Tank cleaning - question the process

Aug 31 2013

There is certainly a great deal of emphasis being placed on making money in a tough market at the present time.*

Tanker Operator is already actively involved, with conferences and articles designed to address the major issues most likely to contribute to boosting the bottom line for owners and operators of both chemical and product tankers.

From an operational perspective, there are several key focal points that apply to all players in this market that tend to form the underlying theme of these discussions:

  • Drive change.
  •  Avoid unnecessary operations.
  • Provide clear and tangible targets.
  • Manage cost effectiveness.
  •  Be focused and positive.
  • Identify/create new markets.

All of which could work equally as well on their own, or combined together to produce better financial results. That said, many of these areas are perhaps better described as cost saving, rather than income generating; but the outcome is the same and that is the objective in one of the most challenging markets that we have seen for generations.

Of particular interest to chemical tanker owners and operators is perhaps the last point relating to the identification. or creation of new markets. Certainly, the opportunity to trade in areas that have been previously been over-looked for a variety of reasons, is a simple yet effective way of creating new income potential.

But of course, this is not as easy as it sounds, particularly when one considers that one of the contributory factors of the current market conditions is an oversupply of tonnage in the chemicals and products sector. In other words, there are more vessels vying for each available cargo and those vessels that are successful are being subjected to more stringent criteria, which typically results in higher costs on cargoes that are paying 50% less than they were a few years ago.

Tie that in with the current cost of bunkers, personnel and cleaning chemicals and it soon becomes apparent that simply identifying new markets is perhaps not the golden chalice.

But looking at this from a different perspective, ‘creating new markets’ could also be seen as “….not accepting something just because it has always been accepted in the past”; or put even simpler - questioning the process.


Question the process

The fact that shippers and suppliers now have a much greater choice of owners and operators to transport their cargoes, has created an imbalance in the market. More vessels essentially means cheaper charter rates but as noted, the running costs are just not keeping pace and are getting higher and higher with the trend only spiralling upwards.

At the same time, cargo receivers are demanding higher quality specifications on delivered cargoes, which most commonly results in stricter pre-loading inspection specifications for the vessels.

Thus, the vessels are earning less money to carry cargoes that require far more tank cleaning than ever before at far higher running costs; and if that was not enough, vessels can only utilise cleaning chemicals that have been approved as safe to use, the majority of which have not actually been tested for cleaning efficiency.

So how does questioning the process make a difference?

There is one major assumption that has a huge impact on the scenario described above. That is, in order to achieve higher levels of purity in the delivered cargo, the vessels have to meet stricter pre-loading inspection specifications. Fundamentally, this is wrong.

In order to achieve higher levels of purity in the delivered cargo, the vessels actually have to be informed of what the required purity specifications are and in many cases this does not happen. Very often wall wash inspections are employed as a means of determining cargo tank suitability, but the specifications are already so strict that it is not actually possible to achieve better analysis results, because the quality of the wall wash sample is already the same as the quality of the pure wall wash solvent.

So what happens next? Wall wash samples are analysed for contaminants that are in such low levels of concentration, they are not picked up by routine wall wash analysis. But does this higher level of analysis actually make the cargo tanks cleaner? Has anybody stopped to work out what the relationship between the wall wash sample and the loaded cargo is? This is a loaded question, which the author knows only too well, but that is the point of questioning the process, particularly when one also considers the legal ramifications of passing, or failing the wall wash inspection.

For example, if a vessel passes the wall wash inspection but the first foot, or final loaded cargo subsequently fails to meet the shipper’s specified export specifications, assuming the cargo is within specification as it is delivered on board, it is the owners of the vessel who are legally responsible for the contaminated cargo. As this scenario is not an uncommon one, it is evidence, if evidence was needed, that passing the wall wash inspection does not actually guarantee that the loaded cargo will be on specification.

Now what happens when the wall wash sample is accepted, but the loaded cargo is subsequently rejected by the receivers’ for a quality point that was not tested for in the load port wall wash, or loaded cargo samples? It is the same outcome (again assuming the cargo is within specification as it is delivered on board), in other words it is the owners of the vessel who are legally responsible.

But is this fair? If there was an opportunity to test a wall wash, or loaded cargo sample for a specific contaminant that was known to pose a direct contamination threat to the loaded cargo, surely this is at least partly the responsibility of the charterers, or their appointed surveyors, for failing to recognise the risk?

