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 PATTERSON Industries Canada designs, engineers and manufactures the PATTERSON® Grease Base Reactor that is used in
the preparation of the soap base "saponification" for the production of the wide
range of automobile, aircraft, railroad and industrial greases.
 The PATTERSON® Autoclave-Style Grease Kettle can be used
for the complete grease manufacturing cycle - saponification, grease finishing and
cooling. However, the process time is extended when compared to saponification being
performed in a PATTERSON® Grease Base Reactor. The Reactor with its jacketed vessel construction - jackets
over both the shell and cone sections - and double wall construction inner circulation
tube offers a greatly increased surface area for transfer of heat to the soap. Coupled
with this is the dramatically increased rate of product circulation brought about by the
bottom propellor agitator that operates at full or half motor speed (typically 1750/875
rpm or 1500/750 rpm.) This type of agitation/mixing action ensures a homogeneous soap base
for transfer to the Grease Finishing/Cooling Kettle where the balance of oils and
additives are charged and the final grease product manufactured.
 Heating can be either by steam or thermal fluid. At the
end of the basic soap manufacturing cycle and after the soap has been initially
transferred, there will still be soap residue remaining in the Reactor. The residue is
removed by adding more of the base oil, circulating the oil and transferring to the Grease
Finishing/Cooling Kettle. This not only removes the residue (removing the potential for
fatty acid attacking the steel and causing corrosion pitting) but in addition cools the
Reactor in preparation for the next cycle.
Due to the faster production of the soap in the PATTERSON®
Grease Base Reactor, one Reactor can generally
service two or more Grease Finishing/Cooling Kettles thus increasing the plant production.
Design Features and Benefits:
- Designed, engineered and manufactured to individual customer specifications.
- Standard sizes range up to a maximum capacity of 1750 USG (6600 litre); can also be
supplied in non-standard sizes.
- High product circulation rates achieved by the bottom mounted propellor agitator ensures
a faster homogeneous product than with the Grease Kettle.
- Increased heat transfer area together with the mixing action results in a dramatically
decreased soap preparation cycle time than with only a Grease Kettle.
- Two-speed motors are standard.
- Pressurized lubrication/cooling system for the mechanical seal included.
- Designed, manufactured, tested and inspected in accordance with the ASME Code Section
VIII Division I and with the stamp of the National Board of Boiler and Pressure Vessel
Inspectors. Also available to PED/CE Label standards as well as to the design standards of the Peoples Republic of China.
- PATTERSON® has over 50 years experience in the design,
engineering and manufacture of Agitated Process Vessels, Reactors and Kettles with either
single or double motion agitation systems.
See the Specifications for the PATTERSON® Grease Base Reactor.
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A
brief technical overview of the production of
LUBRICATING
GREASES
Description
There has
been a need since ancient times for lubricating greases. The Egyptians
used mutton fat and beef tallow to reduce axle friction in chariots as
far back as 1400 BC. More complex lubricants were tried on ancient
axle hubs by mixing fat and lime, but these crude lubricants were in
no way equivalent to the lubricating greases of modern times. Good
lubricating greases were not available until the development of
petroleum-based oils in the late 1800's. Today, there are many
different types of lubricating greases, but the basic structure of
these greases is similar.
In general, grease consists of a thickening agent dispersed throughout
lubricating oil. The thickening agents or gallants include alkali
metal soaps, clays, polymers, carbon black, colloidal silica and
aluminum complexes. The lubricating oil may be petroleum oil or
synthetic oil. The most common type of grease is the soap-based
grease. The soap comes from animal or vegetable fats or fatty acids,
wool grease, rosin or petroleum acids. The lubricating oil is commonly
mineral oil from paraffinic, naphthenic or aromatic hydrocarbons.
Other components of these greases include unreacted fat, fatty acids
and alkali, unsaponifiable matter (including glycerol and fatty
alcohols), rosin or wool grease and water. Some of the other additives
used in grease are oxidation inhibitors, rust and corrosion
inhibitors, color stabilizers, metal passivators, water repellants and
viscosity index improvers.
