TA Instruments AR 2000, Operator'S Manual, Page: 105 / 144

AR 2000 Operator’s Manual 105
c. Once the cell has cooled, set the three-way valve on the manifold to the "Pressure Relief" position
(arrow pointing upward). Note that the pressure cell may reduce very slowly, due to the snubbers in
the manifold.
NOTE: There are two snubbers in the manifold, one of which is located on the cell itself and
the other in the vent line, as described earlier in this chapter. These are used to slow the
build and relief of pressure in or from the cell. The snubbers may become clogged with sample,
preventing the cell pressure from being properly relieved (this problem is more likely to occur
when external pressurization is being used). You must maintain the cleanliness of the
snubbers, ensuring that gas can pass through them. You can verify that they are operating
properly by pressurizing and depressurizing the cell without a sample. If there is any doubt
concerning the cleanliness or operation of the snubbers, they should be replaced.
NOTE: The pressure relief valve on the Pressure Gauge Port on the pressure cell can also
be used to relieve the pressure in the cell. This should only be done if the 3-way valve on the
manifold cannot be used, if, for example, the snubbers have become blocked. The cell should
also be at room temperature before using this valve, and appropriate gloves and safety
glasses should be worn.
The pressure gauge located on the Pressure Gauge Port and the pressure gauge on the manifold can be used
to help verify that the snubbers are not clogged. After relieving the pressure in the cell using the manifold
and three-way valve, the two gauges should read zero (0) pressure. If the snubbers are clogged, the pressure
gauge in the Pressure Gauge Port may still register pressure. If that condition occurs, use the relief valve on
the Pressure Gauge Port to release pressure from the cell.
CAUTION: Although the pressure gauge on the cell may to appear to register zero, the
level of pressure in the cell may still be above ambient.
• Disconnect the pressure cell from the manifold at the designated disconnection point at bottom of the
angled pipe.
• Raise the head and decouple the magnet assembly and the rotor, and remove the Peltier jacket from the
rheometer using the procedures outlined previously in "Step 4: Loading a Sample."
• Remove the cup and rotor for cleaning. See "Maintaining the Cell" for details.