nthetic
lubricants provide superior performance and
extended life as lubricants, sealants, and dielectrics.
Cost-Effectiveness
As Table 1 demonstrates, Krytox
®
lubricants are
cost-effective across a wide range of applications,
because of their long, useful life relative to tradi-
tional hydrocarbons.
Table 1
Life/Cost/Reliability
Typical Hydrocarbon
Application
Lubricant
Krytox
®
Electric Motor
5 days
9 months
227
°
C (440
°
F), 1,750 rpm
Heated Rolls
8 months
24 months
199
°
C (390
°
F), 5,000 rpm
Textile Roll
1 month
24 months
225
°
C (437
°
F), 5,400 rpm
Pressure Relief Valves
50% failures
Less than
1% failures
Paper Corrugating
$144,000
$3,000
Machine
Typical Applications
Aerospace
Bearing Lubricant
Sealant
O-Ring Lubricant
Oxygen Systems
Industrial
Paper Corrugating Bearings
Chemical Plant Maintenance
Valve Lubricant
High-Temperature Equipment
Clean Rooms
Chlorine and Oxygen Service
Textile Equipment
Automotive
Bearing Lubricant
CV Joints
Weatherstrip Lubricant
Antilock Braking Systems
Vacuum Systems
Vacuum Pump Fluids
High-Vacuum Greases
Vacuum System Sealant
1 Applications
Should I use an oil or a grease?
The functions of lubricants in antifriction bearings
are to provide a film of lubricant between rolling
elements, races, and separators and to reduce
friction, heat, and wear. They also provide protec-
tion against corrosion and remove heat. Sealed
greased bearings keep dirt out, and oil lubricated
systems flush dirt out of the bearing as the oil
passes through.
Oils and greases are used over a wide range of
speeds and operating temperatures. Selection for
a given application is determined by evaluating
the bearing housing arrangement, operating
temperatures, contamination hazard, bearing
type, and load.
Grease is recommended when:
Simple housings and seals are used that are not
designed to retain oil or seal out contaminants.
Protection is required from dirt, dust, water,
fumes, or other contaminants.
Long intervals between relubrication are required.
Lubricant contamination of the product must be
avoided.
Oil is recommended when:
The operating temperature is consistently high,
and oil flow is needed to remove heat.
Dirt conditions are not excessive, and oil tight
reservoirs and seals can be used.
It is desired to remove debris from the system
using the oil and filter it out with an exterior
filter.
Krytox
®
oils are available in a variety of viscosities.
Depending on the specific grade, service tempera-
tures range from <70>340
°
C (<94>655
°
F).
Table 2
NLGI Penetration Ranges
NLGI Worked Penetration
NLGI Grade
mm/10 at 25
°
C (77
°
F)
Appearance
000
445475
Fluid
00
400430
Almost Fluid
0
355385
Semifluid
1
310340
Very Soft
2*
265295
Soft
3
220250
Cup Grease
4
175205
Cup Grease
5
130160
Cup Grease
6
85115
Block Grease
* Standard grade. Others available upon request.
NLGI Grease Consistency
Greases are formed by mixing the base oil with a
thickener to form a grease. Krytox
®
greases use a
special high thickening efficiency, low molecular
weight PTFE with very small particle sizes as its
thickener. This is one of the most thermally stable
thickeners for high-temperature, long-term greases.
The lower thickener content in the grease maxi-
mizes the oil for improved grease life.
Greases can be formulated with different viscosity
oils to handle different temperatures and load
conditions. High viscosity oils can be used in
greases for high temperatures or heavy loads or low
speed applications. Low viscosity oils can be used
in greases where low temperature properties are
important or speeds are higher. Lower amounts of
thickener form softer or more fluid-like greases.
Higher thickener levels form harder, stiffer greases.
Additives are often added to the
grease to enhance anticor-
rosion protection, raise
load carrying ability, or
help reduce wear.
2 Rolling Bearings
Krytox
®
greases and oils provide a thick lubricating
film for bearings. This film reduces metal-to-metal
contact in the bearings, resulting in superior load
carrying capability.
Before adding Krytox
®
to a bearing, the bearing
should be cleaned of all existing greases, oils, or
preservative oils used to protect it during storage. If
left in the bearing, these hydrocarbon oils can form
carbon deposits at higher temperatures, which may
accelerate bearing failure. Chlorinated solvents
should not be used, because they can leave chlorine
that can cause corrosion. If a bearing has previously
been packed with another grease, mechanical
agitation or an ultrasonic bath should be used to be
sure of removing all of the grease.
After the bearing surfaces are clean, they should be
lubricated/wiped with Krytox
®
and properly stored
to prevent corrosion. If they are not going to be
packed with Krytox
®
immediately, or if they are
going to be in storage for an extended period, they
can be dipped in a solution of Krytox
®
oil and
Krytox
®
fluorosurfactant to coat the surface and
protect against rust.
