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FAB-EPM Isolation Material

FAB-EPM material is a polyurethane elastomer specificallydesigned to provide low frequency vibration isolation for foundation isolation applications. FAB-EPM material is manufactured in a wide rangeof types, which allows for optimal loading to achieve increased isolator performance. The damping rate of the different material types is between 7% and 11%. Additionally, with increased thickness, the nat- ural frequency is reduced, which also improves isola- tion. FAB-EPM is impervious to most chemicals, alka- line solutions and oil.FAB-EPM material can be supplied and used in fullsheet form, strips or even blocks. However, when used in full sheet form, the material becomes the base formwork for the concrete foundation. This advantage creates a simple construction method.The FAB-EPM material is positioned on the pit floorof the foundation (or directly on soil), butt-jointed and taped at seams, similar to the installation meth- ods of Fabsorb™ isolation material (described on page 17). When using multiple layers, the material should be laid offset from the previous layer.The reinforcing bars can be installed directly on mostFAB-EPM material types, but must not puncture the material. For lower stiffness types, laying down a polyurethane plastic sheet is recommended before placing the rebar.The concrete pit floor should be smooth and level,depending on the thickness of the FAB-EPM material to be used. For a 1" (25 mm) thickness, a pit floor tolerance of 0.12" (3 mm) is acceptable. For thicker material, the level tolerance should notexceed 0.2" (5 mm). Formwork can now be placed at the sides of the foundation to be poured, withadditional FAB-EPM material used on the sidewalls, if required.As with all non-linear, elastomeric isolators, FAB-EPM material reacts more stiffly under dynamic loads than under static loads. The degree of stiffness depends on the material type and the load applied. Additional small dynamic loads can be applied beyond the maximum static load for each type of material.In the additional dynamic load range, a unique fea-ture of the FAB-EPM material is that it will behave "softer"where a lower natural frequency can be achieved with only a small increase in additional deflection. Larger and shorter duration dynamic loads also may be applied; however, the material will behave "stiffer" to these inputs, as shown on the dynamic natural frequency curves for each mate- rial type.Permanent static loads cause a certain amount ofcreep (additional deflection) in all elastomeric mate- rials. The long term creep of FAB-EPM material isvery low (below 30% of its original thickness) when used in the static load range.
Illustration of FAB-EPM used as individual blocks. Full Surface AreaIndividual BlocksPartial Surface Area (Strips) Sidewall isolation is optional for any of these methods of installation, depending on isolation requirements and machine type. 19