Chief said: The tips are ground to a knive edge to limit damage in the case of rubbing against the casing, which appears to be the case in this instant.
That is it then - what seemed overly simplistic is the answer. Thanks very much Chief
rmw, byrdj
I have dug out a photo of the rotor assembly before it was damged, I hope it uploads okhttp://files.engineering.com/getfile.aspx?folder=2c22b4c0-4fb7-4431-857d-4fd7ccc22c96&file=Close_up_LP_blading.jpg
HP, MP, LP are all reaction.
HP and MP blade shrouds have caulked labyrinths to seal against the nozzle boxes, but the LP has nothing in that assembly.
The surface area of the ‘lip’ on the LP blades which is described as ‘tip-thinning’ can’t be much more than about one fifth of the whole...
I’ve seen drum bouncing because of safety’s popping caused by incorrect functioning of valves; turbine by-pass or dump to atmosphere.
Boiler 40 bar; 30 ton per hour steam; turbine using all produced steam on pressure control; turbine trip; safety valves lifting. It certainly got everyones...
I’ve found something else, but the penny still won’t drop, perhaps a light will come on in someone elses nut:
The clearance and rim losses of the HP blades are reduced to a minimum by using shrouds, whereas the LP rows have conically twisted blades, the blade ends of which are tip-thinned on...
Thanks for looking byrdj, it would appear that not many people have. My initial thought was maybe they machine it like that so that if there is a tip rub, the full surface area of the blade won't have to come into contact with the nozzle carrier. But surely thats a bit simplistic?
TheBlacksmith - If you wanted a little chat with rmw who offered me assistance, why didn't you email him or something??
rmw, thanks for your help but I think I worded my first question incorrectly:
The top half casing was removed after the rotor could not be turned by hand the day after a...
The turbine I operate at work was found to have up to 1mm of metal reduction on each of the final three LP blade rows. This meant there was not much of the thinned section left. Why are these final stages fitted with tip-thinned blades, is it something to do with enthalpy or velocity or...