Hach PHOSPHAX sigma Manuel D'utilisation De Base page 129

To begin any work operation in this area, the [+SERVICE] menu must be
selected first, see section Software menu system, page 131
[+SERVICE]. Only this allows the safety panel to be removed.
N O T I C E
On principle, before working on the digestion unit the heater plug (power supply of
the heating wire) must be pulled out of the corresponding board.
The digestion unit must be serviced at an interval of 3 months. The
piston system, the safety valve, the upper cuvette holder and the
membrane seal must be checked. All channels in the lower cuvette
holder must be cleaned. After 6 months, all seals are exchanged.
All work on the digestion unit should be performed by a
Hach Lange Service employee.
Figure 10 Digestion cuvette
Hose pinch valves
The three hose pinch valves used have different tasks to fulfill. The two
valves in the top of the device (pinch valves Q1 and Q2) alternately feed
sample, air and standard solution to the sample pump. The third valve in
the bottom of the refrigerator (pinch valve QA) alternately delivers
reagent A and air to the reagent pump A. The electrical connection
occurs via a control cable, which is routed from the refrigerator going out
of the back into the PHOSPHAX Σ sigma housing. There it is plugged
into the fan plate behind the photometer baseplate.
As the hose pinch valves do not come directly into contact with reagent,
no cleaning or servicing work is required. For the hose change, the
attached hose holders are pulled off to the front.
Then the hoses in the front valve slot can be directly taken out or
inserted again, for the rear valve slot the center piece is pushed back
beforehand.
N O T I C E
For a long-term shutdown (over 48 hours), the pump cassettes must be released
in order to relieve the dosing hoses — but because of the return flow risk the
hoses should first be removed from the screw caps (canister lids)!
Figure 11 Handling of hose pinch valves
English 129