OPERATING INSTRUCTIONS
CO
2
/NH
3
CASCADE UNIT
250 - 1000 KW
_551511_om_kas_gbr_1_.doc 45
— after remedying major damage.
— if the oil is dark coloured or highly turbid
Depending on the results of the analysis, the owner
must decide whether to release the oil charge until
the next assessment date or whether to have the oil
changed.
Impermissibly damp oil must be removed from the
unit immediately.
oil change sequence(see also the maintenance
instructions for the compressor)
The cascade must be run for at least half an hour to
reach its operating temperature before the oil can
be changed.
— In mode 1 "manual + manual" with the
compressor running and intake cut-off valve
closed, transfer refrigerant from the compressor
into the condenser.
If necessary, to this end change the set value of
the minimum suction pressure limit on the NH
3
side to 0.5 bar (a) and reset to the original value
after evacuation
— Use an extraction device to remove the residual
refrigerant (from the compressor).
— Use nitrogen to generate a slight overpressure.
— Drain oil through the filling line into a container
provided for waste oil.
4.5.5 Used oil
Refrigeration machine oil drained from the circuit is
no longer suitable for use in refrigeration plants. It
has to be stored or transported in appropriately
labelled containers. The operator is responsible for
its proper disposal.
4.6 Maintenance Work
4.6.1 General notes
Work involving intervention in the refrigerant circuit
is only to be undertaken by trained fitters in
compliance with the terms of the guarantee.
The CO
2
/NH
3
cascade must always be taken out of
service before dismantling. All live parts must be
disconnected from the power supply and the
refrigerant must be removed from the apparatus
concerned. This work must be performed extremely
carefully in compliance with the safety regulations so
that the operating personnel is not harmed by the
refrigerant or refrigerating machine oil contained in
the system.
Equipment under pressure must not be opened until
it has been completely drained.
The CO
2
/NH
3
cascade and parts of the cascade must
not be left open as penetrating moisture endangers
its function.
The main principle must be to allow as little air and
moisture as possible to enter the cascade. As far as
possible, all foreign substances must be kept away or
eliminated as well, e.g.
• welding residues
• sealant residues
• auxiliary materials such as greases, oils or
solvents
Welding and soldering work may only be performed
with written permission. The necessary safety
measures must be set out in the permit. These
include:
• complete emptying of the respective equipment
• personal protective measures when opening
equipment
• cleaning with suitable substances
• concentration measurements
• ensuring adequate ventilation
Renewed acceptance is necessary after any repair
work or changes are made to pressure vessels
requiring official acceptance. The welding may only
be carried out by approved welders with valid
welder’s qualifications.
4.6.2 Opening the compressor (see also
compressor maintenance instructions)
If the compressor has to be opened to clean the
suction casing or to replace components, it must be
depressurised.
Sequence
Transfer the refrigerant into the condenser while the
cascade is in operating mode 1 "manual + manual"
by closing the suction cut-off valve and the oil return
shut-off valve.
If the intake pressure has dropped to p = 0 bars g.p.,
switch off the compressor and close both manual
shut-off valves on the compressor.
Attach hose to pressure chamber service valve and
use extraction equipment to remove residual
refrigerant.
The compressor may now be opened. Comply with
the relevant health and safety regulations.
The work on the compressor must be carried out in
accordance with the compressor operating
instructions.
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