Category: Sensors

How Gescaser allows you to measure the filling level of the silo at no additional cost

Silos de cereal
Silos de cereal

In order to know the stock level of a storage plant, it is essential to quantify the filling level of each silo. Depending on the type of raw material (cereals such as oat, sunflower, rice, wheat, soybeans, etc.), quality and level of grain, you will be able to find out the capital available in the form of inventory. 

In many cases, the filling level of the stored grain is estimated by visual inspection. Some technicians measure the volume of grain by climbing to the top of the silos and inspecting their interior. However, this method poses serious health and safety concerns, as well as being imprecise.

For this reason, there are much more precise – and safer – options such as automatic grain monitoring.

In this article we cover how our CTC+ software can help you know the filling level, keeping your money safe.

How do we quantify the filling level at Gescaser?

Gescaser’s monitoring system, in addition to controlling the temperature and humidity of the grain, also offers – at no additional cost – a very precise estimation of the filling level. This allows you to maintain inventory control, account for costs or to schedule production, among many other needs.

To quantify the filling level, Gescaser’s CTC+ software applies an algorithm capable of determining which sensors are covered by grain and which sensors are not. Furthermore, since the CTC+ knows the exact location of each sensor, the software is capable of indicating the filingl level of each silo.

With this information in mind, if a grain silo has a capacity of 5,000 m3 and it is currently at 40% of its capacity, you know exactly how much stock you have and, with this, how much money is being stored inside.

So how do we reduce the filling level calculation error?

The calculation error of our algorithm is:

Algorithm_error

With 11 sensors in the probe, we get an error of ± 5% of the total storage capacity of the silo.

So as a result of adding more sensors to the probe, the distance between sensors is reduced and so is the calculation error. An improvement that gives you very precise fill level information, without the need of large investments. And it results indeed much cheaper to add additional sensors to a probe than purchasing external devices to measure the fill level.

If you still decide to acquire an external system to measure the filling level with maximum precision, there are the following methods:

Single point measurement (1D):

Laser technology is used to automatically measure the volume level in silos and other storage tanks without any contact. It obtains the information by measuring the transit time of a light pulse between its emittance by the transmitter and its reflection and arrival. 

In agriculture, this system works well on many types of grains, such as corn or wheat. Also, since it is very narrow, the laser beam can be used in tight spaces and difficult applications.

Still, this type of single point metering systems present different errors depending on the location of the metering system and the shape of the grain during filling or emptying.

Calculation_error

Measurement with radar sensor (2D and 3D):

In a nutshell, the measuring with a radar sensor consists in mapping the entire surface of the silo. The distance travelled by the radar wave is determined by the difference in frequencies between the emitted wave and the one that bounces off the material to be measured.

It is a very precise and safe technology, with an error between ±1% and ±5% depending on the number of devices installed. However, the cost is much higher when comparing it with the other systems. In addition, for silos with large diameters, more devices will need to be added, since the beam angle will not cover the entire surface of the material with a single device.

Comparative table of the 3 filling measurement systems

Comparative table of the 3 filling measurement systems

So, if high precision is not necessary, you can obtain the desired information only with the temperature control system without any additional cost. 

For this, you must assess whether the investment when purchasing an external device (especially when there are multiple measurement points) is compensated by the possible operational gains.

Why should you attach the probes to the silo’s floor?

Sonda atada al suelo del silo
Sonda atada al suelo del silo

It is clear that the higher temperatures inside the silo, the greater chances of developing fungi, insects and, of course, lower quality of the grain. 

For this reason, proper monitoring of the temperature inside the silo is key to good control of the cereal, since it allows us to react quickly to any unforeseen event that may affect its quality.

In this sense, in order to guarantee the quality of the grain, it is necessary to use a temperature monitoring system such as the one offered by Gescaser.

In addition, the placement of the temperature probes is crucial. If the installation of the probes is not carried out correctly, it will be difficult to control the condition of the stored grain.

Why is it important to attach the probes to the silo’s floor?

To correctly measure the temperature of the silo, you must ensure that probes do not move. Why? 

If a probe is not attached to the ground, during filling, it can move to the side and end up touching the wall of the silo, affecting the temperature reading.

Let’s look at an example. 

The following image corresponds to an aerial view of a silo with the location of each probe:

Vista aérea de un silo

Next, we are going to analyse three graphs over two months of data belonging to probes nº4, 5 and 6. 

The graph in Image 1 shows the data from probe nº6. As we can see, at the beginning of August the silo was full because measurements from all probe sensors are stable, regardless of the ambient temperature (in black).

On the left side of Image 1, there is a vertical probe with the arrangement of the sensors inside the silo: the upper sensor is grey and the lower sensor is red.