In soap greases
the metallic soap consists of a long-chain fatty acid neutralized by a
metal such as aluminum, barium, calcium, lithium, magnesium, sodium or
strontium. The fatty acids usually contain 16 to 18 carbon atoms. A
common form of soap-based grease uses lithium 12-hydroxystearate as
the thickener. To properly thicken the grease the soap must be in the
form of fibers of suitable size dispersed throughout the lubricating
oil. The crystalline fibers are usually in the size range of 1 - 100
micrometers with diameters 0.1 to 0.01 of their length. For good shear
stability the fiber should have a large ratio of length to diameter,
and for good oil retention the fiber should be as small as possible.
Therefore, greases need a mixture of these two types of fibers. Also,
there must be a balance between the solvency of the fluid and the
solubility of the soap to get suitable thickening.
Another type of thickener that is not soap-based is prepared from
clays. The clay, such as bentonite or attapulgite, is reacted with a
quaternary amine to change the clay from hydrophilic (water-loving) to
hydrophobic (water-rejecting) and oleophilic (attracting oil).
Effective thickening is achieved by combining the clay with a polar
activator or dispersant, such as acetone, methanol or ethanol, with
small amounts of water and by delaminating and reducing the platelets
to a small size. This process will increase the total surface area of
the dispersed clay, which immobilizes a very high percentage of oil
based on the weight of clay. This will thicken the grease.
Other solid additives produce thickened grease by the nature of their
fine dispersion throughout the fluid and by their particle-particle
interactions. Solid-additive greases extend the operating temperature
range over soap greases. The solid-type greases do not have a melting
point, and their upper temperature limit is that of the oil being
used.
The melting point of greases made with various soaps will
differ appreciably. For example, using the grease dropping-point
temperature, which measures temperature limitation of the grease, the
following demonstrates the differences in these temperatures: aluminum
- 230°F (110°C); sodium - 325 - 350°F (163 - 177°C); calcium
(conventional) - 205 - 220°F (96 - 104°C); calcium (anhydrous) - 275
- 290°F (135-143°C); lithium - 350 - 400°F (177 - 204°C).
The
dropping temperature of soap-based greases can be increased by using
soap complexes. These complexes consist of a soap-salt thickener. For
example, an aluminum complex might consist of aluminum with a fatty
acid, a nonfatty acid and an alkali. Then each molecule of thickener
consists of aluminum complexed with stearate, benzoate and hydroxide.
The dropping point of a complex grease is at least 100°F (56°C)
higher than the dropping point of the corresponding soap grease. The
range of application of greases is also extended by
"multi-purpose" greases that consist of mixtures of soap
bases or different metals and soaps.
Processing
Greases
can be made in either a batch or continuous process. Batch production
is the most common manufacturing method. The steps of manufacturing
include the following. Bulk ingredients are metered or weighed into
the processing reactor. For soap-based greases made by saponification
(the process of forming soap by splitting a fat with an alkali), the
fatty ingredient, alkali and a portion of the oil are added to the
reactor. By heating (300 - 450°F) and mixing, the fat is converted to
soap, and the soap is dispersed throughout the mixture. This may be
done in open atmospheric PATTERSON
double motion stirrer kettles or in closed
PATTERSON double motion stirrers. pressure kettles. After completion of
saponification and dehydration (removal of water), the remaining oil
is added to the batch to lower the temperature. Next, the grease is
milled or homogenized. Alternatively for larger operations a PATTERSON
Grease Reactor can be used for quick and efficient saponification
and after the completion of the cycle the material is transferred to a
PATTERSON
Double
Motion Grease Kettle.
Typically one Reactor will feed 3 Kettles.
The step of homogenization or milling is very important, because it
will produce a uniform crystal and gel structure that will not change
when the grease is used. Homogenizing the grease will break down the
solid particles or fibers and will disperse the resultant small
particles in the liquid. It also breaks up lumps, eliminates
graininess and produces a smooth product. Homogenization of certain
types of greases will stiffen the grease producing lower penetration
value. Homogenization can improve texture and “brighten” a
grease’s appearance. In many cases this homogenization process is
carried out at temperatures greater than 200°F (93°C).
After homogenization, the
grease is further cooled, deaerated and packaged. Of course, it is
understood that there are many different grease manufacturing methods
depending on the type of grease and the manufacturer.
