Cutting of LARGE rotors in the field

[SMF1964]

We have a steel generator rotor that is being scrapped and would like to remove a section from it for analysis (cracked, away from the retaining rings). Does anyone have any suggestions for how to cut this thing up in the field when it is 35" in diameter at the area of interest. We need to maintain the material properties.

Thanks.

 

[EdStainless]

How about using a plasma torch to cut rough sections and then re-cutting them in the shop later? You could allow a 4" HAZ to be safe.
There are portable bandsaws, but you would only be able to cut 3-4" into the rotor.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[SMF1964]

That was one option proposed by the scrap dealer - using what he called a "plasma/oxygen lance" - my concern was the size of the heat affected zone and how big it was going to be.

I had visions of two lumberjacks and a really long hack-saw... Do they make blades for these concrete saws that would work on the steel?

 

[unclesyd]

The use of a Trepanning saw would be my first choice as it doesn't affect the metallurgy of the material.
You could have someone come in and remove the sample for you or you could rent a saw and do the work yourself.

 

[SMF1964]

We have a trepanning saw in-house that cuts a roughly 4" long x 1" wide x 1" deep. I was hoping for a larger piece, something I could cut tensiles and other mechanical property samples from.

 

[metengr]

SMF1964;
I would not use any portable bandsaw or manual sawing device because of the size of the rotor. We have in the past used a portable plasma cutting torch to extract samples from a scrap Westinghouse turbine/generator rotor forging. This should be no different. However, as Edstainless mentioned, you should extract a large enough sample to provide enough material away from the heat affected zone (4" on any cut side is plenty of distance).

Is the generator rotor stripped of copper?

 

[SMF1964]

metengr
- re: torch/plasma: The 4" is what I was looking for in this regards.

- re: copper: It will be prior to any torch cutting, unless we want to generate liquid metal embrittlement samples...

I was wondering if we could rig one of these water-cooled concrete saws with the proper blade and then rotate the rotor...

 

[metengr]

If the wheel is a silicon carbide wheel, it probably would work with water cooling. However, it would create a mess, and would take longer than a plasma cutting torch.

 

[arunmrao]

Use an angle grinder fitted with a cut off wheel(~3mm thick ) and remove the sample. This will provide the least heat input ,but a skilled person should operate as the risk of it breaking is high if not properly done. I use this method regularly to get test samples from castings/scrap.

 

[kailster]

Daimond rope saw might work, depending on how much room you have around the rotor.

 

[SMF1964]

kailster - Diamond rope saw?

 

[EdStainless]

You can Oxy Plasma cut under water if you are worried about Cu LME. But the HAZ isn't really that big. They cut very fast

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[unclesyd]

A diamond rope/cable saw as mentioned by kailster is quite common for cutting underwater pipe lines. I think they were pioneered by Shell. A much larger version was used to cut the Russian Submarine Kursk into two parts.

A more practical approach might be to see if there a tube bundle saw in the area. We have one that could cut on a 48" diameter 8" deep. These saws are a modification of a horizontal bandsaw that increases the blade vertical travel.

 

[GRoberts]

We use large oxy-fuel torches to cut through steel casting risers over 36" diameter. It is not pretty, but you can cut to size later. I also think diamond rope saws have been used to cut rock (marble/granite) slabs for some time now.

 

[kailster]

We use a diamond rope saw to cut up NAB risers in the foundry. Cuts up to app. 40" diameter. Cuts without a lot of heat added. Cuts any shape/size. We also use it to cut large sections for failure analysis.