Following the graph, we can see that, some time later, the temperature of the upper sensor (grey) varies in the same way as the ambient temperature. The measurements of the green and yellow sensors also change accordingly: the silo begins to empty.

Sonda S2 -6
Image 1: Probe nº6 (S2-6)

Analysing Image 2 (probe nº4) we find a similar behaviour to the previous one.

Imagen 2: Sonda S2-4
Image 2: Probe nº4 (S2-4)

Remember that, as a rule of thumb, a silo empties evenly. Therefore, taking into account the first two graphs, we could deduce that probe 5 would show a similar trend. However, this is not the case.

Imagen 3: Sonda S2-5
Image 3: Probe nº5 (S2-5)

According to Image 3 (probe nº5), all sensors are in line with the ambient temperature.

So, why aren’t the three graphs showing the same?  

This is where the clamping of the probes comes in. In fact, probe nº5 is not capturing the real temperature of the grain, but rather the outside temperature of the silo. 

When filling the silo, if the probe is not attached to the ground, the force of the grain inflow moves the probe towards the wall of the silo and this directly affects the actual reading of the grain temperature.

How to attach a probe to the silo’s floor?

We have seen the importance of holding the probes so that the cereal does not displace them. However, how are these probes attached to the silo’s floor?

To prevent the probes from moving at the time of filling, Gescaser supplies special clamping kits that do not damage the grain sweeping nor extraction systems.

Kit de sujeción

In summary, these kits are essential to allow obtaining real data of grain temperature. For this reason, always remember to attach the probes to the ground before filling. 

For more details on clamping systems, please contact our team.

What is the coverage area of a sensor?

Imagen de cereal dentro de un silo
Imagen de cereal dentro de un silo

In this article we’d like to contrast one of the great myths that exist around temperature sensors for stored cereal: their coverage area or radius of action.

In the world of manufacturers of temperature control system, one can frequently find brochures or reviews indicating that sensors cover or have a radius of action of about 2 or 3 meters approximately, with some indicating more and others a bit less.

But which of these statements is correct?

The answer is as simple as it is revealing: none.

Why?

The thermal conductivity of seeds and grains – their ability to transfer or spread heat – is very low, and their behaviour is very different from liquids or other materials such as metal. Therefore, it cannot be scientifically affirmed that there is a percentage of the silo covered by the sensors beyond the cereal or grain that is in direct contact with the sensor itself.

Any statement indicating that a percentage of the silo is covered by its sensors cannot be scientifically confirmed.

So how can the area of coverage in a silo be improved to help detecting a hotspot as soon as possible?

Without a doubt, introducing more sensors inside the silo.

Can one predict where a hotspot will occur? 

Unfortunately, it is not possible to predict where a hotspot will occur inside the silo or warehouse. It could occur near or far from a sensor. As a matter of fact, all sensors available commercially measure the temperature of the grain that is in direct contact with the sensor and cannot measure the grain temperature 3 meters away.

GESCASER sensors are not different from other sensors in this regard and, therefore, when monitoring the grain conditions, it is safe to assume that the temperature in the readings correspond to the temperature of the cereal that is in direct contact with the sensor.

When there is a hotspot somewhere in the silo, the heat is slowly transmitted to other cold areas. The time it takes from the hotspot until it is detected by the sensor depends on may factors (type of cereal, amount of cereal, impurities, degree of compaction, etc.) 

Indeed, the thermal conductivity of the grain is very low. To get a better understanding, the material with the best thermal conductivity is silver, with a coefficient of about 418 W/mK, while cereals such as corn, soybeans or sunflower seeds vary between 0.3 W/mK and 0.1W/mK depending on its humidity. With increased moisture levels, more conductivity (W/mK).

Comparative table of the thermal conductivity of some materials in W/mK
Comparative table of the thermal conductivity of some materials in W/mK

How many probes and sensors do I need?

At GESCASER, manufacturers of temperature control systems for silos with more than 40 years of experience, we provide recommendations with regards to the number of probes and sensors taking into account the type of silo or warehouse and its technical characteristics (diameter, height …).

Based on this information we determine the optimal number of probes and sensors (see graph).

Esquema de las sondas en función del diámetro del silo
Sondas de GESCASER
Our objective is to help finding the right balance between an absolute control of the silo temperature and the economic cost. It is no surprise that with more sensors, one can achieve greater control, but of course at an increased price.

At GESCASER we control the entire manufacturing process: from the receipt of raw materials, to the probe manufacturing, the shipment and the subsequent installation. Thus, probes and sensors can be totally customised to our customers’ needs. 

We hope this article helped resolving some doubts about the sensors and their radius of action. 

Don’t get confused!