HP 5890 SERIES II Service Manual page 239

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Also note the rotor type stamped into the valve body. The letter indicates the rotor installed in the particular
body. The rotors are interchangeable. Polytetrafluorethylene (Teflon) rotors may be used from 0 to 175
degrees C (This low temperature valve may be marked with P). High Temperature (polyimide) rotors may be
used from 100 to 350 degrees C (This high temperature valve may be marked with PT or just T). The rotor
seat of the valve body is a highly polished conical surface. This finish precludes adsorption of most GC
samples. Additionally, the polished surface with a properly seated rotor will prevent leakage around the
rotor and between nonselected ports.
The rotor assembly is an integral molded and machined conical hub, necessary for proper seating. The
sample will contact either Teflon (low temperature) or polyimide (high temperature) as well as the stainless
steel of the valve.
The rotor fits precisely into the body and nests in the conical seat. It is held in place by a preload assembly.
The grooves in the rotor determine the paths between specific ports. The index pin prevents rotation be-
yond either stop of the index lip. Valve ports are connected by the grooves only when the index pin is close
to or against either stop of the index lip. Any intermediate position results in shutoff of flow through the valve.
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