Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
  • G01N11/02—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by measuring flow of the material
  • G01N11/04—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by measuring flow of the material through a restricted passage, e.g. tube, aperture

Definitions

• the invention relates to the manufacture of lubricating greases using a continuous process.
• the invention further relates to a method for continuously monitoring the consistency of the finished grease product by correlating the product pressure drop across a venturi to the consistency of the finished grease. Monitoring the pressure drop allows operators of the continuous grease process to monitor product quality and quickly detect any problems with the ongoing grease production.
• the present invention relates to a method for monitoring the consistency of the grease manufactured by a continuous grease making process.
• Continuous grease making processes were developed in the early 1960 , s. Their refinement has been vigorously pursued due to the potential advantages the continuous process offers over the widely used batch process for grease manufacture. Some understanding of the batch process is required in order to fully appreciate the advantages of the continuous grease making process.
• the batch method is currently the most widely used method for grease making. Batch processing is carried out with equipment having widely varying capacities. That capacity can range from 22.6 kg (50 pounds) of grease to about 9,060 kg (20,000 pounds) of grease.
• the equipment involved can be expansive taking up two floors of a building and employing a large operating crew.
• the major components of a typical batch process are a contactor, a kettle, and various kinds of finishing equipment.
• the contactor is a pressure vessel wherein the thickener that provides the structure to hold the lubricating oil contained in the grease is formed.
• the thickener most commonly used for modern grease production is some sort of metallic soap made from a fatty acid, a metal base, water, and in some cases a small amount of lubricating oil.
• the soap is usually referred to by the name of the metal base used to make the soap.
• Commonly used metals used include aluminum, lithium and barium. These components undergo a saponification process whereby they are mixed in the presence of heat and pressure to fo the soap thickener.
• Greases referred to as complex greas were developed when it was discovered that different kind of fats could be combined to make greases.
• comple grease has been used for many different purposes but toda has generally been accepted to refer to a high temperatur application grease.
• the soap mixture leaving the contactor is quite wet and as in any grease manufacturing process requires removal of excess water.
• the soap mixture will remain in the kettle for many hours where the mixture is heated and water vapor is drawn therefrom.
• the kettles typically contain internal agitators or scrapers that serve to brea up the soap structure to improve the consistency and workability of the grease.
• the scrapers also remove mass of soap from the sides of the kettle.
• the kettles are heated by steam, electricity or via the circulation of so type of hot oil.
• the type of heat source utilized will vary with the maximum temperature required in order to fo the grease.
• From the kettle the grease is pumped to various kind of finishing equipment.
• This finishing equipment is required to ensure that the soap structure and any grease additives are evenly distributed throughout the grease.
• This equipment includes milling machines which break up t fibrous structure of the soap and homogenizers which improve the dispersion of the soap in the grease.
• the finishing step could also include filtration to remove impurities or deaeration to remove entrained air. Air is introduced into the grease while it is beaten in the kettle. Excess air can cause problems with the appearanc of the grease and can prevent the required weight of grea fro being introduced into the intended packages.
• the grease is then cooled and packaged.
• a number of variations on the batch process are possible to include changing the size of the kettle used and carrying out the entire process inside one vessel.
• continuous grease production units take up a fraction of the space required by batch processing equipment and can be operated by a small complement of operators.
• the continuous production process has proven capable of achieving a higher output of a consistently high quality product. Moreover, this process results in less wasted product created during the changeover from one grease to another.
• the parameter most often monitored is the grease consistency. This term has been used to refer to the texture or elasticity of a grease, however, it is now accepted to refer to the degree to which a grease will deform upon the application of a force. Consistency is measured using the cone penetration test specified in AST D217, "Cone Penetration of Lubricating Grease.” The test is conducted using an ASTM penetrometer and is widely kno by skilled operators. Accordingly the details of the tes procedure will not be repeated here. The test is simple easy to conduct and provides reproducible results. Test results are reported in the number of tenths of millimete to which a standard cone sinks into a grease under prescribed conditions. As the penetration number increas so does the softness of the grease. In the context of a continuous grease process, however, the test requires a great deal of time to conduct. Quite a large volume of unusable grease can be produced during the time required take a sample and perform the penetrometer test.
• the present invention relates to a method of monitoring the consistency of a lubricating grease comprising the steps of passing the grease process stream through a venturi so that a pressure drop occurs; measuring the pressure drop using two axially separated pressure tap points along the venturi; and correlating the pressure drop to the consistency of the lubricating grease.
• the pressure drop occurs at a constant temperature, flow rate and pressure into the venturi.
• the method also relates to converting the adjusted pressure drop to an electronic signal which is proportional to the pressure drop.
• the electronic signal may be displayed on a digital display.
• Another aspect of the present invention is to monitor the signal electronically for variation beyond a predetermined range. When the signal leaves that range an alarm would be actuated to alert operators to take steps to correct the alarm condition.
