Open gear is a power-to-axle transmission device that has larger dimensions and more complex design than closed variants. Cement industries, raw materials processing, mines, especially coal production mines, paper mills and fertilizer industries are among the factories that open gears widely in machinery such as rotary kilns, bullet types. And it uses rods, circular cylinders and dryer cylinders.
The type of open gear operation and equipment that uses open gear is such that it is not likely to be substituted in the near future. Since cement manufacturing industries are one of the largest factories in dire need of open gears, this article will provide examples that are relevant to the cement industry in addition to providing general explanations about the characteristics of open gears.
Ensuring the safe operation of lubricants and their lubrication requires a thorough understanding of the operation and characteristics of open gears. Gears for rotary kiln and ball bearings are generally very difficult to design and operate at low speeds, with average speeds of 6 to 10 meters per second and furnaces 3 to 5 meters per second. Other features of the gears include high output torque and high central spacing, medium to high dimensional dimensions, and relatively high tooth widths that sometimes reach 120 cm.
Today, open gear designs are designed to increase the number of teeth without enlarging the gear. As a result, the conditions of internal involvement and contact ratio of the teeth and their load bearing capacity are improved. The type of indentation can be simple or spiral, but in any case, the important principle will be to create a higher contact ratio, softer indentation contact and less noise pollution during work. With changes to the design of open gears, the ability to transmit power up to 7000 KW is common for two-pin and higher systems.
One of the major disadvantages of open gears over closed gears is that the gear rings and pinion are driven by separate bearings, causing problems when installing and adjusting gears. Changes in load, tolerances during manufacturing and assembly, as well as thermal fluctuations of the furnace, will often disturb the equilibrium of the system. This will cause problems in the uniform distribution over the width of the teeth, the first effect of which is the abrasion and localization of the teeth.
In recent years, measures have been taken to improve pinion indentation and the use of chromium, nickel and molybdenum alloy steels, reducing pinion widths and converting curved portions into straight lines and providing the ability to bend pinions. In order to better coordinate the pinion with the gear ring motion, much of the adjustment errors and the imbalance of the gear set have been resolved. Better adjustment of the system means a better distribution of load, under different operating conditions and higher contact ratios, and thus the potential for tooth damage.
If the surfaces of the contacted teeth are completely separated by a film of lubricant, there can be a great deal of surface damage caused by abrasion, but in most cases this is due to the relatively low environmental speed, the pressure. Extremely high surface area and relatively high roughness of the teeth are impossible. This means that large ribs generally operate under conditions of mixed friction. This is why border lubrication is of secondary importance. In this case the type of lubricant and the lubrication process will require sophisticated technology.
Adhesive lubricants with suitable base oils with optimum viscosity, EP additive application, use of special condensers and solid lubricants have shown the highest efficiency in open gear. It is important to choose the type of lubrication process and the method of applying lubricant on the tooth surface from the point of view of lubrication technology. When choosing a lubricant method, it is very important to consider whether it is possible to deliver sufficient amount of lubricant to the desired surface under load. Also, the fluid or fluidity of the lubricant is of great importance and has a direct influence on the feeding system.
Lubrication Methods There are generally two methods of lubrication:
A) Continuous or continuous lubrication:
In this type of lubrication, a certain amount of lubricant is injected endlessly into the contact area of the indentation or friction point.
Continuous lubrication can be performed by the following methods:
Immersion: One of the safest ways to apply lubricants for gear rings is immersion lubrication performed by a lubricant bath. To prevent lubrication loss, the gear cover is well sealed. Benefits of this method include forming a lubricant-resistant film and preventing tooth contact as well as safe and long-lasting operation of the device. One of the major disadvantages of this method is the high consumption of lubricants and the impossibility of preventing lubricant contamination.
Transfer Transfer lubrication is a special form of immersion lubrication that, instead of a lubricant bath, lubricates the surface of the pinion teeth by means of a blade wheel. In terms of lubrication, the transfer method has fewer advantages than immersion, but at the same time the optimum lubricant consumption is superior to immersion.
Circulation: Another method of lubrication is circulation lubrication, which is transmitted to the system by a lubricant. The main advantage of this method is lubricant passage through a filter and absorption of existing contaminants. Also, the distribution of the lubricant film will be more uniform than the immersion method. Circulating lubrication will be economical and useful when the gears cover is well sealed and the excessive penetration of contaminants and dust particles into the lubricant tank is avoided as far as possible. The disadvantages of this method are the complexity of the application process and the need for more equipment as well as the higher maintenance and maintenance costs.
B) Intermittent lubrication:
In this method, the lubrication process is performed in a specified time range. This type of lubrication will save on the cost of lubrication, repairs and maintenance. Similar to continuous processes, intermittent lubrication is performed in different ways, but for open gear fluids with new technology, there are only two methods of practical application and high efficiency:
2- Manual lubrication by spray system
Spray systems, especially automatic ones, are designed to operate with a solid lubricant as well as semi-fluid to fluid lubricants. With the help of a spray pump through the nozzles having a specific angle and distance to the teeth, the lubricant is placed on the surface of the tooth as a thin film and provides the highest contact ratio and best possible surface softness. . In general, the superiority of new designs with automatic spray systems is paramount.
Determine the amount of lubricant
Since open gear lubricants have special formulation and advanced technology and will naturally be very high in price, precise determination of the amount needed for reliable lubrication operations is essential. The numerous experiences and experiments of a leading company in the production of open gear lubricants indicate the approximate amount of lubricants required for different parts and operations.
The indentation width is selected as a reference because it is the best possible parameter to calculate the specific transmission power of the device.
The most important task of an open gear lubricant is to prevent metal-to-metal contact and reduce friction. Other important functions include protecting the teeth against corrosion and abrasion, increasing the dynamic load tolerance of the system, preventing injuries such as abrasion, cavitation, softening of the tooth surface, and increased contact ratio.
To achieve the above, a suitable lubricant must have specific properties such as being free of any solvents, bitumen, heavy metals and chlorine, appropriate behavior at different temperatures, low self-ignition risk, very low evaporation loss and easy lubricant disposal. Operate from the surface of the teeth.
As mentioned, the operation of open gears is complex and unique, and this results in the need for various lubricants from the start of a gear until it stops for repairs. Generally the lubrication stages of open gears are divided into the following sections:
Priming & Pre-Starting: The primary task of pre-starting lubrication is to help set up the pinion and prevent severe damage to the device from operating.
Running-in: The main task of this lubricant is to quickly convert the rough surface to a smooth surface and increase the level of contact between the gears in new or rotated gears.
Operating: The main task of this lubricant is to create a thin film of lubrication with EP additives and solid lubricant contents to maximize gear protection during operation.
3. Repairing: Repair lubrication has also been developed to replace the usual mechanical methods such as grinding and grinding, which can repair severe tooth damage and prevent secondary damage from spreading. However, repair lubricants are not capable of repairing injuries such as sharpening of the outlines and edges of the teeth, smoothing of convex surfaces and abrasion at the end of the tooth with the wheel, and mechanical processes may be more effective in these cases.
Each stage requires a special lubricant, but these lubricants are designed to be compatible with other lubricants and do not require drainage. Pre-lubrication and repairs, however, are of the utmost importance while short-lived.