SE536675C2 - System and method for level measurement and quality monitoring in storage space, and calculate storage time / shelf life by measuring temperature and relative humidity - Google Patents

Description

536 675 Shelf life means the possible storage time in the current conditions, in terms of temperature and humidity. High temperature in a batch of, for example, some form of grain gives a limited storage time / shelf life, the same applies to high water content in the product, or a high relative humidity in the warehouse. A combination of high temperature and high water content in the product or high relative humidity measured inside the product or in the air in the Storage Room can mean a storage time / shelf life limited to a few days.

When humidity is mentioned in this application, it is the relative humidity referred to, unless otherwise specifically stated.

Description General part. state of the art and the problem: To detect and register the level in a stock of, for example, grain in real time.

Today, grain is stored in ever larger silo facilities, it is not uncommon today with a steel silo that has diameters of, for example, 20 m.

With increasing size, the value of the silo's content also increases. In the larger silos, for example 20 meters in diameter, each meter in the level represents a difference of 300 cubic meters, ie for example 240 tonnes of wheat.

Due to the construction of the entire silo, it is not possible to see into the silo. There are no level glasses, windows or other openings.

The manhole cover on the roof can of course be opened, but the road there is often a primitive ladder.

If you go up to the manhole, you look into a dark silo, with no reference points to go on. Without reference points, it is very difficult to determine whether the surface of the grain is 10 or 15 meters down. If reference points existed, there is still the problem of seeing these, if lighting is installed inside, these must meet ATEX requirements, due to the risk of dust explosion. 536 675 There are several devices on the market for measuring the level inside the silo. But everyone has their limitations, such as; Measurements with Ultra sound sensor mounted over the grain, this is disturbed by dust swirling in the air, and the measurement is inaccurate at longer distances.

Flats / sonar principle has been used for these measurements, but the dust that swirls around inside the silo disturbs and complicates the measurement again, and the measurement is inaccurate at longer distances.

Mechanical sensing with a weight that is lowered to the grain, the load on the vertical line is registered and when the weight lands on the grain, this is registered. Popularly called yo-yo, problems can arise if measurement is done at the same time as refilling. With many moving parts, the equipment is subject to wear.

Capacitive sensors mounted at different heights, require that many sensors be mounted to achieve a sensible accuracy of the measurement. The Capacitive sensors are mostly used as limit positions, to signal whether a max or min level is exceeded. These sensors can also be difficult to adjust.

Cereal is a product that causes other problems at level measurement, than for example oil.

The surface of the oil, for example, is flat and horizontal, during the entire storage period.

Cereals, on the other hand, when filled, or filled in a silo, have a pointed cone inside the silo, and the grain level is lowest out at the silo wall.

But as soon as you have lost grain, an inverted cone is formed inside the silo, now the level is suddenly the highest level out at the silo wall. See Fig. 1 for a schematic view of a cut-through storage silo, where draining was the latest activity.

If you know which activity was the last - filling or bottling - you also know a little more about what the surface looks like inside the grain silo.

In today's larger silos, the temperature is closely monitored with temperature measuring lines to detect any temperature increases. As is well known, all biological activity in the product / grain means an elevated temperature. A rise in temperature thus indicates an ongoing undesirable biological activity. Good to know, but a better foresight is desirable. 536 675 It should also be remembered that food easily molds in the refrigerator, mold growth is possible even close to 0 degrees Celsius, as long as nutrition and moisture / water are available.

Normally, these temperature measuring lines can also give a certain idea of the storage height of the grain mass in the silo. This is due to the fact that the temperature in the cereals and the temperature in the air above the product inside the silo, rarely have the same temperature.

But both spring and autumn come a period when the temperature of the air inside the silo and the grain can be the same.

The shelf life / storage time of, for example, the grain is simplified greatly depending on the following factors, the temperature and water content of the grain, and the availability of water / moisture from ambient or supplied air or condensation from roofs and walls.

Normally, the water content, for example in cereals, is carefully checked during storage, and these parameters are noted. If the temperature and moisture content are low, the durability is long, if both the temperature and moisture content are high, the durability is short. It is important to know these initial parameters, they form the basis for a calculation of the possible storage time, but these parameters can change during storage.

So-called humidification means that the water content in, for example, cereals rises during storage, this occurs, for example, during storage over a longer period, for example storage from late summer / autumn to the following summer.

Examples of long-term storage are intervention stocks, formerly called emergency stocks.

