I'm afraid I may have ruined my boiler too. A plug broke off during removal, and I took it to someone who got it out but in the process ran the tap essentially all the way in, leaving a pretty sloppy fit. I found a hex nipple with some extra thread at the top, put RectorSeal 5 on it, and ran it in almost all the way. It still leaks water at 40 PSI.

Before throwing the boiler out, is there any radical sealer/cement that I could try to permanently seal this joint? The hole is too close to boiler tubes to enlarge it. I'm afraid that welding in a plug will distort the top sheet and the nearby tubes will leak.

Any chance of something like JB Weld, liquid steel, etc. creating a permanent fill & seal? I even have some genuine old-fashioned iron cement. I'd appreciate your thoughts.

Kelly

No worry, it can be easily fixed. The oversized tapped hole can be welded shut without any damage using a wire feed welder. To keep the damaging heat down, the person doing the welding welds little dabs at a time. Chances are that the adjacent tube will have to be swagged tight again because as your new weld cools, the metal shrinks and the shrinking will releave the sealing stress to the adjacent tubes. If the oversized hole is along the side of the tube sheet, it will be the easiest to fix because the boiler wall will act as a heat sink to draw the heat away from the tube sheet. The plugged hole can now be redrilled and tapped for your fitting. Due to hard spots and possible scaling in the weld, it would be wisest to relocate the tapped hole to another spot.

I forgot to mention a quick fix that I have used in the past for oversized pipe threads. If the hole was tapped too big, and the next sized pipe tap cannot be used, machine a custom oversized pipe fitting to take the place of the standard sized fitting.

I have found that if you get the high pressure 8000 PSI and above steel hex head plugs they tend to run stronger on the fit. You even sometimes have to run the pipe tap in much more then normal.

Rolly

Kelly,
I think I would try in the order of the easiest...
1. Rolly's suggestion of an 8000 PSI fitting.
2. Have a custom one made.
Bob

Kelly,
Xpando is the best pipe thread sealant for damaged threads.It comes in powder form and you mix it up like hydraulic cement. You will still need to purchase or have a good steel plug made to repair it prorerly. If you have to weld it there are heat sink materials which you can put around the weld area to help minimize the effect on adjacent tubes.

James
Thanks for the tip. I had never heard of this stuff before. It is rated for superheated steam. it is rated for use up to 5000 PSI and 1000 F. Sounds like it would work on the top of the boiler with no problem. 600 F is about as high as you get on stack temperature, and 600-PSI boiler saturated temperature is only 486 F.
JB weld is only rated for 500 F, I wouldn’t use it on a high-pressure steam boiler.

Rolly



Edited 1 time(s). Last edit at 04/13/2010 02:57PM by Rolly.

OK, the boiler shop has finally gotten around to me. They think they can weld up the hole, but they have no tube tools small enough to tighten up the adjacent tubes. (I'm not going to reuse the hole.)

These are copper tubes with a (rusty) steel ferrule inside. I've seen a tool that has a gentle curved flare, that you insert in the tube and hit with a hammer. Will this work for the steel/copper situation?

And, the swaging tools I see for sale don't have that curve, just a 45. Will that work ok? Or should I find a curved one?

Did you try the 8000 PSI plug with the Xpando pipe sealant?
If you not going to reuse the hole I would ream it smooth and round and drive in a 1-1/2 degree tapered plug. Welding should be the very last resort.
See attachment

Someone will have to buy a tube roller. Or should.
[www.tcwilson.com]

Rolly



Edited 1 time(s). Last edit at 05/14/2010 10:51PM by Rolly.

I agree that welding should be a last resort if considered at all.
My background is as a mechanical repair contractor for large tonnage chillers and boilers. Many a tube has been successfully plugged. In the event you decide to re-tube the boiler it can be removed. In the years that I've worked on tubed heat exchangers I've used Elliott Tool Technologies for all of my tube tool needs. They provide tool rental and it is important to get the proper tube rolling motor that is used in conjunction with the tube roller/expander to achieve a tight (leak free) tube to tube-sheet joint. They also have very comprehensive literature for guidance along with a great technical staff that will work to make sure that you get the right tool for the job.
Their web site is [www.elliott-tool.com]
Please consider this avenue.

Larry



Edited 3 time(s). Last edit at 05/15/2010 04:34AM by JW.

Kelly
Hopefully you have not done any welding.
Another fix you may want to try before using a tapered plug.
I am assuming the tapped hole is just a little over size as you stated.

Get a forged steel reducing bushing and a forged steel plug for the reducing bushing. You can get these in two days from McMaster-CARR if your local supplier does not have forged steel.
Heat the forged steel reducing bushing cherry red and let it cool slowly. It’s now annealed.
Install the reducing bushing in the hole with the Xpando pipe sealant, using a socket and breaker bar.
Then take the hex head forged steel pipe plug you got for the reducing bushing and coat it with anti-seize, using a breaker bar and socket or better yet a impact socket and pneumatic gun and drive the plug into the bushing. This should expand the reducing bushing in the hole.
You may need to re- roll the tubes around this fix, as you will have stressed the tube sheet somewhat.
Rolly

Rolly

I'm afraid that, in addition to being oversized, the threads are no longer shaped right, that they've been blunted and don't provide full engagement.

