The Monitor

Production Process Insights

Accurately Sample Marine Oil Sludge to Increase Revenue

Posted by Sentry Equipment on 6/10/15 10:00 AM


Sludges containing oil and water gradually build up on any relatively large ship as a byproduct of its operation of electrical generation machinery and the main propulsion engine. This oil sludge presents operators with issues of safe disposal in compliance with maritime environmental regulations.

Oil sludge legally can be disposed of by incineration in the vessel’s on-board incinerator or transferring it to a barge or shore-based disposal facility, which can be expensive for the ship. A more profitable solution is to sell the oil sludge for conversion into a saleable product allowed by some countries, such as China.

Vessels have two tanks for storage of waste: the oily bilge tank and the sludge tank. The bilge holding tank may have trace oil residue contents but is mechanically separated with a separate pump so the contents of the bilge holding tank are considered pure water for the purpose of calculating oil percentage.

Oil collected is based on the contents of the oily bilge tank and sludge tank. Oil sludge collectors pay for sludge, not water, and they require good quality ship sludge oil with less than 20 percent water. However, current methods of determining the oil-to-water ratio of oil sludge and the related payment have to this point been guesswork and subject to manipulation.

A quality automatic fixed volume sampler for liquid and slurry is a proven way to take a repeatable sample for analysis of oil-to-water ratio.

5 steps of marine sludge sampling

Step 1: Estimate the Amount of Sludge

The crew extends a measurement tube into the ship’s bunker oil tank to indicate the fullness level of the tank. Also called a joint sounding, this helps estimate the total quantity of sludge to be discharged and to determine the sampling rate.

Step 2: Take a Representative Sample 

An automatic sampler is mounted on the sludge discharge pipe to take a representative sample.

Step 3: Continue Sampling to Get a Composite Representative Sample 

Periodic samples are taken over the course of the sludge discharge to arrive at a composite representative sample of the entire sludge discharge. A serialized tamper seal is applied to the sample container in the presence of the crew.

Step 4: Lab Testing

The sample is sent to a laboratory approved by the ship owner, where the representative sample is homogenized and tested to determine the water content.

Step 5: Payment

Payment is then calculated based on total discharge quantity.


Maximize your profits with a reliable, repeatable sample – utilize these five steps to arrive at a fair and verifiable payment.

Download Marine Oil Sludge Case Study

Topics: Upstream & Midstream, Liquid & Slurry

Written by Sentry Equipment

With proven sampling expertise since 1924, Sentry products and services provide business operations the critical insights to optimize process control and product quality. We deliver true representative sampling and analysis techniques to customers around the globe, empowering them to accurately monitor and measure processes for improved production efficiency, output and safety. Standing behind our commitments, we are determined to tackle any application, anywhere.

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