General limits and fields of operation
REFRIGERANT
NH
3
Discharge temperature
t
e
Grasso V
max.
+170 °C
This is the actual discharge
temperature, measured directly in
the gas flow just before the
discharge connection. The given
value also applies to the LP stage
of two-stage compressors.
Discharge temperature LP
Grasso VT
Pressure ratio per stage (p
c
/p
o
or p
c
/p
m
or p
m
/p
o
)
Pressure ratio limits are not
absolute but arbitrary values
based on practical
considerations
j
-
min.
1.5
max.
10
Pressure difference
delta-p
Grasso V
300(T) .. 600(T)
max.
(p
c
- p
o
) <= 25.5 bar
The standard built-in overflow
safety valve(s)
(p
c
- p
ambient
) <= 25.5 bar
Grasso V
700(T) ..
1800(T)
max.
(p
c
- p
o
) <= 19.0 bar
The standard built-in overflow
safety valve(s)
(p
c
- p
ambient
) <= 25.5 bar
Oil temperature in crankcase
t
oil
°C
min.
>30
o
C and > T
saturated crankcase
pressure at stand still
+ 15 K
Indicated minimum value is the
lowest oil temperature at which the
compressor is allowed to be started.
max.
< 70
o
C, depending on type of oil
The maximum oil temperature
depends on the operating
conditions of the compressor and
the oil type used.
A minimum actual oil viscosity of 10
cSt in the bearings is always
required.
Min. allowed start-up
temperature compressor casings
and castings
t
min
start-up
°C
min.
+10
o
C
From 10
o
C the elastomer seals that
seal discharge parts from other
parts have their optimal sealing
capacity
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.
APPENDIX; Product Information (PI)
STARTING UP OF TWO-STAGE COMPRESSORS
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