Wednesday March 2 2022
Radar technology was first used to measure liquid levels in large containers during the 1970s. Although it was successful, it was costly and therefore not widely adopted.
However, by the early 2000s, more advanced, higher frequency radar had been developed, and the technology had become cheaper, leading to a resurgence of interest in it as a silo measurement tool. This was largely driven by the construction industry due to the system being unaffected by dusty environments such as that created by cement.
Since then, radar silo measurement has been adopted by many industries due to its durability and reliability. It is effective for long-range measurements, up to 100 metres, with high accuracy, and can stand a temperate range from -40oC to 200oC, making it very versatile. In this article, we explore how it works and what it is used for.
There are two types of radar measuring equipment. These include:
Pulse generator – This utilises a pulsed radio wave with a set intensity which is transmitted from the radar device and travels through the air. When the signal reaches the material, it bounces off it, and the vibration returns to the sensor. The sensor calculates the time it took for the pulse to return and from that, calculates how much product is left in the silo.
Continuous pulse – This uses the same method of calculating the amount of product in the silo by timing how long it takes to receive the returning waves; however, instead of one pulse, the waves are sent continuously with different intensity levels.
Historically, there were advantages and disadvantages to each method; pulse radar was limited to the shape and size of vessel it could measure and continuous radar was criticised for its accuracy. However, technological progress has allowed both types of sensors to have the same capabilities, although continuous level sensors are becoming more popular as they are more accurate and are able to accommodate more complex vessels.
Radar works well for level measurements in silos due to the radar beam being narrow, and silos structures are generally tall and thin. This means that there will be minimal signal interference from hitting the side of the silo, preventing inaccurate results.
Radar devices are installed at the top of the silo and angled so that the beam is aimed at the point at which the material is dispensed. This is the most effective way to measure the level of the silo, although antenna size and transmission frequency may affect the angle and/or installation location.
The smaller antenna produces a broader beam, which is not ideal for large silos due to the potential for it to hit the sides of the silo bin and give a false reading. This is a particular risk when the silo is running low on product. Therefore, a larger antenna that produces a narrow, more accurate beam is preferred for large silos.
Sensors with a higher transmission frequency have a narrower beam angle, making installations easier and measurements more reliable. This can be paired with improved sensitivity technology for greater reliability and accuracy.
One thing to note, however, is if you change the material in your silo, you may need to adjust the sensor as not all materials react to radio waves in the same way. Some materials reflect them easily, whereas others absorb them, so a reconfiguration may be needed to ensure the sensor relays the correct information.
Radar can be effective in dusty environments such as silos containing cement powder, fly ash, water, coal, flour, grain, animal feed, plastic granules/pellets, wood powder, as dust does not affect the movement of radio waves to the extent it does other types of system, such as ultrasonic.
That said, in very dusty conditions, there is still a risk it could return an inaccurate reading.
One thing that doesn’t affect radar though, is any gases in the silo.
Radar systems are particularly popular in the food production industries as the non-contact method of level measurement causes no contamination to the ingredients.
Another advantage is that radar sensors have no moving parts which could get damaged by continual use and even fall into the silo, contaminating the product inside.
Radar sensors are also entirely compatible with remote silo monitoring systems such as MySilo, which enables operators to monitor the levels in their silos from anywhere with an internet connection.
As well as providing accurate insight into silo levels, MySilo also alerts users when inventory levels reach certain key points, ensuring you never run out of product.
One area where radar is not always the right solution in silos is with materials that produce heavy foam, as foam can absorb the radio waves. However, not all foam is created equal, so it may be worth taking advice on how much foam the contents of your silo will produce and if this will affect the accuracy of radar sensors.
Another disadvantage is the filling stream can intersect the beam, leading to false readings. To work around this, a change in location of the loading stream may be needed or the operator may need to stop and wait for the product to settle before taking a reading.
Usually, the minimum detection distance for radar technology is 0.3 meters which can cause a slight variation on initial readings until it is dispensed.
Conclusion
Having precise knowledge of the material levels in your silos at your fingers tips is crucial to effective, large-scale inventory management.
Radar sensors are an accurate, reliable way to achieve this, particularly if coupled with a remote monitoring system.
This not only enables you to streamline logistics for your business, it will help reduce on-site accidents, carbon emissions and will ensure you never run out of vital materials.
Over time, effective monitoring will provide a detailed picture of how much and often material is getting used, leading to more accurate future planning.
For advice on which sensors are right for your silos, or to find out more about our remote silo monitoring platform, MySilo, get in touch.
Want to learn more about the different types of sensors used to measure silo levels? See our complete guide How to Measure Silo Levels by Product Type which provides a great overview.