APV homogenizers and APV colloid
mills or equal can be used for processing grease. The single-stage
homogenizer with wear-resistant parts may be operated at up to 10,000
psi. The homogenizer is the preferred piece of equipment for the
solid-additive-type greases, because high energy is needed to break up
and delaminate the particles such as with clay dispersions. Although a
colloid mill can be used to process grease, there are advantages to
using the homogenizer. First, the homogenizer is a
constant-displacement pump, and its capacity does not vary with
different grades of greases. This makes it possible to tie into
filling equipment, if desired. The colloid mill must be pump fed and
the capacity will be significantly decreased on the stiffer grades of
greases. The homogenizer
has sufficient pressure to deliver the grease to any point in the
process after it has been homogenized; but a second pump must pick up
the colloid mill product, if the grease is to be delivered to another
location.
There are other methods of
producing grease. A continuous process for grease manufacturing is
described in European Patent Specification 0072184B1 (October 29,
1986), which also mentions other continuous methods. These particular
techniques will not be discussed here. However, another patented
method (US Patent 2,704,363, March 15, 1955) will be briefly
described. In this process a homogenizer was used to accelerate the
saponification reaction by recycling the batch of ingredients from the
reaction kettle through the homogenizer and then back to the kettle.
This reduced the reaction time needed to make the grease. In one
example given, a batch produced by homogenization was compared to a
batch produced by conventional means. The results were that the
homogenized batch had an improved consistency; it possessed greater
mechanical stability; the operating temperature of the homogenized
batch was 320°F compared to 400°F (conventional) and the total
operating time was reduced from 18 hours in the conventional
fire-cooking process to 3.5 hours for the steam-cooking and
homogenization procedure.
Quality
and Evaluation
The formulation and processing
of grease will determine the type of structure the product has and its
physical properties. This is why homogenization can have an important
influence on the quality of the grease. There are several desired
characteristics for grease such as: body or consistency, stability to
shear, surface affinity, thermal stability, flow or viscosity,
thixotropy, syneresis, texture and appearance and water resistance.
There are many tests that can be performed on grease to measure these
properties. One important test is penetration. Penetration is
determined by an instrument that measures the depth (in tenths of
millimeters) to which a standard cone sinks into the grease under
prescribed conditions. Higher penetration numbers indicate softer
greases. The National Lubricating Grease Institute (NLGI) uses
consistency numbers that correspond to penetration values to classify
greases. The numbers are given below.
|
NLGI Number
|
ASTM
Worked Penetration
|
|
000
|
445-475
|
|
00
|
400-430
|
|
0
|
355-385
|
|
1
|
310-340
|
|
2
|
265-295
|
|
3
|
220-250
|
|
4
|
175-205
|
|
5
|
130-160
|
|
6
|
85-115
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References
E. Armstrong,
US Patent 2,704,363; 1955.
C. J. Boner, C. J. Manufacture and Application of Lubricating
Greases, (New York: Reinhold Publishing, 1954)
1993 APV
Homogenizers
A. A. Gordon, European Patent Office 0072184 B1; 1986.
_____________, 1989. Lubricating
Grease Guide, Kansas City: National Lubricating Grease Institute,
1989.
Any statements concerning
the use of products or processes described above are made for
educational purposes only to further the understanding of grease
manufacturing. They are not to be construed as recommending the infringement
of any patent or copyright and no liability for infringement arising
out of any such use is assumed by PATTERSON Industries Canada – Division of All-Weld Company Limited.
****
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Useful
Information from National Lubricating Grease Institute (NLGI) founded
in 1933
PATTERSON
Industries
has been a member of the NLGI for over 20 years. As stated by
President Sandy Cowan during a speech in 2008, "the original
mission of NLGI was to distribute information pertinent to the
manufacture and use of lubricating grease". This
original mission is still valid today. Besides annual meetings during
which new and useful information and a wide assortment of grease
related information is published, including the Lubricating Grease
Guide and the NLGI Spokesman, NLGI is the source for most technical
information concerning lubrication and grease. It is a great example
how an industry can work together and exchange important technical
information for the benefit of industry in general and the consumer.
Below with the permission of NLGI, we are reprinting a regular
feature from the NLGI Spokeman titled "Ask
the Expert".
We are mainly reproducing columns
that primarily deal with technical information on greases and
manufacturing rather than just end user related questions below and
trust this is helpful to our customers for Grease Kettles and
Reactors:
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