The 8000lb pipe plug bottoms out before getting tight.
I found a hex nipple with some extra threads, put a regular sealer on it, and got it pretty tight, but it leaked water at 40psi.

One problem with using these plugs seemed to be that I ended up with a hex, either the plug head or the nipple's hex, that was so close to the adjoining tubes that it wouldn't be possible to get an expanding tool in. The tubes adjacent to the threaded hole are already leaking at 40psi after the botched work on the threaded hole, so they already need re-expanding. Should I measure the ID of the ferrule and choose rollers for the tcwilson tool that fit inside that?

That's why it seemed better to just weld it, return to a more or less flat tube sheet in that area, and re-expand the tubes to take care of the leak that was already there and any additional movement caused by the welding.

Kelly,
See my post above, item #2.
Have a plug made that is slightly over-sized. A slightly over-sized tapered plug will tighten up and wih appropriate sealers likely will not leak. I would give that a try before I moved on to the welding.
Bob

Kelly
Getting the over size plug made, would be my first option. Bobs right on this one.
Second would be to try and expand a reducing bushing. You can still get it out.
Remember anything left out side the tube sheet can be cut off.
Another option is to put in a plug with a drilled hole through the center and drive in a tapered plug into it, expanding the threaded plug. Any thing to not make the hole larger.
If you decide to use just a tapered plug, you will need a clean reamed round hole. I’ve used these plugs up to a 1000-PSI hydro. I make my own but you can buy them.
There are a few more options but they require some machining and skill on making up the parts.
Before you weld look at the Elliott tube plugs.
Also they make tube rollers as well. I use the Wilson but I’m sure they’re just as good.
Measure the inside diameter of your tube and talk to a sales rep. They work over a small range in diameter.
[www.elliott-tool.com]

Rolly



Edited 1 time(s). Last edit at 05/15/2010 06:59PM by Rolly.

This morning in the shop I was into a cabinet and in front of me was my box of standard tappered pins. Knowing I had a good supply of 1/4 forged steel plugs I took two and the larger end of the thread measured out at 0.530
I drilled a hole through them using the lathe to keep the hole centered. I heated them red to anneal them. Using a number 6 pin I swabbed with anti seize and pushed all the way in. The second plug I used a smalled drill bit just large enough to start the pin. I expanded the first plug out to 0.540 and the second one to 0.558 so large it won't start in a standard 1/4 inch IPS hole.
Less then half and hour to make two over size plugs.

Rolly

Gentlemen,

I very much appreciate your encouragement and your ideas. Rolly, thank you for taking the time to work up those samples.

The boiler is now in the hands of a talented machinist, who has done some fairly sophisticated, and successful, custom work, including fabricating mechanical parts for brass cars. (My machine shop expertise so far hasn't gone beyond 1 semester at the vo-tech, and I have no equipment.)

Attached are a couple of photos of the problem - one showing a nice 1/4 pipe threaded hole, not far from the bad one, and the other showing several views of the bad one, including the condition of the threads and how close it is to the nearest tube. (This boiler has 720 tubes.) Also how the hex-head pipe plug runs down with fingers until it bumps into the neighboring ferrule.

I asked him to do the following, actually a combination of some of these ideas, suggested by Don Bourdon. Machine an oversized plug out of plain steel. Run it in snugly, but not cranked in hard enough to risk stretching the narrow web between the threaded hole and the nearest tube. Remove plug material above the tube sheet surface. Apply the lightest touch of TIG around the circle between the plug body and the tube sheet, for a permanent seal. He's confident that he can do the repair this way with minimal additional distortion of the tube sheet around the neighboring tubes.

Then I'll re-expand the neighboring tubes, and let you (& folks who search the forum in the future) know what happens...

Don is right on all points, Don't tighten the plug too tight. Somebody really screwed up on the placement of that tapped hole. It is going to be a fragile operation plugging it.

Tapered plug made on lathe, hole tapped slightly more for a cleaner fit, X-Pando on order, all welding deferred, fingers crossed. It's encouraging to read of Ian's success in tightening up his entire crown sheet - I only have 3 tubes to worry about.

Well, it pretty much worked. I pumped it up to 670psi using the car's pumps, and at that point the pump drive rod was making an occasional odd clunk. Let it sit for an hour, dropped to 625. Swedging a few leaking tubes as found, ensuring that the leaks stopped. Unfortunately a tiny drop was coming through the XPando. Put a blanket over the boiler and pointed a cube heater at the bottom of the boiler. 2 hours later, pressure was 720, and I turned off the heat. No water coming through the XPando.

11 hours later, pressure was essentially gone. Only visible leaks are around the gauge fitting and around the plugs in the blowdown holes. I can't quite figure this one out - the holes are freshly cleaned out and in fact tapped a little deeper, to match tapered pipe depth gauges. And the plugs are cranked in really tight. I'll have to assume that when the fire is on, things will close up. At worst, hopefully the system will be able to just keep up with that amount of weeping.

Using the swedge was pretty nice - just a few drops of a 2 lb hammer allowed the tubes to expand in a nicely controlled way. It's surprising how much bigger the ferrule openings are in those tubes - hopefully the copper isn't paper-thin there now.

Nice job Kelly
I’m glad you did not try welding.
Rolly