On Jul 14, 3:59*pm, cynic wrote:

The pipe is bolted inside a firebox that's red hot and contains steam
at 110 psi.

In that case I would be inclined to change to a fabricated stainless
steel version.

That's probably not permissible, for most steam boiler certification
(depends where in the world you are).

The problem is that an old boiler doesn't meet modern design standards
- often because there's no discernible "design" recorded for it. If it
exists, hasn't killed anyone lately, and some basic objective tests
say that it's in good condition for its original design, then the
design can be grandfathered in and the boiler can be ticketed.

OTOH, if you _change_ its design, even in a fairly minor way, then you
have a new design to contend with, and you're into a world of
paperwork. It also (and this is the problem) loses grandfathering
status for other parts of the boiler. You may very well make an
improvement to one dubious part of the boiler, only to then fail all
hope of certification because some other non-problematic aspect is now
seen as inadequate.

This catch 22 is a reason for scrapping many contemporary boilers that
in a more holistic world could continue operation. You may find an
inspector with literally half a clue, who won't pass the old part
because it's knackered, but won't allow it to be replaced
appropriately without condemining the rest of the boiler.


OTOH, don't introduce stainless into an old boiler unless you know
what you're doing and you also keep a close eye on alloys. You can
really screw things up with galvanic corrosion, if you're not careful.