Disputes relating to “off-spec” or contaminated liquid cargoes are a recurring problem and contamination claims often result in large sums of money being at stake.
Often, the cause and/or location of the contamination can be quickly identified if the appropriate samples are drawn and retained in suitable containers.
While sufficient and current information is available on sampling procedures and techniques, circulation and quantification for testing blends, instrumentation and calibration, there is little formal documentation at hand for the type of sample container utilized in sampling and retention, and this is required to be questioned.
The composition and the construction of the sample container has a significant impact on quality of the sample it contains, and any deviation from standard recommendations may lead to testing laboratory producing “false negative” results.
Cargo surveyors – representing the interests of the cargo owners or the carriers are reminded that improper sampling containers used (often an overlooked aspect) may result in the samples being rejected and not being considered as evidence for a claim.
SHIPOWNERS P&I reports an increase in the number of contamination incidents. The defense of claims of this nature relies heavily on the samples taken during loading and discharging operations. However, the club reports an increase in cases of poor labelling, incorrect sealing, the use of dirty sample bottles or the incorrect bottle type for the product.
In a recently concluded cargo contamination survey, cargo surveyors were appointed by the shippers of the cargo to investigate a potential contamination issue of a parcel of Jet AI being loaded on board a vessel.
Initial independent samples for first foot were taken, basis customary agreement between the shipper and the carrier, from the loaded tanks, however sample tested was a composite, with equal volume from each tank.
The sample tested “off-spec” for particulate contamination.
The cargo surveyor on board recommended a further joint sampling and testing with the carrier’s surveyor, for individual tank sample to be tested, to determine per tank particulate contamination.
The carrier and the shipper were, during the joint sampling, placed under considerable pressure from the terminal on resumption or vacating the berth, in view of the idle occupancy of the berth by the vessel during the sampling process.
In order to expedite the sampling and testing process in the circumstances experienced, the cargo surveyor thought it prudent to use plastic bottles for cargo sample retention, those readily available on board, instead of the acceptable clear or opaque glass bottles.
The samples were drawn and dispatched to the laboratory, thereafter tested expeditiously, and the results were again “off-spec” for particulate contamination, however, carriers raised a concern on the container used.
The results of these samples were thus challenged, which caused further delay to the vessel, subsequently, the vessel was asked and instructed to vacate the berth.
Sample containers come in varying sizes, materials, designs and colors. The most common of these are glass, plastic and metal.
The decision as to which type of sample container would be most appropriate to use will depend very much on the nature of the product being sampled and the analyst’s intentions regarding analysis and storage.
The API manual – Sampling section recommends being able to select the right container for a given application, one must have knowledge of the material to be sampled to ensure that there will be no interaction between the sampled material and the material of the container that would affect the integrity of either.
Additional considerations in the selection of sample containers are the type mixing required to remix the contents before transferring a sample from the container and the type of laboratory analysis that are to be conducted on the sample.
Regardless of the type of sample container used, the sample container should be large enough to contain the required sample volume and enough ullage space for thermal expansion and mixing of the sample.
Plastic bottles made of suitable material may be used for handling and storage of gas oil, diesel oil, fuel oil, and lubricating oil. Bottles of this type should not be used for gasoline, aviation jet fuel, kerosene, crude oil white spirit, medicinal white oil, and special boiling point products unless testing indicates there is no problem with solubility, contamination, or loss of light components.
In no circumstances shall nonlinear (conventional) polyethylene containers be used to store samples of liquid hydrocarbons. This is to avoid sample contamination or sample bottle failure. Used engine oil samples that may have been subject to fuel dilution should not be stored in plastic containers.
Clear glass bottles may be examined visually for cleanliness, and they allow for visual inspection of the sample for free water cloudiness and solid impurities. The brown glass bottle affords some protection to the samples when light may affect the test results.
When cans are to be used, they must have seams that have been soldered on the exterior surfaces with a flux of resin in a suitable solvent. Such a flux is easily removed with gasoline, whereas many others are very difficult to remove. Minute traces of flux may contaminate the sample so that results obtained on tests such as dielectric strength, oxidation resistance, and sludge formation may be erroneous. Internal epoxy lined cans may have residual contamination and precautions should be taken to ensure its removal.
Liquid cargoes are inherently vulnerable to changes in composition through interactions with their surroundings as they have the potential to become damaged or absorb contaminants.
This is fundamental to the choice of containers being used for retention of liquid samples, ensuring testing do not lead to false negative.
It is extremely important for ship owners and carriers to understand that when it comes to liquid cargo disputes, it is easy for cargo interests to have the upper hand due to their access to shore tank samples from loading and discharge ports. It is therefor evident that ships crew should not only be able to take correct and sufficient samples of the cargo being loaded / discharged, they should insure these are stored in correct receptacles capable of long term storage without them altering the inherent property of the sample.
If we assume that a sampling was representative and detrimental to the qualification of a particular cargo / commodity, then we may say that testing is the most important tool in judging a dispute (if it arises) objectively.
For this reason, it is imperative that containers used for retaining samples do not taint or alter the properties of the liquid it contains.
The Swedish Club in consultation with TCI scientific state it is primarily the environment around the cargo that decides if changes occur, and consideration in maintaining ideal conditions must include the use of correct sampling containers being given equal importance, in addition to the normal inserting procedures, strict observance of epoxy curing protocols, meticulous tank cleaning, due diligence for cargo compatibility, and other precautions help to prevent incidences.