Metrohm 797 VA Computrace - Manual (Page 39)

2.3 Multi-Mode Electrode (MME)
797 VA Computrace / Hardware-Manual 8.797.8001EN
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7 Mount new capillary
Proceed as described in section 2.3.3.
8 Fill capillary
Proceed as described in section 2.3.4 or section 2.3.5.
2.3.9 Cleaning the MME
If the mercury in the Multi-Mode Electrode is contaminated and this leads to distur-
bances, the MME must be cleaned and refilled with ultra pure mercury. Proceed as
follows:
1 Remove Multi-Mode Electrode from 797 VA Computrace Stand
• Unscrew FEP tubing 34 and 42 from the MME, disconnect electrode cable
20 from MME.
• Take Multi-Mode Electrode 21 out of measuring head 24 while gently tap-
ping the MME to knock off any mercury drops on the glass capillary into
the measuring vessel.
2 Remove old mercury
• Place Multi-Mode Electrode 21 in a horizontal position in the electrode hol-
der 92 (see Fig. 11-3). The slotted screw 79 is now at the top.
• Unscrew slotted screw using a suitable coin.
• Carefully turn MME and empty mercury through the threaded opening 78
into a waste container placed in the drip pan 91. While doing so, gently
tap the glass capillary 87 and the MME to ensure that all mercury flows out
of the MME.
3 Dismantle MME
• Unscrew retaining nut 86.
• Take glass capillary 87 out of opening 82, the sealing ring 84 and the
locking ring 85 are removed at the same time. Remove these two parts
from the glass capillary.
• Remove insert ring 83 from the MME.
• Unscrew slotted screw 74 with a suitable coin in an anticlockwise direction
from screw thread 76.
• Screw locking ring 73 onto slotted screw and pull out of the MME.
4 Dispose of old capillary
• Connect filling tubing 93 with the tubing coupling 96 to the two gas wash
bottles 95 and the vacuum pump (see Fig. 10).
• Insert glass capillary 87 (capillary end) in the filling cone 94 of the filling
tubing.
• Remove mercury from the capillary with the vacuum pump.