[নোঙর 2016] The Legacy of Marine Bunker fuel : Amitava Talukdar (30)

It was a regular bunkering operation out of many in the year of 1999. I have been sailing as fourth engineer and completed several feeder trips. Ship system and sensitive points of engine room machineries are well known to all the engineers on board. But nothing could prepare us for what comes next. The new bunker was put to use and within a short while the phone rang that one of the purifiers tripped due to overload. A purifier is a large centrifuge rotates at several thousands of rpm and removes water, solid particles from the oil.

Many things came to mind that could cause the problem. We opened up the purifier expecting to see some badly broken or shattered parts but to our surprise we found the whole purifier is filled up with solid sludge like material which seized the rotating bowl. Problem is obvious from the fuel but there is no clue what could have caused it. Due to short feeder route that is the only bunker available. For 5 days we need to assign two persons continuously cleaning the sludge ports, opening up the purifiers and cleaning it manually every now and then. It was sauna from hell with sweat, steam, smell of fuel and God knows what other exotic things. I am sure all of us went through this at least once may be far worse than this. There are several cases ship lost propulsion due to fuel problem ran aground, spilled oil, collided with other ships.

In contrast how many times we had problem with our car due to bad fuel? How many times an air liner need to make an emergency landing due to bad fuel? There probably will not be a single case of this nature. Why we cannot fill up our bunker tank and start using the fuel directly like our car or an airplane?

There are two main reasons:
What we use as heavy fuel oil is the residue of crude oil distillation process which requires addition of lighter fuels to meet the specification limit stipulated in the ISO8217 fuel standard. Many unwanted and exotic material enters into the fuel from this. The more advanced the refineries are the residue get more cracked and more exotic waste find its way into the fuel. To make things further worse the ISO8217 specification stipulates requirement ‘prior to appropriate treatment before use.’ For example, Catfines present in fuel which are next to diamond in hardness scale is allowed to be at 60ppm (global average is 20ppm) in latest ISO8217 standard but at the engine inlet this should be below 15ppm.

If I explain the problem to my daughter who just started her primary education, that these round particles we call cat fines are very dangerous for the ship engine and they can be easily removed by a machine called centrifugal separator, I am sure she will ask why you don’t remove it before you give to the ship. Just consider the possibility how well the process of purification can be controlled ashore and we always could deliver a purified oil to the ship. Till 1996 the allowable limit for water was 1% in ISO8217. Since the conception of the standard 8217 around 1970s, it took almost a few decades for us to realise there is no point buying water at the cost of oil and the limit is now 0.5%. Can it be not controlled and further reduced? Is it technically not possible or economically not viable? Would you accept 0.5% water in your lub oil delivery? Why do we live with the problem?

There are lot of questions we need to ask ourselves. I have just made an attempt from within the limited boundary of my understanding answering two interesting questions frequently asked for clarification.

Selection of fuel and ISO8217 standard specification limit:
Oftentimes you are presented with a table detailing the specification limit of certain grade of fuel and is asked if your vessel can use that fuel. This table is very useful to ensure that storage, pumping, purification plant can handle this fuel effectively so that the quality of the fuel at the engine inlet would be within the engine maker’s requirement. Most of the time the primary focus is on the table and its limiting values. Sometimes such tables are not even from the ISO8217 standard. Is it enough if all the limiting values of the table is within your requirement to protect your interest? The answer is no. A large portion of the fuel that has caused serious machinery damage met the specification requirement stipulated in the table. Further investigation using advanced testing like GCMS (gas chromatography and mass spectrometry), FTIR (Fourier transformed infrared spectroscopy) etc were required to find the root cause of the damage.  Many of these damages are due to chemical waste/contaminant present in the fuel and this table does not cover it.
To address this there is a very important para commonly known as para 5.1 is available in the ISO 8217 standard.

This states that (ISO8217:2005):
“The fuel shall be homogeneous blends of hydrocarbons derived from petroleum refining. This shall not preclude the incorporation of small amounts of additives intended to improve some aspects of performance.

