Gilsulate International, Inc.
Underground Pipe Tank Insulation Corrosion Protection - Gilsulate SAVE BTU’S
Settlement Happens:
Almost all bulk solids settle. The question is, how much? With large bulk solids (think coarse aggregate, rocks, pea gravel, etc.), settlement will be small. However, as the size of the bulk solid decreases, the amount of settlement will generally increase.
This is particularly true for very fine bulk solids or powders which can settle more than 30% of the original bulk volume. As a fine powder is poured into a confined space (such as a trench for piping), the top particles push downward, compressing the particles below. Air between the fine particles is also being compressed, creating an upward air pressure gradient. The smaller the particles, the greater the pressure gradient. This pressure gradient dissipates over time as air escapes from between the particles, resulting in the gradual settlement of the bulk solid.
Compaction(settlement) occurs through pressure (such as the weight of the backfill) and/or vibration. Gilsulate®500XR is engineered and designed to be settled using a concrete type vibrator prior to the backfill of soil over the trench. The vibration allows the smaller particles of Gilsulate to migrate between the larger ones and allows trapped air to escape. Proper consolidation before backfill means proper coverage over your piping system after backfill.
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Did You Know...
One of the most important issues to consider for pour-in-place insulation is the density of the product after backfill. Bulk density and use density are not the same. Bulk density can actually change, depending on how a material is handled. The use density is the mass per unit of volume of the consolidated particles.
Gilsulate®500XR is the only pour-in-place insulation that is consolidated to its use density before backfill. This provides the owner with assurance of proper coverage over the piping system.
The Loose Bulk Density of Gilsulate is approximately 30 to 34 pounds per cubic foot. After proper consolidation, the Use Density of Gilsulate will be approximately 40 to 42 pounds per cubic foot.
Although our small paper bags hold about 1.3 cubic feet of Gilsulate at loose bulk density, we sell them by the use density of 1 cubic foot per bag.
There are many resources and publications available over the internet for those more interested in the science behind bulk solids and powder technology. Some of these resources include:
http://www.powderbulksolids.com
http://www.jenike.com/Publications/
http://www.kona.or.jp/index_e.html
http://www.chemicalprocessing.com/resource_centers/powder_solids.html
http://www.asce.org/PPLContent.aspx?id=17273
http://www.bulk-solids-handling.com/
http://www.aiche.org/publications/aichejournal/index.aspx
http://www.newcastle.edu.au/centre/cbs/index.html
This fine powder settled approximately 30% from it’s original bulk density after approximately 400 pounds was applied for 30 minutes.
Why Are These Issues Important?
The design of the piping system is based upon the performance of the material protecting the pipe. Heat loss analysis, thermal efficiency, freeze protection analysis, temperature gradients, sensitivity analysis, heat transfer calculations, etc. are all based upon envelope dimensions (that is, the volume of insulation surrounding the pipe) and the thermal conductivity of the insulating material. If only the backfill is relied on to complete compaction, coverage over the piping system will diminish. By properly consolidating Gilsulate®500XR before the backfill, you maintain the envelope dimensions and thermal efficiencies specified by the design engineer.
Thermal Conductivity Of A Powder:
Thermal conductivity is tested using ASTM C177. To test a powder using this method a frame is used between two temperature plates to hold the powder and thermocouples are used to measure temperature differences until a steady state is achieved. Thermal conductivity is calculated in this process. To accurately determine the thermal efficiency in a pour-in-place insulation, the use/compacted density should always be used as a basis for thermal conductivity. Bulk density testing of thermal conductivity will provide an inaccurate measure in applications with higher use densities. The thermal conductivity of Gilsulate®500XR is based upon its use density, not bulk density.
ASTM Tests and Density:
ASTM International has more than 40 different definitions of density. Different test methods can and will give different measurements of density. Using the wrong definition or value for density will lead to less than desirable results. For example, ASTM C110 measures compacted density by lightly tapping a graduated cylinder of powder on a thick magazine. This test will not provide an acceptable or accurate measurement of a powder under loading conditions.
We use ASTM D1895 method C to determine density under loading conditions. We modify this test slightly to increase the weight applied to approximate the static loading of soil in a typical application (about 400 pounds per square foot) and by increasing its duration. The static load in this test can be increased to measure for greater loading in deeper burials.
