Mercury

Mercury vapor turbines were developed by General Electric in the 1930s as a heat source for steam generators in electrical plants. However, due to the dangers in using highly toxic mercury as the working fluid for the thermal cycle, only four large-scale plants were built. The last of which was brought online in 1950 at Schiller Station in Portsmouth, New Hampshire. Having been mothballed for years, the plant sat dormant, and in 2018 the owner’s contractor, Manafort Brothers, Inc. of Plainville, Connecticut, asked Cutting Technologies (CTI) to dismantle it using a diamond wire saw.

Traces of mercury at the decommissioned unit presented a serious health risk. Mercury’s low temperature of evaporation makes it an easily airborne contaminant, and for this reason, special measures needed to be taken to safeguard workers and the environment.

Firstly, no heat could be introduced during the cutting process. Typically, CTI combats this by training a stream of water on the diamond cutting wire to cool it and rinse away the cut particles. However, since this would create a large amount of contaminated waste water, CTI used a fine mist of compressed air and water to cool the cut, dramatically limiting the amount of waste water to be decontaminated.

Throughout the process, CTI’s technician had to wear a powered air- purifying respirator (PAPR) as he sectioned up the generator and its components. In all, CTI saw cut the turbines, condenser units, pressure piping, pop-off valves, 3”-thick steel vessels, magnetic windings of various metals, and 24”-inch diameter hardened steel shafts.

The intricate nature of the unit made the cutting, rigging and removal of the component pieces a technical challenge, but CTI was able to safely complete all work without contaminating the area or triggering air monitors, pleasing both the contractor and owner.