Do it while it is hot

July 8, 2016 ALEXEY TARTARCHENKOV

The kiln is the heart of cement plant operations. A well functioning kiln can make the difference between a plant delivering maximum returns and a plant failing to deliver to its potential. 

Kiln alignments are an essential part of a kiln maintenance programme, helping to prevent unexpected or longterm shutdowns, reduce overall maintenance costs, and prolong the kiln’s lifetime.

There are significant savings to be made from taking a proactive approach to maintenance with the aim of preventing unplanned stoppages. Cement plants should be able to perform optimally and without interruption. Particularly in periods of peak production, any lost time will lead to major lost earnings.

Stop unnecessary breakdowns
Kiln failures are usually caused by one or more of four root causes: axis misalignment, shell ovality or flex, crank, and axial misbalance. These can lead to failures from hot bearings, shell cracks, roller and tyre wear, and similar. A kiln alignment identifies such problems in order to prevent a possible kiln breakdown. Understanding the true root cause of potential issues, however, calls for experienced kiln specialists who have the latest measuring technologies at their disposal.

Furthermore, ‘hot’ kiln alignments offer the key advantage of being carried out while the kiln is in nominal operation with full capacity. As the kiln is not shut down during the process, potential losses are reduced even further.

A local service partner
A key success factor of plant operations is time in operation. Whether it is to assist with unexpected stoppages or with planned maintenance activities, plant operators need to be able to rely on a service provider that provides timely, knowledgeable assistance. As one of the world’s most experienced suppliers of equipment and services to the cement industry, FLSmidth has a proud history of working closely with cement plant operators around the world in providing comprehensive kiln maintenance services. FLSmidth typically conducts at least 180 hot kiln alignments every year. The full programme of comprehensive hot kiln alignment is shown in the table below.

FLSmidth's hot kiln alignment programme

The main objective of the alignment is not only to inspect the kiln symptoms and problems but also to diagnose and quantify the root cause(s), a typical FLSmidth kiln alignment approach.

Kiln inspection and measurement
Once on-site, the kiln axis is measured using the one-theodolite method and the kiln shell ovality is evaluated. FLSmidth’s one-theodolite- solution enables the kiln specialists to measure the kiln axis in a quick and flexible way. This method eliminates potential physical obstacles and ensures that the kiln axis is measured with high accuracy and reliability. Particularly the instrument accuracy is fundamental for reliable polar diagrams. Furthermore, kiln crank is mechanically and thermally measured and evaluated. The axial balance is also evaluated considering skewing, hydraulic thrust device (HTD) pressure, inclination, centre distances, bearings temperature, etc.

Diagnosing root causes and potential consequences
The kiln axis may deviate from the optimal with a two-figure number in mm. It may result in uneven wear on the girth gear and pinion teeth. The engineering study helps to reveal high bending stresses in the kiln shell. In this case, if the plant continues its operation, it may increase risk of circumferential cracks. Therefore, the location of the highest stress level is usually identified so a location-specific UT-test can be carried out.

This is to identify any invisible micro-cracks and take preventive action if needed. The axial balance is incorrect, which leads to excessive pressure on the HTD.

No disasters
Following a kiln alignment, FLSmidth provides a detailed report in a meeting and supported by full documentation. The report contains recommendations that help to eliminate causes of the existing and potential problems. For example, a recent kiln alignment at a cement plant in Russia revealed a crack inside the cast material of the tire. The crack was not visible to the naked eye. If this crack had not been identified, it would have led to metal fatigue potentially resulting in severe failure. At another plant, a hot kiln alignment identified major friction problems with the kiln axis caused by dust and oil.

Part of the kiln alignment is the engineering study, which aims to provide “behind-the-scene” knowledge of the kiln and its behaviour. The study identifies possible overloads and excessive stress levels in the kiln, providing information about, for example, kiln stiffness, which is important for kiln alignment and roller adjustment.

As a highly renowned and experienced full-service provider of engineering services, FLSmidth can also provide specialist assistance to conduct any necessary repairs. Regardless of the specific conditions and requirements of the individual cement plant, FLSmidth’s kiln maintenance services are designed to increase operational efficiency and overall lifetime of the kiln, all with the aim of helping cement plants get the maximum from their investments.

Contacts:
ALEXEY TARTARCHENKOV
ATA-RU@FLSMIDTH.COM 

ALEXEY BENDER
AB-RU@FLSMIDTH.COM

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