8
AGL_Stream_ST_A2L_A1_4M_6M_EN_Rev00
2.5.6 Oil pumps
All Stream compressors are equipped with an external oil pump. The oil pump will always work in
the correct direction of rotation, regardless of the rotation direction of the compressor.
Compressors delivered with Copeland
™ compressor electronics (-N) or formerly with CoreSense™
Diagnostics (-D) include the oil pump and the electronic switch for the integrated oil pressure safety
functionality.
Compressors with CoreSense
™ Protection (-P) are designed to accommodate fittings for an OPS2,
FD-113ZU or Sentronic oil safety system or a standard oil pressure switch (OPS2 oil sensor included
in the oil pump).
2.5.7 Oil pressure
Normal oil pressure is between 1.0 and 4.2 bar higher than crankcase pressure. Net oil pressure can
be read by connecting two pressure gauges to the compressor and comparing the readings. One
gauge should be connected to the oil pump. The second gauge should be connected to the
crankcase (oil service plug or any other crankcase connection plug).
NOTE: The pressure measured on the suction service valve, where the refrigerant enters the
compressor housing, does not correspond to the crankcase pressure and should not be used
as reference for the indication of oil differential pressure.
2.5.8 Oil circulation
Oil returns with the suction gases through a suction strainer and separates in the motor chamber
reaching the crankcase by way of oil return relief valve in the partition between motor housing and
crankcase. This relief valve closes on compressor start-up due to the pressure difference arising
between motor side and crankcase, thus slowing down pressure decrease in the crankcase over a
certain period of time. It reduces the foaming of the oil/refrigerant mixture that would occur if the
pressure decreased rapidly. The valve does not reopen until the pressure has been equalized by
means of a crankcase ventilating valve. This second valve connects the crankcase and suction side
cylinder head. It reduces the pressure difference by means of a very small bore in the plate of the
valve so slowly that oil foams less and only limited oil/refrigerant foam is transferred to the oil pump.
Four-cylinder compressors have one crankcase ventilating valve on the left cylinder bank whereas
six-cylinder compressors have two ventilating valves on the left and right cylinder banks.
2.5.9 Oil level
All 4M* and 6M* compressors are delivered with sufficient oil for normal operation. The optimum oil
level should be checked by operating the compressor until the system is stable. The oil level should
be min ¼ and max ¾ of the sight glass.
However, a higher oil level may be accepted if an oil regulator is used.
Figure 8: Oil level on 4M* and 6M* compressors
2.5.10 System oil return
CAUTION
Inadequate lubrication! Bearing and moving parts destruction!
Ensure
adequate oil return from the system into the compressor at any time. No liquid
refrigerant return to the compressor. Liquid refrigerant dilutes the oil, could
wash the oil off the bearings and moving parts and could lead to overheating
and compressor failure.
The system piping must be carefully designed to ensure sufficient refrigerant gas velocity, so that oil
returns to the compressor at all times and conditions. Individual piping diameter calculation depends
on the refrigerant properties, pressure level, mass flow, and density.