Seemingly not, the owners of the vessel are responsible for the quality of the cargo loaded onto their vessel, irrespective of how much, or how little, the cargo tanks are inspected prior to loading.

The following is a real example that shows the charterers wall wash specifications prior to loading and the key export specifications for a cargo of 99.9% purity cyclohexane:

Wall wash specifications (methanol as solvent):

Colour (ASTM D 1209) Maximum 20

Hydrocarbons (ASTM D 1722) Pass

Non-volatile matter Maximum 25

mg/100 ml

Key export specifications on the cyclohexane:

Non-volatile matter Maximum 2 mg/100 ml

Inorganic chlorides Maximum 1 ppm

Aromatics (total) Maximum 150 ppm

Benzene Maximum 100 ppm

Which parts of this process can be questioned?

1) The wall wash solvent is methanol, which is an aggressive, penetrating, polar, water soluble solvent. The loaded cargo is nonaggressive, non-polar and insoluble in water, so how can the wall wash results directly relate to the loaded cargo?

2) There is no colour parameter in the export specifications of the cyclohexane cargo, so why is there such a strict colour specification in the wall wash sample?

3) There is a strict inorganic chloride specification on the cyclohexane cargo, but no chloride specification in the wall wash sample.

4) The wall wash sample should be free from hydrocarbons, when cyclohexane itself is a pure hydrocarbon. That said, there is a fairly strict aromatics specification on the cyclohexane cargo, but like the inorganic chloride specification, no indication at all that the loaded cargo is sensitive to aromatics.

A vessel with phenolic epoxy coated cargo tanks could theoretically present with toluene as last cargo, carry out cargo tank cleaning in accordance with industry accepted procedures and the wall wash sample would pass.

The quality of the loaded cyclohexane may not be so acceptable.

By questioning processes like this, those owners that are equipped to analyse their own wall wash/cargo samples for contaminants that are more closely reflect the quality of the loaded cargo, should be able to say whether they are load ready, or not, without having to pass a pre-loading inspection.

After all, the owners of the vessels and the charterers have a business relationship and with that relationship surely comes trust? If the charterers have not carried out business with the owners previously, then of course it makes more sense to employ an independent inspection company, but if both parties have worked successfully together in the past, the strength of the business relationship could and should count for something.

When the owners indicate that the cargo tanks are load ready, the charterers should have cause to trust this decision, without having to employ an independent surveyor to verify this. If the loaded cargo fails to meet the required quality specifications, the responsibility still lies with the owners, but by certifying their own cargo tanks, the vessel’s owners/operators have far greater control over the efficiency of the tank cleaning processes and as a result can very often save time, bunkers and cleaning chemicals.

In return, the charterers may also save some of these costs but perhaps more importantly, they will be able to develop more rigid loading schedules with the shippers knowing that the start of the loading process is not dependent upon the passing of a wall wash inspection, which very often is difficult to put an accurate timeline on.

In the case of the above mentioned cyclohexane cargo, the vessel’s owners and the charterers already had a good working relationship and agreed to load this cargo without having to pass an independent wall wash inspection. The vessel was able to carry out and accurately analyse far more relevant wall wash samples on board and as a result, the cargo was successfully loaded and discharged.

As a direct consequence of questioning the process, the owners not only earned income from a cargo that they had accepted they would not be unable to load (because of the strict wall wash specifications), they also saved about three days of tank cleaning that had been set aside for this cargo.

The next example refers to the loading of a cargo of benzene. When the cargo was fixed, the voyage orders indicated that the cargo tanks would be visually inspected only. However, some days later, the orders were changed and the vessel was instructed to achieve the following wall wash specifications. This decision was not questioned.

Wall wash specifications (methanol as solvent):

Colour (ASTM D 1209) Maximum 5 APHA

Hydrocarbons (ASTM D 1722) Pass

Inorganic chloride Maximum 5 ppm

 Key export specifications on the benzene

Colour (ASTM D 1209) Maximum 10 APHA

Inorganic chlorides No specification

Which parts of the process can be questioned?

1) The fact that the charterers introduced an independent wall wash inspection some days after the fixture was confirmed, completely changed the way the vessel would have to approach the tank cleaning operation and this should have been questioned by the owners. The difference between ‘visually’ clean and ‘chemically’ clean is enormous (particularly in coated tonnage) and this decision cost the owners time, cleaning chemicals and bunkers, which significantly reduced the expected income from this fixture.

