Comprehensive Guide to Sampling Procedures: Best Practices and Insights
Loss Prevention Bulletin
Last updated 02/06/25
Why take samples?
Given that cargo contamination claims are the most frequent and costly claim that tankers experience, the following bulletin highlights the best sampling practices to be undertaken onboard vessels.
Cargo samples that are taken following best practises and are correctly sealed and stored show the quality of a cargo at the time and point of sampling. Samples must be taken at various stages throughout cargo operations to show the continued quality of the product. Cargo samples then become a vital piece of evidence, in establishing the stage at which the deterioration of the cargo occurred if a dispute for an off-spec cargo is raised.
Tanker cargoes are often called “the invisible cargo” as they are loaded through closed systems keeping the cargo out of sight. Because of this the ship is not able to carry out an inspection of the cargo prior to loading to assess its condition. The shipowner’s only defence against a claim for an off-spec cargo is the samples taken throughout cargo operations. If a claim does arise, the samples taken on-board using the methods and guidance below will be requested for analysis, and the results can help to quickly identify the point at which the contamination occurred. Having samples will significantly reduce the time and costs involved after a cargo claim has been raised and have the potential to clear the vessel of the cause of contamination.
Types of samples and when to take samples
Industry standard is that shore samples are taken unilaterally with no ship’s representative present. However, the vessel may request a shore sample which should be accompanied by a receipt and should be stored with the vessel’s other samples. Additionally, shore samples that are taken after discharge is completed should also be requested and stored with the vessel’s samples in the dedicated sample locker.
Sampling should be laid out in the charter party agreement and discussed in the pre-loading meeting with the cargo surveyor. The number, location and timing of samples should be discussed. Along with confirmation that the cargo surveyor will supply the vessel with a full set of samples and confirm the designated persons that will carry out the task of drawing, sealing and signing the samples.
Samples should always be taken with a member of ship’s crew present, representing the shipowner’s interests, and a cargo surveyor representing the charterer’s interests. Unilateral sampling should be avoided. However, if the cargo surveyor refuses to be present for ship sampling, ship’s crew must take independent samples. These should be undertaken following the same guidance laid out in this bulletin, ensuring proper labelling, sealing and recording procedures as they can still be called for as evidence if there is a claim against the cargo. The cargo surveyor refusal to be present for ship’s sampling should be recorded in the Ship’s Logbook and the vessel should issue a Letter of Protest.
Sequence of sampling
- Shore tanks
- Shore lines
- Ship’s manifold sample
- 1st foot samples
- Ship’s tank running/composite sample
- Ship’s tanks prior to discharge
- Ship’s manifold at start of discharge
If the cargo is homogeneous then a running sample is preferred. If the cargo is prone to stratification or if adequate time has not been given for free water to settle after completion of loading, spot sampling is required to form a composite sample. Commonly lower, middle and upper samples are taken and then combined to form a composite sample as an accurate representation of the bulk cargo in a given tank.
When to take additional samples
- Manifold- if nominated shore tank has changed.
- Manifold- resuming cargo operations following a suspension.
- If there is a question of the cargo being off-spec.
If a cargo is suspected to be off-spec then additional samples should be taken, these should be dead bottom, lower, middle, upper, along with a running sample of the individual tanks in question.
It is common practice to suspend loading after receiving the first foot of cargo for sampling and analysis. If the samples pass analysis, loading will resume. If not, then we advise to contact ship’s management and a P&I representative.
If the terminal does not require first foot samples, the vessel must still take samples when innages have reached one foot. First foot samples are taken to confirm the vessel’s systems and pipes are clean. They also cover a large percentage of the overall tank surface area. This is especially important when loading high-specification or sensitive cargoes, to reduce the risk of contaminating the entire cargo parcel.
Pump stack samples may also be taken on chemical tankers to ensure vessel’s lines are clean before cargo enters the tanks.
Pre-discharge samples should be taken from all tanks. For high specification cargoes, these samples must often pass analysis prior to commencing cargo discharge operations. If the condition of the cargo is being contested, these samples will be analysed and compared to the post-loading samples to confirm if the condition of the cargo has changed whilst onboard. A pre-discharge manifold sample must be taken as this shows the cargo was on-spec as it left the vessel.
If the cargo has been contaminated an investigation will take place. The chain of samples that were taken from shore tanks and lines to ship’s lines and tanks back to shore tanks will be analysed. The sequence of sampling enables identification of when and where contamination took place.
Another type of sampling not mentioned in the sample sequence is a drip sample. Drip samples are commonly taken at the manifold. It could be considered a ship’s running sample, however, it is not an accurate representation, as the loading rate may vary throughout the cargo operations, but the sample rate is constant.
The manifold sample
The manifold sample is the most significant sample taken. The manifold is the point at which the custody of the cargo passes from the terminal to the vessel. The sample represents the condition of the cargo the vessel has received.
If there has been no manifold sample taken at the commencement of cargo operations and the first foot samples fail analysis, the vessel will be held liable as there is no proof of the condition of the cargo when it was first received on the vessel. If a manifold sample has been taken and that too is off spec, then the shore tanks or lines are the cause of contamination as the cargo had not yet passed through the vessel’s lines.