Proper lubrication is achieved by using the correct
amount of grease. Too little grease in the bearings
causes premature failure. Too much grease at the
initial fill or during relubrication can cause over-
heating of bearings that are running at medium to
high speed, resulting in bearing failure. The amount
of grease put in the bearing depends on the applica-
tion and operating speed. For applications such as
conveyor rollers and low-speed machinery with DN
values (inner race ID in mm x rpm) below 50,000,
the bearing can be filled to capacity. For medium-
speed applications, i.e., DN 50,000200,000, the
bearing can be filled 5070%. For higher-speed
systems, the fill is typically 3040%. Some
extreme-speed special applications have grease
fills of only 1015% (see Speed Factor for
definition of DN values). Because Krytox
®
is
heavier than hydrocarbon lubricants, its higher
density must be considered when determining
the fill quantity by weight.
Grease fittings should be changed to a different
style, such as button-head or pin type, to ensure
that another type of grease is not accidentally put
into the bearing. A dedicated grease gun that
matches the fitting should be used.
Table 3
Ball Bearing Grease Performance Tests
with Krytox
®
Greases
Test Conditions*
240AB
240AC
283AC
GPL225
10,000 rpm, 204
°
C (400
°
F) >500 hr >5000 hr
10,000 rpm, 260
°
C (500
°
F)
>750 hr 20,000 rpm, 204
°
C (400
°
F) >500 hr * ASTM D3336Light Thrust Load.
Bearings that are converted from oil to grease
lubrication generally run hotter internally, because
grease does not remove heat as does circulating oil.
This higher temperature gradient causes the bearing
to expand more and can lead to failure if the
bearing does not have adequate internal clearance.
Depending on the type of equipment and operating
conditions, a bearing with a larger internal clear-
ance might be needed. The bearing or equipment
manufacturer should be consulted before converting
equipment from oil to grease.
3 Anticorrosion Lubricants
Additives are combined with Krytox
®
to enhance its
ability to protect metallic surfaces from corrosion
caused by moisture and oxygen.
Antiwear Greases
Krytox
®
greases containing antiwear additives have
properties that give high specific load carrying
capacity and the highest protection against wear.
Soft/Fluid Greases
These soft or fluid greases have free-flowing
characteristics. They belong to NLGI penetration
classes 0000 and are often used for lubrication of
sealed gear drives.
Extreme Pressure (EP) Greases
These heavy-duty greases are used for high loading
or slow speeds. EP greases have high load carrying
capability and good characteristics under boundary
and mixed friction conditions. Krytox
®
is a natu-
rally good EP lubricant, but additional high-
pressure additives can be included in the grease.
Table 4
Extreme Pressure Properties*
of Krytox
®
Greases
240AZ
240AC
250AC GPL225 GPL226
Load Wear Index
75
127.8
>161
None*
None**
Weld Point, kg
400
620
None
None
None
* ASTM D2596, Measurement of Extreme Pressure
Properties of Lubricating Grease, Four Ball Method.
** These samples maxed the load limit of the test apparatus,
and a load wear index cannot be determined.
Channeling Greases
Some applications require a grease that is stiff and
does not fall back easily into the bearing races.
Often, these systems run at higher speeds. Harder
NLGI Grade 3 Krytox
®
greases are recommended
for these applications.
Chain Greases
Drive chains, such as roller chains, require lubrica-
tion. They are often exposed to the atmosphere and
require a lubricant with anticorrosion properties.
The lubricant must also have good adhesion and the
ability to wet the chain linkscharacteristics
provided by Krytox
®
. Often, EP additives are
included to reduce chain wear caused by oscillating
and sliding friction.
High-Temperature Greases
Because of its thermal stability and nonoxidizing
characteristics, Krytox
®
is a natural high-temperature
lubricant. Krytox
®
grease has a drop point of 325
°
C
(617
°
F). Dropping point (thickener melting point)
test results can be confusing or misinterpreted with
PTFE thickened greases. Testing shows that some
oil separation occurs at about 210
°
C (410
°
F), and
this has sometimes been reported as the dropping
point. Krytox
®
greases are available with useful
temperature ranges up to 288
°
C (550
°
F) for con-
tinuous use. Special thickener formulations have
been blended to give useful lubrication up to
371399
°
C (700750
°
F) with spikes at 427
°
C
(800
°
F) or higher with more frequent relubrication.
4 Low-Temperature Greases
Krytox
®
grades formulated with low viscosity
oils can be used at temperatures as low as
57
°
C (70
°
F).
Valve Lubricants
Krytox
®
is used in all types of valves to lubricate
moving parts, seal connect