I am a mechanical engineer who primarily oversees work on GE 7FA combustion turbines that drive generators that produce electricity at power plants. That is my job. These units contain a large axial compressor that feeds combustion and cooling air for the gas turbine section. During a recent inspection on one of the units, we discovered damage within the compressor that required an emergency repair.
The outer case is assembled with over a hundred bolts that are approximately an inch diameter by a foot long. These are removed with the force of a hydraulic wrench and then our crane can remove the upper case which weighs over five tons. The stationary vanes in the forward part of the compressor are mounted into carrier rings that slide into a hook in the case. With significant metal-to-metal contact, rust and corrosion tends to seize these rings in place making them extremely difficult to remove. In this case, the damage is down at the bottom (six o’clock position) and we need to remove the lower rings.
If that description does not give you a mental picture, here are a couple visuals….
Chemists from around the world have developed various solvents that dissolve certain types of corrosion without attacking the base metal. Some of these solvents are brushed on, some are sprayed on, some are poured into a tank and have parts dipped into them or set in overnight to soak like dishes in a kitchen sink. On this compressor, there is a narrow gap between the carrier ring and the case, and typically, various solvents or penetrating oils are poured down this gap to loosen and dissolve ring-to-case rust and corrosion. This step is necessary if there is any hope of removing these carrier rings.
I don’t want to give away too many trade secrets, but there is a solvent that is much cheaper and perhaps more effective than others. This product is also pretty useful for cleaning toilets, among other things. And… it’s the real thing.
A fact that continues to amaze me is that some people are known to voluntarily pour this powerful solvent into their mouths and down their own throat. You can’t make this stuff up. As they say, sometimes truth is stranger than fiction.