Source of 8mm Dia flexible stainless steel tubing

[GreensandsParticipant @greensands]

I am piping up the superheater ‘tails’ of a 5″ gauge locomotive which are currently made from 5/16″/8mm  copper tubing and it is proving the devil’s own job to get them to line up with the external steam pipes which pass out through the smokebox. I have seen these short tail pieces made up from flexible jointed stainless steel tubing which of course makes the job of alignment so much easier but I have not been able to track down a possible supplier. Is anyone aware of a possible source of supply? It would help if I knew the proper term for this type of flexible tubing but other than describing it as being of concertina like construction and of course steam tight, I am not able to add anything further.  All views and opinions would be most welcomed,

[John HaineParticipant @johnhaine32865]

It might be a bellows if it looks like a concertina.

[noel shelleyParticipant @noelshelley55608]

though it may be of little consequence concertina pipe will not help gas flow. Noel.

[peak4Participant @peak4]

I think the term you’re looking for is “corrugated”, but beware, as some pipe/conduit using that description is the flex conduit made out of a spiral strip, which unwinds like a spring.
Whether you can find it as small as 8mm OD, or ID might be a different point
This type of stuff I presume, but smaller
https://www.esska-tech.co.uk/shop/Corrugated-stainless-steel-tube-for-flexible-connectivity-from-stainless-ste–7016KW211B00-24580

See also
https://www.bse3d.com/pliable-corrugated-stainless-steel-tube-for-gas-installations

This lot seem to do 10 or 6mm
https://www.undercontrol.co.uk/search?options%5Bprefix%5D=last&page=1&q=flexible+stainless

and
https://www.oilandgaspipingmaterials.com/stainless-steel-corrugated-tube-suppliers.html

Bill

[Martin ConnellyParticipant @martinconnelly55370]

At work we used stainless flexible pipes with convoluted pipe inside a braided sleeve. The problem with such pipes is that the convolutions are great at trapping any liquid or solid passing along the pipe. This can lead to corrosion forming in what is a thin and stressed piece of pipe. We even had to do hydrostatic pressure testing with treated water, that had all the chlorides in the water removed by RO followed by treatment in a cylinder of special media, to avoid corrosion in these sections of convoluted pipe.

Martin C

[PeteParticipant @pete41194]

If you want a metal surface on the line, then braided but still flexible hydraulic line with the correct fittings might also work? The interior is smooth. I’m unsure of it’s maximum heat range, but it’s not unusual to see hydraulic oil temperatures well over the boiling point of water. Visually it wouldn’t be something used at full size, but that may not be important to you.

Any hydraulic line will also have listings for multiple different busting pressure levels since it’s not at all uncommon for some systems to operate at 1,000-2,000 or upwards of 5,000 psi. This is a link to what’s standard in North America, https://www.mfcp.com/technical-info/tips/dash-size but searching for a UK website should turn up what might be available there. Any hydraulic repair shop should be able to properly answer how suitable it might be with straight steam.

[Alan CharlestonParticipant @alancharleston78882]

Hi,

I used to use these guys for flexible piping in a chemical handling system. I see they go down to 3mm. You may find their website is useful to see what is available. Being in NZ they’re not much good to you I suppose but I’m sure there’s someone local to you that you can use.

One thing I found when I was making pipelines was that if you want to connect two pipes which don’t line up and are close together, the solution is to attach the flexible hose to one pipe and wind it in a circle before connecting it to the second pipe.

Regards,

Alan C.

[JasonBModerator @jasonb]

Would the plastic/rubber within the braided options stand up to the heat within the smokebox?

[JasonB]

On JasonB Said:

Would the plastic/rubber within the braided options stand up to the heat within the smokebox?

I suspect not. AFAIK the most heat resistant option will be PTFE and that would be limited to around 220degC. There’s the pressure as well.

