There have been several passenger aircraft in recent years that have experienced fan blade separation events during flight, and so I wondered about ground-based steam turbines and gas-turbine engines. AIUI, these don’t have the weight constraints of aircraft (so maybe the blades can be made more robust), and also tend to have more constant-power operation and fewer start/stop cycles (less fatique cycles per hour of operation), so I might expect it happens less often for these. Is that the case? Does it ever happen?
A little confirmation of that point at the end of the introduction of this .pdf - Land Based Gas Turbines for Power Production
ETA: This is also an issue for wind turbines also, but the constraints are very different from gas turbines.
Can I point out that a land-base turbine in, say, a power plant doesn’t have the same problems with weight limitations and can therefore have a much more robust “containment” structure around it, meaning a failure is less likely to cause mayhem and death in the surroundings?
There are two different things: steam turbines, and gas turbines.
To my limited knowledge, they don’t shed blades often. There are known problems with the axle bending out of shape (I think jet engines have the same kind of problem), and with blade corrosion, but that they don’t normally cause blade shedding ???.
Steam turbines are low temperature, but suffer from having steam go through them:
Steam Turbine Rotor Vibration Failures: Causes and Solutions (powermag.com).
I think that corrosion failure of a ground based steam turbine is detected by vibration failure before anything else.
When the blades get to hot, they suffer corrosion failure, which I think is the main cause of blade shedding in a gas turbine. Corrosion may be accelerated by stop-start cycles. To prevent this, the blades are special material, coated with a special material, protected by special gas flow. And, I think, on a large ground based gas turbine, by being thicker and heavier and a different shape. Very large gas turbines are covered by different emission standards than aircraft engine, which I think means that they operate at lower combustion temperatures than aircraft engines.
Proper containment definitely helps keep failures like these from making the news; I remember a professor telling the class stories about a turbine failure in which the blade bits were found deep in the walls and floor. Despite this, when my company decided to start testing gas turbines, our largest warehouse was designated as the testing space. There was nothing special about this building’s construction – basically a tall metal building with a cement slab floor and light insulation in the walls – but it was located far away from the offices and other work areas. I’m not entirely sure what the setup was like (regardless of department, employees who weren’t directly involved weren’t allowed in the building) but I’m sure there wasn’t a proper containment area built for it. A blade failure was deemed a serious concern though, so an employee was designated to walk around the building to ensure no one was outside during testing, and an announcement would be made on the intercom prior to startup to make sure other employees stayed away. (This only lasted a few months, and was never really discussed after that.)
You may find this interesting:
Rolls-Royce | Ben Khoo – Manufacturing the hollow titanium wide chord fan blade - YouTube
On the tangent of steam turbines…
In my Navy days we were most concerned with uneven heating, corrosion, and lubrication failures.
We reduced the risk of uneven heating by always engaging the “jacking gear” whenever there was steam present. This was a relatively small electric motor that went through multiple worm gear reductions to the point where it would rotate the bull gear perhaps 1 revolution every few minutes.
By doing this, the turbines were rotated like a roast on a spit, so any steam coming in wouldn’t heat the rotors unevenly, causing bowed shafts.
We reduced the risk of corrosion by meticulously maintaining the quality of our feed water–we ran chemical analysis every few hours and had salinity alarms and devices to remove oxygen, all to minimize the chance of corrosion in the plant.
As far as lubrication goes, every bearing was checked every half hour for oil flow and temperature, and the loudest alarm in the engine room was a big red siren that sounded when oil pressure dropped too low–immediate action was to stop the shaft by opening the reverse throttles. “Main engine low lube oil alarm! Stopping the shaft with steam!”
I worked a pipeline company that used Gas Generators (gas turbines) to run a centrifugal compressor to run natural gas down the line. There were “scatter shields” which were just a ring of 0.5 in steel around the hot section of the engine. In all the 10 years I worked there, each engine running about 8000 hours a year x 100 engines, there were no failures. I had heard of one years before my employment there, but haven’t heard of one since. If someone made me guess at the mean time between failures, I would say, using my anecdotal evidence, there might be a failure every 5,000,000 running hours. IANAS (statistician), and even if I was, I don’t have the data to make a meaningful conclusion, I’m just a guesser.
Hm, if one were concerned about a turbine blade breaking loose and flying outward from the turbine disk, I would expect that the plane of the disk would be the danger zone. So merely rotating the turbine axis such that the disk does not intersect the office / parking spaces of the facility, you could be minimizing damage even if the building is lightweight and not built to contain the turbine failure.
That brings up another thought: I’ve heard about the occasional aircraft turbine failure, and for a number of years I tried to avoid sitting in a seat in the plane (actually region) of these aircraft engine turbines. You know, to prevent being hit by a loose turbine blade cutting through the nacelle then the fuselage. Call it paranoia; I have since stopped worrying about that particular failure mode in aircraft, seeing as how it’s pretty rare.
I think it also depends on large part on the type of gas turbine as well. For example, the GE F404 is used in the F-18 A thru D and also in the co-gen (steam and electricity driven by natural gas) plants in the oil field in Alberta. To my knowledge neither one has had that type of engine failure whereas the Hawks they use for pilot training have had several catastrophic failures.