Boiler Fitting Seal

[electrosteam]

In the book "Building the Climax" by Kozo Hiraoka, many of the boiler fittings use a tapered seal without a gasket.
This design seems to be used only on brass/brass, not brass to boiler copper.

The diagram below shows the arrangement.
There is a small rebate, typically dia 8.1 for a M8x1 thread, providing a 90 degree edge on the housing which is contacted by the 45 degree taper on the plug.
The dotted line shows the contact point between the plug and the housing.

Can anyone comment on the effectiveness of this design ?

John

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[Deleted]

I've no experience of that type of joint, but the fitting would appear to be very weak if it gets an accidental knock.

[pault]

Hi John,
It would seal well without sealant, however I totaly agree with Superseven that it would be very weak, and for that reason i would not use it.

Regards
Paul

[RGR 60130]

I've seen a similar idea used before and these are a tighten once type of joint as designed. If you need to try to re-use them then you need a good quality thread sealant like 'SWAK'.

Without the ability to fit a copper washer to get your alignment correct (say screwing a manifold into a bush on the boiler top), getting the bush correctly orientated when silver soldering it in is going to be quite critical.

Reg

[electrosteam]

Thanks for the comments, I raised the subject because I was a bit dubious myself.
Note that this seal seems to be only used brass/brass, so a certain amount of persuasion could be applied knowing that the two parts can be replaced, if necessary.

A typical application is the bottom water gauge fitting.
The boiler copper connection is a banjo with gasket to a water column, described by Kozo as providing gauge stability, with the glass fittings soldered to the column.
The banjo bolt and the column vent are tapered seals as described.

I have since discovered that Village Press have a Forum for Hiraoka subjects, so I may make enquiries there.
Apparently Kozo will be starting a new build thread, for a D&RG K27, later in the year - it will be interesting if Kozo uses the same design.

John.

[Nigel Bennett]

I find that sealing of threaded components is readily achieved by using Loctite 542 Hydraulic Sealant. You would not necessarily need the tapered sealing face as shown above. I would never use brass for boiler fittings, particularly those below the water level if you are going to steam the thing.

[electrosteam]

I got one response in the US that the K. Hiraoka design has operated well for several years.
I re-checked the Climax, brass is happily specified widely for boiler fittings.
Apparently though, in the later book on the Shay, phosphor bronze is specified for the steam tubing nipples.
I am a recent entry into this field and I will discuss with local boiler inspectors the use of brass.
John

[nonort]

Kozo's background is in heavy plant and this kind of fitting is very common as it requires 'no' sealant. Which can at high pressures can cause many problems ie oil on oxygen fittings. Truth is the pressures we use are miniscule compared to the world of the chemical industry, were I think Kozo works. It's all horses for courses.

[Shawki Shlemon]

In our club , the club engine , a Lima 7.25" G had brass fittings , after 15 years of operation , that is every Saturday running all day hauling passengers ( except when the engine was in repair , not many times as most maintenance was done on working day ) we had to replace blow down fittings which started giving trouble . While bronze is better for sure it depends on what engine is for and how much will be used .A matter of decision .

[Nigel Bennett]

When (as I have done) you've broken brass fittings off a boiler with your fingers, revealing a spongy material with the strength of chocolate cake, you become a little circumspect. I thought a brass plug in the end of my bronze water gauge fitting on Edward Thomas would be OK in brass - but it broke like a carrot when I wanted to rod the fittings through after perhaps 100 hours of steaming.

[Shawki Shlemon]

May be we have better water in OZ .

[steam4ian]

No disrespect meant.

This discussion is getting a little TDS!

Ian