An Overview Of Fluid Level Measurements

With automated processing, stringent process control and regulatory compliance – process engineers need precise and reliable ways to measure fluid levels, bulk solids, and gases. Whether measured in storage tanks, silos or moveable containers, fluid levels that are accurately measured allow facility managers to ensure product quality, plant safety and efficiencies, while reducing waste.

Simple level measurement devices

In the past, most industries used a simple level measurement device, the sight glass level indicator. While this allowed a manual approach to measurement, sight glasses were eventually replaced by more advanced technologies – mainly due to safety issues from the use of hazardous materials and inaccurate readings from residual buildup which led to inefficiencies.
This resulted in the use of buoyancy or float measurement indicators. To measure fluid levels, engineers place a buoyant object between the process fluid and the headspace vapor, then attach a mechanical device to read out the buoyant item’s position. The float will sink to the bottom of the headspace vapour and float on top of the liquid.

While the float offers a simple solution to locating the surface of a liquid, reading the position (making the actual level measurement) was rather difficult. Early float level devices provided discrete level measurement through resistors and reed switches, which meant that the devices’ output changed in discrete steps. However, unlike continuous level-measuring devices, these devices cannot distinguish between level values on discrete steps, which was a significant limitation.

Nowadays, engineers can address this issue by installing float switches inside the storage container or tank. As the switch floats on the surface, its position can be detected by a sensor, which triggers the switch. This allows you to accurately pinpoint the level in liquids, in a much more reliable and cost-effective way.

Advanced measurement devices

With more advanced measurement technologies (e.g., ultrasonic, radar, capacitive and laser), one can measure levels in liquids and bulk solids with zero contact or maintenance, even under extreme process conditions. As advancements in digital technology become more accessible, these devices allow level measurement to be more user-friendly, reliable, and inexpensive.

However, most of the advanced level measurement solutions feature sophisticated digital encoding – which requires AI to format the codes. These measurement devices typically contain embedded microprocessor-based computers that allow such communication capabilities. Improved interfaces feed the measurement data obtained into the plant’s control and information system.

Modern level sensors also comprise a variety of materials and alloys to combat harsh substances such as chemicals, oils and acid and allow for variable or extreme temperature and pressure. Innovative materials help process instruments meet specialized requirements across almost every application, including corrosive applications and stringent cleanliness requirements.

The following article in this series, 3 highly accurate and reliable fluid level measurement devices, takes a closer look at more advanced devices to measure fluid level including ultrasonic measurement, guided radar, and capacitive sensors.

For more information on the fluid level measurement devices we stock and recommend, call our toll-free number 1-800-367-4180. We have experts on hand to help you choose, install, and maintain a variety of equipment. And to answer questions about things you’ve previously tried gone wrong.