Today, only the temperature of the product during the storage period is measured, no measurements of the water content of the product, for example the cereals, nor any measurements of the humidity, neither relative humidity nor otherwise, are normally made, other than any manual "sampling".

The result is that you do not receive warning signals until the temperature rises in the product and the temperature measuring lines indicate that an unwanted biological activity has already started. 536 675 A known problem in steel silos is that condensation can form inside the roof, and drip onto the product in the silo. This occurs when the relative moisture content of the air is high enough, at the same time as the temperature of the roofing sheet is low enough, below the dew point of the air. The exact values when this occurs can be found in tables.

A surface layer of condensation, which is damaged by dripping condensation moisture, can mean that the batch as a whole receives a lower quality classification, and becomes unusable as human food or animal feed. Mold spores are very harmful to health, and the product present in the surface layer of the silo will be pulled down in the middle when emptied and mixed throughout the mass.

To counteract this, ventilation fans can be started when the above-mentioned conditions are such that condensation can occur, and ventilate the space above the grain, but unfortunately today the necessary information is missing to know when you need to start the ventilation fans.

In order to be able to place an order for a new product in, for example, a feed silo at the right time, it is required that you can continuously monitor the level reduction day by day. The requirements for "Just in time" are increasing in virtually all industries.

Special part, description of the ugg invention: Compilation of drawing base: DRAWING The drawings show a possible embodiment of the invention, in a schematic way.

Fig. 1. Cross-cut silo with two measuring lines, measuring points marked with points on the lines. The silo appears a little more than half full, with grain, for example.

A = measuring line B = measuring points on measuring line C = the product, for example grain D = ventilation opening under the eaves E = the air over the product 536 675 Fig. 2. measuring point on measuring line, the sensors can change places, or be combined in a sensor.

F = sensor for measuring relative humidity G = sensor for measuring temperature The object of the invention is to solve the above-mentioned problems.

This is achieved by providing the above-mentioned temperature measuring lines with an additional function which also measures the relative humidity. And that the monitoring in the warehouse may be supplemented with a temperature sensor on the roof / roof plate.

The solution can be achieved by using a sensor that in addition to measuring the temperature, also measures the relative humidity. Or by using two sensors. One to measure temperature and the other to measure relative humidity. It can be stated here that all measurements of relative humidity also require a measurement of the temperature, but we need a separate and clean temperature signal.

The temperature and the relative humidity can thus be measured with a combined sensor or with two basically separate sensors mounted together or close to each other. See schematic sketch in Fig. 2, which shows two sensors (F and G) one for temperature measurement and the other for relative humidity.

For level measurement, temperature values and humidity values are treated separately, this gives the operator or computer program two parallel level values which can be compared and one level value verifies, so to speak, the other.

A level in the warehouse is thus produced based on the temperature measurement and a level based on the humidity measurement, these are combined into one level, thus ensuring that the reliability increases markedly.

For durability measurement, both measurement values from each measurement point are combined, ie the temperature and humidity at each measurement point are jointly analyzed and 536 675 compared with other measurement points in the same storage space, the most critical measurement point is presented in the system as a guide for calculating storage time.

The temperature in the grain mass is normally even, with slow changes due to the inertia of the mass - this is in contrast to the temperature in the air above the grain which varies with the outdoor temperature in a daily cycle.

The relative humidity measured below the grain is normally even with slow changes due to the inertia of the mass, but in the air above the grain the humidity varies in circadian cycles - as does the temperature.

This means that you get the variations of the day both when you measure the relative humidity in the air, as well as in the temperature measurement. collected measured values can be evaluated / processed manually by the operator, or with the help of a program in a computer.

Data from these measurements are sent to a computer with a suitable program, for evaluation of the measurement curves and registration for history / log, when evaluating, measurement data is compared between sensors on the entire line, over the day some sensors will show typical diurnal variations.

In addition to these cyclic diurnal variations displayed by certain sensors, certain values measured by temperature and relative humidity can also be identified as typical or safe grain values or as air values.

Typical temperature measurement today is to hang a measuring line in the middle (or near the middle) in a smaller silo - say up to a diameter of 6 - 8 meters. Larger silos then get more ropes. Although a large storage silo is equipped with 12 temperature measuring lines, not everyone needs the extra function to measure the relative humidity, and thus calculate the level and / or the shelf life of the product, one or two are normally sufficient. Fig. 1 shows a schematic storage silo with two measuring lines mounted / hanging in the roof construction. 536 675 The measuring line, or the measuring lines, which are to measure both temperature and relative humidity can be mounted at a distance of 1/3 of the radius of the silo from the wall, thereby achieving the most accurate measurement result for level measurement - regardless of whether the most recent activity was a refill or an emptying.

