A bunker surveyor is an independent inspector who checks how much fuel a ship receives from a bunker barge or tanker. The surveyor measures the tanks before and after delivery, records temperature and density, and works out the tonnes delivered.
This page explains what a bunker surveyor does, the survey types, how the quantity is calculated and where disputes start. It also covers qualifications, which come from employers and, in Singapore, from national standards. It is written for engineers, charterers and anyone weighing the career.
What Is a Bunker Surveyor?
A bunker surveyor is an independent third party who measures the fuel delivered to a ship and checks the figures against the tanks. The surveyor works for the buyer, not for the supplier or the crew.
Bunkers are bought by weight but delivered by volume, so every measurement carries small corrections. The buyer, usually the shipowner or a charterer, is rarely on board, and the surveyor acts as its eyes at the manifold.
The role sits inside a wider bunkering operation and the commercial deal described in how bunker trading works. The surveyor does not run the delivery. The chief engineer stays responsible for the ship’s side.
What Does a Bunker Surveyor Do During a Bunker Delivery?
The surveyor confirms the appointment, measures the ship’s tanks and the barge before and after delivery, checks safety and sampling, and issues a quantity report. A typical job runs from boarding to the signed report.
- Before delivery: confirm the letter of appointment and record the draughts for trim and the list. Check the certified sounding tables and tank reference heights with the chief engineer, then check the sounding tape. Measure each tank with temperature and density.
- During delivery: check mooring, safe access, and the hose and its connection. Witness sampling at the manifold. The surveyor can call for a shutdown if something is unsafe.
- After delivery: re-measure the tanks, compare the barge’s delivered figure with the ship’s received figure, and investigate any gap. The report is normally signed by the chief engineer and countersigned by the master.
The MARPOL sample is drawn continuously at the receiving ship’s manifold, sealed with a numbered seal and kept on board for at least 12 months. West of England lists a surveyor’s sample as one of the typical five samples when a surveyor attends. The rules behind the sample are in MARPOL Annex VI and the bunker delivery note guide.
Does a Bunker Surveyor Check Fuel Quality?
Not by testing. A bunker surveyor witnesses sampling and sealing, but a laboratory measures viscosity, sulphur and other properties against the ISO 8217 specification.
ISO 8217:2024 is the seventh edition and replaced the 2017 edition, according to IBIA. Distillate grades are covered in MGO and MDO marine fuels. For a distillate delivery, the surveyor can use water-indicating paste on the tank sounding to detect free water.
How Does a Bunker Surveyor Calculate the Quantity?
The surveyor converts each tank’s corrected sounding to volume, corrects it to 15°C, then converts to tonnes: quantity = volume × VCF × WCF. The delivered quantity is the closing total minus the opening total.
| Step | What the surveyor does | Where the value comes from |
|---|---|---|
| 1. Corrected sounding | Reads sounding or ullage, then applies trim and list corrections | Certified tank table and reference height |
| 2. Temperature and density | Measures temperature per tank and takes density at 15°C; averages by quantity if grades are mixed | Tank thermometers, last supply report, engine logbook |
| 3. Volume correction factor (VCF) | Corrects volume at observed temperature to 15°C | ASTM Table 54B |
| 4. Weight conversion factor (WCF) | Converts volume at 15°C to metric tonnes | ASTM Table 56 |
| 5. Comparison | Compares the barge’s delivered quantity with the ship’s received quantity and investigates any gap | Barge figures, BDN, ship’s tank totals |
Contracts set an agreed tolerance for the gap. A figure of about 0.5% of the received quantity is often quoted, but the contract decides.
Trim and list matter because tank tables assume a level ship. Measurements are most reliable with no cargo or ballast work under way and the ship on an even keel, which real operations rarely allow. The effect of trim by the head and by the stern is the reason surveyors record draughts and list before and after soundings.
What Types of Bunker Surveys Are There?
The main types are the bunker quantity survey (BQS), remaining on board (ROB), on/off-hire, sludge and de-bunker surveys. Each fixes a quantity at one point in time for a specific reason.
