During my years serving onboard Engineer, I participated in countless bunkering operations. (Before worked on LNG vessel)

At first glance, bunkering appears straightforward.

A bunker barge comes alongside, fuel is transferred, paperwork is signed, and the vessel sails away.

In reality, however, bunkering is one of the few shipboard operations where even experienced Chief Engineers can spend hours debating figures with bunker suppliers.

Most people assume these disputes are related to fuel quality.

Surprisingly, they are usually about one simple question:

Did we actually receive the quantity we paid for?

This is exactly why Bunkering Surveys exist.

What Is a Bunkering Survey?

A Bunkering Survey is an independent verification process conducted during fuel delivery operations.

The purpose is to determine whether the quantity delivered by the supplier matches the quantity received by the vessel.

The surveyor acts as an independent third party representing neither side.

Their role is to document facts, verify quantities, witness sampling procedures, and provide evidence should a dispute arise later.

In simple terms:

A bunker surveyor is there to verify that the vessel receives exactly what it pays for.

What Does a Bunker Surveyor Actually Do?

Interestingly, much of the work performed by a bunker surveyor is very familiar to marine engineers.

In fact, when I first learned more about bunker surveys, I realized that many of the tasks were things I had already been involved in as a 2nd Engineer.

Before Bunkering

• Verify Remaining On Board (ROB)
• Witness tank soundings
• Check vessel trim and list
• Review tank calibration tables

During Bunkering

• Monitor fuel transfer operations
• Witness sampling procedures
• Observe for irregularities

After Bunkering

• Conduct final soundings
• Verify temperatures and densities
• Calculate delivered quantities
• Review bunker delivery documentation
• Prepare survey reports

Looking back, I now realize that the person standing beside us taking notes throughout the operation was often the bunker surveyor.

Why Do Chief Engineers Argue Over a Few Tons?

One of the most memorable aspects of bunkering operations is the final quantity verification.

I have witnessed numerous discussions between Chief Engineers and bunker suppliers before the final Bunker Delivery Note was signed.

Sometimes the disagreement involved only a few tons.

To someone outside the industry, that may seem insignificant.

However, consider the following example:

• Delivered Quantity: 1,500 MT
• Fuel Price: USD 400 per MT

A discrepancy of just 10 MT equals:

USD 4,000

At fuel prices of USD 600–700 per ton, the financial impact becomes even greater.

This is why experienced Chief Engineers are often reluctant to sign documents without carefully reviewing every figure.

Once the paperwork is signed, the argument is usually over.

The Famous Cappuccino Effect

Perhaps the most famous cause of bunker quantity disputes is the so-called Cappuccino Effect.

Despite its harmless name, it can create significant disagreements.

The principle is simple.

Air becomes mixed with the fuel during transfer operations, creating foam inside the receiving tank.

As a result:

• Sounding levels appear higher
• Tank volume appears greater
• Actual fuel mass remains lower

In other words, the tank appears fuller than it really is.

Many engineers have experienced situations where the final sounding figures simply did not seem reasonable.

This is often where disputes begin.

During my time onboard LNG carriers, I saw several occasions where Chief Engineers requested additional settling time before accepting the final figures because foam was suspected inside the tanks.

If Mass Flow Meters Exist, Why Are Surveyors Still Needed?

This is one of the most common questions today.

Modern bunkering hubs such as Singapore increasingly rely on Mass Flow Meter (MFM) technology.

Unlike traditional sounding methods, MFMs directly measure fuel mass and are generally more accurate.

So does that eliminate the need for surveyors?

Not really.

Because a bunker surveyor does much more than verify quantity.

Surveyors may also verify:

• MFM certification status
• Calibration records
• Sampling procedures
• Documentation accuracy
• Operational observations during transfer

In other words:

An MFM is a measurement device.

A surveyor is an independent witness.

These are not the same thing.

Even in ports where MFMs are mandatory, surveyors continue to play an important role in protecting the interests of owners, charterers, and suppliers.

Is Hiring a Surveyor Worth the Cost?

Typical bunker survey fees vary depending on location and scope.

South Korea

USD 300–800

Singapore

USD 500–1,500

Emergency / Night Attendance

Additional charges usually apply.

At first glance, some owners may consider these costs unnecessary.

However, when a single bunkering operation can involve fuel worth several hundred thousand dollars, the survey fee becomes relatively small.

A survey costing a few hundred dollars can potentially prevent disputes involving thousands of dollars.

For many operators, that is a worthwhile investment.

Why Marine Engineers Have an Advantage in Bunker Surveys

Many bunker surveyors come from cargo, insurance, or marine claims backgrounds.

Marine engineers bring a different perspective.

We understand:

• Fuel transfer systems
• Settling tanks
• Service tanks
• Purifiers
• Flow meters
• Fuel consumption patterns

More importantly, we understand how fuel physically moves through a ship.

This practical knowledge often helps identify inconsistencies that may not be immediately obvious from paperwork alone.

For this reason, I believe marine engineers can transition naturally into bunker surveying and other technical survey disciplines.

Final Thoughts

Many people assume a Bunkering Survey is simply about measuring fuel.

In reality, it is about protecting evidence.

The surveyor’s role is not merely to calculate quantities but to provide an independent record of what actually occurred during the operation.

Having personally experienced numerous bunker quantity disputes as a 2nd Engineer, I now understand why bunker surveyors continue to be valuable, even in an era of advanced measurement technology.

Fuel quantities may differ by only a few tons.

But those few tons can easily represent thousands of dollars.

And that is why, long after the hoses are disconnected, discussions over bunker figures often continue around the Chief Engineer’s desk.