Metrohm 746 VA Trace Analyzer - Manual (Page 51)

3 Installation
746 VA Trace Analyzer / 747 VA Stand
3-24
3.4.8 Changing the capillary
Contamination of the glass capillary can necessitate its replacement (see also sec-
tions 7.4.2 and 7.4.3). In such a case, proceed as follows:
1 Remove multi-mode electrode from 747 VA Stand
• Unscrew FEP tubing 51 51 and 59 59 from the MME, disconnect electrode
cable 37 37 from MME.
• Take multi-mode electrode 38 38 out of measuring head 41 41 while gently
tapping the MME to knock off any mercury drops on the glass capillary
into the measuring vessel.
• Place multi-mode electrode 38 38 in a horizontal position in the electrode
holder 114 114 (see Fig. 15-3).
2 Unscrew slotted screw 96 96
• Using a suitable coin, unscrew slotted screw 96 96 out of screw thread 98 98
until the contact surface of the black O-ring at the Plexiglas wall (thin,
black stripe) is just visible below the metal thread 98 98.
3 Dismantle old capillary
• Position multi-mode electrode 38 38 vertically in the electrode holder 114 114
(see Fig. 15-1).
• Undo retaining nut 108 108 completely by turning anticlockwise and lift up
until the lower part of the glass capillary 109 109 with the wide opening is
visible.
• Gently tap the glass capillary 109 109 to knock off any residual mercury in the
wide opening into the MME.
• Press the retaining nut 108 108 downward with one hand and with your other
hand take glass capillary 109 109 completely out of the mount.
4 Dispose of old capillary
• Connect filling tubing 115 115 with the tubing coupling 118 118 to the two gas
wash bottles 117 117 and the vacuum pump (see Fig. 14).
• Insert glass capillary 109 109 (capillary end) in the filling cone 116 116 of the filling
tubing 115 115.
• Remove mercury from capillary with the vacuum pump.
5 Replenish mercury if necessary
Proceed as described in section 3.4.2.
6 Mount new capillary
Proceed as described in section 3.4.3.
7 Fill capillary
Proceed as described in section 3.4.4 or section 3.4.5.