2) As in the case of the cyclohexane cargo, the properties of the wall wash solvent and the loaded cargo are not the same so, again one could question the relevance of the wall wash sample results against the quality of the loaded cargo?

3) The colour in the export specification on the benzene cargo is higher than the maximum colour of the wall wash specification.

4) There is a strict inorganic chloride specification on the wall wash sample, but no chloride specification in the benzene cargo.

5) As in the case of the cyclohexane cargo, the hydrocarbon specification on the wall wash sample was zero, when benzene itself is a pure hydrocarbon, meaning one has to question the relevance of the presence of undetermined hydrocarbons in a methanol wall wash sample prior to loading a hydrocarbon cargo.

The owners of the vessel in question had worked with the charterers before and it was eventually agreed that the vessel would be accepted for loading even though four of the nominated cargo tanks failed to meet the required wall wash specifications.

The vessel had carried out extensive tank cleaning in order to achieve a chemically clean standard, but the four tanks that were rejected by the load port surveyors all failed for hydrocarbons and colour, but passed for chlorides.

All cargo tanks were then loaded with a first foot of cargo whereupon one tank failed to meet the first foot cargo specifications, due to the presence of colour. The tank that failed the first foot sample, had passed the load port wall wash inspection.

This case is very interesting because it shows very clearly that the additional tank cleaning the vessel carried out to bring the cargo tanks up to a chemically clean standard actually had no impact on assuring the quality of the loaded cargo.

The cargo tanks that failed the load port wall wash inspection all passed the first foot inspection and the one tank that failed the first foot sample, passed the load port wall wash inspection.

In other words, the extra time, cleaning chemicals and fuel that the vessel consumed in its endeavours to achieve the wall wash standard, were largely wasted, because passing the wall wash inspection did not result in the first foot sample passing.

The reason for the first foot sample failure was later identified as being contamination of the cargo in the shore line, so had the vessel been able to question the process and maintain the original voyage orders of preparing the cargo tanks to a visually clean standard only, the first foot sample would still have failed, but the vessel would have saved a considerable amount of expense in reaching the same point.


Chemically clean

The counter argument to this case is quite simply that the cargo tanks needed to be chemically clean in order to prevent contamination of the first foot loaded cargo from residues that may have been retained inside the cargo tanks at the start of loading and the fact that all but one cargo tank met the first foot specifications, could be seen as proof that this level of cleanliness was required.

But of course this is not the case, because not all tanks met the load port wall wash specifications and indeed those cargo tanks that failed the wall wash inspection went on to successfully load the first foot cargo and ultimately these tank were also fully loaded and discharged without incident.

The reason for this is quite simple. The first foot loaded cargo very rarely comes into contact with the area of the cargo tank that is wall washed, so it is impossible to say that the result of the wall wash sample directly impacts the result of the first foot sample.

The first foot sample is a measure of the quality of the first drops of cargo loaded onto the vessel and as such reflects the quality of the cargo after it has passed through the loading terminal line system and the vessel’s own line system.

Verification of the quality of the cargo from the storage tank through to the vessel’s loaded tanks has to be in place in order to identify the source of first foot contamination and in this case, the sample of cargo taken from the vessel’s manifold at the start of loading indicated the benzene was off specification and indeed only the first cargo tank loaded failed to meet the required first foot specifications. All other loaded tanks met the first foot specifications.

Sometimes it is difficult for owners and charterers to change their perception that a process is right just because it has always been carried out that way in the past. In challenging market conditions, where margins are very tight and the difference between earning and losing money is minimal, processes must be questioned and alternative solutions must always be considered, before entering into contract negotiations, otherwise arbitration is very often the end result.

The quality of loaded cargoes can meet new levels of quality, but this does not mean the vessels have to blindly clean longer and harder; what it does mean is that vessels have to know what standards they are cleaning to and once they know this, they can take the necessary steps on board to meet these standards, using whatever means/experience /equipment they have available to them.

Finally, consider the following:

  •  Each hour of hot washing saved is approximately equal to 0.75 tonnes of HFO.
  •  At $600 per tonne this is $450 per hour.
  • According to statistics, combustion of 0.75 tonnes of HFO liberates about 2.5 tonnes of CO2 into the atmosphere.
  •  Each drum of cleaning chemical saved is approximately $800.
  • Each hour of manpower saved is priceless.

*This article was written by Guy Johnson, director L&I Maritime (UK) Ltd; Tel: +44 (0) 1909 532003; Email:guy.johnson@limaritime.com

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