Question:
A friend of mine was given a Brewtus that had been back to the Brewtus
dealer 4 times for repair of the plastic pipe connecting the feedwater
preheat (in the steam boiler) to the inlet connection to the brew
boiler. The manufacturer uses a plastic pipe, which appears to end in
a flare of some sort. The flared tube fits over an internal ferrule
in the fitting to which the plastic tube is attached. The flare is
captured by a nut that compresses the flare against a sealing surface
on the fitting. The design seems pretty sketchy to me because the nut
imparts compressive load to a pretty thin flare. There's gotta be
stress concentration in the corner of the flare, and in fact the
failure of the tube occurred precisely at that point.
Answer:
Flaring plastic sound pretty lame. For that matter, using plastic to carry
hot water sounds lame also. How much would it have cost them at the factory
to use 6 inches of copper tubing for this line?
OTOH, a lot of home machines use nylon tubing with compression fittngs for
cold water. I've also used this tubing with compression fittings to run
water lines to filters, etc. I must say that it is easier to work with (more
flexible) than copper. The traditional compression fittings (which include
an extra metal insert when used with plastic) appear to work very well and
I've never had any leaks once they were tightened down. I can't say the
same thing for the "John Guest" quick connect type fittings which rely on a
o-ring for seal - it's only a matter of time befor the o-ring rots, while
compression gives a metal on metal seal that should be good for life once
tightened.
Flare tubing (in copper) is very common in the auto industry where it's used
for brake lines, etc. where pressures are extremely high. Again, if
properly done it's a leakproof metal on metal seal. I've never heard of
plastic being flared, probably for good reason.
As you say, the dealer should have tried another approach after the 2nd
failure. One definition of insanity is doing the same thing over and over
and expecting a different result.
Actually there are plastics that work fine at boiling water temps, so
I'm cool with the correct use of plastics. But this implementation
deserves a swift boot to the head.
The Techno is plumbed internally with 1 mm wall Teflon tubing going
into metal instant fittings of some sort. The larger (6 mm OD/4 mm ID)
tubing has a brass insert that reinforces it, but the smaller stuff is
used as-is. As long as I cut a fresh end on the tubing if I remove and
replace it, it's proven perfectly reliable in the six or so years I've
owned the machine.
