Bunker operation explained…

Bunkering is a process of transferring fuel oil or lube oil in which two vessels positioned alongside each other supply fuel oil from one to another.

Bunker barge alongside vessel

Damage from poor bunkers and financial loss from insufficient bunker supply are key issues for the marine sector, and this because there is a lot of money involved due of the big amount of fuel oil that is frequently bunkered.

Because the fuel is given in volume but paid for by weight, you must know the exact density of the fuel to determine how many tones your vessel receives.
The cappuccino effect makes the volume of fuel appear greater than it is if the fuel contains a lot of air. As a result, if the quantity determination process is not controlled properly, your company may suffer significant financial losses.

Cappuccino effect on bunker

On the other hand, bunkering process involves several environmental hazards, most notably oil spills, which are not only hazardous to the environment but also unlawful and as a result, local law enforcement teams are particularly focused on monitoring any spill, because any vessel found to be in violation of laws may face huge fines.

Vessel oil spill during bunkering operation

Emission Control Areas (ECA) are also very essential since they enforce rigorous airborne emission standards, and ships now trading in ECA areas must use fuel with no more than 0.01 % sulphur content and the maximum sulphur limit outside ECA’s is 0.5 % unless the vessel is fitted with an approved Exhaust Gas Cleaning System, therefore checking the quality of bunkered fuel has become even more crucial, due to the fact that Port State Control inspectors may scrutinize fuel inventory records to ensure the ship utilized the correct fuel within an ECA or an EU Community port and complied with other national sulphur standards. MARPOL Annex VI, Singapore’s Standard Code of Practice for Bunkering, EU Sulphur Directives, and other national rules may apply, therefore it is a good practice to consult with the vessel’s local agent before vessel arrival in port.

Most ships have bunkering checklists and procedures in place, but if your vessel does not have one, the IMO has created a “Bunkering Precautions including Bunkering Checklist” in the document “Updated recommendations for the safe transport of dangerous cargoes and related operations in port areas.”

Example of a bunker checklist

This will be useful while planning a bunker operation or drafting a bunker plan for the ship. It includes general advice on maintaining efficient two-way contact with a responsible person on board the bunker barge. It also suggests that you ensure that fire hoses, fire fighting equipment, and oil spill equipment are available for use, as well as that scupper plugs are properly fitted and drip trays are appropriately positioned under connections and bunker tank vents.

Drip tray under bunker hose connection
Preparing scuppers on deck

Prior bunkering operation, the Chief Engineer should create a bunkering plan that specifies which tanks would be used for bunkering and to achieve an efficient and safe operation, all staff must be fully aware of this before the operation begins. There should also be enough known-quality fuel on hand to use until the newly bunkered fuel is tested by a certified laboratory.
As part of pre-bunkering preparation you must check the following:

  • All tank lids are closed and locked, and that all bunker tank air vents are open and clear.
  • Overflow tanks must be empty
  • All level gauges, high-level alarms, and remote-controlled valves on bunker tanks must be operational.
  • Check that manual sounding tapes are available and that the soundings pipes are not clogged or obstructed.
  • Check that all valves to the receiving bunker tanks are properly aligned and that all other valves are closed.
  • Check the filters and safety valves on the bunker lines, if installed.
  • All bunker lines and transfer hoses should be pressure tested, and safe operating pressures should not be exceeded.
  • Check that the bunkering hose is properly and securely connected to the ship manifold.
  • Check ahead of time that you have the proper equipment to take a sample before bunkering: a continuous drip feed sampler (which must be a MARPOL Annex VI compliant line sampling device), a cubitainer to collect the sample, and lots of clean sample bottles will be included.
Example of bunker sampling equipment

During bunkering operations, the hose connection must remain intact and leak-free, and this must be checked regularly during the operation, especially when the barge switches tanks and pressure is dropped for a brief period of time. If the fuel is not homogeneous, the bunker line pressure may also fluctuate. To sample properly, we must employ adequate equipment to collect representative samples that are acceptable to all parties involved.
The dependability of test results from fuel quality analysis and the fuel density used in quantity measurement calculations is based on proper sample methods being followed.

The sampling device is installed at the point of Custody Transfer, which is typically at the ship bunker manifold, which is the preferred location for joint sampling in agreement with the fuel supplier (this is very important in case to any future quality disputes).

Sample cubitainer installed on the bunker line

The Chief Engineer must examine the quality of the fuel given by the bunker barge supplier when the barge first arrives. They accomplish this by validating the quality and quantity of fuel mentioned on the Bunker Delivery Note (B.D.N).

Example of a Bunker Delivery Note

“Details of fuel oil for combustion purposes delivered to and utilized on board shall be recorded by means of a Bunker Delivery Note,” according to MARPOL standards. As a result, a BDN should be presented for each delivery and fuel grade delivered, and it should be stored on board and easily accessible for inspection at all times. The ship and the provider are both required to keep it for three years after the fuel oil has been delivered.
The BDN must include information such as the receiving ship’s name and IMO number, the bunkering port, the date the bunkering began, the name, address, and phone number of the marine fuel oil supplier, the product name and grade, the quantity in metric tones, the density at 15 0C in kg/m3, and the sulphur content in percentage by mass.
The IMO further suggests to include the seal number of the MARPOL Annex VI fuel sample on the BDN for cross-referencing reasons, as well as a declaration signed and validated by the supplier’s representative declaring that the fuel complies with MARPOL Annex VI.
The BDN may be prepared prior to delivery in some situations, but this will not reflect the realities of the delivery.

It is very important to note that you should NEVER sign the BDN, sample labels, or any other document until the bunkering operation is complete.

