57
Vol. 2.6 © 2020 Hanbell Precise Machinery Co., Ltd. All rights reserved
R1=P1-P2
≥
1.0 bar warning
R1=P1-P2
≥
1.5 bar shut down
Note
：
1. Unexpected power trip often occurs in many areas, causing the system to shut down
abnormally and compressor shuts down when the oil pump is stopped. For compressors using
hydrodynamic bearings, lack of lubrication can cause jamming and damage of the rotor.
Hanbell RT-series compressors use rigid bearings which does not require additional power trip
protection as the residual oil can be used for free rotating shut down.
2. Compared to hydrodynamic bearings, rigid bearings have the advantage of less mechanical
loss and less lubrication required.
3. Pressure sensor installation point: Pressure sensing point P1 should to be installed behind the
buffer tube, while P2 should installed before the inlet of gearbox lubrication.
4.2 Oil pump
4.2.1 Specifications of the oil pump
The built-in oil pumps of RT series centrifugal compressors are of the positive
displacement gerotor type.
Item
Specifications
O
il
p
u
m
p
Flow rate
L/min.
26~30
32~36
Pressure difference
operating range
bar
2~4.5
m
o
to
r
Output
W
446
560
Voltage
V
3
ψ
/220V/50Hz 3
ψ
/380V/50Hz 3
ψ
/220V/60Hz 3
ψ
/380V/60Hz
Max. operating
current
A
3.6
2.1
3.5
2
LRA
A
19.1
11.06
17.6
10.2
Table 4.1 Specifications of the oil pump
Note
：
Voltage Specifications: 3
ψ
/220V 50Hz & 60Hz are shared oil pump. With different power
supply frequencies, the motor output and oil flow rate will also be different. This is similar for
3
ψ
/380V 50Hz & 60Hz. However, the internal windings of oil pump motor for 220V and 380V
are different, therefore please contact Hanbell service technicians for different power supply
voltage.
4.2.2 Features of oil pump
The primary function of the oil pump is to provide enough lubricant for lubrication and cooling of
the bearings and gear, and the flow rate of lubricant and the temperature of bearings and gear after
cooling are the decisive factor. Thus, protection mechanism is necessary to ensure the oil pump
overcomes the internal resistance of compressor (R2) and provides adequate flow rate of oil.
Compressor internal resistance (R2) protection
Hanbell RT-series centrifugal compressor has been tested and verified that the optimum flow rate of
oil is 20~25L/min. in the form of oil-jet and ensures the bearing outer ring temperature to be less
than 80
°
C
after cooling. Therefore, the pressure difference between oil pressure before entering the
compressor P2 and oil tank pressure P3 is the key to overcome compressor internal resistance R2.