TIMKEN EXTREME PRESSURE TESTS
ASTM D 2509-Lubricating Greases
ASTM D 2782-Lubricating Fluids
For machine parts that encounter high unit load-
ings, the lubricant must be capable of
maintaining a film that prevents metal-to-metal
contact under the extreme pressures involved.
Otherwise, scoring of the surfaces and possible
failure of the parts will result. Special extreme
pressure (EP) lubricants are required for such
applications.
ings, the lubricant must be capable of
maintaining a film that prevents metal-to-metal
contact under the extreme pressures involved.
Otherwise, scoring of the surfaces and possible
failure of the parts will result. Special extreme
pressure (EP) lubricants are required for such
applications.
The Timken EP test is one of a number of bench
tests that have been designed to simulate ser-
vice conditions of extreme pressure, and to
evaluate EP lubricants accordingly. In the
Timken test, as In other EP tests, a rotating
member is brought to bear against a stationary
member, with lubrication provided by the lubri-
cant under test. The lubricant is evaluated on
the basis of its ability to prevent scoring of the
metal surfaces.
tests that have been designed to simulate ser-
vice conditions of extreme pressure, and to
evaluate EP lubricants accordingly. In the
Timken test, as In other EP tests, a rotating
member is brought to bear against a stationary
member, with lubrication provided by the lubri-
cant under test. The lubricant is evaluated on
the basis of its ability to prevent scoring of the
metal surfaces.
Apparatus and Procedure: The Timken EP
Test set-up consists of a special machine with a
rotating mandrel and a lever arm upon which
graduated loads can be placed to vary the pres-
sure that the mandrel exerts on the stationary
member. In the test, the mandrel is fitted with a
hardened steel ring (actually the outer ring or
cup of a tapered roller bearing). A flat steel
block, against which the ring is rotated in the
test, is also provided, together with a sufficient
quantity of the lubricant under investigation.
Test set-up consists of a special machine with a
rotating mandrel and a lever arm upon which
graduated loads can be placed to vary the pres-
sure that the mandrel exerts on the stationary
member. In the test, the mandrel is fitted with a
hardened steel ring (actually the outer ring or
cup of a tapered roller bearing). A flat steel
block, against which the ring is rotated in the
test, is also provided, together with a sufficient
quantity of the lubricant under investigation.
If oil is to be tested, provision is made to circu-
late the oil to the mating surfaces; if grease is to
be tested, a grease gun or special grease cylin-
der is provided to feed the grease at a uniform
rate to the surfaces. To begin the test, the ring
and block are locked into position, and lubricant
is fed to the point of contact of the ring and the
block, A specified load is placed on the lever
arm and the machine is run (usually at 800 rpm)
late the oil to the mating surfaces; if grease is to
be tested, a grease gun or special grease cylin-
der is provided to feed the grease at a uniform
rate to the surfaces. To begin the test, the ring
and block are locked into position, and lubricant
is fed to the point of contact of the ring and the
block, A specified load is placed on the lever
arm and the machine is run (usually at 800 rpm)
for 10 minutes, or until failure occurs.
At the end of the run, the test block Is inspected
for scoring. If the block is scored, the procedure
is repeated with progressively lighter loads,
using a new steel ring and test block each time.
When the edges of the wear scar show no
irregularities due to metal pick-up, the last
weight used is reported as the Timken OK load,
in pounds.
for scoring. If the block is scored, the procedure
is repeated with progressively lighter loads,
using a new steel ring and test block each time.
When the edges of the wear scar show no
irregularities due to metal pick-up, the last
weight used is reported as the Timken OK load,
in pounds.
If no scoring occurs on the first run, progres-
sively heavier loads are used until the block is
scored. The maximum load that can be applied
on the lever arm without scoring is reported as
the Timken OK Load. The minimum load re-
quired to cause scoring is reported as the score
load.
sively heavier loads are used until the block is
scored. The maximum load that can be applied
on the lever arm without scoring is reported as
the Timken OK Load. The minimum load re-
quired to cause scoring is reported as the score
load.
In addition to the OK and score loads, the actual
pressure at the point of contact is sometimes
reported. This requires the use of a Brinnell
microscope, with which the area of the wear
scar is determined. Using the OK load, the unit
loading in psi on the area of contact can then be
calculated.
pressure at the point of contact is sometimes
reported. This requires the use of a Brinnell
microscope, with which the area of the wear
scar is determined. Using the OK load, the unit
loading in psi on the area of contact can then be
calculated.
Significance: Only very general conclusions
can be drawn from the Tlmken EP or any other
EP test. Results should be related to additional
information about the lubricant, such as anti-
wear properties, type of additive, corrosion
characteristics, and so forth. Used in this way,
Timken EP results can provide an experienced
engineer with valuable information pertaining to
the performance of one lubricant relative to
others. In addition, the Timken EP test is often
used in the quality control of lubricants whose
performance characteristics have already been
established.
can be drawn from the Tlmken EP or any other
EP test. Results should be related to additional
information about the lubricant, such as anti-
wear properties, type of additive, corrosion
characteristics, and so forth. Used in this way,
Timken EP results can provide an experienced
engineer with valuable information pertaining to
the performance of one lubricant relative to
others. In addition, the Timken EP test is often
used in the quality control of lubricants whose
performance characteristics have already been
established.
A-17 (FIST 2-4 11/90)