GEA Grasso Manual page 47

Grasso
Refrigeration Division
2.7.1 Oil system monitor of piston compressor packages
The oil system monitor is responsible for monitoring the functionality of the oil system. The package is switched
off if alarms occur.
The difference between the oil pressure and the crankcase pressure is monitored. In case no crankcase pressure
is measured, the suction pressure is used in stead.
2.7.1.1 Switching sequence in the normal case
Start conditions fulfilled
Output — compressor motor on
'Oil dif press' OK
'Oil dif start' timer active
'Oil dif run' timer active
'Low oil differential pressure' alarm
A.. During start up
B.. Brief lowering of the oil differential pressure during running
•
If (1)
→
(2)
Then
→
Then (3)
•
If (3)
→
Then (5)
•
If (4)
and
•
If (5)
→
Then (6)
If the oil differential pressure is OK again within the appropriate delay time, there is no alarm shutdown.
01.2004/1
Unloaded start
Figure 2.13, Oil system monitor in the normal case
Start conditions fulfilled
Set the actuating signal 'Unloaded start'
Output — compressor motor on
Output — compressor motor on equals 1
Start 'Oil dif start' timer
'Oil dif press' OK equals 0
'Oil dif start' timer expired
Start 'Oil dif run' timer
638660E_chapter2.doc
GRASSO SYSTEM CONTROL
Chap. 2 - 11