Detecting coal self-combustion hazards

Overslag Bedrijf Amsterdam (OBA) is a dry bulk terminal company operating in the Amsterdam, Rotterdam, Antwerp (ARA) region. It operates from two terminals in the port of Amsterdam, transferring and loading several commodities including coal, agricultural bulk goods, minerals and biomass goods. Due to excellent rail and waterway connections via the North Sea and the Dutch hinterland, OBA offers multiple modes of shipping that include seagoing vessels, push barges, trains and trucks.

The storage and handling of coal is approximately 80% of OBA’s business, consisting of round-the-clock shipments to Germany, the Northeast of France, the UK and the Netherlands.

When coal is exposed to oxygen, its temperature rises and can ignite suddenly. It’s no wonder that spontaneous combustion is a real worry around OBA’s stockyards. Being such an extremely valuable product, it needs to be protected under a watchful eye 24/7.

For some coal types, it’s not a question of whether or not it will happen, it’s a matter of when it will happen. “Self-combustion of coal is something we have to take into account every day,” says Dick Meijer, planner at OBA. “To prevent it from happening, we need to take the appropriate measures. More specifically, we send out an excavator or wheel loader to dig out and spread the suspected area. And we have dedicated combustion fighting equipment that allows us to compact the area and to release the oxygen out of the coal stack.”

Needless to say for OBA, reaction time is of utmost importance. Not only will coal combustion amount to high expenses resulting from energy and quantity loss, it also can have safety and environmental implications.

“In order to minimise those costs as much as possible, we were looking for a way to monitor the temperature of our coal stock before it’s loaded onto the barges,” comments Dick Meijer. “Thermal imaging turned out to be the perfect technology to do that. We already conduct weekly inspections via an external agency, but in 2013, we also invested in our own thermal imaging cameras from FLIR Systems to be sure that all the coal leaving our site has a temperature that is safe to be transported.

When the coal is on the conveyor, thermal imaging cameras show the temperature of the entire coal mass, not just of the coal surface.

The big advantage of thermal imaging compared to other technologies is that thermal imaging cameras can monitor entire areas of the coal stack. When the coal is on the conveyor belt, thermal imaging cameras allow us to read the entire coal mass temperature, not just the coal surface. Thanks to thermal imaging cameras, we can see if something goes wrong and immediately take the appropriate measures.”

Certain European countries impose additional requirements for the transportation of coal. In a multilateral agreement between various EU countries, it is mandatory that the temperature of a coal load - before, during and directly after the loading process - be below 60°C. “Therefore, every load of coal that leaves this terminal to Germany needs to be backed with a valid temperature monitoring certificate. With Germany as an important market for OBA, thermal imaging allows us to meet these requirements more easily,” says Meijer. The company used to engage external measurement professionals for this function, which resulted in additional costs for the end customer. Now they do the measurement themselves, periodically as well as continuously 24/7, and can now provide customers with a valid certificate as an extra service.

The OBA terminal is now equipped with three rugged FLIR A310f cameras. Each camera is positioned on a tower with a wide view overlooking several conveyor belts that deliver the coal to barges. This way, OBA can detect coals with high temperatures. By positioning the thermal imaging cameras as close to the barges as possible, OBA can visualise the entire conveyor belt stretch (up to 900 metres) and monitor the coal temperatures up to the last second before loading, which helps prevent the risk of a combustion incident onboard.

The thermal video images are sent over a network to a central control room where they are continuously monitored. Operators make use of a proprietary software system that offers intuitive colour codes to communicate about the real-time status of the coal loads. Code green means the coals are below a dangerous temperature and there is no danger for self-combustion. Yellow means the temperature is rising. In practice, this usually means temperatures are between 40 and 50°C. When that occurs, OBA takes preventive measures, such as digging out and spreading the coal. Code red means that temperatures are above 55°C, prompting an alert that forces the conveyor to stop, preventing coals with excessive temperatures from being loaded.

For this situation, OBA selected the FLIR A310f, a highly sensitive, high-speed camera in an environmental housing. The housing increases the camera’s environmental specification to IP66, without affecting any of the camera features. “After thorough consultation and testing with FLIR distributor Rato, we decided to choose the FLIR A310f, because it gave us very accurate and consistent results,” says Meijer. For example, snow falling on the coal stack can generate steam. A thermal imaging camera is able to provide reliable temperature measurements regardless of this phenomenon.”

For inspections OBA combines the use of a temperature probe and a FLIR E6 handheld thermal imaging camera.

Along with monitoring coal on the conveyor belt before it’s loaded onto barges, large piles are inspected at least once per week. For this application, OBA combines the use of a temperature probe - the traditional way of measuring temperatures - and a FLIR E6 handheld thermal imaging camera. The big difference between both technologies is that a probe will measure pinpoint temperature, while the E6 and A310f infrared cameras show temperature patterns and provide measurements for a larger area.

Meijer explains that the FLIR E6 is an intuitive, valuable tool for operators to have at their side to quickly spot where something has gone wrong. “When we receive a code yellow in the control room, we use the E6 to go up there and see with our own eyes what is going on. The camera is very robust and very easy to handle, even with gloves on.” To put it simply, thermal imagers are a powerful solution to help keep resources and lives safe.