• FIG. 1 is a schematic of a typical continuous grea making process.
• Figure 2 is a schematic representation of the presen invention.
• Figure 3 is a graphical representation of the empirical relationship between the pressure drop and grea consistency.
• Fig. 1 a continuous grease making process incorporating the present invention is illustrated in simplified form.
• the process is initiated in a reactor 4 where three inputs are heated an mixed under turbulent conditions.
• the inputs are lubricating oil 1, alkali 2 and a fat 3.
• the saponification or soap forming step described herein abov takes place in the reactor which is maintained at a superatmospheric pressure and at a temperature consistent with the desired final product.
• a portion of the output the reactor is recycled via pump 5 back into the reactor as to maintain a high flow rate through the reactor.
• the recycling also speeds the mixing process of the inputs therein.
• the product of the saponification reaction then passes through a soap base heater 6 to a flash chamber 8.
• the flash chamber is also known as a dehydration chamber.
• the soap base is dehydrated of the moisture formed as a resul of the saponification process. The dehydration takes pla under subatmospheric conditions. The resulting water vap is drawn off at 8A.
• the soap base is conditioned by the recycling of the flash chamber output by pump 9. is also typical to agitate the flash chamber mixture with agitator 8B.
• the temperature maintained in the flash chamber and the residence time of the soap base in the flash chamber can vary widely with the type of grease being made.
• After h& soap base leaves the flash chamber it is blended in-line with additives represented by 10 and additional oil 11. The mixture is then passed through a static mixer which conditions and ensures adequate dispersion of the additives therein.
• the rough grease thus formed then goes through a final finishing section pump 13 and on to a series of shear valves 14, 15.
• the grease undergoes a pressure drop and shearing action in the valves to improve soap and additive dispersion.
• the shear valves also give the grease its final smooth appearance.
• From the finishing section the now final grease process stream grease is pumped by booster pump 17 to the consistency monitoring venturi 18 where a pressure drop occurs. This pressure drop is correlated to the consistency of the final grease stream 19 as described herein below.
• the venturi 18 is positioned in the line carrying the final product stream 19.
• the venturi 18 is provided with two pressure tap points 20, 22 which are axially separated along its length.
• the pressure drop that occurs in the venturi can be measured by comparing the observed pressures at the two tap points. That pressure differential can then be converted by appropriate electronic computing means to a pressure drop reading given in inches of water.
• the venturi must be positioned in the process so as to ensure that the pressure drop occurs at a constant temperature, flow rate, and pressure into the venturi. Each of these parameters will vary with the particular product being produced but will remain essentially constant during the production of any one product.
• a venturi offers many advantages as a device to create a measurable pressure drop for the purposes of the instant invention.
• a venturi is manufactured to much closer tolerances than standard seamless pipe which could be used for this purpose. This characteristic provides for repeatability and consistency of measurement from installation to installation.
• the design of a venturi is such that a pressure drop is developed in a relatively short length of piping. Thus its use in space constrained plant environments is quite beneficial.
• the open flow design of a venturi avoids the problems encountered with the prior art consistometers described herein above relating to the adverse effects of polymeric additives on rotating members. Those additives improve the tackiness or ability of the grease to adhere a metal surface in actual service use.
• ⁇ P is the observed differential pressure drop across the venturi
• T is the finished product temperature in degrees Fahrenheit
• R is the production flow rate in pounds/min Xj and X 2 are temperature and flow rate factors respectively.
• This adjusted pressure drop is the observed pressure drop adjusted for the difference between actual system conditions at the instant a measurement is taken and ideal design condition of 100 pounds/min flow rate and production temperature.
• the factors X : and X 2 are related to venturi size. They must be determined anew in the event a different venturi is to be used.
• venturi size 3 inches or less should be used. Most preferable is a venturi size of about 1-1/2 inches.
• pressure and flow rate must be maintained into the venturi to provide stable, accurate, and repeatable results. Only after the completion of the last of the finishing steps is the grease in a relatively steady state condition so as to permit accurate monitoring. By steady state condition it is meant that no wide fluctuations of temperature, pressure or flow rate take place.
• the present invention has been described with the use of a manual correlation process, it is easily adaptable to automatic operation and control of the continuous grease making process. It can also be converted into an electronic signal proportional to the pressure drop through the venturi. That signal can be converted to a digital display so as to be continuously monitored by operators either by a local display unit or remotely via a microcomputer. Alternatively, the signal can be monitor remotely by a microcomputer means for variation from a predetermined range so that a pressure drop variation outside that range would actuate an alarm to alert operators to the problem condition, thus permitting corrective measures to be taken. Conceivably the alarm condition could trigger the shut down of the continuous grease making process.

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• Physics & Mathematics (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
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• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Lubricants (AREA)

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• 1994
  • 1994-09-13 US US08/304,966 patent/US5583284A/en not_active Expired - Lifetime
• 1995
  • 1995-09-05 AU AU35036/95A patent/AU3503695A/en not_active Abandoned
  • 1995-09-05 WO PCT/US1995/011202 patent/WO1996008708A1/en not_active Ceased
  • 1995-10-03 TW TW084110285A patent/TW305932B/zh active

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