Hello. I’ve got a project on hand at work that I need some ideas for. My team and I have ran out of talent! We have a 1/4” dia. X 47” long thermocouple probe stuck and broken off inside of its 1/2” ID steel thermowell. This probe is used to measure internal metal temperature at the inside of our steam turbine. After several failed attempts at extraction, we are now left with the probe broken off about 8” up this steel pipe (thermowell). That leaves about 38” of probe still left in place. For a little bit of background, we tried pulling on it with a cable grip and slide hammer, tried pulling on it with a small come-a-long, tried twisting it, tried putting heat to it…. All to no avail. Now it’s broken off so far inside that we can’t get a bite on it.
The last plan of action I can come up with is to drill out the probe because I am assuming that the end of this wedged so tight way up in there it would not come out with normal extraction methods. It gets to over 1000 deg during normal operation so I’m sure there is some galling and debris wedging it in place. It hasn’t been removed since 2007 so that’s 16 years of thermal expansion and contraction seizing this probe in place.
This thermocouple is basically a 1/4” OD thin wall stainless steel tube with 6 small gauge wires and epoxy filler inside of it. It is mounted vertically inside of this steel well. Since the well is 1/2” ID and the probe is 1/4” OD, there is an air gap all the way around it with the exception of the very end where it has a slight taper according to the very vague drawing I have seen.
I’m on to our last ditch effort for removal. Since it’s mounted vertical, gravity will work in my favor if I can get some type of movement. I was thinking about ordering some extra long HSS drill bits to try drilling it out slowly. Maybe start with a 1/2” or 3/8” bit and see where thst goes. No one has cobalt drill bits that long readily available so I’m left with only HSS. Does this sound like a plan that might work, or would anyone else have a better idea? Are there any better tools or methods that could tackle this job?The hard thing is we cannot damage that outer steel casing well because it’s our barrier between 1000 deg steam at 2400psi and ambient conditions. Any tips on drilling it? It’s all going to be done with a cordless drill. It’s about 30’ up and I’ll be working off of scaffolding.
Any ideas would be much appreciated. I’m all ears on this one. This probe reads a very important temperature for starting our unit up. Without it, we are flying blind and guessing on temps.
The last plan of action I can come up with is to drill out the probe because I am assuming that the end of this wedged so tight way up in there it would not come out with normal extraction methods. It gets to over 1000 deg during normal operation so I’m sure there is some galling and debris wedging it in place. It hasn’t been removed since 2007 so that’s 16 years of thermal expansion and contraction seizing this probe in place.
This thermocouple is basically a 1/4” OD thin wall stainless steel tube with 6 small gauge wires and epoxy filler inside of it. It is mounted vertically inside of this steel well. Since the well is 1/2” ID and the probe is 1/4” OD, there is an air gap all the way around it with the exception of the very end where it has a slight taper according to the very vague drawing I have seen.
I’m on to our last ditch effort for removal. Since it’s mounted vertical, gravity will work in my favor if I can get some type of movement. I was thinking about ordering some extra long HSS drill bits to try drilling it out slowly. Maybe start with a 1/2” or 3/8” bit and see where thst goes. No one has cobalt drill bits that long readily available so I’m left with only HSS. Does this sound like a plan that might work, or would anyone else have a better idea? Are there any better tools or methods that could tackle this job?The hard thing is we cannot damage that outer steel casing well because it’s our barrier between 1000 deg steam at 2400psi and ambient conditions. Any tips on drilling it? It’s all going to be done with a cordless drill. It’s about 30’ up and I’ll be working off of scaffolding.
Any ideas would be much appreciated. I’m all ears on this one. This probe reads a very important temperature for starting our unit up. Without it, we are flying blind and guessing on temps.