The Steamboating Forum

Hi
I have to replace a number of 40 mm boiler tubes in a special water tube boiler. See picture.
The outer and the inner barrel (flue gas uptake) is bolted together.
I can cut all the tubes inside the flue gas pass - but I wonder how to remove the remaining pieces from the tube sheets - without damaging the holes?
In one end they are fittet with bushings - but I anticipate that does not affect the procedure.
Regards
Jørgen

Others will chime with good advice but mine is to use a simple adjustable fly cutter. It should be guided by the inside diameter of the bushings. Light cuts until you know the size of the holes in your tube sheet. You could

Depending on how much crud is on the outside of the tubes they should drive out without too much drama.

Lots of lubrication and a six pack of beer. Oil lubrication that is.

Mike

On a separate note, with the tubes horizontal as they are in that boiler, it seems as though the water circulation would be very poor. Better that they be inclined as in most water tube designs. I suppose it has worked for quite a while.

Mike

I can't tell just how big those are, but if large enough, catch a cold chisel on the edge and collapse the tube into the hole.

Lopez Mike wrote: ↑Fri Dec 04, 2020 3:47 am On a separate note, with the tubes horizontal as they are in that boiler, it seems as though the water circulation would be very poor. Better that they be inclined as in most water tube designs. I suppose it has worked for quite a while.

Mike

Mike, I'm not sure they are horizontal. the right side layer rises to the right and the left side to the left so they must lay off level. Difficult to see clearly or visualise.

https://www.youtube.com/watch?v=vqnMJmjtvGw
This might be a little over the top, but on a smaller scale the operation is much the same. Instead of a plane round nosed gouge a " safety ripping chisel " was used by the boilermakers when they removed a tube for inspection on the ship I was on. The tool is ground with the sides cut back allowing only the center to cut just less than the thickness of the tube wall. Hard to explain clearly, I'll see if I can find a drawing of one that I can post.

Dave

I found it much quicker than I thought it would be. A little work with an angle grinder and a standard chisel could be modified. May not be worth the effort if only a couple of tubes are involved.

Good luck
Dave

With an oxygen/acetylene or propane cutting torch, its very easy cut those tubes without cutting edges of the holes. Just concentrate the heat on the tube only and they can be slit, collapsed and removed. The torch will only cut what's been heated to the proper temperature, the heat will not transfer where the tube and tube sheet touch. A plasma arc will cut whatever is grounded, so don't use that.

After four or five tubes it would be advisable to run some water on the tubesheet to cool it down. Or maybe after each one?

Also, I would have the shell ultrasound thickness tested, it looks badly corroded.

A cutting torch is a mechanics right arm, can cut nuts off bolts without damaging the bolt. I've done it quite a few times successfully. Cut bearings off old Ford rear axles. Lopezmike is probably familiar.

Thanks for the advises guys.
Just a commet - the tubes are not horisontal - I gues sloping some 4 degr.
Have a nice weekend
Jørgen

Ron, turning me loose with a cutting torch for any precision or delicate work is like a drunken surgeon with a chain saw. Not pretty sight.

Reminds me of a YouTube video I just watched that starts out, "We made a defibrillator at home." This not going to end well.

Now I have blown out a busted off bolt in cast iron many a time. Set myself on fire a time or two as well.

Mike