Threaded Pipe Removal Question

[Cass]

I want to pose a question.

You have an old 2" steel threaded 90 with a pipe on it and you need to remove the pipe. You put your 2' pipe wrench on it and it won't budge. So you get out your trusty torch and heat it up and bingo out comes the pipe because you heated the fitting and it expanded.

Right?

Here is my question.

When you heat steel it expands, but I don't think it expands in only one direction. I think it expands from the center outward which would make it expand away from the threads on the outside of the fitting but towards the threads on the inside of the fitting.

What say ye O wize ones.

 

[Master Plumber Mark]

duh???

I have never really thought too much about
how this little trick works, the thermodynamics
of it all ect, ect, when takeing out a large stink pipe..


If you are like me,
you havent had a vacation in a while, have you??

you got to get a hobby or something...LOL

 

[Sponsor]

 

[Cass]

Yes I haven't had a vaca. for many years. I just take off days here and there. I have a hobby. I make soap.

 

[hj]

pipe

True, but normally you heat the fitting so it will expand faster, or if it is a different material it will have a different coefficient of expansion. And sometimes you just need the heat to soften whatever is keeping it from turning, like when you do a Delta faucet repair.

 

[Cass]

I shouldn't matter how fast it heats, as it expands it is expanding towards the threads not away.

I think, like you said, it is affecting the old pipe dope or whatever is holding it.

 

[hj]

expansion

Not true. Everything is trying to expand away from the rest of the material. Therefore the molecules at the thread are trying to get away from their neighbors which causes the "thread" to get larger. As one of my professors said, "If you draw a circle on a square piece of metal and heat it, the circle will get larger. If you cut out the circle and then heat the metal, the opening will still get larger". The surrounding metal will not 'shrink' to make the hole smaller, which would mean that the metal at the opening was contracting rather than expanding.

 

[Cal]

Somewhat along those lines,,,,,,,,, Why do people advise wd-40 on threaded pipes that they can't break loose? We put these things together 40+ years ago so that NOTHING would come through the threads,,,,Now we think some little spray bottle of lube is going to change that ?,,,,go figure

I'm not sure why the heat trick works,,,Maybe because the heat expands the fitting first if we heat that,,,,the heat hasn't gotten to the threaded nipple yet and doesn't expand that outward to the fitting threads.

I need a vacation too !

Cal

 

[FloridaOrange]

You are assuming that the one part will heat evenly. With your torch you're heating the outside of the material first. I would think that the heated material is going to expand outward, it's easier for the material to do so as opposed to trying to expand towards solid metal.

I think your hypothesis would be more correct if you were heating the entire assembly evenly.

 

[Master Plumber Mark]

heating the pipe to cherry red

Hi, you need a vacation too......


anyway, when you heat an old 2 inch galvanized pipe

it seems best to heat the "fitting only" and not try to get

everything else involved....


by heating the fitting evenly around the end that
the pipe is stuck into, to a nice "cherry red"
it does expand away from the inner joint......

and then usually with a large pripe wrench and cheater bar

everything goes ... your way...

---------------------------------------------------------------------


on another note

my vacation starts next week when my 350 lb sister in law comes
to town for x-mas and stays with us for a

---full ----fun ---week----thats 7 days and nights


I will be heading to land of Jack Daniles and I might stop off to see
Johhy Walker too

It gets me through the holidazes

my posts here could start getting a little sloppy


ho ho merry x-mas

 

[Speedbump]

I'm joining Mark for Christmas.

Wouldn't just heating the metal which softens it be sufficient for making the threads come out easier?

I do it all the time to remove the 1" plug from the top of a 42 gallon galvanized tank for our sulphur removal system. They really crank them in there, my impact wrench won't remove them until we make the welded coupling cherry red.

Why do people use WD-40 for anything but displacing water, that is what it was designed for. Remember the old Plymouth distributor caps?

Well it's lunch time, let's go have a beer!

bob...