20 Minutes With Anoop Kumar
Karl M. Phipps, Managing Editor | TLT 20 Minutes May 2014
Nicknamed the ‘Grease Guru,’ this R&D specialist discusses the fascinating world of lubricating greases and how performance issues impact today’s machinery.
ANOOP KUMAR - The Quick File
Anoop Kumar is the director of R&D and business development for Royal Manufacturing Co., LP, in Tulsa, Okla., a small, family-owned, 100-year-old company that manufactures and markets lubricants and greases. He also serves as a member of the company’s senior management board.
Previously, he joined the research and development center of Indian Oil Corp. in 1991 after receiving his doctorate in chemistry from India’s premier Indian Institute of Technology, Roorkee, where he worked for more than 15 years in product and process development of lubricating greases. During this period, he invented novel titanium complex grease.
Anoop holds several worldwide joint patents and has published and presented papers at numerous technical conferences. He’s a member of STLE, The Tribology Society of India and NLGI’s board of directors, where he also helped with the formation of the NLGI-India chapter, serving two terms as treasurer and 10 years as an education course instructor.
Dr. Anoop Kumar (left) and Bill Mallory, president of Royal Manufacturing Co., LP, reviewing Inductively Coupled Plasma (ICP) metal analysis results in the lab.
TLT: How did you get started in your career?
Kumar: I did my doctorate in electro-organic chemistry in 1991, which had nothing to do with the petroleum field. During the later part of my program, I got a research position at the prestigious Tata Institute of Fundamental Research (TIFR) in Mumbai, India, but I decided later to look for a job that was closer to my hometown of Bareilly.
During that same period, one of my friends who used to work for a state owned company advised me to apply for a job at Indian Oil’s R&D Center at Faridabad. Fortunately, I got the job at Indian Oil and worked as a research officer. During my orientation program, the company’s head of lubricants research asked me if I wanted to work with the industrial oil, metalworking oil, automotive oils or lubricating greases department. While I knew nothing about lubricants, I was arbitrarily assigned to work with the grease group and have enjoyed working in this field ever since.
TLT: Why do enjoy working with lubricating greases?
Kumar: I always wanted to do research that has some direct applications in industry, and working in the field of lubricating greases for a company like Indian Oil, which covers 60 percent of the market share, was the right step in this direction.
Soon after joining the grease research group, I was assigned with the project of developing lubricating greases with indigenous raw materials to substitute lithium hydroxide, which are widely used lithium greases that are imported from the U.S. and China. Since Indian Oil is a government-owned company, they are always developing import substitution that makes the country self-reliant.
Accordingly, I started working on exploring the possibility of developing titanium grease. There were two basic reasons for selecting titanium metal: (1.) titanium compounds were indigenously available in India and (2.) the titanium metals has close resemblance in properties with aluminum metal, and aluminum complex greases have already been known in the industry.
Aluminum complex greases are prepared by reaction of either aluminum isopropoxide or its trimer with benzoic acid and stearic acid, forming aluminum benzoate stearate molecule. Attempts to make titanium complex grease using this approach miserably failed and, therefore, I started working on exploring the possibility of using other kinds of acids and salts, which included inorganic acids, aliphatic and aromatic acids, etc., but without much success.
In July 1992 while working on a reaction of titanium tetra isopropoxide with aromatic dibasic and a long-chain fatty acid, I accidently added a few drops of water in the reaction pot, which surprisingly suddenly gave rise to thickening of entire mass like a chain reaction and looked like a grease.
I carefully repeated and finished the reaction, and it gave rise to shiny grease with +500 F drop point having excellent extreme pressure properties (Weld Load > 315 kg) and rust preventive characteristics. This invention of titanium complex grease was patented worldwide and received many awards and recognition in India. I was then given the responsibility of scaling up the process from reaction under atmospheric conditions to 10,000 lbs. batch size to be under vacuum due to low flash point of isopropanol liberated during the reaction. Another interesting part of this project was to market end-use applications. This gave me ample opportunities to visit many industries like steel mills, cement plants, power plants, sugar mills, mining, food and transportation. The experience of nurturing little lab-scale inventions like titanium complex greases and bringing them to market was very fulfilling and self-satisfying. All of this impressed me so much that working with greases became my little world, and I never thought of switching over to any other field.
