The vertical Loesche Raw Mill in Festus, Missouri has run for the last 10 years without requiring replacement of the upper labyrinth seal on the classifier. Recently, this upper compartment was in need of replacement due to extensive wear and reduced efficiency of the classifier, along with frequent leaks from the upper housing of the separator. The wear components of the original design were integrally combined with the outside housing, so in order to replace the seal, the entire separator housing needed to be replaced. These components were heavily worn when inspected in early 2018 and process material was eating into the frame. Given this, Festus initiated discussions with Loesche for a change-out that was being planned for early 2019.

Loesche was contacted in early 2018 about the materials needed for the upper classifier seal replacement, and they informed management about an upgraded seal design that allows for better gap control in the separator, and ideally more efficient production. Along with this seal upgrade, Buzzi management proposed a design change that allowed the wear components to be bolted into the frame, instead of being a part of the frame itself. Another design change was to further sectionalize the upper seal compartment. Standard Loesche designs of this seal is two pieces, but at the suggestion of a Buzzi maintenance supervisor, this was re-designed into four pieces to make future replacement more efficient. Additionally, with the two piece assembly, the associated duct is required to be taken out, which requires a large crane for an extended period of time. With four pieces, the compartment sections are small enough to be handled without a crane, greatly simplifying the maintenance process. Collectively this would allow for easier replacement and lower maintenance costs. Loesche welcomed these modifications and the final design of the replacement seal had the wear component bolt-in change with the seal compartment divided into four sections.

Installation of this new classifier seal was completed in January 2019 during Festus’ winter outage. Implementation was not without its difficulties, as the top separator duct had to be completely removed in order to remove the cover from the separator. Next, since the new seal design included a housing change, a 360degree cut around the entire separator needed to be made in order to fit the new seal housing in place (see Figures 3 through 6). Next, the new four-section housing was set in place and welded. This alignment was not without its struggles, as maintenance had to trim along the entire edge old separator to get the new sections to fit, causing an unexpected increase in time. Once all excesses material was trimmed away and alignment holes were lined up, the new sections could be set in place. Finally the classifier duct was reinstalled, with the expectation that it will not be removed again for a long time, due to the changes made to make the components more sectionalized. The installation was scheduled for 10 days, and all jobs were completed in time, even with the additional modifications needed to have the seal installed.

With over 2 months of run time with the new seal and wear components, production performance has been highly reliable with no issues. This upgrade not only assisted with classifier gap control, but is also expected to reduce future maintenance costs due to the bolted wear components and the ability to remove top seal sections without the assistance of a large crane. This upgrade was completed safely and we would like to thank all workers and supervisors who were involved with this project for their hard work and dedication.