broken thread hole on Danfoss valve

[easternbob]

Been living with a slow drip on some of the piping around back on my boiler. But over the weekend I decided I was sick of it. I knew it was going to be a tough spot to sweat, and it was. took three trys but I think I got it (wasn't able to totally take the joint apart because of where it was would have had to take apart 5 other joints to do that). To drain the water out of the pipe I took the cover off the Danfoss. Well as I was tightening the four bolts down, thought just a little more and suddenly the one bolt got easier to turn, not good! I looked and I had broke out the side of the female thread in the body of the valve. It not leaking right now, I had used a little silcone on the mating surface.
Any thoughts on how to fix this? Replacing the whole valve is going to be tough, a ton of joints would have to be broken to replace, and then re-sweated (more potential leaks....). Thoughts on JB weld, and tapping the hole back out?

 

[ewdudley]

Could probably be done correctly with helicoil. But since all you're trying to do is put pressure on the plate you might consider some field-expedient can't-be-seen-from-the-road solution: cut a couple feet of 3/4" or so wide strip of inner tube/rubber roofing/etc. material, wrap tightly, and hold in place with a wrap of 14.5 gauge malleable iron [baling] wire.

 

[easternbob]

Is the helicoil going to work?? I didn't strip the threads but rather I broke away part of the cast body exposing the the bolt/thread hole, maybe 1/2-1/3 of the hole.
Was kicking around the idea of a u-bolt to apply pressure to that corner of the plate. You big rubber band idea would be easier.
Has anyone used JB stick, is that better than the JB in the tubes?

 

[mr.fixit]

How about a c clamp to clamp the cover to the valve body?
I never had much luck with jb weld.

 

[rkusek]

If you have 1/2 to 1/3 of the threads left to work with, can you find some all thread that size. Gently screw that in all the way and "gently" snug a nut on that without damaging the rest of the threads. I'm not a big fan of JB, silicone, or any of that stuff either.

 

[easternbob]

I might combine those two ideas. Put a c-clamp on to hold it in place and then screw in some threaded rod till it bottoms out and see if I can snug it up. Might work. Or at least will keep it till spring when I can be without the boiler without freezing

 

[Fred61]

Is there a solid space at the bottom of the drilled and tapped hole to possibly drill a little deeper and run a tap in to cut two or three more threads? You would need a #7 tap drill and a starting tap followed by a bottoming tap. And of course a longer screw. Trouble with a helicoil is that the helicoil tap opens the hole up even further reducing the width of the mating (sealing) surface as well as opening the fractured side.

 

[easternbob]

I thought about drilling the hole deeper and tapping it out. Little nervous don't want to drill to deep of course. will have to check to see if I can tell where those holes are in the casting. How do you know it's a #7 drill did you take your's apart or did you have to do something similar?

 

[velvetfoot]

Or at least will keep it till spring when I can be without the boiler without freezing

That's the best to hope for. On the other hand, you don't want to make it worse. If it's not leaking and you could apply some temporary clamp, or whatever, and keep a close eye on it, maybe that's the way to go. They have cheap water detectors, like $12 or so, that you could put near it. Maybe in a pan under the valve?

 

[Fred61]

I thought about drilling the hole deeper and tapping it out. Little nervous don't want to drill to deep of course. will have to check to see if I can tell where those holes are in the casting. How do you know it's a #7 drill did you take your's apart or did you have to do something similar?

You said it was a 1/4 inch screw so that is the tap drill size. If it is not 1/4 you must get a tap drill size chart and use the appropriate tap drill for it. I just have the tap drill size imprinted in my head as a result of 40 years stumbling through these things.

 

[huffdawg]

could you drill the hole a little larger ,tap it and then use a 5/16 bolt?

 

[easternbob]

Guys thanks for all the ideas. The plan right now is to put a c-clamp on it to get thru the rest of the cold weather and then when spring rolls around I'll see about drilling the hole a little deeper and putting a longer bolt in that hole.

 

[taylorfarms]

If it is a bigger cast valve take the sensing element out and weld in a piece of all thread with NI-55 rod and use it like a stud, if it is brass do the same with low melt brazing rod, or put a bolt in it, braze it and turn it out while still hot, run a tap through it and you are done.