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Focus: Kiln Conversion Project - Shortening & modifying 6 -pier cement kiln at National Cement.

Focus: Kiln Conversion Project
by Jim Munson, Repair Manager

The project we did for Bechtel at National Cement in Lebec, CA this year was one of the most unique jobs Phillips has ever performed. We were immersed with this project for almost a year, converting the existing 15.5' x 17.5' x 560' long wet process kiln into a three-pier precalciner. Phillips Kiln Services Ltd. was employed to supply new shell components, for field construction of the kiln conversion, and to do all the pre- and post-alignment and reconditioning. We are very proud of all those who helped make this project a success.

National Cement - Lebec, California
by Bruce Bosmeny, Project Manager

Background: The customer had a 1966 vintage Traylor cement kiln with 6 piers, an overall length of 560', a 17' 6" dia feed end and a 15' 6" dia discharge end. It was driven by a twin pinion drive arrangement through a spring-mounted girth gear at the #4 pier. A massive kiln modernization project was implemented to increase production and modernize the controls. It included shortening and modifying the existing 6 pier kiln to use only the last 3 discharge piers, and installing a preheater tower to feed raw materials into the new feed end uphill of pier #3. Other than moving the drive arrangement from pier #4 to pier #3, the rest of the kiln would be abandoned in place. Because the plant did not want to lose any more production than necessary, the preheater tower was constructed ahead of time straddling the kiln between piers #3 and #4 while it was in full production.

Bechtel was selected by the plant to be the general contractor over the whole project. There were large numbers of sub-contractors on site at different times throughout the job doing all of the various mechanical, refractory, electrical, and instrumentation work associated with a project of this scope. TIC built the preheater tower and Phillips Kiln performed the necessary kiln work.

Kiln Prework: Since the existing ring on #3 pier would become the new thrust pier, it was resurfaced while the kiln was still in production. This included grinding the straight side faces to incorporate the thrust angle. As a result of the successful grinding, the customer decided to have us grind all of the tires and rollers. The repair crew arrived at the plant about a week before the kiln was shut down to assemble two shell sections that would eventually be installed as the new feed end. This was done using a new set of subarc rollers. We also built a rail system so the existing shell, straddled by the preheater structure, could be removed, and the new shell, which would become the new feed end, could be installed. There was also some preliminary work done assembling and positioning falsework, and setting the new drive component bases.

Kiln Main Job: Once the kiln had been shut down and control given to Phillips, we installed the necessary spider supports inside the kiln. The kiln shell was then supported between piers #2 and #3, and some of the existing shell was cut out downhill of pier #3. Once this was done, a hydraulic jacking arrangement was constructed on the inside of the shell to pull the kiln uphill approximately 14". The existing discharge seal, cowl, hopper, and ductwork was dismantled and the existing discharge end section was cut off and removed. A new discharge end section was then set into place, and the seam hardware was installed. The kiln was then pushed back downhill.

Once the kiln was repositioned, the rest of the existing shell was removed and the finish cuts were made downhill of pier #3 for a new heavier shell section to support the relocated girth gear. The new shell was set into place and the seam hardware was installed. Runouts of the shell were checked. Once satisfactory results were obtained, the 3 seams were partially welded while we could still turn the kiln with the existing drive.

At this point, all of the drive components that were going to be relocated were removed. This included the pinions, motors, auxiliary drive, and the girth gear. The pinions were sent out to be reversed with new couplings and bearings installed. New spring mounts were then installed on the halves of the girth gear for a reversed mounting. The girth gear was then installed on the new heavier shell downhill of pier #3 with new splice bolts and the appropriate adjustment chairs.

All of the old shell from #4 pier downhill to within the new preheater tower was then removed. The new feed end shell section was then moved into place and the seam hardware was installed. The rail system was then dismantled to make room for other contractors to finish their work within the preheater tower. Once the pinion assemblies returned from the machine shop, the individual drive component bases were installed. All of the new and used drive components were then installed and rough-aligned. A new thrust roller base frame was set into place and new hydraulic thrust rollers were installed.

Now that the kiln could be rotated again with the auxiliary drive, the new shell at the feed end was checked, and adjusted to achieve minimal radial runout. This seam was then partially welded to hold its position. Then the welding on all four seams was completed on the outside. The hardware and spider supports on the inside were all removed, the inside of the seams backgouged and welded, and then all of the field seams were ultrasonically tested for integrity.

The girth gear was then adjusted to minimum axial and radial runouts, the leaf springs were welded out, and the mounting hardware removed. The gear enclosure was then re-installed and all of the drive components were final aligned.New nose castings were also installed at the feed and discharge ends along with a discharge end seal and cooling air system.

Conclusion: All in all, our crews spent approximately 5-1/2 weeks at the customers plant on this project. At the peak of the job, we had a total of 23 people working between the day and night shifts. Even though we were in California, just an hour or so north of Los Angeles, the region is considered to be high desert country. As a result, we experienced high winds, and cold temperatures with occasional snowfall throughout the job, rather than the anticipated “southern California climate”. We also had a 300 ton crane and our standby generator break down during critical parts of the job, and a large number of our crew was sick with the flu at one time or another. Despite all of this, the job went extremely well and most importantly, was completed on time and within budget.

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