What is the minimum tensile strength recommended for a concrete foundation that will have epoxy grout used to set rotating equipment?

You should have concrete with a minimum tensile strength of 350 psi.  This recommendation would be considered a “best practice” when using Escoweld, chockfast or most other epoxy grout brands.

Is it recommended to add additional mass to an existing concrete foundation?

When you add new concrete to existing concrete the interface will result in a cold joint and vibration will not transfer across a cold joint.  In this situation, special materials will need to be considered in order to bond with the existing concrete.  A foundation or mass can be extended with Escoweld or Chockfast materials if the correct concrete preparation is done.

How do I keep my equipment from vibrating?

Equipment creates vibration when in operation.  Most vibration can be dissipated from the equipment, if installed properly.  A good installation would include a properly sized foundation mass, specific to the equipment being installed.  Epoxy equipment grout is important to the success of the installation.  A good epoxy equipment grout will form a positive bond between the equipment and the foundation, providing a pathway for vibration to travel.