3 Installation
757 VA Computrace – Hardware
32
3.3.9
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 ultrapure mercury. Proceed as
follows:
1 Remove multi-mode electrode from 757 VA Computrace
Stand
•
Unscrew FEP tubing
30
and
38
from the MME, disconnect electrode
cable
16
from MME.
•
Take multi-mode electrode
17
out of measuring head
20
while gently
tapping the MME to knock off any mercury drops on the glass capillary
into the measuring vessel.
2 Remove old mercury
•
Place multi-mode electrode
17
in a horizontal position in the electrode
holder
93
(see
Fig. 11-3
). The slotted screw
80
is now at the top.
•
Unscrew slotted screw
80
using a suitable coin.
•
Carefully turn MME and empty mercury through the threaded opening
79
into a waste container placed in the drip pan
92
. While doing so, gently
tap the glass capillary
88
and the MME to ensure that all mercury flows
out of the MME.
3 Dismantle MME
•
Unscrew retaining nut
87
.
•
Take glass capillary
88
out of opening
83
, the sealing ring
85
and the
locking ring
86
are removed at the same time. Remove these two parts
from the glass capillary
88
.
•
Remove insert ring
84
from the MME.
•
Unscrew slotted screw
75
with a suitable coin in an anticlockwise direc-
tion from screw thread
77
.
•
Screw locking ring
74
onto slotted screw
75
and pull out of the MME.
4 Dispose of old capillary
•
Connect filling tubing
94
with the tubing coupling
97
to the two gas wash
bottles
96
and the vacuum pump (see
Fig. 10
).
•
Insert glass capillary
88
(capillary end) in the filling cone
95
of the filling
tubing
94
.
•
Remove mercury from the capillary with the vacuum pump.
5 Clean MME
•
Clean inner compartments of the MME, contact pin
81
and the screw
threads
77
,
79
and
83
with a lint-free cloth.
•
Thoroughly rinse all inner compartments of the MME and the unscrewed
individual parts with dist. water and then dry with N
2
.
Do not use any organic solvents.
