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Turbine engine repair welding
bigcitybill
Member Posts: 4,913 ✭✭✭
For those who are interested in such things as precision TIG welding, I've put together an album
of pics I took recently at work, showing the tedious process of repairing a 2nd stage nozzle segment
for a GE Frame 7 gas turbine engine.
This part had multiple areas of severe foreign object impact damage.
Damaged areas are cut away and new metal welded in and blended back to original contour.
Sidewalls are repaired first to strengthen the part, then airfoils are repaired.
A piece of heavy scrap metal is temporarily welded to the outer wall to help maintain it's correct radius.
Struts are made from 3/4" all-thread to help control warpage, and are placed as close
to the area to be welded as possible, without getting in the way.
1/8" thick copper is used to backup the weld, and in the pics where the trailing edge is being rebuilt,
a small copper "paddle" about 1/16 x 5/16" is used to support the weld metal and keep the cooling slots open.
In the repair of the center airfoil, about 1 1/4" of the trailing edge is completely removed and partially
replaced with a coupon to create a "floor" and part of the ribs that divide the cooling slots.
I've just finished putting the album together and have not yet added descriptions to the individual pics,
and some of them need cropping, but you'll get the general idea of what's being done.
You can zoom in on the pics using the little magnifying glass at the bottom right corner.
Originals were very large (3-4 megs)
http://s261.photobucket.com/user/bigcitybill/library/GE Frame 7 2nd stage nozzle segment?sort=4&page=1
of pics I took recently at work, showing the tedious process of repairing a 2nd stage nozzle segment
for a GE Frame 7 gas turbine engine.
This part had multiple areas of severe foreign object impact damage.
Damaged areas are cut away and new metal welded in and blended back to original contour.
Sidewalls are repaired first to strengthen the part, then airfoils are repaired.
A piece of heavy scrap metal is temporarily welded to the outer wall to help maintain it's correct radius.
Struts are made from 3/4" all-thread to help control warpage, and are placed as close
to the area to be welded as possible, without getting in the way.
1/8" thick copper is used to backup the weld, and in the pics where the trailing edge is being rebuilt,
a small copper "paddle" about 1/16 x 5/16" is used to support the weld metal and keep the cooling slots open.
In the repair of the center airfoil, about 1 1/4" of the trailing edge is completely removed and partially
replaced with a coupon to create a "floor" and part of the ribs that divide the cooling slots.
I've just finished putting the album together and have not yet added descriptions to the individual pics,
and some of them need cropping, but you'll get the general idea of what's being done.
You can zoom in on the pics using the little magnifying glass at the bottom right corner.
Originals were very large (3-4 megs)
http://s261.photobucket.com/user/bigcitybill/library/GE Frame 7 2nd stage nozzle segment?sort=4&page=1
Comments
The company has a very firm "NO PHOTOGRAPHY" policy that is enforced with gestapo like precision. Get caught with a camera, they destroy it, and you get time off! Cell phone cameras included. Have to ask permission, and you get the 10th degree on why you want photos. We were allowed once, when we installed a brand new GE high pressure steam turbine section that was specially built to be retrofit onto a Westinghouse combined turbine. It was a once in a lifetime thing.....everyone was watching, right up to the CEO who flew in from Houston. 250 ton lift, and the gantry crane was only rated to do it ONCE, so we could not screw it up! I forgot my camera the day we did the lift[V]
Definitely some cool stuff!
OK i still ain;t flying in that thing[:0]
[:D] Neither is anyone else [;)]
It's a stationary engine that powers a generator.
WOW!! [:0][:0]
VERY IMPRESSIVE!
That must be one ex-pen-sive gas turbine to warrant that kind of work on any sizable scale!!
Knowing what I know 'bout turbine costs...
I'm pretty positive that 5 day fix likely saved several times the hands on cost of a new replacement segment.
Normally not... BUT... Sometimes... Man hours are the cheapest methodology. [;)]
You can bet yer sweet bippy those parts are gonna get rebuilt
after it goes hand grenade.
I worked on some parts not long ago that were engraved with
names and numbers from every time it had been reworked dating all
the way back to 1978.
disassembled. Stage 1 has no segments, only an upper and lower half.
On the edge of the table, just to the left, is the most popular tool
in the shop - the Garland No.5 rawhide hammer.
The dark grey blurry slanted object on the table on the right
is a transition. They are arranged around, and feed into the nozzle.
On the left behind the waffle table are two combustion liners. One of them
feeds into each transition. The flange on the end that is up in the pic will accept the fuel nozzle,
and the end that is down (hidden) will go into the transition. The two smaller perpendicular flanges
are for crossfire tubes.
My machine shop buddy, who died a few years back, had secured a contract with Teledyne Allvac to do the "rough" machining on the forged titanium common shaft in a new GE Turbine engine design...
EACH shaft paid him $12,000.00 and he did two a week...
These were then sent off to another shop in Tennessee that did the "final" machining.
Before he died, he was working on securing a parallel contract to machine one "final" machined shaft every two weeks at a dollar amount of around $60,000.00
He was able to buy two new CNC lathes and stage them face to face to do the rough machining... Half on one... The remaining rough machining on the other. Both lathes being manned by one machinist. Lathe time was maximized and tolerances minimized by reducing necessary setups.
He also kept every shard of titanium to be sent back to the foundry... To be recycled. They paid him 100% of scrap value.
I built a cradle for my ATV sprayer and repaired a buggered step on the IH 756. Most of the welds looked pretty good.
