We are planning to use a Wilmad pressure tube (522-PV) for studies at
pressures of up to 150 psi and temperatures up to 150 C. According to the
Wilmad literature (Resonance Report NMR-003), this tube should handle
pressures < ~500 psi very well. But no information is available regarding
performance at elevated temp. Paul Cope of Wilmad offered caution
regarding the difference in the expansion of Teflon (used in the pressure
valve) and the glass tube at high T: a tightly torqued Teflon valve could
expand and shatter the tube as temp is elevated. Our glassblower noted
some stresses at the valve/tube joint, but we don't want to do any heat
annealling that will likely alter the critical dimensions of the NMR tube.
Should we be concerned about these stresses, or are they acceptable
compromises in the design? As you might expect, we are currently testing
the performance of the tubes (outside the NMR probe!) prior to actual
usage.
I was wondering if any of you had any personal experience with these tubes
at high T. Any tricks of the trade? If I get any substantive replies,
I'll post a summary to the list. THANKS!
David R. Kinney |All opinions are purely mine.
ARCO Chemical Company |
3801 West Chester Pike |
Newtown Square, PA 19073 USA |
Voice: (610)359-3455 |
Fax: (610)359-5573 |
EMail: cvxdrk@arco.com |