On Sun, 15 Feb 2009 00:20:32 -0800, "Leo Lichtman"
wrote:


"Bill Noble" wrote: (clip) instead of the inside of the
valve body and the stem as with every other valve I've ever seen? There
must be some reason. (clip)
^^^^^^^^^^^^^^^^^
It could be that the designer is using the heavy valve handle on the outside
if the valve to add strength. But, what puzzles me as well is that the
valve handle appears to double as a packing nut. But that means that you
can't tighten it and leave it to eliminate leakage around the stem. Every
time you open the valve, you loosen the "packing nut."

I'm guessing different seals than packing for 3000 psi. Even a plain
o-ring would be marginal, would probably be chevron seals or o-ring
with backer.

Like Leo said, bigger threads equals more strength, plus better
protection from dirt in hydraulic service, possibly a non-rotating
stem as well, which would help prevent wear on seals and seat.

Pete Keillor