There are some special high-performance greases in the market with about 80,000 to 100,000 miles of relubrication interval in buses and trucks.
TLT: How are lubricating oils different than lubricating greases?
Kumar: Although lubricating greases constitute about only 2 to 3 percent of the total lubricants market, they are highly specialized products that are required in certain applications and can’t possibly be substituted by lubricating oils. A majority of bearings used in different equipment are grease lubricated. Unlike lubricating oils, lubricating greases:
1.
Don’t require a complex lubrication system.
2.
Remain at the lubrication site and prevent leakage.
3.
Act as a sealant and prevent dust, dirt and water ingress.
4.
Are preferred wherever application temperatures are high and bearing loads are exceptionally high.
Lubricating greases, basically non-Newtonian fluids, are complex mixtures of:
•
Thickener (10 to 15 percent)
•
Base oil (80 to 85 percent)
•
Additives (0 to 5 percent).
Thickeners form the backbone of lubricating greases and govern their major properties. Thickeners in lubricating greases acts like a sponge, absorbing oils which they retain in their cavity and release at the point of application as a result of motion of bearing/ gear or pressure and from the protective film between two metal surfaces. Technically, these thickeners possess fibrous structure where oil is entrapped into the cavities of the thickener by the following forces:
•
Capillary action
•
Van der Waals forces
•
Hydrogen bonding.
Additives are added to meet certain specific requirements like extreme pressure, antioxidant, antiwear, etc. Lubricating oils are a homogeneous blend of base oil and additives, which are solubilized by simple agitation, whereas preparation of lubricating greases is much more than just simple blending.
In general, a particular application that uses lubricating oil or lubricating greases is governed by its DmN factor, which can be calculated as follows:
DmN factor = N x (D + d) /2
D= Bearing outer diameter, mm
D= Bearing bore diameter, mm
N= Bearing operating speed, rpm.
Lubricating greases are generally recommended up to 1 million DmN factor with few exceptions. For a lower DmN factor, ranging from 100,000 to 500,000, mineral oil-based greases with suitable viscosity may be used. However, for a higher DmN factor, synthetic oil-based greases are preferred. Beyond this, oil lubrication is recommended.
TLT: What are the challenges in developing lubricating greases?
Kumar: According to the NLGI lubricating grease market survey, a majority of lubricating greases are either soap or complex soap-based. Conventional soap-based greases are prepared by a simple saponification reaction:
R CO2H + M-OH → R COOM + H2O
Long Chain Fatty acid, Alkali, Soap, water
(R- Alkyl group; M-alkali or alkaline earth metals like Na, K, Li, and Ca etc.)
Unlike lubricating oils, preparation of lubricating greases is regarded as complex in terms of processing parameters. The most popular lithium greases preparation involves the reaction of 12-hydroxy stearic acid with lithium hydroxide in mineral/synthetic oil media. Reaction is carried out predominantly under pressure (70-80 psi) under vigorous agitation and heating up to 400 F. These reactions are highly sensitive to rate of heating, pressure, mode and speed of agitation and time duration.
As reactions are carried out predominantly in situ and in non-polar oil media, the rate of reaction is much slower. As mineral oil used in these reactions are poor conductors of heat, uniform heating throughout the reaction vessel at commercial scale (5,000-10,000 lbs) is always a challenge. Additionally, these saponification reactions are carried out between weak acid (organic fatty acids) and weak base (e.g., lithium hydroxide), which the kinetics of reaction is complex and slow. Furthermore, what makes these reactions more complex is the reaction between different matter of states. For example, in preparation of lithium-based greases, the reaction between 12-hydroxy stearic acid (liquid at >170 F) and solid lithium hydroxide takes place. In the entire process, the phase transition from solid –> liquid –> semisolid takes place.
