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Specifications and Certificate of Quality (CoQ)

Updated: Jan 13, 2021

There is often common confusion between the quality of bunkers and products being ‘within spec’. In this blog, we share our knowledge and expertise to bring more clarity to these issues.

A spec sheet or product specification sheet is a detailed, concise document that clearly labels all of your products specifications.

This is the latest ISO 8217:2017 specs for VLSFO (see blow) is following, and the Sulfur content is max is 0.50% as of January 2020.

COQ is the Certificate of Quality – This is the actual test results on the product that will be delivered. Testing may include the tank sample that was stored, or a sample from the barge which will be used for delivery.

In short, spec is the sheet that tells you the product specification of the product being produced and CoQ is the specification of the actual product that’s being delivered.

Often the delivery is scheduled several days in the future, and at the moment of booking, a CoQ won’t be available. In this case, we obtain a Typical Spec which refers to an old CoQ from a past delivery. This is an approximation so you will have some idea of what the product actual figures will be.

One of the main reasons to obtain the typical specs, especially for VLSFO (Very low-sulfer fuel oil) is due to varied on viscosity. Proposed VLSFO specs have 3 clusters, and Viscosity varies between 30CST to 380CST. (article for reference)

Depending on which cluster suppliers pick to produce their product, we can see quite significant variation in viscosity from below 100 cst – to over 300cst. Viscosity is basically the thickness of the product, which will need a different lubricant for the engine to match that viscosity. Therefore, having a typical spec helps the engineers on board to plan their requirements.

How can sulfur of 0.53% still be compliant with the 0.50% sulfur limit?

When we talk about the product being “within spec” there is often confusion if a supplier has a tested result of 0.53% sulfur and this is seen to be “within spec”.

Due to the nature of bunkers and the variance in viscosity, this often prevents the ability to have unified results and the test results come back inconsistent. Typically, a 95% confidence level is used – this link explains more about the approach.

The technical calculation aside, there is often an acceptable range that means figures between 0.47% -0.53% are accepted within the specification of 0.50%.

A cargo fuel with an overall sulfur content of 0.50% limit can be expected to yield samples between 0.47% and 0.53%.

(Article reference)

How do we test samples? What happens if the tests are out of specification?

The samples are taken during delivery, using a continuous drip method. There will be a small hole collecting samples from different points of delivery, so it will become an averaged product within the tank.

The supplier will have already tested the sample (CoQ) and they will only supply to the customer if the test results are within specification.

Customers will test one bottle of the collected sample, and if they find any figures outside of specification, a retained sample will be retested. If the retest comes back within spec, the buyer will pay for the test, and if the tests are outside spec, the supplier will pay for the retest, and this can often proceed to a commercial settlement. These test results will be final and binding.

If you have any queries about the information contained within this blog or if you would like more information – please contact

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