..Now you're talkin' my language. If it can't be done with a plasma
cutter, oxy/acetylene and a stick welder, I shouldn't touch it. My
hat's off to you, Bill, and the other skilled welders here...[^]
By the looks of some of the other welds (or pieces) in progress, I'm guessing you must have to balance that nozzle similar to a wheel when you're all done so it doesn't explode from centripetal force, correct?
What RPM does it turn at? ...and how do you balance it (if my assumption is correct)?
Good questions... [?]
quote:Originally posted by Flying Clay Disk
By the looks of some of the other welds (or pieces) in progress, I'm guessing you must have to balance that nozzle similar to a wheel when you're all done so it doesn't explode from centripetal force, correct?
What RPM does it turn at? ...and how do you balance it (if my assumption is correct)?
Good questions... [?]
That is a stationary blade, it doesnt turn. This allows the expanding gas something to "push" the rotor off on....to keep it simple. There are blades on the rotor also. They start in a smaller diameter and increase is size as they go down the rotor. The blade rows can be opposed (ie mirror image rows, which is most likely to control trust)or just one set of ever expanding rows of blades. This design requires a larger thrust bearing opposite the generator. That would be an older, less efficient design. The rotor (not shown)spins and that is the part that MUST be balanced. This is done with weights screwed into the rotor at one, or both ends. Sometimes is takes a couple "balance shots" (ie....run up and downs with info gathered from the vibration sensors and a lot of math applied to determine the amount of weight needed, and its position on the rotor).
RPMs can differ by type of unit (ie Gas turbine, or steam) but its determined by the number of poles on the generator. Most steam turbine run at 3600, some 1800. If memory serves me correctly, a lot of the gas turbines spin faster....but its been awhile since Ive worked on one.
Ive spent many, many hours of my life running all over the east coast tearing these down, repairing, and rebuilding......its fun, but heavy, hot (they want that thing apart NOW....time is money in the generation business....so as soon has the RPMs hit zero, you are on it!)and very dirty work. But it pays damn good.
They direct the flow of hot gas into
the rotating turbine blades at a more
advantageous angle of engagement
A) We ain't set up for that.
axle/blade unit in the repair business.
C) The blades on the spinning parts
of the engine are removeable from the
hub and are repaired and rebalanced
individually.
I' d love to oblige but:
A) We ain't set up for that.
axle/blade unit in the repair business.
C) The blades on the spinning parts
of the engine are removeable from the
hub and are repaired and rebalanced
individually.
You must be a small shop. Ours are sent out when they get wrecked badly...places like Reliable turbine, or GE get them. Normal outage, we do the work ourselves right on the turbine deck.
On the big steam units, the blades do not come off easily. Takes special equipment and LOTS of heat, then usually re welding and machine to fit the new/repaired blades. That kind of work gets farmed out.
We are talking about a Low pressure rotor with a diameter of 35 feet blade tip to blade tip....F%$king huge!
10 or 12 of us on days,
6 or 7 moreon night shift.
I started to edit this post
so it wouldn't sound like l was
I was calling the night shift guys
morons.
Then l changed my mind.
A small shop indeed.
10 or 12 of us on days,
6 or 7 moreon night shift.
I started to edit this post
so it wouldn't sound like l was
I was calling the night shift guys
morons.
Then l changed my mind.
[:D][:D] Cool pics, thanks for sharing!
From one TiG welder to another- OH Joy!!! X-ray stuff!!![:D]
Before and after heat treat.
This kinda work will make
you pull your hair out by
the roots.
quote:Originally posted by FrancF
From one TiG welder to another- OH Joy!!! X-ray stuff!!![:D]
Before and after heat treat.
This kinda work will make
you pull your hair out by
the roots.
Been there- with Toxic Gas SST tube welding, I feel your pain![:D]
I gotta ask- Common sense tells me during damage inspection, the entire turbine is X-rayed for hidden cracks/damage etc. When does it become trash? IE what percentage of cracks/inclusions is beyond repair.?
If blades are cracked, they get replaced. If the rotor has cracks (very rare....they are made outta the very best metal)..it depends on where the cracks are...in the hub areas...its red lined.....coupling areas....RED LINED NOW.....other places, it depends. Ive seen some pretty messed up stuff that was brought back and still in use. You are talking 3 to 4 year lead time to get a replacement made...and its EXPENSIVE!!!!!! They only replace as a last resort. Ive only seen it once, and they used the old rotor at reduced load rating for the time it took to get the replacement made.
As welders- No matter what field of welding your in, Failure on our part can result in life changing consequences for the ones that don't know better.
Another one of a coupling failure.
This was a nasty one. When it failed, live steam was released....steam that is at 1050 degrees at 2000 psi.and also opened up the generator....which is hydrogen cooled...100% pure....they got lucky with that...the h2 didnt explode.
[imghttp://www.forensic.cc/images/07693m_turbine_generator_gearbox_disintegrated_overspeed.jpg][/img]
This is one where the same thing happened...and the hydrogen DID light off!! In Iran.....
They had a safety stand down at work after that one because we have a unit in the system just like that one (Alstom unit)....it was one hell of a mess...destroyed the whole thing, couple people killed.....
Yes, the welders MUST be good at what they do....lives are on the line!
The welder was built by Aaronson co, you operated the welder from a boom in a chair and all the controls on board. Graham Mfg. was the builder of the unit. This is about as far from tig welding as you might get but thought it interesting.