Omni Instrumentation & Electrical Services was called in by a process engineer we had worked with to participate in a dryer drum refinishing and maintenance project. Having been responsible for the initial installation of power, instrumentation, and controls for the dryers several years earlier, we were approached to provide our services on the project.
The project entailed the refurbishment of five large high-pressure steam dryers, each equipped with two dryer drums measuring 4 feet in width and 16 feet in length. The challenge was to refinish each drum individually while ensuring the continued operation of the other dryers. Through close collaboration with the client and the refinishing contractor, a detailed plan was developed outlining the necessary steps.
To gain full access to the drums, various instruments, such as large actuators, limit switches, auger motors, temperature transmitters, as well as the large fenders and chutes covering the drums, needed to be removed. Omni supplied temporary 480V power and 100 PSI dry compressed air to the refinishing equipment as per the vendor's requirements. For safety purposes, steam and condensate valves were turned off and locked out.
During the refinishing process, specific components required continuous operation via their associated variable frequency drive (VFD) in manual mode while the rest of the machine was not operating. This included the overhead exhaust fan, which ran at full speed throughout the process. To initiate the refinishing process, the dryer drums had to run at approximately 4 RPM. This was achieved by running the drum VFD at a very slow speed through the drum gearbox. The vendor could manually adjust the drum RPM as needed during different stages of the refinishing process.
Upon the completion of each dryer drum, a finish test was conducted using a profilometer. The reassembly process followed, with all instrumentation meticulously reinstalled. Before returning each dryer to operation, a full functional test was executed in collaboration with the process engineer, followed by the removal of safety locks to reintroduce steam to the refinished dryer. This process was repeated for each dryer, taking approximately 3 days for each, with the refinishing vendor working 12-hour shifts. The entire project was completed in 16 days.
Along the way, we also diagnosed and addressed operational issues with several limit switches that were opening unexpectedly. The client expressed satisfaction with the timely and safe completion of the work while ensuring uninterrupted operation during the refinishing process.
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