Merry Christmas and Happy Holidays to everyone, here's a brief update on the 28:





All tubes are now physically in the boiler. Actual numbers are 168 boiler tubes and 27 superheater tubes. Next steps are welding and beading on the rear tube sheet, replacing 4 staybolts and testing the superheater elements before the Hydro.

Duluth & Northeastern 28 was front page news recently in the Lake County (Minnesota) Chronicle: http://www.lcnewschronicle.com/news/two ... bygone-era



This covers final payment for all boiler work performed by Fraser Shipyards back in November and December. Myself and other shop volunteers finished cleaning up all the staybolts on Thursday (2/18). Waiting on Teflon washers to reinstall the staybolt caps and a couple other small projects before we're ready for the hydro.

While major boiler work is complete, we are still accepting donations towards fabrication and installation of boiler lagging and jacketing. http://northshorescenicrailroad.org/fireupthe28.html

Never heard of Teflon staybolt cap gaskets. Be interesting to see how they work. I've only seen copper.
Good luck, you're coming right along.

Not as well as copper. Proper copper gaskets are only about $1.50 to $1.75, how much are the teflon ones running these days?

Since this is a "captured" installed location, teflon might be OK, but teflon stays fluid. There are/were some steam operators who would fire you on the spot if they found teflon tape in your tool box, as it likes to string out inside a steam line and then cause problems.
You have to be careful with modern material, sometimes they are not a good "upgrade."

I used Teflon rings in 1522's throttle stuffing box and never had any issues with it.

I just hadn't heard of it used in staybolt caps. I've been out of the game for a while, so I'm sure there are a lot of new things around. Back then, we bought one of the laser temperature guns and paid a fortune for it. I see them at the Chinese hardware store for twenty something now.

That's true, kinda, but for a different reason. Teflon thread sealing tape is, first and foremost, tape. It might be finer than frog fur, but it's still tape. In a threaded connection, there is no way to ensure that strings of tape don't squeeze out of the joint and get carried away with the fluid flow.

I won't use teflon tape on hydraulic systems, because those strings of tape, as thin as they are, are just marginally thicker than the clearance of the spools in control valves and can cause a stuck valve.

It's also not a good idea to use teflon tape on air brake systems, for the exact same reason.

Correct me if I am wrong, but I sincerely (steamcerely? ;-)) doubt we are talking about using Teflon pipe tape on a washout plug or staybolt cap.

This would be the same kind of 'hard' Teflon bushing discussed for 1522, used in place of deformable copper, no?. Dope or tape on the threads wouldn't be the same, would it?

BTW, my understanding is that Teflon in cylinder bushings or rings is NOT suitable on locomotives that develop a substantial degree of superheat (this if I recall coming in part from the European SLM/DLM), and that might extend to use in some post-element poppet throttles under conditions of heavy sustained steam demand... somebody with distinctive materials knowledge 'confirm, deny, or amplify'.

No. No tape or dope. This is a hard, machinable product.

Nor is it used for piston or valve rings; just staybolt cap gaskets.

Can be used in throttle stuffing boxes, too.

Correct, we are talking about staybolt cap gaskets only.

I understood the application, I just wanted to be certain the folks understand that while appearing hard, and a machinable material, it remains plastic and can move around. As I mentioned, stay-bolt cap gaskets are a fairly contained usage, as is valve packing, where its plastic nature and slipperiness can be used to good advantage, although, as has been pointed out, maybe not so good at elevated temperatures.
I'm cautious with "new technology" as, in my day job (player piano repair), modern materials were tried back in the 1970s that were going to revolutionize player repair and provide artificial materials that would never go bad, as the natural materials sometimes do (natural being leathers, rubberized natural cloths). 15 years, or less, down the road, these miracle materials were failing, badly. Worse, the new glues made it difficult, sometimes impossible, to take the units apart and replace the failed materials.
I think you can now see why I am cautious of new materials. New technology, though, has made a lot of our work much easier,; non-destructive thickness testing, etc.

Another issue - PTFE also starts to off-gas around 390 degrees. Steam temp at 200psi is 388 and crown sheet temp is well above that, so any additional heat transfer to the teflon (hot spots transmitted through the stays themselves, particularly shorter ones) puts you well into gas territory. If your tea-kettle is operating above 200, you're getting into dangerous territory. At 500 degrees, PTFE starts to go deteriorate, and decomposes at something like 660. PTFE gasses can cause Teflon Flu. I realize a steam locomotive cab is more or less an outdoor environment, but Teflon is not your friend.

http://www.greenhealthwatch.com/newssto ... eflon.html

I know this is a green article on "frying pans" but it gives you the heat and gas off temperature ranges for C-8/Teflon.
I went to a safety training class sponsored by a major University for their facilities and invited guests. The topic was eliminating Teflon on the campus due to "concerns". I was taken back with several items including Teflon and the unseen impacts. We formerly used Teflon packet washers in high pressure steam pumps and flow valves, the University eliminated them on a replacement process back to the old style parts with a small improvement in life. I even use pipe dope over Teflon tape if near any heat source.
so be it! Just a word of caution to your process.

Unless the caps are leaking, how will any Teflon fumes get out of those sleeves?

I think the concern here is the possible structural integrity of the Teflon if it is off-gassing.
Methinks it is time to anneal some copper!
But, what do I know??