Test Kits for Marine Bunkers

Bunker Supplement No.9 Tanker Safety Circular No. 213/September 1999

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March 2000

This month’s Bunker Supplement provides advice on onboard test kits for marine bunker fuel testing. INTERTANKO is grateful to the International Bunker Industry Association (IBIA) for sharing this information.

If fuel tests are undertaken in order to assess the acceptability of a fuel to the shipowner, then some very basic questions need to be asked about the test being performed, namely:

1. Are the results of the test sufficiently accurate to initiate a letter of protest and subsequent laboratory analysis of a fuel delivery?
2. Are the results of the test sufficiently accurate to support acceptance or rejection of a fuel, bearing in mind the associated cost implications?

In the event of a dispute, it is advisable to always send a sample of the suspect fuel for a laboratory analysis - the costs involved are simply too great to do otherwise. If a particular test does not correlate with recognised methods or if the repeatability is sensitive to operator error, then there is little point in undertaking this particular type of test at all.

Many commercially available tests, particularly those utilising the more expensive electronic test equipment, are not a simplification of a standard test procedure. Instead, they use alternative methods that have been correlated against laboratory results. As such, results from this type of equipment can be relied upon as being accurate and can be used in making decisions on the acceptability and the suitable treatment of a fuel oil. Manufacturers’ literature should always be scrutinised carefully in this respect and not simply accepted at face value. Some of the more basic tests offer a simple go/no go type of result or basic trending information. The results of tests utilising this type of equipment are often of less direct value. However, they can provide either some information on the likely fuel properties or an indicator that further laboratory analysis would be advisable.

Methods employed for the various tests display good commonality between the various types of test kits available form the specialist equipment manufacturers. The various types of bunker tests and associated test kit equipment can be summarised as follows:

Viscosity

Viscosity tests generally utilise the falling ball type of equipment, with the heated versions providing greater accuracy. It is difficult to accurately predict the viscosity/temperature relationship for a marine fuel oil. Thus, correcting the viscosity for an unheated instrument will introduce error.

Density

Density tests generally use a hydrometer, most types - with the exception of Parr Scientific - being acceptable. Some rely on a manual correction for temperature, the hydrometer itself and the meniscus. The more expensive versions are provided with microprocessor-based correction functions.

Water

A chemical reaction with metallic hydrides or carbides is the most popular method of testing for the presence of water. Such tests usually rely on a simple pressure gauge to provide a readout.

Compatibility

All such tests follow the ASTM test methods for compatibility/stability, some being more sophisticated than others. In all cases heating of the oil is a fundamental requirement.

Flash point

virtually all test kit suppliers use the Seta Flash test equipment. This is a simple and very popular method, widely used in marine bunker fuel applications.

Salt

All methods utilised in testing for the presence of salt are based on a colour change to a reagent caused by chloride ions. Because the reagents are sensitive to some other metallic ions (and sweat!), care is needed. The test works best when used as a pass/fail type rather than providing a qualitative result.

Pour point

Some test kit suppliers provide appropriate equipment suitable for pour point testing but the procedure can easily be carried out onboard ship using a beaker and thermometer.

Cat fines

A "scratch plate" type test is sometimes offered for the detection of cat fines. However, some experts believe that such tests are unlikely to be able to detect contamination levels below 80 parts per million (ppm) and, also, that they are subject to operator error.

Microbiological testing methods are also available but these invariably rely on testing samples in a prepared culture medium. Because of the nature of the process, i.e. the physical growing time, the testing times involved are considerably longer than those associated with the many physical test methods.

Lastly and most importantly, the validity of any test is dependent upon the fact that the sample is representative of the entire fuel delivery. As a typical fuel sample represents only 1 part per million (ppm) of the total delivery, it is important that adequate fuel sampling and storage systems are used. Further information on bunker fuel test kits can be obtained, along with a list of suppliers, from INTERTANKO.

See also related article: "BUNKERS - Practical Solutions to Practical Problems"