Grouting steel baseplates
A good quality precision grout, whether resin-based or cementitious must provide good load transfer and be easy to apply under most conditions.
American Concrete Institute ACI 351.1R-93 report Grouting And Support of Equipment And Machinery. This report provides an overview of accepted practices for grouting of equipment and machinery and describes materials and installation methods for grout used as load transfer material between machine or equipment bases and their foundations. Machinery and equipment which have precise tolerances for alignment or require uniform support cannot be placed directly on finished concrete surfaces.
1. Choosing the right grout
The selection of a suitable bearing grout depends on the machine loading, size of bearing, gap size and grouting method. Choosing the wrong grout can lead to failure of the bearing grout; for example, most cement grouts are not able to resist continuous impact loading such as under vibrating machinery. Cement grouts are weak in tension and undergo fatigue failure. This can have serious repercussions on safety and the cost of remediation can outweigh the initial short-term cost benefit a hundred fold.
2. Voids in the grout
The support provided by a grout is the Effective Bearing Area (EBA). This can be affected by grout leakage, unlevel plate, shrinkage of grout, inadequate mixing of grout, wrong placement method, poor grout flow or entrapped air voids. EBA can lead to point loading on the grout which in turn can result in cracking and crumbling of the grout under the baseplate. This could have disastrous consequences on the machine.
3. Cracks in the grout around the baseplate
Cement grouts rely on expansion to provide the non-shrink properties required of a precision bearing grout. This expansion needs to be confined under the baseplate, but if allowed to expand freely, the grout may crack due to shrinkage. This cracking is often seen where a cement grout has not been finished properly. Epoxy grouts are not affected as much as they have low inherent shrinkage.
4. Grout not flowing under the baseplate
Rapid installation of machinery is essential. A grout with poor flow will slow down the process. Some inferior epoxy grouts are cut back with diluents to improve flow but this can lead to excess shrinkage and loss of EBA. Weber grouts have been developed to give good flow without any undesirable side-effects.
Correct grout selection and application
Both the concrete surface and the machine base have irregularities which result in alignment difficulties and bearing load concentrations. For this reason, machine bases or soleplates are aligned and levelled by shimming or other means and the resulting space between the machine base and the foundation is filled with a load transfer material. The load-transfer materials most frequently used are hydraulic cement and epoxy grouts.
Solution with the following Weber products
High-flow, high-strength, shrinkage-compensated, cementitious precision grout.
General-purpose, shrinkagecompensated, cementitious grout for dry packing, grouting, bolt fixing and bedding of machinery
High-strength, chemically-resistant grout