[noel shelleyParticipant @noelshelley55608]

In answer to petes point about using hydraulic pipe. On the matter of pressure2500psi would be considered normal, 4000psi common enough, and 10,000 not uncommon. There is no common type of pipe that would do this task in any size readily available. Being flexible is fine but you still need the space for the fittings, and it’s the space that the OP is lacking ! That the pipe is in the smoke box means you have the very abrasive char if coal fired, then there is the temperature – allow for 500c.

Copper elbows in 8 or 10mm are cheap and available, use silver solder to assemble, just a thought. Noel.

[Alan Charleston]

On Alan Charleston Said:

Hi,

I used to use these guys for flexible piping in a chemical handling system. I see they go down to 3mm. You may find their website is useful to see what is available. Being in NZ they’re not much good to you I suppose but I’m sure there’s someone local to you that you can use.

…

Hi Alan,

Is there supposed to be a link in your post? I’m always interested to learn of any suppliers of engineering-type stuff here in NZ…

[MichaelRParticipant @michaelr]

As Noel suggested in his post look into the possibility of using copper end flow elbows in 8mm size and silver solder.

See what’s available, I have no connection with this company

https://www.superdiscountplumbing.com/plumbing-supplies/end-feed-copper-fittings-plumbing-capillary-fittings

 

[parovozParticipant @parovoz]

I’m with the ‘definitely avoid corrugated pipe’ camp here. If one wants to slow something down in a pipe, corrugations are the way to go, it’s how a firearms silencer works. Slow the gas down and allow it to expand. Not what we want for our nicely superheated steam….

Look at the joint between the steam pipe between the superheater tail and the top of the steam pipe and utilise a fitting that has some alignment tolerance. Potentially and 8mm microbore compression fitting plumbing joint i.e. copper tube straight into an olive and nut it up. I used stainless steel joints like this on my wet header with great success, but with a 9 inch i.d. smoke box there was no great shortage of space. The dry ends of my Superheater have a lot of flex which eliminated the alignment issue for me.

 

An Example….

https://www.bes.co.uk/straight-adaptor-uk-compression-8mm-x-1-4in-6676/

 

To paraphrase and probably miss quote the great Chapelon, ” Any £#@# wit can get steam into a cylinder, it takes a genius to get it out. ” 🙂

[noel shelleyParticipant @noelshelley55608]

Following on from the above quote, the work of Porta carried on from Chapeleon. But neither of them, or others could do much about the poor thermal efficiency compared to an internal combustion engine. Noel.

[parovozParticipant @parovoz]

Yes Familiar with L.D. Porta too….. the Su class has a Lempor draughting arrangement. And yes, thermal deficiencies aside to basically take a bad loco and double it’s power is amazing…..

[noel shelleyParticipant @noelshelley55608]

Hi Parovoz, Gas flowing for IC engines had been known about and used in racing circles from 1900, steam is a gas for practical purposes, why did it take almost to the end of steam for the likes of Porta to tell what I would have thought was obvious to any body who understood gas flowing that it should work, and indeed it did – with spectacular results.  Look out IMLEC here I come . Noel.

[GreensandsParticipant @greensands]

Following a link made in another well known ME forum I have been able to establish contact with a company who can supply 1/4″ bore corrugated stainless steel tubing, (sales@iceoxford.com) and who make it available in metre lengths at a relatively reasonable price. Initial investigations would suggest that this was the product successfully used in a previous application and a fellow model engineer has informed me that it was perfectly satisfactory when used for the tail pieces of a superheater making assembly within a restricted 5″G smokebox so much easier. Failing any further information I have every intention of buying a length and carrying out some tests.

[Alan CharlestonParticipant @alancharleston78882]

Sorry, I forgot to include the link.

https://www.flexiducting.co.nz/product_cats/flexible-stainless-steel-hose/

Regards,

Alan C.

[Kiwi BlokeParticipant @kiwibloke62605]

Thanks Alan. I never cease to be amazed by what’s available here – (and frustrated by what’s not…).

[Speedy Builder5Participant @speedybuilder5]

I had a similar problem on my SPEEDY 5″ loco, so I modified an 8mm compression joint as the pipe exited the smokebox.  The small tube on the steam pipe is the steam oil feed.

[Author]

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