HP 5890 SERIES II Service Manual page 247

graph oven during a temperature- programmed run, the valve temperature can lag behind the pro-
grammed oven temperature by as much as 20 degrees depending on the rate employed. The mass of
the programmed valve is responsible for this lag. For this and other reasons, gas chromatograph
oven- mounted valves are not offered on the HP 5890.
An actual 6- port valve viewed from the actuator side is illustrated in Figure 2- 4. A functional two- di-
mensional diagram representing the same valve is shown in Figure 2- 5.
Note that with this type of diagram, not only the external ports are drawn, but rotor grooves are easy to
see. The transverse grooves appear as curved lines. Note the change in the port- to- port connec-
tions by the grooves when the valve rotor is moved from the left stop to the right stop. Also note that
the rotor grooves move, but the ports do not. Figure 2- 6 Illustrates a Simplified Valve Diagram.
Note that the essential valve features are not lost; namely the index pin, stops, ports, and grooves. This
is the type of diagram that will be used throughout this section. The 6- port, and 10- port valves and
the LSVs function in the same basic manner but with different port locations and rotor grooves.
Some other symbols used in the plumbing configuration diagrams are shown in Figure 2- 7.
Adjustable Restrictor
This restrictor is not designed for temperatures greater than 175 degrees C; for this reason this adjust-
able restrictor is NOT compatible with high- temperature valves.
Gas Sample Loops
A 1.0cc sample loop is included with all valve systems configured for gas sampling. 10.0cc and 5.0cc
loops occupy one valve position, limiting the number of valves that can be housed in a valve compart-
ment.
Six- port General Purpose Configurations
Liquid sampling valves are designed for use with liquefied gases under pressure such as ethane, pro-
pane, butane, LNG, etc. They are not intended for use with nonvolatile liquids (at room conditions)
where a concealed leak may allow an accumulation or pool of liquid to form that may present a signifi-
cant fire hazard.
TO REDUCE THE POSSIBILITY OF FIRE HAZARD WHEN SAMPLING FLAMMABLE
GASES OR LIQUID UNDER PRESSURE, THE OPERATOR SHOULD ROUTINELY
MAKE A CAREFUL PRESSURE- LEAK TEST OF THE PLUMBING, FITTING AND
VALVES COMPRISING THE SAMPLING SYSTEM IN OPERATION.
POSITIONS SHOULD BE CHECKED. THEREFORE DEPENDING UPON THE NATURE
AND PRESSURE OF THE SAMPLING STREAM, PERIODIC PRESSURE LEAK TEST
AND VISUAL INSPECTION SHOULD BE MADE AS WEAR OR USE COULD CAUSE
LEAKS TO DEVELOP . THESE LEAKS MAY OCCUR IN THE INTERIOR OF THE VALVE
BOX AND BE CONCEALED FROM THE OPERATORS VIEW.
All standard liquid sample valves have 1/16inch fittings and are classified by the sample size of the in-
stalled rotor (0.2µl, 0.5µl or 1.0µl capacity). The two types of valves available are standard or low pres-
sure (1000 psig) and high pressure (5000 psig), in the four- port, single- purpose liquid sampling valve.
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SVC 7- 11
BOTH VALVE