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

The internet has some excellent resources on the market that can assist guide you to making the fitting decision.

One such resource is the Machinery Lubrication web site, the place we found a superb primer on all the factors that it is advisable to consider in deciding on the proper kind of high temperature grease.

Once you’re working in a machinery situation the place the temperatures get a little heated, selecting the best grease is a critical choice to get right. How do you make the suitable choice?

The internet has some wonderful resources out there that can help guide you to making the fitting decision.

One such resource is the Machinery Lubrication web site, the place we discovered an excellent primer on all of the factors that you must consider in deciding on the best kind of high temperature grease.

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

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

What To Consider?

There are numerous criteria to consider when choosing a high-temperature grease for warm, 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 variety of details to resolve, the selection of greases that should accommodate excessive temperature conditions is a difficult decision, and given potential for incompatibility problems and the high costs for a lot of 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 metal mill roll-out table application could also be exposed to process temperatures of several hundreds of degrees, and may expertise sustained temperatures of 250ºF to 300ºF (120ºC to ±150ºC). Automotive assemblers dangle painted metal parts on long conveyors and weave them through giant drying ovens to dry painted metal surfaces. Operating temperatures for these gas-fired ovens are maintained around 400ºF (205ºC). You may see that there’s a wide temperature range to consider here.

In these cases, the choice factors differ appreciably. In addition to heat resistance, the grease for use in a scorching metal mill application could require distinctive load-carrying capability, oxidation stability, mechanical stability, water wash resistance and good pumpability, and at a value suitable for large-volume consumption. With all of the important factors to consider, it is helpful to have a grease choice strategy.

Where To Start?

A reasonable starting level for selecting a high-temperature grease is to consider the nature of the temperatures and the causes of product degradation that are inherent to whatever place you are going to be utilizing it. There is general correlation between a grease’s useful temperature range and the expected value per pound. As an illustration, a fluorinated hydrocarbon-primarily based (type of artificial oil) grease may work effectively as high as 570ºF (300ºC) in space applications but may additionally value 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 vital: mechanical (shear and stress) stability, oxidative stability and thermal stability. Oxidative and thermal stresses are interrelated. High-temperature applications will generally degrade the grease through thermal stress, in conjunction with oxidative failure occurring if the product is in contact with air. This is similar to what is to be anticipated 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 energy of its additive package, that continues providing lubricating protection after other parts of the grease might have broken down as a consequence of these factors in normal use.

What’s In A Grease?

high temperature greaseFor the uninitiated, grease consists of a base oil with a thickener added, plus further 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 supplies that holds the bottom oil collectively like a sponger holds liquid.

Base Oils

When deciding on 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 will be subdivided into mineral and artificial types. Mineral oils are probably the most widely used base oil element, representing approximately 95 percent of the greases manufactured. Artificial esters and PAO (synthetic hydrocarbons) are subsequent, followed by silicones and a few different exotic artificial oils.

The American Petroleum Institute divides base oils into five classes based on their performance limits (Teams I-V). They have an inclination to vary by how well they resist thermal or oxidative break down, and the way well they disperse and hold the additives which might be 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 individual oil molecules in a highly refined (Group II+, Group III) mineral oil and synthetic 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 supplies given their familiarity, and maybe availability, of the raw materials. If the manufacturer makes a particular type of artificial base fluid and is intimately familiar with the various destruction mechanisms of that fluid, then it is likely that this type of artificial base will typically be selected for new product development.

Thickeners

The materials selected as the grease thickeners may be natural, resembling polyurea; inorganic, equivalent to clay or fumed silica; or a soap/complicated cleaning soap, corresponding to lithium, aluminum or calcium sulfonate complex. The usefulness of the grease over time is dependent upon the entire package together, not just one thing like the thickening system or the type of base oil. For example, a silica grease thickener has a dropping level of two,732ºF (1,500ºC) as one extreme example. However, because grease performance depends upon a combination of supplies, this doesn’t characterize the useful temperature range. Some examples of the kinds of thickeners you’ll have to choose from could possibly be:

Organic polyurea – presents temperature range limits much like the metal cleaning soap-thickened grease, however additionally it has good antioxidation and antiwear properties that come from the thickener itself. Polyurea thickeners may develop into more common but they’re troublesome to manufacture, requiring the dealing with of a number of toxic materials. While the thickener has a high dropping level, the composition begins to thermally degrade at temperatures which limit its usefulness over time at high temperatures.

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

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