Care when lubricating agricultural machinery

Agricultural machines and implements require specific lubricants according to the conditions of use and manufacturer's recommendations.

The growing global demand for food, combined with the expansion of cultivation areas, directly depends on mechanized processes, requiring increasingly complex mechanical systems, aiming to meet current production standards.

Many of these systems comprise mechanisms that, when in operation, work under direct friction, which must be reduced through lubrication, thus prolonging the useful life of the components and, consequently, of the agricultural machine. As it is one of the main items that make up periodic maintenance, lubrication must be understood and practiced so that the optimal operating characteristics of agricultural machines and equipment are maintained.

As already mentioned, the surfaces of numerous components of agricultural machinery are in constant contact with each other and in relative movement, producing friction, generating heat and, as a main consequence, wear. As a result, lubrication aims to reduce friction between the components of agricultural machinery and equipment systems, ensuring that they reach the maximum durability for which they were designed, thus avoiding loss of performance and interruption of their operation. In addition to reducing friction, lubrication has, in certain cases, the function of cleaning and sealing some mechanisms, as well as cooling certain parts of the machine, for example, the lubricating oil present in internal combustion engines.

Simply put, components that require lubrication are gears, joints, chains, pistons, shafts, shafts, pumps, bearings, friction bearings and rolling bearings. To carry out lubrication, a substance called lubricant is used, which is placed between the components in contact in order to reduce friction and heat and provide smooth operation, maintaining the normal working temperature and causing as little wear as possible.

LIQUID LUBRICANTS

Lubricants can be classified into different forms, depending on their origin, viscosity, physical state, density, among other factors. Depending on their origin, the majority of lubricants used come from petroleum derivatives obtained from chemical synthesis. Less commonly used are lubricants of organic origin, obtained from vegetable oils and animal fat, such as castor oil, with their use restricted to improving the quality of some types of lubricants. Lubricants of mineral origin come from petroleum and are classified according to their molecular structure, with wide use in agricultural machinery and equipment. Lubricants of synthetic origin developed in the laboratory, using various chemical substances, have as their main objective to provide superior characteristics to mineral lubricants, however, they present higher costs.

In relation to their physical state, commonly used lubricants are classified into liquids (lubricating oils in general), pastes and solids.

The lubricating oils used in engines and transmissions are of organic, mineral, synthetic origin, compounds (a mixture of organic and mineral oils, however, due to their greasiness, they easily form an emulsion in the presence of steam) and additive oils, which have additives (chemicals), whose function is to increase the quality of the lubricating oil. These additives have different functions, such as antioxidants, dispersants, anticorrosives, viscosity enhancers, antifoams, among others.

Lubricating oils used, mainly in internal combustion engines and gear transmissions, must have a certain quality and specific characteristics. In order for the manufacturing standards of these oils to be met, there are certifying bodies, such as the Society of Automotive Engineers (SAE), the American Petroleum Institute (API), the International Organization for Standardization (ISO), the Association of European Manufacturers of Automobiles (Acea), among others.

SAE CLASSIFICATION

The SAE classification is the most used today, considering viscosity ranges, being a measure that indicates the resistance of a given liquid to flow, presenting a specific classification for engine oils and another for transmission. American society classifies oils into two types: summer oils and winter oils. According to Márquez (2012), in the case of engines, summer oils are classified according to a categorization established based on the kinematic viscosity measured at 100ºC, presenting four categories ranging from the most fluid (SAE 20) to the one considered most viscous (SAE 50), divided into intervals of ten. As for winter oils, according to the same author, four categories are defined ranging from zero to 25, divided into intervals of five by five, identified by the letter W, for “winter”, which translates as winter in Portuguese. In low temperature conditions, the oil must maintain the required kinematic viscosity characteristics at 100ºC, and can be pumped in the case of SAE 0W at -35ºC and at -10°C if it is a SAE 25W lubricating oil.

The classification, according to Márquez (2012), does not result in an indication that summer oils can only be used in hot periods of the year, and winter oils only in cold periods. These are just ways to differentiate the viscosity of the oils, their adaptation to the climate in which they will be used and the low temperatures that would make it difficult to start the engine.

Oils that have only one viscosity class are known as single-viscosity and must be replaced if changes in weather conditions occur. Those that have more than one SAE viscosity grade are known as multiviscoses, and can be used throughout the year, because their viscosity is satisfactory at high or low temperatures. In this sense, a SAE 15W-40 oil behaves at high temperatures like a SAE 40 and at low temperatures like a SAE 15W.

