Pete Deal
Titanium
- Joined
- Apr 10, 2007
- Location
- Morgantown, WV
Can you just make a new one?
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Thermocouple drilling/extraction
- Thread starter herthbn
- Start date
- Replies 80
- Views 5,023
Farmer Phil
Aluminum
- Joined
- Dec 12, 2017
I would approach it the following manner:
- . 450 OD tube/sleeve between well and t/c;
- Get some 1/4" carbide tipped masonry drills- you get the benefit of carbide without the disastrous effects of solid carbide most likely breaking;
- Weld 1/4" dia. round stock in whatever lengths you need. Start short and work your way to length. You could even shrink fit some bushings along the length to keep center of the sleeve.
Air will be your friend with chip removal.
- . 450 OD tube/sleeve between well and t/c;
- Get some 1/4" carbide tipped masonry drills- you get the benefit of carbide without the disastrous effects of solid carbide most likely breaking;
- Weld 1/4" dia. round stock in whatever lengths you need. Start short and work your way to length. You could even shrink fit some bushings along the length to keep center of the sleeve.
Air will be your friend with chip removal.
Lots of interesting ideas here, please let us hear how you make out. The only thing I would suggest is to mock up an example of the assembly on a workbench and try some of the ideas, refining the process as you go. Get a good bore scope to have a look in there. If you can get some thin wall tube to slide between the thermocouple it may be possible to fabricate a thermocouple that could fit in the annulus. The new thermocouple will probably not read exactly the same as the old probe but may provide more insight than running blind. Thermocouples can be made from very small wires or long strips or tubes of metal
WizardOfBoz
Diamond
- Joined
- Sep 30, 2006
- Location
- SE PA, Philly
So I think thermocouple construction for this termperature are usually a twisted pair insulated with ceramic mixe in an SS tube filled with ceramic.
So this is way into MacGyver territory but:
Get a thin-wall 1/4 od tube. Get a 3/16 x 18 drill bit to fit inside. Put the tube in until it bottoms out. Drill into the t/c through the tube. Peck and remove. Then weld a wood screw to a rod and see if it will engage. Possibly a wood screw with CA glue. ORRRR.... drop a little solder into the hole you've drilled, put flux on a rod that fits the hole, and heat the area up to melt the (small! amount of) solder. Cool everything then heat the rest of the thermowell.
Orrrr, the outer tc wall may guide a long drill in. The drill would remove the relatively softer ceramic and iron and constantan wires.
It does sound like t/c corroded around the point it broke. It may be unrecoverable.
What does a new thermowell cost? $1000 or so?
So this is way into MacGyver territory but:
Get a thin-wall 1/4 od tube. Get a 3/16 x 18 drill bit to fit inside. Put the tube in until it bottoms out. Drill into the t/c through the tube. Peck and remove. Then weld a wood screw to a rod and see if it will engage. Possibly a wood screw with CA glue. ORRRR.... drop a little solder into the hole you've drilled, put flux on a rod that fits the hole, and heat the area up to melt the (small! amount of) solder. Cool everything then heat the rest of the thermowell.
Orrrr, the outer tc wall may guide a long drill in. The drill would remove the relatively softer ceramic and iron and constantan wires.
It does sound like t/c corroded around the point it broke. It may be unrecoverable.
What does a new thermowell cost? $1000 or so?
Bill D
Diamond
- Joined
- Apr 1, 2004
- Location
- Modesto, CA USA
The problem with all these drilling ideas is the well is bent 15 degrees. Any drill and guide will need a a flex shaft to go around the bend.
Bill D.
Bill D.
Farmer Phil
Aluminum
- Joined
- Dec 12, 2017
I am under the impression that he is going to cut past the bend.
kb0thn
Stainless
- Joined
- May 15, 2008
- Location
- Winona, MN, USA
Look at a well overshoot. Female tapered aggressive thread.
Ill provide everyone with an update today. Refer to the attached drawing. The probe we are working on extracting is one of the two long ones.
Yesterday, we started by cutting out the bend and having a straight shot into the well. Then we took the route of using a piece of 3/8" x .049" wall stainless tubing and using it as a sort of stiff sleeve around the t/c. Our goal was to try to encase the broken thermocouple inside of the 3/8 tube in a hope to use the new tube as a guide to straighten out the probe. If it worked, the t/c would have been inside of the tube, and theoretically, the tube and t/c would just fall right out of the well once we got past the point in which was holding the probe in. We were able to drive the tube in the well only about 16", which I figure it about halfway. Looking at the drawing, this is likely at or near the point where the top well and bottom wells overlap each other. If I haven't said it yet, this is a two-piece well because there is an inner shell and outer shell casing. It was a HARD stop at this point. The 3/8 tube wont go past it no matter what. We tried about 7-8 different times with new tube and each time the tubing stopped and came out of the hole bent. The last time, we actually had to use a 1ton puller to extract the tube. With that much force to remove the sleeve, I would have thought it was bringing out the probe with it. NOPE.
