Scale-Tron, automation, sensors and weighing systems

SiloWeigh - Applications and examples

Siloweigh and SiloWeigh.Net are being used on a wide variety of storage vessels, from small bins and silos up to silos of over 4000 tons capacity and liquid tanks of all sizes.  It is also applicable to many structures, showing real time stress and giving timely warnings.

H-beam silo legs

At right is an example of installation of the now obsolete Silex sensor on an H-beam leg, the most common type in North America.  This installation uses the Through-Hole installation kit, which includes tools and a jig for installation of up to 8 sensors.

Before installing sensors on any silo, check the available stress in the legs using the Stress Calculator.  This easy to use tool gives you a go-nogo indication in a few minutes, based on theory plus a lot of experience.

Stress calculator - download Excel file.

O-beam silo legs

Picture at left shows installation of now obsolete Silex sensors on a silo with round legs.  The weld tabs installation kit is used on this type of installation;  the kit holds parts for up to 8 legs and a jig for positioning the tabs while welding. The L-Strain sensor uses 3weld tabs but the principle is identical.

The exact position of the sensors on the legs is important for best results.  The detailed manual includes examples for most types of structure, plus rules for other types that may be encountered.  Scale-tron also offers free engineering help and assistance with more difficult applications.

 

Skirted silos

At right are skirted silos, where the wall of the silos runs right down to the ground and supports the weight of the whole silo.  This application uses the through-hole kit again, with spherical washers to allow for the curvature of the wall, and installation is quite simple.  Some of these silos use additional reinforcement by beams bolted to the inside wall of the silo.  In cases like this, contact Scale-Tron`s engineering team for advice on sensor positioning.

Aluminum and stainless steel skirts are no longer a problem because the L-Strain sensor compensates for the difference in coefficient of expansion.  Accuracy may be reduced, however, and you should contact us for the latest update from our extensive installation experience.

Load cells

If you can lift the vessel, the legs can be mounted on load cells.  The feed silos at left were converted to a highly accurate vessel weighing system without lifting by cutting the bottom of each leg in turn, refitting the foot and bolting onto the load cell mount.  This gives full load cell accuracy; typically 0.1% of full scale.  Useful when fine accuracy is required or when dealing with awkward leg styles that either do not allow gauges to be fitted or are too flexible for accuracy.

All SiloWeigh display systems are compatible with load cells.  We have supplied many load cell systems where this exta accuracy is required.  These systems are not approved for use in trade, however.  If you need an approved system, we can supply different indicators.

No cable run available?

No way you can run a cable? - No problem! we can use a radio link to replace a long cable or even a run of several miles between outlying silos and the base station.  We also have solar power kits when no power is available at these outlying sites; this is particularly useful with explosives silos that are located in the backs of quarries and mines.  A choice of low power or higher power radio plus high-gain antennas allow low-cost basic short distance communication of several hundred feet up to multiple location sites at several miles distance with single base-station.  The radio link replaces the serial digital cable from silos to SiloWeigh II indicator, or DAQ in the case of SiloWeigh.Net, and radios can be networked to allow multi-hop routing when distances are too great to reach from the most distant location to base.

 

Analog 4-20 mA converter

Each DJB (Digital Junction Box), which normally handles load cells, can be fitted with four converters, making it compatible with all sensors having 4-20 mA output.  This opens a world of applications to all the features of SiloWeigh.Net's Internet database.  Since each DJB has 4 inputs, the overall cost of putting your inventory on-line is low, and level measurements can be converted to volume during calibration, so you get a direct readout in gallons or liters.  See the applications below:

Liquid tanks

By fitting a pressure sensor into a T-adapter in the outlet pipe, a measurement of the head of liquid allows this level to be displayed.  In addition, if the tank is symmetrical, as shown here, the level can be converted to volume and displayed in gallons, liters etc.  Since the pressure measurement corrects for specific gravity, the reading is always correct to the temperature at which it was calibrated, regardless of volume change with temperature.

The liquid displays can be combined with the weight displays in the same cabinet to show both;  for example, the displays can show both silo weights and admixture tank volumes in a typical concrete plant.

Petrochemicals require special attention and intrinsic safety barriers.  Contact us for information on how this can be handled.

Level measurement

When leg or skirt sensors cannot be used - for example, with joined vessels or concrete silos, you can use radar or ultrasonic level sensors and the level measurement can be converted to volume or weight.  The analog 4-20 mA converters above give Internet accessibility and all the features of SiloWeigh.Net at low cost.

Temperature monitoring

Temperature monitoring is important in many applications. One example is in precast and block plants to record the temperature trend in the mixer or during the nighttime curing cycle. Temperature probes can be connected and scaled to read, for example, 0 to 100 degrees Celsius or 50 to 200 degrees F.

Moisture monitoring

In concrete plants, moisture sensors have analog outputs and can be displayed on the bar indicators. These can be calibrated to show 0 to 20% moisture in the sand bins, or record mix moistures for batches running through the mixer.