High Temperature Greases
High temperatures harm greases more than they harm oils. Grease, by its nature, cannot dissipate heat by convection like circulating oil. Consequently, without the ability to transfer away heat, excessive temperatures result in accelerated oxidation or even carbonization where grease hardens or forms a crust. Effective grease lubrication depends on the grease’s consistency. High temperatures induce softening and bleeding, causing grease to flow away from needed areas. The oil in grease can flash, burn, or evaporate at temperatures above 177 oC. High temperatures, above 73-79oC, can dehydrate certain greases such as calcium soap grease and cause structural breakdown. The higher evaporation and dehydration rates at elevated temperatures require more frequent grease replacement.
There are many criteria to consider when selecting a high-temperature grease for hot, grease-lubricated equipment. The selection must include consideration of oil type and viscosity, oil viscosity index, thickener type, stability of the composition formed by the oil and the thickener), additive composition and properties, ambient temperature, operating temperature, atmospheric contamination, loading, speed, relubrication intervals, etc. With the variety of details to resolve, the selection of greases that must accommodate extreme temperature conditions poses some of the more challenging lubrication engineering decisions.
Given the variety of options, the potential for incompatibility problems and high prices for a given high-temperature product, the lubrication engineer must be selective and discriminating when sourcing products to meet high-temperature requirements.
Krytox High Temperature Lubricants
Krytox® Takes the Heat!
When the heat is really on, you need a high temperature grease or high temperature oil that can take it without performance degradation. Krytox synthetic lubricants are specially formulated for extreme high-temperature applications. Krytox lubes are a perfluoropolyether- (PFPE-) based polymer composed of fluorine, oxygen and carbon. No hydrogen is present in the molecule, resulting in exceptional stability and non-flammability.
Targeted for use in the very high-temperature range, these ultra-high-temperature-grade oils and greases offer low evaporation and remarkably stable lubrication performance at temperatures above the range of normal PFPE-based oils or conventional hydrocarbon-based lubricants. Krytox™ XHT lubricants are available in several grades that offer anticorrosion, extra bonding, and non-melting properties. These lubricants serve a variety of industries, including chemical, textile, tire, aviation, conveyor, oil and gas, glass, plastic film, and non-woven manufacturing, as well as mining and metal processing.
Krytox™ XHT lubricants offer a host of operational benefits, including:
- Non-flammable — Krytox™ XHT will not burn or support combustion, even in 100% liquid or gaseous oxygen — providing high-temperature stability up to 399 °C (762 °F)
- Longer component use-life, less downtime and less frequent re-lubrication
- No oxidation and low volatility
- Undamaged by — and non-reactive with — acidic or caustic cleaners and disinfectants, steam, moisture and high temperatures
- Insoluble in most solvents — but soluble in highly fluorinated fluids and some supercritical fluids such as CO2
- Ideal for all components, including bearings, seals, valves, O-rings, chains, gearboxes and agitators
- Minimal environmental footprint
- Chemically and biologically inert and silicone-free
- Safe for use around oxygen, and non-reactive with chemicals typically used in industrial applications
- Contains no volatile organic compounds (VOC) materials or chlorine
- Krytox GPL Series
- Krytox Aerospace Series
- Krytox ‘K’ Series
- Krytox ‘E’ Series
- Krytox XHT Series
Setral Chemie GmbH, Germany
The following table summarizes High Temperature Greases from Setral Chemie GmbH, Germany
|SYN-setral-INT/300||For rolling and plain bearings, lubrication of ejection pins (plastic injection moulding), without solids, up to +300 oC, insert, NSF H! – authorisation|
SYN-setral-INT/250 S series
|For rolling and plain bearings, with PTFE, continuous up to +250 oC, intermittent up to +208 oC, inert (e.g. oxygen)|
|SYN-setral-54 N||Synthetic grease for rolling and plain bearings, contains MoS2, up to +180 oC|
|Synthetic polyurea grease for rolling and plain bearings working under severe conditions, -40 oC up to +180 oC|
|SYN-setral-INT 250 A-2||For rolling and plain bearings, with PTFE, continuous up to +250 oC, intermittent up to +280 oC, e.g. bearing of corrugating rolls|
|SYN-setral-HT 2||For rolling and plain bearings, contains PTFE, -20 oC up to +180 oC up to +108 oC|
|MI-setral-LI/C-2||Lithium-complex-grease for rolling and plain bearings,-30 o C up to > +150 oC|
|setral-K 300 plus||Synthetic special grease with new combination of solids, stable at high temperatures, in aggressive atmosphere|
|MI-setral-AL/C-2-3 N||Al.- complex-grease for rolling and plain bearings, -20 o C up to +150 oC|
|MI-setral-PU 100||Polyurea grease for rolling and plain bearings, -30 oC up to +160 oC|
|SYN-setral- INT/Special||Synthetic special grease, stable at high temperatures and aggressive atmosphere, ejection pins, -20 oC up to +300 oC|
Ultrachem Inc, USA
Greases & Gels
Chemlube Vischem series Greases & Gels are 100% synthetic, state of the art lubricants, formulated to reduce friction and wear. These will not melt or drip and leaves minimal residue. It provides corrosion protection, seals bearings from water and contamination, retains its structure and consistency while in service and remains stable under high shear and high temperature. It will not emulsify and will perform exceptionally well in wet applications. The lubricants are virtually waterproof!
Diester High Temperature Greases:
Applications: Ball and roller bearings, cams, slides, gears for appliances, automotive, business machines, electric motors and instrument applications. Especially useful where unusual thermal and oxidative stability are required. Vischem 4076 is used for continuous casting.
Polyolester High Temperature Greases:
Applications: Outstanding heat stability. Long life, synthetic non-melting greases. These greases are superior for high temperature applications such as: conveyors, ovens, electric motors, appliances, high temperature processing equipment, etc. Lower cost than silicone greases, they should be evaluated for use where silicone greases have been used satisfactorily, as well as those high temperature applications where petroleum and other synthetic greases fail.
|Products||NLGI Grade||Base Oil||Tackifier|