A manifold sample is to be taken immediately upon commencement of loading, with the manifold valve closed if permissible. A prudent Chief Officer would ensure that sample points are cleaned and dried during tank cleaning operations. However, if tank cleaning has not taken place there may be remnants of the previous cargo in sampling point, if this is the case then the sample point should be flushed briefly prior to taking the sample. Note that if this is carried out, it will also flush any previous cargo, water or particular matter from the shore line or connection.
Manifold samples should never be disposed of regardless of their quality.
Another reason to take a manifold sample is to ensure the vessel is receiving the correct nominated cargo. Although there is no laboratory analysis carried out for a manifold sample at this point, a visual analysis must be carried out. If there is any suspicion that the manifold sample is not representative of the nominated cargo or it looks off-spec, operations should be suspended immediately and ship’s management and P&I contacted for advice. Loading off-spec cargo or the wrong cargo into the vessels tanks will result in time-delays and additional costs. This could include backloading the cargo to the shore tanks and proceeding to anchor to re-prepare the tanks for loading.
Visual analysis
A visual analysis must be carried on all samples throughout the loading and discharge operations to ensure continued quality of the cargo.
Sample can be checked visually for:
- Appearance, colour and brightness
- Presence of water
- Foreign particles
- Odour or taint (for non -toxic cargoes)
- Temperature
- Approximate pour point (if heated)
If at any time during the cargo operations the samples show any signs of being off-spec, operations must be suspended and ship’s management and P&I contacted for advice.
Sampling methods
There are three main sampling methods. Namely, closed, open and restricted. To prevent the risk of spoiling the cargo it is imperative that the right method is used.
Closed sampling is the preferred method for most cargoes. There are two ways to carry out closed sampling. The first is using a dedicated sampling/ullage point. Portable equipment is used with a vapour lock system to ensure it remains a closed system. Secondly, a fixed inline system can be used. These are common on vessels which deal with high specification or sensitive cargoes.
Closed sampling must be used for any cargo which the following applies:
- Requires inerting or
- A nitrogen blanket
- Toxic or very toxic cargoes
- Corrosive cargoes
- UV sensitive cargoes
- Hygroscopic cargoes
- Oxygen sensitive cargoes
Open sampling is when the cargo hatch is opened and the sampler is lowered into the tank with the cargo in sight. If open sampling is being carried out the tank opening should only be uncovered long enough to complete the sampling. This kind of sampling can be acceptable for vegetable oils.
Manifold sampling can be considered restricted sampling as there is a small quantity of cargo and vapour exposed to the atmosphere.
It is worth mentioning that not all portable sampling equipment that uses dedicated sampling/ullage points are considered closed samplers, some are restricted samplers. The correct type of sampling method should always be undertaken. If this is not possible, a risk assessment must be carried out and approval sought from ship’s management and P&I prior to carrying out sampling.
Depending on the cargo, incorrect sampling method could result in the cargo becoming off-spec, pose health risks to the crew drawing the samples, or cause damage to the vessel or the environment.
There is a risk of combustion if open sampling is carried out on a cargo that requires inerting. Carrying out open sampling on cargoes that require a nitrogen displaces the nitrogen blanket exposing the cargo to UV light and moisture which risks turning the cargo off-spec. If open sampling is carried out on a cargo that is inerted or has a nitrogen blanket, the atmosphere in the tank may be displaced with the normal atmospheric conditions putting the crew drawing samples at risk of asphyxiation. If open sampling is used for corrosive cargoes, they may cause harm to the crew, damage the vessel or the environment. Toxic cargoes carry health risks to crew if open sampling is carried out.
Safety concerns
The Safety Data Sheet (SDS) for the cargo must be supplied to the vessel prior to commencing loading. It should be supplied to the vessel as early as practicable so the crew can familiarise themselves with the safety aspects and health hazards of the cargo. Also to ensure the correct personal protective equipment (PPE) is in place for safe handling of the cargo.
The level of PPE required for taking samples depends on how hazardous, corrosive or toxic the cargo is.
Example for coveralls:
- non-hazardous and hazardous cargoes require flame proof coveralls
- corrosive and toxic cargoes require additional chemical splash suits
- very toxic cargoes require a gas tight chemical suit
Static accumulating cargoes should be sampling at least thirty minutes after completion of loading. This gives time for the static electricity to dissipate.
Sampling equipment must be earthed in accordance with manufacturers’ recommendations and instructions properly adhered to.
Personal gas meters must be worn by crew working on deck throughout cargo operations but in particular when sampling. Gas meters must be certified and calibrated to manufacturer’s standards.
Cargo sample bottles should not be filled more than 85% of their capacity, this is to allow for the safe expansion of the cargo.
Equipment
The size of the sample bottles should be 500 ml to 1000 ml. Always use the correct sample bottle required for the nominated cargo. The sample bottle material depends on the cargo being sampled. Generally speaking, for crude oils and fuel oils use metal or plastic sample bottles and product cargoes or chemical cargoes are suited to glass bottles. However, some chemicals do require plastic bottles. Glass and plastic bottles should normally be clear but if a cargo is UV sensitive an amber coloured sample bottle is required. For oxygen sensitive cargoes sample bottles need pre-purging with nitrogen.
