Deciding on a high temperature grease – what to look for

While you’re working in a machinery situation the place the temperatures get a little heated, choosing the right grease is a critical decision to get right. How do you make the right determination?

The internet has some glorious resources out there that may assist guide you to making the fitting decision.

One such resource is the Machinery Lubrication web site, where we found a wonderful primer on all of the factors that it is advisable to consider in selecting the appropriate kind of high temperature grease.

Whenever you’re working in a machinery situation where the temperatures get a little heated, choosing the proper grease is a critical resolution to get right. How do you make the proper determination?

The internet has some wonderful resources on the market that can help guide you to making the proper decision.

One such resource is the Machinery Lubrication web site, the place we found a superb primer on all of the factors that it’s essential to consider in choosing the fitting kind of high temperature grease.

choosing a high temperature greaseWe’ve referenced much of that information here.

For the complete article, check out Machinery Lubrication’s web site here.

What To Consider?

There are lots of criteria to consider when selecting a high-temperature grease for decent, grease-lubricated equipment – 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 number of details to resolve, the number of greases that must accommodate excessive temperature conditions is a challenging resolution, and given potential for incompatibility problems and the high prices for many high-temperature grease, you really have to be selective and discriminating when making the choice of which grease to use.

‘High temperature’ is relative when characterizing temperature conditions. Bearings running in a steel mill roll-out table application may be exposed to process temperatures of several hundreds of degrees, and may expertise sustained temperatures of 250ºF to 300ºF (120ºC to ±150ºC). Automotive assemblers grasp painted metal parts on long conveyors and weave them by way of large drying ovens to dry painted metal surfaces. Working temperatures for these gas-fired ovens are maintained around 400ºF (205ºC). You possibly can see that there is a wide temperature range to consider here.

In these two cases, the selection factors differ appreciably. In addition to heat resistance, the grease to be used in a sizzling metal mill application may require exceptional load-carrying capability, oxidation stability, mechanical stability, water wash resistance and good pumpability, and at a worth suitable for giant-volume consumption. With the entire necessary factors to consider, it is helpful to have a grease selection strategy.

The place To Start?

A reasonable starting level for selecting a high-temperature grease is to consider the character of the temperatures and the causes of product degradation that are inherent to whatever place you’re going to be utilizing it. There may be normal correlation between a grease’s helpful temperature range and the anticipated value per pound. As an illustration, a fluorinated hydrocarbon-based (type of artificial oil) grease might work successfully as high as 570ºF (300ºC) in space applications however may additionally price hundreds of dollars per pound. How well the grease holds up long-time period is influenced by the causes of degradation, three of which are particularly essential: mechanical (shear and stress) stability, oxidative stability and thermal stability. Oxidative and thermal stresses are interrelated. High-temperature applications will usually degrade the grease by way of thermal stress, in conjunction with oxidative failure occurring if the product is involved with air. This is analogous to what’s to be expected with most industrial oil-lubricated applications. Bell Performance’s X-tra Lube Grease provides some advantages in these types of situations because of the residual lubricating power of its additive package, that continues providing lubricating protection after different parts of the grease could have broken down attributable to these factors in regular use.

What’s In A Grease?

high temperature greaseFor the uninitiated, grease consists of a base oil with a thickener added, plus additional additives thrown in to bulk up certain essential properties of the grease. Think of the entire thing like a sponge – the thickener is the spongy materials that holds the base oil collectively like a sponger holds liquid.

Base Oils

When choosing lubricants for oil-lubricated applications, one usually begins with the consideration of base oil performance properties. This can also be a superb starting point for grease products. Base oils could be subdivided into mineral and artificial types. Mineral oils are the most widely used base oil part, representing approximately ninety five p.c of the greases manufactured. Artificial esters and PAO (artificial hydrocarbons) are next, adopted by silicones and some other unique synthetic oils.

The American Petroleum Institute divides base oils into 5 classes primarily based on their performance limits (Groups I-V). They have an inclination to differ by how well they resist thermal or oxidative break down, and how well they disperse and hold the additives which are added to the grease product. Generaally speaking, the higher Groups are more resistant but cost more.

Mineral and artificial base oils degrade thermally in conjunction with oxidative degradation if the product is involved with air. The break level at which the person oil molecules in a highly refined (Group II+, Group III) mineral oil and artificial hydrocarbons will begin to unravel, releasing carbon atoms from the molecular chain, is about 536ºF to 608ºF (280ºC to 320ºC). 3,four The grease manufacturer will choose materials given their acquaintedity, and perhaps availability, of the raw materials. If the producer makes a particular type of synthetic base fluid and is intimately familiar with the varied destruction mechanisms of that fluid, then it is likely that this type of synthetic base will often be chosen for new product development.

Thickeners

The supplies chosen because the grease thickeners may be natural, akin to polyurea; inorganic, reminiscent of clay or fumed silica; or a cleaning soap/complex soap, such as lithium, aluminum or calcium sulfonate complex. The usefulness of the grease over time will depend on the entire package together, not just one thing like the thickening system or the type of base oil. For instance, a silica grease thickener has a dropping point of two,732ºF (1,500ºC) as one extreme example. Nonetheless, because grease performance is determined by a mix of supplies, this doesn’t represent the helpful temperature range. Some examples of the kinds of thickeners you’ll have to choose from might be:

Organic polyurea – presents temperature range limits much like the metal soap-thickened grease, however additionally it has good antioxidation and antiwear properties that come from the thickener itself. Polyurea thickeners would possibly develop into more in style however they’re tough to fabricate, requiring the handling of a number of toxic materials. While the thickener has a high dropping point, the composition begins to thermally degrade at temperatures which limit its usefulness over time at high temperatures.

Calcium sulfonate – much like the polyurea, it possesses inherent antioxidant, rust-inhibiting properties, but in addition has inherent high dropping points and EP/antiwear properties.

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