WINTER 2016

164 THE DISTRIBUTOR’S LINK
GUY AVELLON WHAT FASTENER DISTRIBUTORS NEED TO KNOW ABOUT PIPE FITTINGS from page 120
The second type of pipe threads, which are more
commonly used, is the NPTF, National Pipe Thread Fuel, or
also known as Dryseal Pipe Thread. The primary difference
between the NPT and NPTF is a change in truncating the
thread crest to match the truncated thread root. This
change allows contact between the roots and crests before
the thread flanks engage. Therefore, when the fitting is
tightened, the flanks of the threads are crushed producing
a metal-to-metal joint.
No thread sealant compound is necessary when the
Dryseal joints are used for the first time in a low pressure
application. Once the connection is broken, the threads
remain in their new form and will not be able to produce the
same interference fit as before. Therefore, if the fitting is to
be reused, a sealant is recommended.
Most all brass and hydraulic fittings with pipe threads
have the NPTF thread design. However, some black iron
pipe, galvanized pipe and pipe ports on older equipment
may contain the NPT thread design. Therefore, when the
NPT and NPTF are mated together, it is always wise to use
a pipe thread sealant.
In Closing;
At the beginning, I mentioned concerns of quality
issues. It appears that some manufacturers have
produced a forged fitting that looks as good as an
extruded fitting. This can have disastrous results if used
in a fuel application. If in doubt, cut or break the fitting.
A forged fitting will exhibit a coarse grain structure on the
inside whereas the extruded fitting will be much denser.
It was also reported that the wall thicknesses on some
fittings were thinner. In a competitive world economy,
this is an obvious attempt to save a little in cost but it
can only create problems during assembly and in use.
Lastly; brass fittings always had the ANSI/ASME
required manufacturer’s marking. Since importers are
using ISO specifications, there are no marking
requirements. That can lead to warranty issues and
claim responsibilities when manufacturers are not
identified.
So, the “buyer beware’” saying now applies to the
distributor as well.
GUY AVELLON
YOUNG FASTENER PROFESSIONALS - SPEED
NETWORKING EVENT, NIFMSE - OCTOBER 21, 2015