API Service
The American Petroleum Institute (API) grades motor
oils (oils designed for use in engines in cars and trucks)
with a two letter classification. Oils with API grades “SA”
through “SH” are obsolete and should never be used
in modern engines or gas compressors. Unfortunately,
motor oils with an “SA” and “SB” ratings are still readily
available at parts stores, service stations, and other
retail outlets at low prices. These are low quality oils and
should NEVER be used in Corken compressors. If motor
oil is used in a Corken compressor, it should have an
API Service of SJ or better. Multigrade motor oils such
as 10W-40 tend to have a higher viscosity index.
A
P
I
S
E
R
V
I
C
E
S
N
E
N
E
R
G
Y
C
O
N
S
E
R
V
I
N
G
SAE
5W-30
API (American
Petroleum Institute)
Quality rating
Service classification
S=gasoline engine
C=diesel engine
Example of API “Donut” symbol used on motor oil.
Oil suppliers post product data sheets on line that
contain various physical properties of the oil , and the
API Service classification. If there is any doubt, do not
use the oil.
Oil Change Intervals
Oil change intervals can vary significantly depending
on local environmental conditions, the gas being
compressed, and the oil being used. Unless there are
factors that shorten the life of the oil, the following
recommendations apply:
Conventional oil: 2200 hours or 6 months – whichever
comes first
Synthetic oil: 6000 - 8000 hours* or one year –
whichever comes first
*Oil change intervals in this range should be confirmed via oil analysis.
Factors that shorten the life of the oil:
• Dirty or dusty environmental conditions that cause the
oil to become dirty or discolored
• Oil dilution caused by condensation or other liquids in
the gas stream (see below)
• Change in viscosity for any reason (various oil additives
can break down over time)
• Changing ambient temperature may cause the need for
a different viscosity
The oil should be changed as often as necessary
to maintain clean, undiluted oil. Each time the oil is
changed, the oil filter (Corken part number 4225) should
also be changed.
Ammonia Services
Never use a detergent oil in a compressor in ammonia
service. Ammonia will react with the detergent and cause
lubrication failure.
Oils that can be used in ammonia compressors:
• Royal Purple: Uni-Temp
• Phillips 66: Ammonia Compressor Oil
• Chevron: Capella P68
Crankcase Oil Heater Option
Corken offers a crankcase oil heater as an option on
all models except the small model 91. This heater is
available in 110V and 220V versions and is rated for Class
1, Division 1 and 2, Group B, C, D service. The heater
includes a thermostat set at 70°F (21.1°C).
If a crankcase heater is desired, it is best to order the
heater with the compressor (crankcase specification
“MH”). The mounting hole for the heater is not drilled
unless the heater is ordered with the compressor. It is
also possible to order the compressor with the hole
drilled (1" NPT), but without the heater (crankcase
specification “MR”). With this option, a customer can
supply their own heater.
2.7 Relief Valves
An appropriate relief valve must be installed at the
compressor discharge. On Corken 107-style mounted
units a relief valve should be fitted in the piping between
the compressor discharge and the four-way valve (see
figure 1.3A). Relief valves should be made of a material
compatible with the gas being compressed. Local codes
and regulations should be checked for specific relief
valve requirements. Also, relief valves may be required at
other points in the compressor’s system piping.
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