Today, we shifted plans to hand drilling. We are using a range of 3/8" bits from 6" all the way up to 48", if needed. Some are cobalt and some are HSS. We have gotten about 8" in so far. It seems to be drilling pretty decent so far. The ceramic filler is a non issue. Its just crumbing out. However, we started walking a little bit for some reason that I cant figure out yet. The well is getting scored up when viewing it with a boresope. We will keep at it with this method for now and hopefully get back on track. I'm interested to see what's at the 16" depth and why a tube cant penetrate it.
Yesterday, we started by cutting out the bend and having a straight shot into the well. Then we took the route of using a piece of 3/8" x .049" wall stainless tubing and using it as a sort of stiff sleeve around the t/c. Our goal was to try to encase the broken thermocouple inside of the 3/8 tube in a hope to use the new tube as a guide to straighten out the probe. If it worked, the t/c would have been inside of the tube, and theoretically, the tube and t/c would just fall right out of the well once we got past the point in which was holding the probe in. We were able to drive the tube in the well only about 16", which I figure it about halfway. Looking at the drawing, this is likely at or near the point where the top well and bottom wells overlap each other. If I haven't said it yet, this is a two-piece well because there is an inner shell and outer shell casing. It was a HARD stop at this point. The 3/8 tube wont go past it no matter what. We tried about 7-8 different times with new tube and each time the tubing stopped and came out of the hole bent. The last time, we actually had to use a 1ton puller to extract the tube. With that much force to remove the sleeve, I would have thought it was bringing out the probe with it. NOPE.
Today, we shifted plans to hand drilling. We are using a range of 3/8" bits from 6" all the way up to 48", if needed. Some are cobalt and some are HSS. We have gotten about 8" in so far. It seems to be drilling pretty decent so far. The ceramic filler is a non issue. Its just crumbing out. However, we started walking a little bit for some reason that I cant figure out yet. The well is getting scored up when viewing it with a boresope. We will keep at it with this method for now and hopefully get back on track. I'm interested to see what's at the 16" depth and why a tube cant penetrate it.
Attachments
I would be tempted to make a pressure washer wand for water to go in the well. As much pressure as you can get of a pump, 3000+, 5000+ better. Make a straight nozzle that is offset from center so you can get a different impact spot by rotating the wand. It would remove debris around and inside the tube.
guythatbrews
Titanium
- Joined
- Dec 14, 2017
- Location
- MO, USA
Figuring loctite at 3000 psi shear strength gives about 2300 lbs of pull on 1" joint length. If the tc is .03 wall the ultimate tensile strength will be around 1800 lbs assuming 316SS. At least those numbers are favourable.
At least it's not 30' in the air and upside down.
Peter from Holland
Diamond
- Joined
- Jan 15, 2005
- Location
- The Netherlands
Why not tried the hydraulic methode first It would not have prevented other methods If filled properly a couple of inch overlapping the thermocouple would be enough
Peter
Peter
Even with such a thorough description I am having trouble picturing the entire scenario.
I like peters idea as well. I would start there.
I would think hand drilling is going to give sub optimal results. Could you modify a drill press of mag drill to at least give you some consistent feeds if you insist on going the drilling route?
Good luck with whatever you end up trying next.
I like peters idea as well. I would start there.
I would think hand drilling is going to give sub optimal results. Could you modify a drill press of mag drill to at least give you some consistent feeds if you insist on going the drilling route?
Good luck with whatever you end up trying next.
I was all
I was all for that method but the internal temps are still 400 deg. Any grease or sealant would likely just fall right out quick. The probe is actually drilling quite nicely but it appears that the well has a slight bend to it so it slowed down. Another day or two of cooling may allow us to use the hydraulic method.
Bill D
Diamond
- Joined
- Apr 1, 2004
- Location
- Modesto, CA USA
The hydraulic method can use playdough window putty, etc. other very stiff semi liquids that will take more heat.
careful selection will choose stuff that if it gets baked hard can be removed easily by acid or caustics.
Sand blasting has not been mentioned. use a really long nozzle so as not to erode the wells wall?
Bill D
careful selection will choose stuff that if it gets baked hard can be removed easily by acid or caustics.
Sand blasting has not been mentioned. use a really long nozzle so as not to erode the wells wall?
Bill D
jim rozen
Diamond
- Joined
- Feb 26, 2004
- Location
- peekskill, NY
Abrasive slurry pumped in under pressure though a tube, with the tube rotating to cut the part out.
All great ideas found here. Unfortunately, after getting only 8" in, we realized that the thermowell is not straight as the drawings shows it should be. This is why the tubing we were trying to insert over outside of the probe kept getting fouled up. We found that in only about 4", the well juts off to one side enough so that I lose sight of 1/2 of the 1/4" probe when viewing it with the borescope. My 3/8" bit was not flexible enough to make the bend. The only way to drill it would be a flex bit (if they even make that in HSS), and any type of tubing method is out as well unless it is super flexible.
Bill D, is stainless steel able to be eroded by sand, while not eroding the carbon steel well? Ill give my sandblast contractor a call and ask him on his experience.
Bill D, is stainless steel able to be eroded by sand, while not eroding the carbon steel well? Ill give my sandblast contractor a call and ask him on his experience.