Multiple Systems Working Together Prevent Tank Overfill Disasters

In Hydrocarbon Engineering’s Tanks & Terminals Supplement, Emerson’s Helena Hjortsberg looks at all the elements of a comprehensive overfill prevention system in her article, A Coordinated Strategy.

Overfilling a tank storing hydrocarbons or other flammable chemicals can cause an environmental incident under the best circumstances, but also a high probability of an explosion and fire. Given the costs in lost product, cleanup, equipment damage, and possibly human life connected with an incident, you’d think most facilities would have highly sophisticated overfill prevention systems.

 Many facilities do have excellent systems and operate safely, but at some locations, the efforts can be surprisingly haphazard. Building a comprehensive protection system with elements able to support each other is the topic of my article in Hydro carbon Engineering’s Tanks & Terminals Supplement for Summer  2020. As it turns out, a lot has to go wrong to cause a major product release.

The most common source of releases, outside of a pipe or valve failure, is overfilling, as was the case in the incidents mentioned above. Such incidents happen when operators do not have an accurate indication of a tank’s contents and end up forcing in more liquid than it can hold. This stems from ineffective level instrumentation, resulting in poor situational awareness for the operators: the tank they are trying to fill is already fuller than they realize. This should be stopped by an automatic safety system able to shut down a liquid transfer, or at least trigger an alarm to warn operators of the developing situation.

Any one of those mechanisms should stop an incident. And if fuel does start running onto the ground, there should be flammable vapor and gas detection systems to sound an alarm before the fuel finds an ignition source, or to start a fire suppression system in the worst case.

Arguably, the first line of defense should be effective level gauges, and the best approach these days is radar, such as Emerson’s Rosemount 5900S Radar Level Gauge, which delivers ±0.5 mm (0.020 in.) instrument accuracy, reducing level measurement uncertainty to a minimum. The Rosemount 5900S takes overfill safety to a higher level with an innovative 2-in-1 feature which includes two radar gauges in one housing for independent level and overfill measurement. It is SIL 2 and SIL 3 certified according to IEC 61508 and enables API 2350 compliant solutions.

This capability needs to be part of a coordinated strategy with all the other elements of sensors and systems necessary to support this critical safety function. The article goes into more depth on all sides, so give it a full read. It covers a lot of material.

So which category does your facility land in? Comprehensive and coordinated, or haphazard? A lot could be riding on the answer. Visit the Tank Gauging System pages at for more info. Rosemount Tank Gauging Systems ensure accurate level, temperature, and pressure measurements for inventory control, oil movement, and overfill prevention to secure efficient operations. You can connect and interact with other design teams in the Refining and Chemical groups at the Emerson Exchange 365 community.


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