They sit among the wider types of surveys carried out on ships.
| Survey | When it is done | What it establishes |
|---|---|---|
| Bunker quantity survey (BQS) | During bunkering | Fuel delivered by the barge against fuel received by the ship, with sampling witnessed |
| Remaining on board (ROB) | Any time, on request | Measured quantity in every tank against the logbook, with an ROB certificate |
| On/off-hire survey | At delivery or redelivery under a charter | Exact fuel on board at the time and place of delivery or redelivery, so owner and charterer can settle the fuel (see charter types) |
| Sludge survey | Before sludge is landed | Quantity of sludge discharged to a barge or truck, and sludge as a share of fuel consumed (sludge comes from the fuel oil purifiers; disposal is recorded in the Oil Record Book) |
| De-bunker survey | When off-spec fuel goes back to the supplier | Fuel on board and on the receiving tanker before and after transfer, with samples |
Where Do Bunker Quantity Discrepancies Come From?
Many discrepancies come from ordinary measurement errors: inherited spreadsheets, poor interpolation, wrong temperatures and uncorrected list. Deliberate manipulation is a separate problem, covered next.
These are the patterns I see most often as a surveyor:
- Inherited spreadsheets: engineers often use the Excel calculation they received from the previous crew and never re-check the formulas. Some cannot interpolate volumes in the tank tables, and the error carries into every report.
- Missing temperature data: some storage tanks have no temperature gauge, so seawater temperature goes into the calculation. A thermometer lowered into the fuel gives the real figure, but with heavy fuel oil it is a dirty job and is almost never done.
- List on bulk carriers: the list changes with cargo work, so soundings drift. The best fix is to stop cargo operations with the chief officer, but this is often ignored and the measurements are repeated.
- Spare bunkers: chief engineers often hold back a margin of fuel as a safety measure, not for any improper purpose. They want cover if the next delivery is short or consumption rises, and they often feel over-controlled and poorly supported by the company.
Tank tables, trim corrections and density figures all leave room for judgement. An experienced chief engineer or surveyor can read the same measurements in one party’s favour. That is why the buyer appoints an independent surveyor.
How Can Bunker Quantity Be Manipulated?
Known methods include blocked or shortened sounding pipes, tampered sounding tapes, wrong-sized bobs, doubler plates and unlisted tanks. Finding them takes an experienced surveyor and strict documentation of every gauging.
Ship & Bunker describes weights placed at the bottom of sounding pipes so that measured heights differ from the true reference height. The countermeasure is to record each tank’s reference height, compare it with a physical measurement and treat any missing length as a full sounding. Use your own tape and ruler for readings below 20 cm, and read the millimetres carefully when tanks are nearly full.
In my experience the risk of equipment manipulation is higher in parts of Asia, Latin America and Africa. I have seen clogged sounding pipes, doubler plates, sounding pipes cut short above the deck and hidden tanks. Cases like this call for a surveyor who investigates, which is why such surveyors are sometimes called bunker detectives.
The surveyor reports to the client, so the crew does not have to agree with the result. If the crew disputes the figures, the surveyor informs the client before leaving the ship. The ship’s own remedy is a remark on the BDN and a letter of protest.
Does a Mass Flow Meter Replace the Bunker Surveyor?
No. A mass flow meter measures what leaves the barge, while the ship’s figure still comes from manual tank measurement. The surveyor checks the meter set-up, tank gauging and sampling, and settles differences.
Seatrade Maritime makes the same point: differences persist because the two figures come from different methods. Rules now differ by port.
| Port | Rule | Date |
|---|---|---|
| Singapore | Mass flow meters mandatory for bunker deliveries; SS 648:2024 is the current meter code; SS 600:2022 covers suppliers, craft operators, surveying companies and surveyors | Meters from 1 Jan 2017; SS 600:2022 from 1 Jan 2023 |
| Rotterdam and Antwerp-Bruges | Bunker vessels supplying conventional marine fuels and biofuels must be fitted with mass flow meters | 1 Jan 2026 |
Sources: MPA bunkering standards, Port of Antwerp-Bruges and Seatrade Maritime, checked 15 October 2026. Under SS 600, tank gauging is the fallback when a meter fails, and the operator needs permission from the authority to switch.
