Alphatec Engineering recently completed a foundation repair and regrout of a gas compressor for a major oil refiner in Germany. The compressor was originally installed in 1963, and the electric motor drive had been replaced in the 1980s.
The compressor had been vibrating quite badly for a number of years, and a temporary repair was carried out by an in-house maintenance contractor in 2007 to try to reduce the vibration levels. This had limited impact, and in 2010 Alphatec Engineering was invited to inspect the installation, and update an earlier repair proposal.
Since a major shutdown was already planned for March 2011, Alphatec's proposed repair work was integrated into this planning, and materials were shipped to site in February. The Alphatec team, from both Dublin and Valencia offices, mobilised on 14 March, and started work on the motor foundation the same day. With any regrout project, it is important to address all the potential problems, as well as the directly observed issues. In this case, the possibility of corrosion of the motor mounting frame was considered, and when the encasing grout was chipped out, found to be extensive. The motor frame was then grouted in place with ALPHATEC® 800 epoxy grout. Oil-induced degradation of the compressor grout was very obvious, and around 250mm of damaged cement grout and underlying concrete was chipped out.
At the same time, holes were drilled through the motor and compressor plinths, into the underground mat, which was some 600mm thick. Dywidag reinforcing bars were introduced into these holes, together with injection and vent tubing, and the holes sealed for pressure resistance. ALPHATEC 342 injection grout was pumped into place to fill all separations, cold joints, cracks, fissures, and other imperfections, to join all the elements of the foundation together, and enhance its vibration damping capability.
The compressor was now aligned with the motor, allowing for some vertical expansion when the motor is operating, and grouted in place. Crosshead supports, cylinder head supports, and pulsation tank supports were all regrouted in a similar manner.
Work was complete on 29 March, and the machine returned to service in mid April on completion of all other shutdown work.