This invention adds another parameter, namely the relative humidity / water content, and the probability of both temperature and water content must be equal for the cereals and for the air inside the silo is very small.

We therefore look for the sensors on the measuring line that have variations of the day, the sensors that have these regular variations can with great certainty be assumed to be in the air, or the sensors whose values indicate that they are in the air, for example by measuring a clear lower temperature, for example at 7 - 8 degrees, when we know, for example, that the product is around 12 degrees.

The level of the product in the cereals is below this level.

We also look for the sensors that do not have the variations of the day, those that are in the cereals / product, or the sensors whose actual values indicate that they are in the cereals.

The level of the product / grain is above this level.

If we start looking from below, a number of sensors will show equivalent results, indicating that these sensors are in the product. Somewhere along the measuring line, temperatures and relative humidity will begin to vary more - indicating that they are in the air above the product.

For even if the temperature in the air above the cereals and the temperature in the cereals can coincide at certain times of the year, and if the daily variations would be minimal at the same time, the probability is very small that the humidity will be the same in both media.

However, being able to determine the level in the silo is not the only reason to measure the humidity in the bottom of the stored product. The relative humidity in the air down in the stored product has a relationship to the water content in the product - which can thus also be measured 536 675. During storage, the temperature outside the silo will vary, one side of the silo will face south and be heated more by the sun, than the north side.

This phenomenon combined with the fact that almost all newer silos today are sheet metal silos with the wall consisting of a simple sheet metal, gives an impact on the product inside the silo.

A steel silo does not really offer any insulation against climate change, when the sheet metal wall is heated by the sun, the temperature in the stored product closest to the wall will start to rise.

With changing seasons and changing weather, temperature differences will occur inside the grain mass, and also in the air over the grain.

Temperature differences give air currents, and the air that flows in the product / grain gives a slowly varying water content seen along a time axis during the storage time. Even if this is slow, there is reason to monitor the process.

Circulating air inside the grain mass and circulating air in a silo can transport water at all and thus moisturize the previously dried grain.

The relative humidity will also vary in the air over the grain.

Normally, the relative air humidity is highest in summer, and lowest in winter.

The air circulation in the warehouse will increase when the temperature differences increase, for example in the spring when the sun begins to heat the south side of the silo.

Some silos for storing, for example, grain have cooling fans / aeration fans mounted, so that you can blow air through the stored mass. You normally blow air from below and up through the mass.

According to an article by Gunnar Lundin at JTI, 2008, entitled: "Aeration reduces mold growth in cereals", aeration inhibits mold growth.

In an article by Nils Jonsson, Hans Pettersson, Johan Schnürer, also at JTI, 2008, title: "Risk of poisoning when storing grain", it appears that the time grain can be stored 536 675 without mold formation can be doubled either by storing the grain with 1 - 3% lower water content, or in 5 degrees lower temperature.

In other words, a humidification of 1 - 3% can halve the appropriate storage time.

When aerating and cooling the grain, measured values from measuring lines are valuable information on whether the aeration has been sufficient and effective in the whole mass or only in parts of the stored mass.

Without measuring possibilities, the fans may run longer than necessary, despite the fact that the grain mass as a whole is cooled / aerated, which leads to excessive energy consumption.

Without measuring possibilities, there is also a danger that the economically minded operator will switch off the fans too soon, before the entire grain mass has been aerated.

Moisture / water from the part of the product that is aerated can then collect in a moisture front, for example halfway up the product.

The only possibility to detect a moisture front / a wetter subset in the product / mass early, are measurements of the relative humidity inside the product / grain.

The reaction of the temperature sensors only comes when a biological activity is started, and then you have lost some time, and maybe also quality.

But with continuous measurements of temperature and relative humidity, cooling, aeration fans can run the time it takes to process the entire amount of grain, neither more nor less.

With a division / a distance / between the sensors (sensors refer to measuring sensors for both temperature and relative humidity) of, for example, 2 meters, a corresponding resolution of the measurement is obtained.