Is a Bunker Survey Worth the Cost?
In my experience, yes. A survey can cost about as much as 1–2 tonnes of fuel, while discrepancies can reach 10–50 tonnes depending on vessel size. Many owners and charterers undervalue the service.
The gain from an uncorrected error goes to one party, and the loss to the other. An independent surveyor removes the argument before it starts.
What Qualifications Does a Bunker Surveyor Need?
There is no worldwide bunker surveyor licence. Requirements come from the employer, the client and local rules. In Singapore, bunker surveying companies must be accredited and follow SS 600:2022.
The Singapore Accreditation Council accredits the companies. Outside Singapore, requirements are mainly contractual: the inspection company’s procedures and the client’s instructions. Check local rules before relying on this.
In practice the work suits people who have been to sea and know fuel systems. A marine engineering degree, for example from one of the US maritime academies, and an STCW engineering certificate are a common base. Sea service as an engineer under the chief engineer, as described in shipboard organization and ranks, teaches how the other side of the manifold works.
- Reading tank tables and interpolating volumes without a spreadsheet.
- Using the ASTM correction tables and checking someone else’s formulas.
- Knowing fuel grades and the MARPOL Annex VI sampling and BDN rules.
- Writing a clear report that stands up in a dispute.
- Working at height and on barges: ladders, PPE and a calm approach to a ship that is not yours.
How Much Does a Bunker Surveyor Earn?
I found no reliable published pay survey for bunker surveyors, so this page gives no figure. Pay depends on the employer and the port. For seagoing pay by rank, see working on a merchant vessel.
Related Topics
- LNG bunkering: how gas fuel is delivered to ships
- Bunker adjustment factor (BAF): meaning and calculation
- How to become a naval architect
Frequently Asked Questions
What does a bunker surveyor do?
A bunker surveyor measures the fuel a ship receives and checks it against the barge’s figures. The surveyor also witnesses sampling and safety and issues a quantity report to the client. The role is independent of the supplier and the crew.
What is a bunker quantity survey (BQS)?
A BQS is the measurement of fuel delivered to a ship, made before and after the transfer. The surveyor sounds the tanks, corrects for trim, list and temperature, and compares delivered and received tonnes. It is the most common bunker survey.
How does a bunker surveyor calculate the quantity of fuel delivered?
The surveyor takes a corrected sounding for each tank, finds the volume from the tank table and corrects it to 15°C with the VCF from ASTM Table 54B. Table 56 converts that volume to tonnes. The delivered quantity is the closing total minus the opening total.
Does a bunker surveyor test fuel quality?
No. The surveyor witnesses sampling and sealing, and a laboratory tests the sample against ISO 8217. The MARPOL sample stays on board for at least 12 months.
Do you need a licence to be a bunker surveyor?
No global licence exists. Singapore requires bunker surveying companies to be accredited and to follow SS 600:2022. Elsewhere, requirements are set mainly by the employer and the client.
How much does a bunker surveyor earn?
I found no reliable published figure for this role. Pay depends on the employer and the port, so ask inspection companies and recruiters for current ranges.
Who appoints and pays the bunker surveyor?
The buyer of the fuel appoints the surveyor, usually the shipowner or a charterer. The buyer is rarely on board, so the surveyor acts for it at the delivery.
What is a bunker detective?
A bunker detective is an informal name for a surveyor who investigates suspected quantity manipulation. The work includes checking sounding pipes, reference heights and hidden tanks, and documenting every gauging strictly.
- Great Lakes Maritime Academy: Programs, Cost and Admission – October 14, 2026
- Bunker Delivery Note (BDN): Contents, MARPOL Rules and Checks – October 11, 2026
- Oil Record Book: Part I and Part II Entries, Rules and PSC Checks – October 11, 2026
