Can Blade Breakage Be Detected without External Sensors?

[mhabbal]

Dear all,

The idea is to detect break down of a group of blades inside a pipe. It’s very difficult to install any type of sensors inside a pipe without having them damaged, given that the pipe is an air vacuum suction system.
How about concentrating on the physical properties of the blade itself. i.e.: Current conductivity, internal wire detection, to tell whether the blade is broken or not.

We cannot observe the change in material resistivity or conductivity and tell by that, because that would require external circuitry or connections around the blades. What we need is some internal wiring. Any ideas?

Please reply as soon as possible.

 

[mhabbal]

Some parameter proportional to the LENGTH and/or CROSS-SECTIONAL area of the metal blade should be observed to reach a certain value at fracture/break down.

 

[Danger]

Welcome to PF, Mhabbal.
Your question is a bit vague, but I think that I get the gist of it. My first thought is to put a run-out sensor on the 'blade' axle. If it breaks, it will immediately go out of balance. The vibrations from that should be easily detectable.

 

[mhabbal]

what kind of sensor do you suggest? wouldn't a wire connected to the edge of the blade be better? (if the blade breaks, the wire would be cut off, and hence we have an open circuit)

 

[Danger]

I can't really think of an easy way to set that up. Keep in mind, though, that I never graduated high-school. Fred Garvin is an expert in this sort of thing, and Brewnog and Astronuc have a lot of knowledge about it as well. They can help you a lot more than I can.

 

[mhabbal]

loooool! how about you forward my message to these guys? i don't see how i can reach them

 

[Danger]

You don't need to reach them; they read these threads regularly. If you have no response from any of them within the next couple of days, I'll contact them and request input.

 

[mgb_phys]

Could you have some sort of induction sensor (metal detector) outside the pipe and sense each blade as it goes past, any change in the signal is a damaged blade.
I don't know how fast a blade speed this could handle - but might be easier than getting connections into a vacuum and onto a moving turbine.