The fuel shall be free from inorganic acids and from used lubrication oils. The fuel should not include any added substance or chemical waste which
1)    Jeopardizes the safety of ships or adversely affects the performance of the machinery; or
2)    Is harmful to personnel; or
3)    Contributes to overall additional air pollution “
So when you are asked to advise if a certain fuel can be used don’t forget to mention that it is very important to ensure that the fuel that is going to be purchased is guaranteed against the ISO8217 in its entirety and always keep in mind the protection that is offered by the para 5.1.

When off-spec is not out of specification:
Testing a bunker fuel sample before it is put to use is now almost a standard practice. When you receive a report from your testing lab that the fuel is off-specification on certain parameter, first thing you do is bring it to the attention of the concerned parties. Although the tested parameter exceeds the limit specified in the standard at times you get a response which states that the fuel is within the R&r limit and is not off-specification. There is a standard called ISO4259 which provides detailed guidance on this and the basis of the response is this standard.

A 10kg rice packet you buy from the market is not exactly 10kg. It could be 9.99 or 9.98 kg or 10.1kg etc. There is always a band of uncertainty involved which depends on the measurement uncertainty of the instrument, measurement process. Two persons may use the same weighing balance but is likely to come up with two different results. One may place the packet exactly at the centre of the weighing pan and the other a bit careless at the side while taking weight. This will cause the result to vary. The same things happens with the test results of bunker fuel. If the same sample is tested in two different laboratories there would be some difference in the two test results. If this is the case how do you manage this variation when comparing against a set specification limit?

Firstly, the variation is determined statistically by testing the same sample in different laboratories and published along with the test method. This variation is called the Reproducibility ‘R’ of the test method. In simple terms it means if the same sample is tested in two different laboratories following the same test method, the difference between the two tested results would not exceed the R value. Well, it could exceed but chances are one out of 20 cases (95% confidence).

The ISO4259 applies this ‘R’ in the following way,  if the buyer does not have any other source than one single test result he can accept the product meets the specification limit as long as the tested value does not exceed specification limit value + 0.59R. For example, R for HFO density by test method ISO12185 is 1.5kg/m3. So a fuel is considered fails to meet the specification limit (991kg/m3 is the maximum limit for RMG380 grade) in density when the value exceed 991 + 0.59 * 1.5 = 991.9kg/m3. This is what the suppliers refers to when they say that the fuel falls within the variation limit and not off-specification.

This 0.59R allowance is not the right of the supplier to claim that that fuel meets specification. The standard also states that if both parties do not agree to the above they should follow certain prescribed method to establish if the parameter meets the limit of specification. The elaborate procedure is not followed in the industry but a second sample is tested to come to a conclusion. In this context you need to realize the fact also that due to the reproducibility of the result samples that are within this variation limit may come in spec when tested in another lab (the result can vary +/- 0.59R).

Lets get back to what we started with; problem faced by ship staff due to bad fuel who is the direct user of it. They do not have any say in the fuel supplied on-board. One level up as operator of the ship, we agree to take oil which is not readily usable. It’s just a settling tank and purifier that stands in between getting a fuel that can readily be used on-board. In the age of supercomputers, supersonic jets technical shortcoming is not to be blamed. It may not likely to give substantial economic gain that we have to put ourselves in way of danger.

So what is it? Looking back at the days we worked on-board, if there is a problem, we knew, we had to solve the problem at sea by ourselves. Has that made us complacent to the danger and we would like to allow some irregularities to exist; that we don’t care much about what problems are thrown at us.

There is a paradigm shift taking place in the industry with the introduction of stringent environmental regulation. It is a matter of time the other qualities of fuel beside sulfur would come under scrutiny. We should let go our prejudices and take a fresh look at the fuel related issues and take this opportunity to make an evolutionary leap.
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Amitava Talukdar is an alumnus of Bangladesh marine academy (30th batch) from the engineering stream. Currently he is working with a leading marine fuel testing company providing technical support to users of the oil.

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