It is also possible to hang two or more measuring lines so that the sensors end up at different heights above the floor, ie mutually offset in height. This is to increase the resolution / accuracy of the measurement. By using a different division between the sensors, other Resolutions can be achieved, as desired.

By mounting more than one line in the storage silo, the accuracy of the measurement can be further increased. not least depending on the grain angle of the grain, regardless of whether filling or bottling is in progress, the surface of the grain will be sloping towards the middle, sometimes the surface is convex and sometimes concave. A changing lunar landscape.

Two measuring lines, mutually at different distances from the outer wall, can reveal whether the surface of the grain is convex or concave inside the silo. Information that can be evaluated manually by the operator, or using the appropriate software on a computer.

The computer can calculate the storage level / storage height, as well as the volume of the stored item.

Based on the volume, the number of tonnes can then be calculated if you have the specific weight.

With the exception of gas-tight storage, a silo is not built to be completely filled, you want a ventilated space above the grain. On a steel silo, for example, there is normally an opening all the way around under the roof overhang, this opening is there to ventilate the space above the product. For a schematic view of the ventilation opening under the eaves of a storage silo, see Fig. 1 (D).

During normal storage and operation, there will be at least one sensor in the air above the grain. This measuring point reports the humidity in the air and the temperature in the air to the system, this information is important to be able to avoid condensation forming inside the roof.

When supplementing measuring lines with humidity measurement according to this invention, the dew point of the air can be easily calculated, and with a temperature sensor that measures the temperature of the ceiling / roof plate, the danger of condensation can be calculated manually with a table or in a computer program. The above-mentioned temperature sensor can also be mounted so that it measures the temperature on the cylindrical wall of the silo, high up. You probably then choose the north side to measure on the coldest side.

This information means an opportunity to, if necessary, start the ventilation fans, and ventilate the space at the top of the silo, to avoid condensation forming inside the roof / roof plate, or the silo wall. If you take in cold outdoor air, or cooled air, it is as cold as the roofing sheet and no water is condensed on the sheet. With the device and method according to this invention, the danger of condensation inside the roof can be detected early.

With the help of a suitable program in the computer, ventilation / fans can be started automatically, so that condensation can be avoided even if the system is unmanned.

The temperature sensor for the roof plate is suitably mounted by means of a well-dimensioned magnet, or glue, rivet or screw. One can also imagine a temperature sensor mounted on / or built into one of the elements / sheet metal sections, ie mounted from the silo manufacturer.

High temperature, as well as high relative humidity, each gives shorter storage time for, for example, a batch of grain, a combination of these two parameters gives significantly shorter storage time.

Maximum suitable storage time can be calculated according to experience and / or practice and / or tables / schedules.

Having access to measurements of both temperature and relative humidity also makes it possible to warn in time of mold risk, and other similar biological hazards, when the humidity and / or temperature is high.

If a biological attack starts at a place in a warehouse, it spreads quickly if conditions such as temperature and access to water / moisture exist. The water can be present in the product being stored, or in the air mass in and / or over the product.

With this invention, in addition to the temperature, the humidity can also be monitored at a number of places in the stored mass / the stored product, for example cereals.

Both current temperature and relative humidity inside the product are measured and registered, these values can be presented on a computer screen and manually converted to a maximum storage time.

It is also possible to directly recalculate these parameters with a suitable computer program to a maximum suitable storage time / shelf life.

Of course, one should take into account the future use of the product, and include an appropriate safety margin, meaning that, for example, future foods have greater safety margins than, for example, cereals that are to be used for heating.

Short shelf life of the product is equal to short shelf life. With more storage space in operation at a plant, it is important to know where you have the shortest shelf life. This 12,536,675 must of course be sold the fastest. If the product is to be stored for a longer period of time than the current shelf life allows, you can, for example, run the product through the grain dryer, before continuing storage. Even if only a part of the product in a silo has too high a humidity and / or temperature, a drying of the entire batch may be necessary, all in order to maintain the quality of the product / batch.

