to remove water-related sludge from the fuel purification systems. There are therefore financial as well operational reasons to test marine fuel for water content.

According to a leading test laboratory, which specialises in assessing the quality of marine fuel, it regularly encounters water contamination but it tends to be at low levels. This is generally the result of condensation, especially when bunkering in ports with a hot, humid climate such as Hong Kong and Singapore, although moisture may also enter the system during fuel transfer from the barge. However, the lab reports that during the first half of 2017 approximately 0.7% of all samples tested contained water at concentrations capable of triggering engine liner damage if left undetected. Replacing a single cylinder liner in a container vessel’s engine costs around £53,500 – for a ten cylinder engine a vessel owner could be facing a bill of £535,000.

Sludge formation

There are two types of water contamination – fresh water and salt water. Fresh water can be removed from fuel by on-board purification. However, in cases where insufficient water is removed various operational difficulties can occur, such as sludge formation in the fuel tanks, which can lead to problematic filter blocking. The presence of water in fuel may also adversely affect its calorific value and viscosity. If densities and viscosities are out of spec it can have an added undesirable consequence for the performance of purifiers with regards to the level of moisture removed. Water can additionally have a detrimental impact on the atomisation of the fuel during injection into the engine, reducing combustion speeds.

There is also the possibility of corrosion and the dilution of cylinder liner lubricants, which can lead to scuffing. Both of these issues can cause highly costly cylinder liner and piston ring damage, which in worst case scenarios can be extremely expensive to rectify.

The presence of salt water in fuel is a much more serious problem and every effort should be made to eradicate it. Once again there are corrosion-related problems but in this case they are more severe due to the high salt levels present. Furthermore, sodium from sea water will combine with any vanadium present in the fuel during combustion, which triggers the production of sticky, low-melting point salts that adhere to exhaust valves, valve seats and turbocharger turbine blades. This in turn can attract other combustion deposits, leading to mechanical damage. As with pure water, salt water can be removed on-board using purifiers.

Testing for water content

As far as ISO 8217:2012 is concerned there are two main methods to detect the presence of water in fuel. The first, ISO 3733 (Petroleum products and bituminous materials – determination of water – distillation method), is the standard distillation test, which takes between 60-90 minutes to complete. The second, ISO 12937 (Petroleum products – determination of water – coulometric Karl Fischer titration method), is much quicker and can be completed within a few minutes.

Marine fuels are barely soluble in methanol so water determination using Karl Fischer titration therefore requires the addition of an appropriate solubiliser. For light oils, long-chain alcohols are suitable, for dissolving of heavier oils toluene, xylene or chloroform are added. Also, due to the very low water concentration, titrants with a low factor (2 mg/mL or 1 mg/mL) are recommended.

Importantly, oil samples can have an uneven distribution of water and should therefore be homogenised prior to Karl Fischer determination. Coulometric analysis is not suitable if fuel additives are likely to cause side reactions. In these instances the Karl Fischer oven technique can be employed in combination with coulometry; using this approach the release of water is best achieved at temperatures between 120 ­– 140°C.

Avoiding the risks

Purchasing marine fuel that isn’t contaminated with some degree of water isn’t a realistic possibility so it is crucial that vessel operators know what moisture levels they need to counter each time they bunker. This way, suitable remedial measures can be taken on board before complications occur. These problems break down into three main areas of risk. First is the loss of calorific value, which can adversely affect fuel consumption. Second is the additional cost of disposing of the water removed by the treatment system. And finally, water – especially sea water – can trigger corrosion in engines and damage fuel injectors, turbochargers and exhaust valves.

It is therefore essential that test labs have a quick, accurate and reliable method of determining the presence and percentage of water in any given marine fuel sample. For most applications, Karl Fischer titration offers the most efficient approach. However, in order to maximise its potential it is not only important to have a good quality titrant, it is also vital to have the best possible working medium as this helps ensure fast water extraction as well as the suppression of side reactions. Having access to certified reference materials is also advantageous for control purposes.

In order to provide marine customers the optimum service test labs should identify a supplier that offers a combination of high quality chemicals and an understanding of their business needs. By choosing one with the highest levels of certification and a track record of delivering consistent quality, backed up with a true commitment to partnership, it is possible for test labs to ensure that their analytical results will always be reliable and traceable to internationally accepted references. Crucially, the reassurance that this offers to the marine industry will be doubly important during the introduction of the new fuel types that will result from the IMO’s revised sulphur cap.

the Author:

Michael Jeitziner is Global Marketing Manager Honeywell