Starting Up Of Two-Stage Compressors - GEA Grasso 5 Installation And Maintenance Instructions Manual

General limits and fields of operation
Discharge temperature LP
Pressure ratio per stage (p
Pressure ratio limits are not
absolute but arbitrary values
Oil temperature in crankcase
temperature compressor casings
4.3

STARTING UP OF TWO-STAGE COMPRESSORS

Procedure for starting from compressor standstill
In the case of two-stage compressors it is very important that immediately after
the period of automatic fully unloaded start (ensured by the corresponding three-
way solenoid valve in the control pressure supply line from the oil pump; only one
or more H.P. cylinders become operative, viz. only those cylinders of which the
suction valve lifting mechanism is directly and permanently connected to the
control pressure supply of the oil pump via the starting solenoid valve mentioned.
This means that during starting none of the three-way solenoid valves for the
capacity control are allowed to be energized.
0089288_imm_v_english_19
07.04.2021
REFRIGERANT
Discharge temperature
/p
c o
or p /p or p /p )
c m m o
based on practical
considerations
Pressure difference
Min. allowed start-up
and castings
STARTING UP OF TWO-STAGE COMPRESSORS
Grasso V
t
e
Grasso VT
j -
Grasso V
300(T) .. 600(T)
delta-p
Grasso V
700(T) ..
1800(T)
t
°C
oil
t
min
°C
start-up
APPENDIX; Product Information (PI)
NH
3
+170 °C
This is the actual discharge
temperature, measured directly in
the gas flow just before the
max.
discharge connection. The given
value also applies to the LP stage
of two-stage compressors.
min. 1.5
max. 10
(p - p ) <= 25.5 bar
c o
The standard built-in overflow
max.
safety valve(s)
(p - p ) <= 25.5 bar
c ambient
(p - p ) <= 19.0 bar
c o
The standard built-in overflow
max.
safety valve(s)
(p - p ) <= 25.5 bar
c ambient
o
>30 C and > T
saturated crankcase
+ 15 K
pressure at stand still
min.
Indicated minimum value is the
lowest oil temperature at which the
compressor is allowed to be started.
o
< 70 C, depending on type of oil
The maximum oil temperature
depends on the operating
conditions of the compressor and
max.
the oil type used.
A minimum actual oil viscosity of 10
cSt in the bearings is always
required.
o
+10 C
o
From 10 C the elastomer seals that
min.
seal discharge parts from other
parts have their optimal sealing
capacity
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