Simple Solutions That Work! Issue 17

32 Contact: KEN STRAUSBAUGH [email protected] STORAGE LOCATION The location of storage for new sand must allow easy access to blower or dump trucks, or rail access to the area without restricting movement of foundry vehicles during the unloading process. Pits will be necessary if the sand delivery will be made using dump trucks or bottom unload railcars. The area must be designed to prevent any contamination of sand from moisture. Pneumatic transporters or bucket elevators will be required to move the sand from the pits to the top of the silo. Transporter piping with the correct fitting will be required to receive sand from blower trucks. Minimizing internal distance to and from storage systems will lower the cost of compressed air, maintenance of pneumatic transporter pipe, or conveyor belts. STORAGE DESIGN Silos can be subject to stresses from earthquakes, explosions, soil conditions, pressure - positive or negative - from pneumatic transporters or dust collectors, and from the points of loading and unloading. Professional engineers should be consulted before the final design of the silo is chosen. Storage vessels must be fitted with “bin vents” or dust collector systems which are active during filling. In addition, pressure relief valves are required to keep the pressure from being greater than 1.0 psi or less. In some cases, it is also necessary to have a relief valve open in case of very small negative pressure. Dust leaking out of a pressure relief valve is a bad sign—it is designed to open only in case of an emergency. It means that the dust collector or “bin vent” is not operating correctly. Bin vents should be positioned to discharge the dust external to the storage vessel. Then the receiver for the dust must be routinely emptied so that dust does not get discharged on one side of the pile of sand. Silos should be loaded from the top center and unloaded from the bottom center. If this is not the case, the engineers must be informed of this and again if the loading or unloading orientation is subsequently changed. Each storage vessel should be designed to incorporate an anti- segregation device. Larger sand grains always migrate to the outside of a pile of sand and fines will be removed first from the center of the storage vessel without an anti-segregation device. Skirted or leg supported designs should be decided before choosing the final design. It is sometimes necessary to provide a sufficiently warm environment below the silo to prevent freezing of air supply to pneumatic transporters. A skirted design provides a much more easily heated area for this purpose. STORAGE LEVEL SENSORS Generally, there should be (3) level sensors in a storage vessel. The top level should be located 10 – 12” from the discharge of the fill pipe or sufficiently low to hold a full transporter load without plugging the discharge port. The second level sensor from the top should be located at the point where the silo will hold the maximum reloading vessel container whether that be a truck or bulk bag. The lowest level sensor should be located at the point where there is the minimum amount of sand to supply the next step in the process without interruption. All sensors should be placed where they can be accessed in case of malfunctions. STORAGE CONTAINER SAFETY OSHA ladder safety regulations for guarding and ladders must be followed on sand storage containers. The standards vary based on height and construction date of the vessel.