Tank Level Inspections

Determining the liquid levels in a storage tank might seem obvious, one part is liquid, the rest is air or gas, right? Not so fast, measuring the contents of an enclosed tank isn’t always that straightforward, but it can be simplified with infrared thermal imaging.

For industries needing to comply with OSHA safety practices, this reading has become a critical need to get right. Other industries might utilize this type of reading to get a handle of how full the tank is, how much more volume they can add or need to maintain, or more simply, for record keeping purposes. Regardless of the need for the reading, one quick and reliable method that has emerged is infrared thermal imaging. Thermal imaging allows for locating, measuring and verifying the contents of a storage tank.

Prior to thermal imaging, an operator would have to physically enter the tank and use a stick or measuring device to gauge the levels manually, potentially putting themself at risk of physical injury or coming in contact with harmful elements. While most storage tanks have a level indicator for measuring purposes, operators and industrial engineers oftentimes have a need for a secondary reading to validate their storage tanks readings. Over the course of the last five decades, thermal imaging has proven to be a safe, faster way to get those results.

While there are many options available, a portable, hand-held thermal imaging device in the hands of a skilled technician can give you all the results you are looking for and more. While there are many models that produce various types of output, you need a device that detects infrared heat signatures in the Electromagnetic Spectrum.

Almost every substance found on Earth emits a temperature reading. Infrared thermal imaging uses those temperature readings, or more importantly the differences between those temperatures to accurately produce readings.

Let’s start with what we know about storage tanks. They are generally filled with a liquid or solid material, with the rest of the space filled with air or a gas substance. Consider a storage tank filled partially with liquid. The remaining area is filled with air or gasses. Gasses typically change temperature more quickly than liquids, creating two distinct heat readings. Let’s not forget about the area where gas and liquid meet; this area, the ‘sludge’ layer, produces yet another heat reading. Within one storage tank you will find multiple heat readings, as each element heats at different temperatures and speeds. Now add a heat source, like the sun heating the exterior on an outdoor storage tank, and you’ve got the perfect environment for an infrared thermal reading.

During the day, the tank will absorb the sun’s heat and the elements within start to heat as well. It is these temperature differentials that create very distinct infrared thermal readings. The temperature of the gasses will rise more quickly than the temperature of the liquid, with the sludge layer giving off a third temperature reading, somewhere in between. The liquid/sludge temperature differentials might be less obvious to decipher, as their contents could be close in mass to that of the liquid.

In good weather conditions, they produce a predictable heating pattern. The gas layer heats quicker than the liquid, producing a hotter temperature at the top of the tank than the liquid in the bottom of the tank. This heating component is key to infrared thermal imaging. Without the temperature differentials, it might be difficult to find a precise reading if there is a substantial sludge layer. Subsequently, dusk is also an ideal time for a thermal reading, as the temperature variation of the elements cooling will have different readings as well. The temperature differential is key in infrared thermal imaging. The area of the greatest temperature differential is your level line. The gas/liquid differential is apparent in the heat signatures.

The ease at which infrared readings are able to decipher storage tank levels, it’s no surprise that thermal imaging has become the preferred method. No longer are physical readings, manually entering the tank or coming in contact with the elements inside a necessity. Infrared thermal imaging is safe, fast and cost-efficient.