This chapter deals with the starting and stopping
of the compressor in a plant which, after the test
run, has been delivered completely ready for
operation by the installation engineer. If further
contains instructions for resetting the lubricating
oil pressure regulator and pressure safety
switches, if this should be necessary.
It is recommended to start and stop the
compressor according to a fixed procedure in
order to prevent errors and possible damage.
Especially in the case of plants with manual
control, the sequence of the necessary operations
has to come up to certain requirements.
Therefore, in the instructions given below,
reference is made, wherever necessary, to the
plant manual. If at some point the plant manual
differs form this instruction manual, the
installation engineer should be consulted.
7.1 STARTING THE COMPRESSOR
When starting the compressor, distinction should
be made between:
1)
Starting the compressor for the first time after
the plant has been out of operation for a long
period of time
(for example, on account of
seasonal standstill or maintenance operations).
for manually controlled plants as well as for those
operating automatically the starting procedure
given below should be followed exactly.
2)
Restarting the compressor in an already
operational plant.
In the case of manually operated plants only the
instructions mentioned under b, e, f, h and j need
to be followed, as well as those included in the
plant manual. In the case of automatically
operating plants, this starting procedure is
incorporated in the control system and therefore
does not generally require any special care.
The starting procedure is as follows:
a) Consult the plant manual.
b) Make sure that the oil level in the crankcase is
correct (see Chapter 8) and check whether the
shaft seal housing and both oil filter housings
are filled with oil (especially after maintenace
work).
c) Check whether the suction stop valve and the
stop valve in the return line of the oil separator
are closed.
d) Check whether the discharge stop valve, the
pressure gauge valves and (in the case of
two-stage compressors) the stop valves in the
intermediate pressure line are open.
e)
In the case of a compressor provided with a
manually operated capacity control:
set the oil
distributor to position 1:
In the case of a compressor provided with an
electrically operated capacity control:
Check
whether the manual control lever of all solenoid
valves is in its lowest horizontal position.
f) (not within 3 minutes after the compressor was
stopped) Start the compressor and check
whether the oil pressure increases.
g) Slowly open the suction stop valve, thereby
watching the suction pressure which may not
exceed 6 bar (on gauge). Also be careful that
no liquid hammer occurs, especially in plants
with lower suction lines.
h)
In the case of single-stage compressors with
capacity control:
After the compressor has
started up and one or more cylinders have
automatically become operative, cut in the
other cylinders as and when required, thereby
watching the maximum allowable amperage (it
must not be higher than the amperage stated
on the motor).
In the case of two-stage compressors with
capcity control:
3-4 minutes after the
compressor has started and one HP-cylinder
becomes operative automatically, cut in the other
cylinders stepwise, thereby watching the
discharge temperture on both the HP- and LP-side
(max. 140 °C), the intermediate pressure (max.
saturation intermediate temp. +10 °C) and the max.
allowable amperage (not to be higher than the
amperage stated on the motor nameplate).
j) (if cylinder jacket cooling is applied). Check the
cooling water flow.
k) Adjust the opening of the pressure gauge stop
valves so that the gauge pointers do not
vibrate any longer.
l) (not during the running-in period of the plant).
Open the stop valve in the return line of the oil
separator.
CAUTION! In case of reduced cooling load it is
not allowed to cut out so many cylinders
of a
compressor already operating in two stages that
only the HP-cylinder is still operating. At least
two LP-cylinders should remain operative.
Refrigeration Division
Grasso
7. STARTING, STOPPING AND ADJUSTMENT OF COMPRESSOR
v002.97.10.en
Refrigeration Compressors Series RC9
Page 7.1