As soon as the reaction proceeds in forward direction, formation of lithium 12-hydroxy stearate, for example, begins to form, which is non-Newtonian in nature. These limitations of reactions makes the scaling process of lubricating greases from lab scale (3-5 lbs) to commercial plant scale (10,000-20,000 lbs) much more complex. On the other hand, preparation of lubricating oils is a simple blending process that takes place only in one (liquid media) with very nominal heat (100-150 F) with just a simple agitation process, and there is no chemical reaction.
TLT: Where do you think the industry is moving in terms of lubricating greases?
Kumar: With the increase in the complexity in modern machinery design and construction, the requirements of lubricating greases are also becoming more complex. Today industry is looking for lubricants with longer life, longer relubrication interval, less downtime and enhanced productivity. For example, there was a time where calcium and soda base greases were used in automotive wheel bearing applications with relubrication on about 20,000 miles; these products now are replaced with better lithium greases having relubrication frequency of about 40,000-50,000 miles. There are some special high-performance greases in the market with about 80,000 to 100,000 miles of relubrication interval in buses and trucks. In railroad applications where lubrication greases once had a life cycle of about 100,000-200,000 miles, synthetic greases with a life cycle of 800,000 to 1 million miles have also been used.
This trend is also supported by NLGI’s lubricating grease market survey data. For example, in the U.S. and Europe, use of high-performance grease is much higher than in Asia. In a nutshell, the industry is moving toward using more high-performance, long-life greases like lithium complex, calcium sulfonate, polyurea and aluminum complex. Usage of conventional lithium, calcium and soda base greases is becoming the declining trend.
TLT: What are the compatibility issues in using different types of lubricating greases?
Kumar: There are many applications in industry where greases are pumped through centralized lubrication systems, even sometimes to long distances. In such applications, cleaning of lines and application site is practically impossible. Even during manufacturing, switching over to one type of grease to other, cleaning of lines and kettles is very difficult. In such cases, compatibility of grease plays a significant role.
There are greases which are not compatible with other greases. For example, lithium, lithium complex and calcium sulfonate greases exhibit comparatively better compatibility with other greases, whereas greases like polyurea, aluminum and clay base greases are more sensitive to compatibility. On the other hand, synthetic oil-based greases show poor compatibility with mineral oil-based greases, and bio-based greases are not even better, as well. NLGI has published a grease compatibility chart in its grease guide for reference.
TLT: What is the potential growth of food grade and synthetic greases?
Kumar: The industry has started looking for long-life greases having wide temperature operability, which is where synthetic lubricants and greases come into the picture. For example, in mining operations in the mountains in Canada and Chile, where temperatures reach subzero, synthetic greases are the preferred choice. Conventional mineral oil-based greases exhibit temperature operability between 0 F-350 F. Therefore, with temperatures beyond this range, synthetic greases need to be applied.
As the industry moves toward more efficient, long-life greases, the use of synthetic greases should increase. Similarly, due to increased consumer awareness and compulsions from governing authorities, there is an increasing trend to use food-certified greases in food-processing areas. Some religious organizations like Halal and Kosher also are helping to drive the demand.
TLT: What is the future of bio-based lubricating greases?
Kumar: Buzz words like environment friendly, biodegradable, bio-based, renewable, etc., are often echoes in the industry, and there is certainly a curiosity and sometimes compulsions from environmental agencies to use environment friendly products. The use of renewable fuels has further fueled the demand of bio-based greases. However, industry expectations from these bio-based lubricating greases is that these products must perform at par with mineral oil-based greases.
Bio-based greases, on the other hand, possess some inherent limitations like inferior thermal and oxidative stability, limited shelf life, storage hardening over time, etc. In spite of having these limits, there are applications like marine, mining, forestry, municipality and other environmentally sensitive applications where the use of bio-based greases is on the increasing trend. Additionally, efforts are being made to improve the performance characteristics of this class of greases. I personally feel that the usage of this class of grease should increase. Even though there are some limitations of bio-based greases, efforts to develop more consumer friendly greases must continue, as this class of greases is going to be the only choice for lubrication if petroleum-based mineral oil starts depleting.
You can reach Anoop at anoopk@royalmfg.com.