The Chief Engineer will decide which tanks will receive the fuel before the barge arrives, and the contents of each receiving tank should then be measured and documented. These should ideally be empty, as different types of fuel may not be compatible. Blending fuels should be avoided unless absolutely necessary, as it can cause operational issues.
Because some vessels lack a remote level measuring technology, you may need to use a sounding tape.

Bunker tank measurement using measuring tape

Check that the barge’s documentation show the correct grade and quantity of fuel, and agree on sample protocols when it arrives.
Careful measurements of the barge tank contents must be taken before connecting the bunker hose. Use your own sounding tape or ensure that the equipment onboard the barge is in good working order and has not been tampered with.

Example of rigged measuring tape used to cheat on bunker measurement

Some barges will feature calibration tables for ullages and others for tank content soundings. Check that the right reference point on deck is being utilized for taking ullages as this information should be available in the barge calibration tables.

Always accompany the Barge Master while taking ullages or soundings of any barge tanks. It is critical that all of the tanks on board barge are dipped and their levels recorded and this includes tanks that have been reported empty as well as those that may contain fuel for another vessel.
After taking each measurement, make a note of it and double-check that the barge operator agrees with your reading as these are critical measurements in determining the amount discharged by the barge, and both parties should sign the opening measurement records. Temperature readings of each tank are also critical, because the volume of bunkers rises with temperature. Temperature changes can create considerable mistakes in calculations, hence thermometers should be checked on a regular basis.

Typically, the terms and conditions of the sale indicate that the quantity of fuel delivered will be determined by shore meters or barge outturn measurement. The Chief Engineer or a representative from the ship should be present at the bunkering barge to observe the opening and closing meter readings, barge soundings, and temperature readings.

Fuel sampling should be carried out by continuous drip method for the entire duration of the bunkering process. The sample is first collected in a cubitainer which is screwed onto the drip sampler and secured with a seal in order to prevent any unauthorized changes in the adjustment of the drip rate during sampling. Barge Master and the Chief Engineer should be invited to witness the adjusted drip-rate and sealing process and security seal number should be recorded. To ensure that the sample represents all of the fuel bunkered, the sample needle valve should be adjusted to collect enough of each fuel type for all of the required fuel samples without overfilling the cubitainer, which needs to be able to hold enough oil for all of the samples that you may need:

  • a MARPOL sample
  • a retained sample for the ship to keep
  • a retained sample for the barge to keep
  • a retained sample for the testing laboratory
  • if the vessel is utilizing a bunker surveyor, an extra sample may be required.

The ship should also be given a retained sample from the bunker supplier, which should be taken properly on the bunker barge.

If the sample cannot be obtained from the ship manifold for any reason (vacuum in the line, extreme weather, etc.), the cause should be recorded in the ship’s log book and the sample taken elsewhere.

Throughout the bunkering operation, specific crew members should be appointed to ensure that there is always one vessel representative overseeing the activity (monitoring the bunker manifold and the sampling equipment, continuously checking for leakages etc.). Record any start and stop times as well.
All of the above responsibilities can be overseen by an experienced and certified bunker quantity surveyor, who can assist the Chief Engineer in ensuring proper bunkering and sampling procedures are followed.

When the delivery is complete, the vessel representative should witness the closing soundings on the barge in order to determine and validate the actual volume provided.
To accurately calculate how much fuel has been received the following steps should apply:

  • check the volume received and the observed temperature of the fuel.
  • take soundings or ullages of all tanks that have received fuel and correct the soundings or ullage according with the vessel’s trim and list.
  • after correction the observed volume you have received can then be calculated.
    It should be noted that vessel calibration tables for fuel storage tanks are rarely approved by recognized bodies, but bunker barge calibration tables are routinely reviewed and certified by local authorities.
  • after determining the observed volume, you must correct it to the standard of 15 0C.
  • to determine the correct Volume Correction Factor (VCF), you must first check the density of the fuel at 15 0C, which will be provided by the supplier.
  • the observed volume is then multiplied by the temperature correction factor contained in tables such as ASTM 54B to determine the standard volume at 15 0C.
  • because density in a vacuum is an absolute relationship between mass and volume, it will not be the same as weight to volume in air. To calculate the right density in air, multiply the supplied density by a Weight Correction Factor, which may be found in ASTM 56 table.
  • after that, we can multiply the standard volume at 15 0C by the corrected density to determine the number of tons of fuel received.

Many fuel testing laboratories discover that the density on the BDN is frequently exaggerated, implying that the supplied weight was less than it seemed.
If the density cannot be found from a representative sample, the BDN should only be signed for volume at the observed temperature, but if the supplier insists on a signature for weight, add “For volume only – weight to be determined after density testing of a representative sample” to the Remarks section in the BDN.

When the delivery is finished, the surveyor should concur with the Chief Engineer and Cargo Officer that the bunker delivery is completed.
When the bunkering is finished and the cubitainer is full of fuel, close it and shake it for a few minutes to completely mix the sample. Because we will frequently be preparing at least four samples, fill all of the sample bottles one-third at a time, making repeated passes to fill each bottle evenly.

Example of filling the fuel sample bottles

Close and seal the sampling bottles, and record the seal numbers on the Sample Details Form.

Example of sealed and labeled sample bottle

Sign the labels on the fuel quality testing samples with the supplier representative. and put a label on each bottle with both signatures.

Under no circumstances should you sign any blank labels or accept any samples that have been created or supplied in advance of the bunkering process.

It is critical that you keep one sample on board in a secure area since this may be the only sample remaining that accurately represents the fuel delivered to the ship.
If the supplier provides a sample but it was not witnessed, apply the mark “Only for receipt. Unknown source” on its label. The fuel supplier is required to give you a representative MARPOL sample, which must be sealed and signed by a representative of the company. This MARPOL sample must be kept under the ship’s control until the fuel oil is considerably depleted but not for less then twelve months after delivery.

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