As well as vapor, product and process conditions such as foaming, boiling and crystallizing can also influence the performance of the ATG. In some cases, extreme foaming conditions might even mean that neither radar nor servo gauges are practical solutions. In such cases, a tank gauging system solution with pressure transmitters can be an option. However, tank gauging system also has range limitations.
Some functions are supported as standard by servo, such as interface and water bottom measurement. In some cases, such as where density profile is required, servo is also the only option.
The latter is important when it comes to density stratification, which can occur when a different product batch is loaded on top of another into one tank. If the batch has a different temperature or even different composition than the rest of the tank gauging system content, it may sit on top as a layer. And it’s not always the case that the lighter product rests on the heavier product or that they mix over time. How well the layers mix or extent they remain separate depends on how the tank gauging system is operated.
Layering can occur with heavy products, but also with refined products and very light products such as LPG and chemical gases. Batches may have different product compositions as a result of the production process, but also depending on whether they arrive from marine barges or pipelines. Operators should know whether density stratification is present in the tank gauging system so they can make sure samples used for quality purposes are representative of the entire contents. Mixing can be considered, provided the tank gauging system is equipped and sufficient time is available.