The equipment described here can also flag / signal that one or more levels in the warehouse have been passed, this can give a reason for an operator to act, or with a computer automatically perform, for example, an order for a new delivery. 13

Claims (1)

536 675 Claim 1: Claim 1 System for determining the level of a stored product in a warehouse, characterized in that sensors, for measuring both temperature and relative humidity, are arranged on at least one measuring line, which measuring line hangs down in the stored product. from a roof structure, wall or the like arranged above the product, that the sensors are mounted at a suitable mutual distance from each other on the measuring line, that measurement data from the sensors are processed manually or by means of a program in a computer and that the level of stored goods is determined by to identify the sensors whose measured values, regarding both temperature and relative humidity, vary or do not vary with the day. Claim 2 System according to claim 1, characterized in that measurement data from the sensors are processed in a computer program, that the measurement values are registered / logged in a history / log and that the determined level of stored goods, for example cereals, is presented on a screen. Claim 3 System for measuring the level in a warehouse according to one of the preceding claims, characterized in that the durability of the stored product can also be assessed, by manually or with a computer program analyzing and matching temperature and humidity measurements from each measuring point, which gives a comparative value for the supply on both heat and humidity at each measuring point, as well as the combination of these measured values, and by comparing these values from all measuring points in the storage space, the most unfavorable measured values / measuring point in the product can be identified and form the basis for calculating the maximum suitable storage time / shelf life. for the party as a whole. 14 536 675 Claim 4 System for measuring the level, and also the durability of the stored product in a warehouse, according to claim 3, characterized in that both temperature and relative humidity are measured continuously, with vertical measuring lines in the storage space, for example mounted along the inner wall, or hanging from the roof or roof structure and down into the product, these sensors continuously record temperature and relative humidity, the measured values are logged in, and presented with, a computer and measured measured values for temperature and relative humidity are monitored separately and processed in combination to find the most exposed / critical measuring points in the lot, as well as the most exposed / critical measuring point, so that a value for sustainability for the lot can be obtained. Claim 5 System for registering the storage level in a storage space, according to one of the preceding claims, characterized in that condensation can also be foreseen on the ceiling. A temperature sensor mounted on the ceiling / roof plate measures the temperature of the ceiling or plate, this temperature is compared with measured values from the measuring line concerning the relative humidity in the air under the roof, and the equipment can warn of the risk of condensation forming on the inside of the roof plate. Measurement values can be processed manually or with a suitable computer program. The system includes a device for warning the operator or for automatically starting a ventilation and cooling device that takes in outdoor air or cooled air into the space. By selecting appropriate margins when processing measured values, the device can warn before a condensation has occurred. Claim 6 A preamble for determining the level of a stored product in a warehouse, characterized in that sensors, for measuring both temperature and relative humidity, are arranged on at least one measuring line, which measuring line hangs down in the stored product from a roof construction arranged above the product , wall or the like, that the sensors are mounted at a suitable mutual distance from each other on the measuring line, that measurement data from the sensors are processed manually or by means of a program in a computer and that the level of stored goods is determined by identifying the sensors whose measured values, regarding both temperature and relative humidity, vary or do not vary with the day. Claim 7 Method according to claim 6, characterized in that measurement data from the sensors are processed in a computer program, that the measurement values are registered / logged in a history / log and that determined level of stored goods, for example grain, is presented on a screen. Claim 8 Method according to claims 6 and 7, for measuring the level in a warehouse, characterized in that the possible storage time of the product can also be calculated, by means of measurements of temperature and relative humidity inside the product. These sensors continuously record temperature and relative humidity, these measured values are logged in, and presented with a suitable program in a computer / computer screen and measured measured values for temperature and relative humidity in each measuring point are monitored individually and in combination. By manually or with a computer program analyzing and matching temperature and humidity measurement from each measuring point, we get a measure of, a comparable value, for the availability of both heat and moisture at each measuring point, and the combination of these measured values, by comparing these values from all measuring points in the storage space, the most unfavorable measured values / measuring point in the product can be identified and form the basis for a calculation of the maximum suitable storage time / shelf life for the batch as a whole. Evaluation / calculation can be done manually or with the help of a computer, or PLC, with a suitable program. Claim 9 Method according to claims 6 - 8, for registering the storage level in a storage space, according to any one of the preceding claims, characterized in that condensation on the ceiling can also be foreseen. A temperature sensor mounted on the ceiling / roof plate measures the temperature of the ceiling or plate, this temperature is compared with measured values from the measuring line concerning the relative humidity in the air under the roof, the processing of measured values can be done manually or in a computer with a suitable program. By selecting the appropriate margin to the dew point, the equipment can warn in time of the risk of condensation forming on the inside of the roof. An operator can be warned with a suitable signal, or a ventilation and cooling device can be started automatically. Through ventilation, outdoor air, or cooled air, is taken into the space under the roof and condensation is avoided. 17