Stockpile Inventory Energy Minerals
MONITORING QUANTITY LEVELS OF COAL
Intensive industries must maintain large inventories of coal. For business planning, financial reporting, and regulatory reasons, one must accurately determine the quantity of your coal inventory. Coal quantities are expressed in weight, however, the vast amount of coal in a stockpile makes weighing the entire inventory impractical and extremely costly.
SGS provides the industrial, operational and technical resources required to determine the quantity and quality of solid fuel (coal, petroleum coke, etc.) in storage. With SGS’ expertise, we provide physical inventory related services at 230 separate sites and over 1800 individual piles.
SGS’ global technical expertise can calculate:
Determining The Coal Quantity
The industry standard method for determination of coal quantity is to ascertain the density of the coal and the volume of the stockpile. From this information, the total weight is calculated.
Density Determination
SGS uses the latest state-of-the-art technology through nuclear depth density gauges. The probe source is a radioactive material that emits gamma radiation at a constant average rate. The gamma rays interact at the atomic level with the surrounding medium. The number of interactions, or scattering events, per unit time is a function of the density of the sample.
The variation in chemical composition of the different coal sources represented in most stockpiles requires calibration of the nuclear depth gauge. This allows a representative sample of coal in each stockpile. Once the nuclear gauge is calibrated to the coal, a borehole is made and access tubing is inserted. The nuclear probe is then lowered into the stockpile via the access tubing and readings are taken at pre-determined depth intervals. These are recorded for use in the pile density calculation
Volume
The volume of the coal stockpile is determined by using a Triangular Irregular Network (TIN) software package. The TIN model represents a surface as a set of contiguous, non-overlapping triangles. All areas where the shape of the coal pile undergoes major shape changes and any elevation changes in the ground beneath the coal pile are documented using ground level or photogrammetry methods.
Using these data points the TIN software package creates a surface that best describes the irregular exterior of the coal pile. The volume of coal within this TIN is then computed by electronically filling the volume of the TIN above the soil elevation with prisms or polyhedrons of known volume. The software then totals the number of polyhedrons required to fill the TIN to produce a reliable final stockpile volume.
The prismoidal method uses a data point file to create a TIN of the coal surface within the storage area. The volume of coal within the TIN is then computed by electronically filling the volume of the TIN above the soil elevation datum with prisms or polyhedrons of known volume. The software then totals the number of polyhedrons required to fill the volume of the TIN and recorded using the pile density calculation
Tonnage Computation
Once the density (in pounds per cubic feet) and the volume (in cubic feet) are known, total tons of coal in the stockpile can be readily determined (usually referred to as “wet” tons because the coal is exposed to atmosphere in its natural state), using the following calculation:
Wet tons of coal = Volume (ft3) x Density (lbs/ft3) / 2,000 lbs