If the incorrect type of sample bottle is used there is a risk of an off-spec result from the laboratory sample analysis. This would not be an accurate representation of the bulk cargo which may still be on-spec.
The vessel should have sampling equipment on board, but the cargo surveyor may bring their own. The equipment should be certified, intrinsically safe if required, clean and fit for purpose. The sample bottles, sampling equipment and any containers used must be free from previous cargo residues, water and particulate matter. Sufficient sample bottles and labels should always be kept in stock onboard.
Labelling, sealing and recording
All samples drawn must be labelled, sealed, recorded and retained onboard in the designated sample locker.
Sample bottles should be labelled accordingly:
- Name of ship
- Port and berth/anchorage no.
- Tank/manifold/pump stack no.
- Product
- Operational status - load or discharge
- Type – first foot/running/composite/upper/middle
/lower/dead bottom - Date and time
- Identity of sampler
- Signature – Surveyor/ Chief Officer
Labels should be written directly onto the samples or on sample labels immediately after the samples have been drawn. This will mitigate any risk of mislabelling. They must not be prepared in advance.
Samples must be sealed with individual seal numbers. A sample receipt must be issued listing all samples taken with their seal numbers. The sample receipt should be retained with the cargo documents. The seal numbers must also be recorded in the sample log. This provides a chain of custody reference of the samples if later released.
At least one full set of sealed samples must be retained on board the vessel. These act as the owner’s evidence of the condition of cargo carried onboard if there is a claim raised against the cargo. A well-documented, properly labelled and sealed sample even if not signed by the sample surveyor, will have value as evidence in case of legal action.
Storing
Samples must be kept in a dedicated sample locker, located outside the accommodation and away from provisions. The sample locker should not be exposed to extreme temperature changes. It must maintain a dark environment to minimise exposure to UV sources. Ensure the space is well ventilated. The sample locker must be fitted with appropriate fire-fighting apparatus if flammable samples are to be stored inside. The sample locker should be cell divided to avoid shifting of sample bottles whilst at sea.
For chemical carriers it is worth noting that some chemical samples cannot be stored onboard due to their hazardous nature. Other arrangements will need to be made to ensure that owner’s samples have sufficient storage ashore, maintaining the proper chain of custody for traceability when landing samples. Some cargo samples are known to deteriorate over time.
Samples should be stored onboard for a minimum of 18 months. A claim can be raised up to 12 months after the cargo has been delivered to the receiver, however, West recommends a 6-month buffer period for the cargo to be transported from the place of discharge to the place of delivery. These recommendations are based on the charterparty and bills of lading incorporating the Hague/Hague-Visby Rules.
If the charterparty or bills of lading are written under the Rotterdam Rules or Hamburg Rules this claim window is extended to 24 months from date of delivery. Then samples should be retained onboard for 30 months.
The charterparty should be checked thoroughly for time limits before disposing of samples. If the bills of lading are under a charterer, then the charterer should also be contacted prior to the disposal of the samples to ensure there has not been a time extension put in place for claims. If there is an ongoing dispute with a cargo, those samples must be retained onboard until the claim is settled regardless of the advised retention times previously mentioned. If in doubt, contact management and a P&I representative.
Releasing samples
Proper chain of custody is paramount when releasing samples to third parties. A detailed receipt should be issued for each sample that is being released including seal numbers. The sample log on board should be updated after the release. Samples should only be handed over to an independent surveyor appointed by the vessel’s owner or P&I Club. Samples must not be surrendered to a third party without the approval of the shipowner.
Disposing of samples
Samples should not be disposed of without first confirming with the shipowner and P&I Club that there are no outstanding claims against that cargo. If there is a dispute against the cargo, samples should be kept onboard until resolved. Samples must be disposed of to an approved shore reception facility. A receipt should be issued by the reception facility and retained onboard for record purposes.
Additional considerations
It is important for a sampling procedure to be laid out in the ship’s Safety Management System. Crew must be familiar with the procedure and receive training on the equipment used.
West has experience claims where the post-loading samples have been on-spec and the pre-discharge samples have been off-spec. This is an example of where taking samples chronological throughout cargo operations can identify where the contamination has taken place. Charterer’s specifications for the care of carriage of a cargo should be carried out to minimise these kinds of claims. It is important to consider the cargo’s compatibility with the tank coating. Some cargoes are prone to absorb into tank coatings and then desorb into proceeding cargoes carried.
Throughout this bulletin cargo operations have been discussed regarding vessel and terminal operations, however the same principals apply when carrying out ship-to-ship operations between two vessels.
For additional resources, industry standards for sampling are set out by:
- American Society for Testing and Materials (ASTM)
- American Petroleum Institute (ΑΡΙ)
- Energy Institute (EI)
- International Organization for Standardization (ISO)
Contact us
Members requiring further guidance should contact the Loss Prevention department.
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