As we always suggest, before selecting any lubricants for any application, we should know a bit about the application & its requirements. So, today we are discussing Rotary Kilns of any Sponge Iron Plants or any cement plant. A rotary kiln from a sponge iron or cement plant does not matter where its situated because more or less its area of application is the same. By the way, Rotary Kiln is a huge chapter & this is quite not possible to include all types of machine parts thar require lubrication in one article. So, today we are discussing Rotary Kiln Tyre Lubrication methodology. A rotary kiln is a pyro-processing device that raises materials to very high temperatures in a continuous process. It is used to create cement, lime, metakaolin, titanium dioxide, alumina, iron ore pellets, and more.
Application: Rotary Kiln Tyre Lubrication.
- Rotary Kiln widely used in cement, ore processing and chemical industry.
- Kiln consists of cylindrical shell supported on ride-rings (Kiln Tyre) riding on pair of
- rollers.
- Gear rim and pinion assembly rotates the entire system.
- Kiln shell has fire brick lining to protect the outer shell from the higher temperatures
- existing inside.
- The Kiln Tyre is a cylindrical steel Tyre connected to a shell and rotating with it.
Kiln Tyre Material composition
A kiln tire also called a riding ring, is one important part of a rotary kiln. It transmits all gravity of the rotary barrel (including refractory bricks, internal devices and raw material, etc.) to the supporting roller. Thus, it ensures that the barrel rotates smoothly on supporting rollers and strengthens the radial stiffness of the barrel. Therefore enough strength, durability and rigidity of rotary tires are necessary.
Kiln Tyre material should be high-grade cast steel along with the below-mentioned properties.
Rotary Kiln Tyre’s Properties
- High strength and good durability.
- Advanced double medium quenching process.
- High quenching hardness.
- Good wear resistance.
- Simple structure and easy to adjust and repair.
The function of Kiln Tyre / Ride ring in Kiln System
Greatest shell deformations occur in the vicinity of ride-rings. Theoretical and experimental investigations prove this point.
- Service life of ride –rings is around 20 years, rotation speed 0.5 – 3 rpm.
- The load of the kiln shell is transmitted to the ring through the base plates (20 – 40 nos).
- Welded on the outer surface of the shell.
- At the top, there is some clearance between rings plate and Kiln drum; There are some reasons behind it which is mentioned below.
- The working temperatures inside the kiln are in the range of 1000-15000°C., the shell temperature is around 3000°C. The riding ring temperature is around 1000°C. Shell temperature should be maintained as low as possible to assure the structural strength of the shell.
- Ride-ring and the kiln drum are matched with a loose tolerance to take care of thermal expansions.
- Differential expansion, if not carefully accommodated, the Tyre may restrict shell expansion, distort it permanently, and the refractory in this area can be crushed, yielding undesirable results.
- Due to clearance, Ride –ring and Kiln shell rotate at different speeds. This phenomenon is called CREEP.
What is CREEP in Rotary kiln Tyre Lubrication
Creep is the indicator of good kiln operation.
- Creep indicates correct ‘tyre to shell’ fit or gap. This must be maintained.
- Excessive gap is as much of a problem as no gap.
- When no gap, Tyre may restrict the shell expansion and distort it completely (may damage/break the refractory lining inside the kiln, allowing gas channeling leading to excessive shell temperatures)
- When there is an excessive gap, Tyre fails to provide a cradling effect to shell. This creates a flattening effect on the shell. This continuous change of curvature during rotation, analogous to the flat spot of a car tyre where it contacts the road, can aggravate the mechanical integrity of the refractory.
- Hence maintaining the right amount of Creep is the key to success.
- The desirable limit of Creep is 12-15 mm as a standard.
The function of Kiln Tyre
- Facilitates the rotary motion of the kiln. Provides “Cradling effect” when shell rotates.
- Responsible for maintaining Kiln Shell roundness.
- The mechanical integrity of the refractory lining inside the shell depends on kiln shell roundness.
Kiln Tyre lubrication and Why is it important
- Kiln Tyre comes in contact with base plates and retainer blocks
- Sliding friction acts in between Kiln Tyre and base plates and retainer block
- The heavy loads associated with kilns result in extreme metal-to-metal stresses, including sliding and rolling friction.
- High temperatures and heat radiations. Outer shell temperatures around 3000°C. Inside
- Shell temperatures around 15000°C.
- Any damage in refractory lining will expose Kiln Tyre to high temperature.
- Dusty environment.
- Relative motion between kiln tyre and shell.
Purpose of Kiln Tyre lubrication
- To reduce axial wear between kiln tyre and kiln shell
- To maintain dry lubricating film between the wear surfaces.
- To take care of linear motion due to thermal expansion
- To maintain the desired migration level (CREEP) between 12 to 15 mm depending on
the size.
Proper Lubricants Selection for Kiln Tyre
To lubricate between Kiln Tyre & Chair pad, you have to choose good quality lubricants. If lubrication between Kiln tyre & chair pad is not done, we may face huge problems in Kiln operation & sudden breakdown also. So, for Kiln Tyre Lubrication, you must have to use a good quality graphite bar. Graphite is one of the solid lubricants that can be able to lubricate even at very high temperatures. Suppose you have 5000 TPD kiln, then to get optimum performance of Kiln you should lubricate Kiln tyre once in a 4 to 5 days with good quality graphite bar.
If you use a low-quality graphite bar, then lack of lubrication will create scoring inside the tyre surface. The chair pad will wear out very fast. The air gap will increase. After increasing airgap, slippage will also increase. It will create a chance of creating ovality in the shell. This will result in unwanted vibrations between the tyre & Kiln shell.
Good Quality Graphite Bar Parameters
Within 100% of lubricant composition, 35 to 40% should be graphite composition. Lubricants auto-ignition point should be more than 540°C.No tackey, or stickey residue should be left after application. And one of the major criteria to find out good quality bar is Bar color should be brown color. The melting point of a good quality graphite bar should be more than 45 to 50°C.
Achieve Cost Benefit by Using Good Quality Lubricants?
If you are using any good quality graphite bar, then you may face high price of a good quality graphite bar than an inferior quality graphite bar. But by using good quality Kiln tyre lubricants, you can achieve cost benefits by reducing the usage of lubricants. You will also not face any types of unwanted failures or sudden breakdowns in the application. Using a high-quality lubricant, Kiln & Kiln component’s life will also increase & it will run for a long time with trouble-free operation.
To understand in detail the Kiln Tyre Lubrication, you can check out the video mentioned below.
Conclusions on Reliable Lubrication Solution for Tyre Lubrication of Rotary Kiln in Cement And Sponge Iron Plant
So, whatever lubricant you use for any application, you should choose lubricants as per the application requirements. Different applications of the different industries require different types of lubricants. You can check different application lubrication procedures by visiting our website, Industrial Lubricants home page.
