Three gas turbine and steam combined cycle power generating units in Virginia discharged spent steam to a large air cooled condenser system through a series of 176 inch diameter main vertical riser ducts which then split into branching 126 inch diameter horizontal distribution ducts. The vertical and horizontal ducts were thermal expansion compensated by restrained expansion joints. On initial start-up in 2018, the vertical compensators failed in compression and the horizontal compensators failed in transverse shear.
The design engineers assigned responsibility for this failure to the installation subcontractor. Therefore, GES Tech Group, Inc. (GES) was retained by the installation subcontractor to determine the root cause of the total failure of the thermal compensation system and to represent the subcontractor in legal proceedings initiated by the plant owner.
GES determined that the designers had failed to consider that the vertical ductwork was subject to gravity loads in addition to thermally induced loads. The system had been assumed be oriented horizontally rather than vertically, leading directly to the failure.
The subcontractor was found to have no responsibility for this failure mechanism.
