If you keep up with workplace technological advancements, you’ve undoubtedly heard of the Internet of Things (IoT). It’s time to get involved in the game because the Internet of Things is changing it fundamentally.
But how even do you start? One example is the monitoring of tank levels.
Whether tracking frack tank levels for a well stimulation project or keeping an eye on a simple water tank, tank level monitoring (TLM) is a great way to get started with the Internet of Things. Like any IoT project, the goal of tank level monitoring is to collect reliable and accurate data so that you can act and see results. If your data is incomplete, erroneous, or delayed, people won’t trust your tank monitoring system, and you won’t get the intended business results.
Any remote tank monitoring system’s “bedrock” is its tank level sensor. Since your sensors generate the data that ultimately aids in decision-making, they are the first point of contact on the data route for tank level monitoring. If your tank level sensors are not receiving accurate data, then nothing else matters. Poor quality tank sensors cannot be made up for by the best analytics or the most visually appealing dashboards.
As they say, “garbage in, garbage out.”
Given the importance of tank level sensors to your entire tank monitoring system, we wanted to talk about how to choose the best one for your project. With a little assistance, you can buy reliable and accurate tank sensors that produce top-notch field data without having to spend a fortune.
Five Common Types of Tank Level Sensors
There are five types of tank level sensors:
Pressure sensors for water
Ultrasonic sensors
Thermal sensors
Deployment sensors
Capacitive sensors
We’ll list the key advantages and disadvantages of each tank level sensor to help you make an informed choice for your tank level monitoring project. Your application will dictate which tank level sensor is best.
Hydrostatic Tank Level Sensors
Hydrostatic tank level sensors are a tried-and-true way to get accurate, reasonably priced tank level data. The hydrostatic pressure of the fluid column is measured by these sensors. Hydrostatics are usually installed on discharge piping at tank bottoms and submerged in the liquid there.
Because hydrostatic tank level sensors are reasonably priced, precise, energy-efficient, and have adjustable ranges, they can be installed in a variety of tank types without the need to create a new sensor.
Regretfully, hydrostatic sensors can suffer from higher failure rates because they are often completely submerged in liquid. This can be very challenging, particularly when dealing with caustic or corrosive solutions. One of the most common places for hydrostatic sensor failure is the cable gland, where fluids can get in and short circuit the sensitive electronics that power the sensor.
Ultrasonic Tank Level Sensors
As their name implies, ultrasonic tank level sensors use sound waves to determine the liquid level. They are mounted atop your tanks, “bounce” off the liquid surfaces using ultrasonic waves, and measure the level by timing the duration of the “echo.”
One of the main benefits of ultrasonic sensors is that they are non-contact, which means they don’t come into direct contact with the liquid in the tank. Less consideration is given to compatibility with fluids, and they can work well in liquid-containing tanks that have mixers or other moving mechanical parts (keep in mind that accurate level readings require turned-off mixers because turbulence and sloshing interfere with ultrasonic sensors).
These sensors are also reasonably priced, with prices between $300 and $400 per sensor. However, you should budget closer to $1,000 if you want certifications for hazardous areas or better performance.
One of the main disadvantages of ultrasonic sensors is how much electricity they consume. Their power requirements can be up to 100 times higher than those of hydrostatic sensors, which makes them unsuitable for battery-operated installations.
Additionally, ultrasonic sensors usually need more maintenance than other types of sensors. They need to be installed precisely, have a dead band, or “blanking zone,” maintained between the fluid and the sensor, and have the detecting device cleaned on a regular basis (some fluids can create a film that affects performance)
Not to mention, noise interference poses a serious risk to ultrasonic sensors. If there is foam or vapor present, the ultrasonic waves that travel to and from your sensors may encounter issues.
radar-based tank level sensors
Radar sensors are similar to ultrasonic sensors in that they measure tank levels based on the time it takes for radio waves to pass between the sensors and fluid surfaces. Operators find radar sensors appealing because, like ultrasonic sensors, they are non-contact. But thanks to more precise electronics, radar sensors are more accurate and more resilient to interference than their sound-based predecessors.
Generally speaking, radar sensors are significantly more costly than the other two devices we’ve covered so far. The total cost of a good radar tank level sensor should be more than $2,000. Despite the more accurate electronics, radar still needs a sizable blanking zone between the top of the tank and the bottom of the sensor. Because light waves travel so much faster than sound, it can be difficult to take accurate measurements as tanks fill.
The capacity of radar sensors to measure fluid interfaces, such as the presence of oil in water, is one of their advantages. More advanced electronics can account for even a small amount of emulsion between the interface and still maintain accurate measurements.
Level Sensors for Float Tanks
Float sensors use a probe to reach into the liquids close to the bottom of your tank. Floats activate continuous detecting elements along the probe. With this method, it is possible to achieve incredibly accurate float tank sensors. Because they don’t have interference or noise problems, they can even monitor fluid interfaces by using multiple floats for different liquid densities.
However, the cost of float sensors can be extremely high. Tank height and float sensor prices almost immediately correlate inversely. Price ranges for shorter tanks (those under five feet tall) could be $1,000–2,000. Larger tanks, however, that are longer than 25 feet, can cost as much as $3,000.
One issue with float tank sensors is “sticking.” Even though this problem has been partially resolved by manufacturers’ recent technological advancements, it may still occur in specific situations. For example, in liquids that produce sticky or waxy substances, floats may stick to the probes and cause inaccurate static level readings. Making regular cleanings or investing in non-stick oleophobic probes can help ensure the accuracy of float sensors.
Capacitive Tank Level Sensors
We’ll talk about capacitive sensors as our final category. The two electrodes in these sensors are conductive probes that stick into your tank. To measure the amount of fluid present, these probes measure changes in capacitance as the fluid level in the tank rises and falls.
One of the key features that makes capacitive tank level sensors so appealing is their versatility. They can be used on a range of media, such as non-liquid solids and powders. They are also reasonably priced. In terms of cost relative to the other sensors we’ve covered, capacitive sensors lie in between hydrostatic and radar/float sensors.
Before making a purchase, it is important to understand the sensitivity and susceptibility of capacitive sensors. Readings from capacitive level sensors can be affected by fluid type, temperature, and humidity. Another layer of operational complexity is added by capacitive sensors, which necessitate that operators calibrate equipment while tanks are both full and empty.
