F
OR
M
ODELS
: JGI, JGM, JGN, JGP
AND
JGQ
S
ECTION
4 L
UBRICATION
PAGE 4-14
SAE 40 wt engine oil is also acceptable in the frame, but contains significant amounts of
additives that are not necessary in a compressor.
In limited circumstances and with prior approval from Ariel, cold weather installations may
use multi-viscosity oils in the compressor frame if the oil supplier can certify that the oil is
shear stable. The viscosity of shear stable oil degrades less through use. Most oil suppliers
will certify their oil as shear stable if the viscosity degrades less than a certain percentage in
specific tests. As a result, multi-viscosity oils are subject to a shorter oil life than single
straight grade oils by 30% to 50%.
Synthetics such as PAG, PAO, or ester based lubricants are acceptable in the compressor
frame provided they meet the operating viscosity requirements as outlined below.
Compounded lubricants are prohibited in the frame.
Oil Viscosity
The minimum allowable viscosity of the oil going into the frame is 82.6 SUS (16 cSt). Typi-
cally this is the viscosity of ISO 150 grade oil at about 190°F (88°C).
The maximum viscosity of the lube oil for cold ambient temperature starting is 15,000 SUS
(3300 cSt). Typically this is the viscosity of ISO 150 grade oil at about 25°F (-4°C).
Oil Pressure
Normal pressure on the discharge side of the lube oil filter is factory set for 60 psig (4.1 bar
g
)
for compressors that were tested mechanically complete (has inspector tag). If tested at fac-
tory as mechanically incomplete (without inspector tag), normal oil pressure must be set by
packager or at initial start-up to 60 psig (4.1 bar
g
) at full rated speed and normal operating
temperature. If the lube oil pressure drops below 50 psig (3.4 bar
g
), the cause should be
found and corrected. A low lube oil pressure shutdown, set at 35 psig (2.4 bar
g
), is required
for protection of the compressor during a sudden loss of oil pressure. The compressor
should not operate for prolonged periods of time at less than 50 psig (3.4 bar
g
) oil pressure.
For proper operation of the thermostatic control valve, the maximum differential pressure
between the hot oil supply line and the cooled oil return line is 10 psid (0.7 bar
d
).
Oil Temperature
The minimum lube oil operating temperature is 150°F (66°C). This is the minimum tempera-
ture required to drive off water vapor.
Maximum allowable oil temperature into the compressor frame is 190°F (88°C).
A thermostatic control valve supplied by Ariel is set at 170°F (77°C). The oil temperature
should be maintained as close to this temperature as possible. Higher temperatures
increase the oxidation rate of the oil. For every 18°F (10°C) over 150°F (66°C), the oxidation
rate of the oil doubles.