The lubricants used in transmission systems use a classification similar to that of engine oils, using four grades of winter oils (SAE 70W to SAE 85W) and three grades of summer oils (SAE 90, 140 and 250), without any relation the degrees established with those defined for the engines. Multiviscosity oils can also be used in transmissions, such as SAE 80W-90 and 85W-140.

API CLASSIFICATION

The API classification system specifies the “quality” of lubricating oils depending on the conditions in which they must be used.

To classify oils used in engines, two letters are used, the first indicating the type of engine (S for gasoline engines and C for diesel engines) and the second the quality level, using the sequential order of the alphabet. , with A being the first letter. The specification most used by diesel engine manufacturers is CF-4. Furthermore, in the API system there are other classifications for more modern engines that use fuels with low CG sulfur content.

It is not recommended to use oils with a specification lower than that recommended by the manufacturer of the agricultural machinery, for example, API CF-4 or lower, when the manufacturer recommends the use of API CG. In the same way as engine oils, in terms of quality, lubricating oils for transmissions are established in six levels, which are designated sequentially between API GL-1 and API GL-6. The GL-4 and GL-5 categories are the most used in agricultural machinery transmission systems.

The specifications for the classification of lubricating oil that must be used in agricultural machinery are always provided by the manufacturers, and the specification of the type of lubricating oil is contained on the packaging of any oil used.

PASTY LUBRICANTS

Pasty lubricants, better known as greases, result from a mixture of a thickening agent (metallic soap or clay) and liquid lubricants (of mineral or synthetic origin). They are used to lubricate points where the application of an oil would not be efficient due to their fluidity, construction and maintenance factors, such as crossheads, bearings, bearings, etc. This type of lubrication is done through elements known as grease fittings or “grease fittings”.

The measurement of the quality of a grease is based on its consistency, which is measured in the laboratory using ASTM (American Society for Materials Testing) testing standards. From a significant number of penetration measurements of a cone of known weight, in a grease contained in a standard cup, under specific time and temperature conditions, the NLGI (National Grease Institute) created nine different consistency grades, which serve as the basis for classifying greases found on the market, which range from 00 to 6. The lower the number, the “softer” the grease.

According to the requirements, the greases most recommended by manufacturers of agricultural machinery and implements (depending on construction and material aspects) fall into consistency class 00 to 3 and must withstand temperatures of around 150ºC without compromising their lubricating quality.

At high speeds and small bearing clearances, and where there is a need for greater fluidity in the conduits, more fluid lubricating greases are applied, which compete with classes 00 to 1. For larger bearing clearances, a seal against external agents is required ( dust, water and soil) that can penetrate, in which case greases in consistencies 2 and 3 must be used.

In bearings, NLGI 1, 2 or 3 greases are generally used. However, the grease must offer: resistance to water and load, protection against corrosion and oxidation, good sealing capacity, good adhesion and validity for a long period.

SOLID LUBRICANTS

Solid lubricants, such as graphite and molybdenum disulfide, are used as additives in the formulation of liquid and paste lubricants, offering great resistance to temperature and high pressures. In agriculture, graphite is used to lubricate the seed tanks of seeders, with the purpose of improving the distribution process and reducing mechanical damage to the seeds.

Recommendations for using fertilizers

- Do not lubricate while the machine or equipment is running.

- Check the oil level in the tanks (sump and hydraulic system) of the machines daily, on level ground, with the engine turned off and the equipment “cold”. Top up the level with lubricating oil only when the level is below the minimum level, checking and respecting the oil usage time. Furthermore, if the change is close to being carried out, adding more lubricating oil will not prolong its usage time.

- Lubricating oil must always be used with the correct viscosity and recommended by the manufacturer of the agricultural machine or implement.

- Respect the periods indicated by the manufacturer for lubricating agricultural machinery and equipment components and changing the lubricating oil.

- Do not mix lubricating oils from different brands, as the use of different chemical elements for the same additive purpose, for example, can cause incompatibility problems between the substances present in the oils, causing damage to the components to be lubricated.

- Check for oil leaks and, if so, correct them, as this could lead to the possibility of penetration of external contaminants and unnecessary loss of lubricant.

- Before checking the lubricating oil level, replacing it, as well as lubricating with grease, the surfaces must be cleaned of dust or impurities (leaving them clean and dry) to prevent contaminants from entering the surfaces. internal components of the machines, thus preventing premature wear.

- When changing the oil (change period), the oil filter must always be changed.

Marcelo Silveira de Farias, José Fernando Schlosser, NEMA/UFSM; Alexandre Russini, Unipampa – Campus Itaqui

Article published in issue 165 of Cultivar Máquinas.