From gas pipelines to floodgates at big power plants, from onshore and offshore oil rigs to research stations in Antarctica or in the Earths orbit, lubricating pastes are needed for numerous applications that operate in extreme temperatures or that are exposed to steam or water.
They are also widely used for applications prone to explosions, high loads and heavy vibrations. Demand volumes are very small, but officials at Dow Corning predict they will rise significantly, particularly in Russias oil and gas industry.
A Different Type of Lube
Pastes are certainly novel forms of lubricants.
In many cases when people talk about lubricants, they basically think about a certain product or type of product — usually oils or greases, Victor Parashchuk, application engineer at Dow Corning, said during the Lubricants Russia 2010 conference in Moscow in November. Though, it is more appropriate to use an application approach. This is even more the case regarding Russia and neighboring countries, where the approach of choosing a lubricant and the culture of its usage in every industry might be different.
Pastes are similar to greases insofar as they contain solid lubricants or lubricant additives in a carrying oil. The difference is that in pastes the percentage of solid material is very high so the pastes themselves seem more solid, or less fluid. Pastes are designed to be easily applicable and to solve tribological problems in the boundary and mixed lubrication regimes – that is, when moving mechanical parts are under loads sufficient to bring their surfaces into contact. Such conditions increase the likelihood of component wear, unless the lubricant can create a solid film that remains between the surfaces and minimizes friction between them.
Under conditions where oils and greases might be squirted out of the lubricating contact, solid lubricants form thin adhering films that can help prevent damage. Some industry pundits say that another special feature of these films is that they can regenerate themselves because the pastes themselves are resistant to wear and tear. In their book, Lubricants and Lubrication, Theo Mang and Wilfried Dressel explain that this avoids the need for re-lubrication where pastes are used.
According to Dow Corning, a supplier of specialty lubricants and silicone-based products headquartered in Midland, Michigan, U.S., pastes are an economical way to protect contacting metal surfaces. They do this by creating a thin but solid lubricant layer that keeps surfaces from contacting. Industries such as oil and gas, automotive and heavy machines are in great need of different solutions for particular applications, noted Parashchuk, who is based in Dow Cornings Moscow office. In such cases anti-friction coatings are sometimes an alternative to pastes.
According to Parashchuk, the chemistry of lubricating pastes can vary depending on application and conditions, but the key ingredients are usually metallic. Among the solid components used are molybdenum disulfide, graphite, calcium hydroxide, calcium phosphate and aluminum phosphate, as well as inorganic oxides and metals such as copper or zinc. Carrier fluids include mineral oils, polyalphaolefins, polyglycols, silicone oils and white oils.
Pastes are used in applications that might have taken greases, Parashchuk said, but pastes provide much more robust performance.
For example, greases made with calcium complex soap thickeners have good shear stability and water resistance, low oil separation and good load-carrying capacity, he said. But their upper temperature limit is 160 degrees C. Alternatively, aluminum complex greases have good low-temperature performance. Both of these technologies were developed in the 1950s and 1960s.
Oil and Gas Niche
Lubricating pastes were developed more recently and are significantly more robust in their performance. Pastes can tolerate temperatures of several hundred degrees C, some above 1,000 degrees C. In certain applications they can also provide better extreme pressure protection. Common applications include manufacturing assembly, bearings, gears, mechanical threads and slow-moving, high load-bearing parts.
Their primary use is in the oil and gas industry where high-torque threaded connections are ubiquitous, Parashchuk said. These pastes help to prevent cold welding, seizure and breakage of threaded connections tightened up to extremely high torques.
Equipment used in oil and gas drilling equipment is exposed to extreme conditions. Drills operate at high speeds, come under extremely high loads and are subjected to high levels of friction. Lubricating pastes may be applied to the threads on sections of drill. Industry standards call for these threads to be tightened to torques as high as 84,000 newton meters.
Highly pure thread paste with less than 500 milligrams per kilogram sulfur and less than 200 mg/ kg chlorine and fluorine, not containing lead and nickel, can withstand very high loads and temperatures, Paraschuck revealed. Their temperature range is from -35 degrees C up to 1,200 degrees C, he said, and they have stable coefficient of friction, high temperature stability and resist corrosion.
Parashchuk said Russias oil and gas industry is likely to increase its demand for lubricating pastes in coming years because of a basic shift in the industry. Russia is the worlds biggest crude oil producer, based on 2009 data. Currently, 95 percent of its fields are land-based – primarily in Eastern and Western Siberia, the Urals and the Timan-Pechora region.
However, 70 percent of existing drilling rigs are worked out, and one in three is older than 20 years, he said. The industrys focus is now shifting to larger, off-shore projects. Over the next decade, it is expected that 70 percent of new projects will be located in water, in places such as the Barents, Okhotsk, Caspian and Black Seas. Energy companies are also developing offshore gas projects.
On Point Offshore
Offshore oil and gas projects involve undersea pipelines made of many sections that are connected by bolted threaded flanges. The threads must be lubricated, Parashchuk explained, and this application is also difficult due to the corrosiveness of the environment, the absolute need to guard against leaking and the constant clamping pressure from the bolts. In addition, temperatures can reach up to 650 degrees C.
Once again, Parashchuk said, lubricating pastes offer an ideal solution. The results of our measurements found that the coefficient of friction [for threads with lubricating paste] is unchanged even after several bolt re-tightening and loosening processes. He and Dow Corning expect a significant increase in demand for those products from the oil and gas industry.
We assume that demand for specialty pastes will be much higher in this decade, he said. These are underwater applications where harsh conditions exist and where leakage is environmentally not acceptable. Applications such as drilling equipment or bolted connections are prone to constant friction and clamping force.
Parashchuk cited other applications that are suited for lubricating pastes. One was floodgates in big power plants and dams. Their lubricants must be resistant to washout because the main component, the chain, is in constant contact with water. They also must be environmentally friendly, must protect against corrosion, and must provide good penetration.
These issues can be solved with pastes for open chains that have excellent adhesion and anti-corrosion protection, Parashchuk said. The pastes must have high load-carrying capability, be very adhesive, resistant to water wash-out and contain no metals.
According to the All-Russia Research Institute of Oil Refining in Moscow, the volume of pastes and solid lubricants produced in Russia is approximately 3 metric tons annually. The institute is known by its Russian acronym, VNIINP.
It is a very small part of the total greases volume produced in Russia and a miniscule part of it comes from our institute, said Marina Semtyurihina, head of the institutes solid lubrication coatings lab. She added that the institutes outputs of solid lubricants depend on the occasional orders from customers. The countrys volume of grease production has been stagnant during this past decade at around 45,000 to 50,000 t/y, the institute said.
If Dow Cornings predictions are correct, volumes for lubricating pastes could grow from very small to a little bit bigger.