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Alignment or optimisation of forces is important, otherwise the unbalanced forces on the kiln will result in the damage of some components / loss of production / expensive replacement / repairs, all of this reducing the kiln reliability, says Shailesh Kumar, Manager (Engineering) Allan Smith Engineering. Excerpts from the interview.
How important is kiln alignment?
A kiln is a huge machine weighing several hundred tonnes rotating on support rollers located between two to eight stations, with a length ranging from 40 to 160 m and inclination of 2-4 per cent. The kiln is used as calciner / roaster with inside temperatures at several hundred degrees Celsius. Due to the operating conditions mentioned above, complex forces generate / act on the kiln system. Optimising / balancing of the complex forces on the kiln support rollers / bearing's, called alignment, is vital.
Alignment or optimisation of forces is important, otherwise the unbalanced forces on the kiln will result in the damage of some components / loss of production / expensive replacement / repairs, all of this reducing the kiln reliability.
How does kiln alignment impact energy efficiency?
The energy required in a machine is to overcome resistance / friction sliding / rolling. The higher the friction at support roller / journal-bearing / thrust roller / tyre chairpads - stopper blocks, the higher the energy consumed. Higher resistance is concomitant with higher misalignment and reduced efficiency.
Kiln alignment is often seen as additional expenditure by plant engineers. What is your take on this?
Usually it is observed that a reduction in the power required to turn the machine is up to 40 per cent after HKA. The reduction is dependent upon misalignment; the higher the misalignment, the higher the reduction.
The payback period is a couple of months. In addition to this saving, better alignment results in the increased life of mechanical components with reduced wear and tear on journal bearings / rollers, tyres, etc. A higher and more consistent production is added advantage.
What are the diagnostic symptoms that serve as an indicator of kiln misalignment?
Hot kiln alignment is a preventive maintenance tool and we suggest carrying out checks at regular interval to ensure a trouble- free and optimised kiln operation.
Generally, symptoms are erratic with increased journal bearing / thrust collar temperature, kiln operating at a position for longer duration, excessive wear on tyre / roller rolling surface, side-stopper blocks, chairpad surface, gear teeth, premature crack in kiln shell / support roller / tyre, etc.
What are the common causes of kiln misalignment?
A kiln is designed to operate for 24 hours with higher shell temperature. The temperature at some time increases in excess of 4000 Celsius. Excessive temperature and variation results in deviation of the kiln alignment axis. Also, process disturbance causes big boulders to form inside the kiln.
Furthermore, misalignment is a complex issue, when we consider three different axes, the kiln shell, support system and rotation axis. We also consider three different possibilities of misalignment for which we can list main causes:
a. Support system: wear of sliding bearing, sinking of foundation, clearances in the system.
b. Shell: mainly thermal factors, build-ups, loose lining.
c. Rotation axis: mainly determined by support system axis, position of gear rim axis, local slope of support rollers, reaction on the piers, etc.
How detrimental are the different types of wear to the equipment?
Abrasive wear is predominant wear in kiln mechanical elements and occurs between rolling elements / sliding surfaces. The surface is:
a. Rolling surfaces: tyre / roller rolling raceways, thrust rollers.
b. Sliding surfaces: chair pad, under tire surface, tyre retainers, journal - bearings gear / pinion, etc.
Both the above both type of wear contributes toward kiln misalignment and initiates problems in the kiln.
What are the different methods of aligning a kiln?
It is difficult to explain all the methods as each company will say their method is the best. So we think it would be better evaluated by independent representatives.
The majority of alignment correction carried out by us has recorded a maximum of 40 per cent amperage reduction in the main motor compared to data recorded prior to the alignment. In addition, we also observed the kiln float on its own, a reduction in bearing temperatures and pier vibration. Kiln operation was smooth with a higher rpm.
Please elaborate on some basic kiln maintenance procedures.
Regular and meticulous inspection of the kiln and components help to notice if any changes occur after the earlier inspection. The changes can then be recorded and analysed to take appropriate action. Further, in-depth inspection / analysis can be requested from an external professional agency. What is the best time to do kiln alignment and what is your recommended schedule? Our suggestion for the alignment schedule is with reference to kiln rpm / repairs carried out / typical problems observed during operation, etc. Our statistically based experience is as follows:
a. Standard kiln: minimum once per year.
b. Slow rpm Kiln: once in two years.
c. High rpm kiln: every six months.
We recommend carrying out kiln alignment when the kiln is under normal production with more or less normal kiln shells temperatures.
What are the services you provide?
We commenced operations in 2007 with the aim of providing a global standard of service at a local price. We work systematically and take the help of specialised equipment to locate root causes of observed recurring problems. Once the reason is established, it is relatively easier to eliminate the problem permanently.
We work meticulously and our engineers have both specialised experience in world class organisations and global exposure.