A Day in the Life of a Mellott Service Technician-HP400 Repair

Feb. 27, 2018

The Mellott Company service technician is essential to our clients in the aggregates industry. The technician diagnoses and troubleshoots complex issues, related to crushing machines, in order to get them back up and producing properly in an efficient manner. For this particular job, our client knew that their Metso HP 400 cone crusher was not running properly, but the client could not pinpoint the source of the problem.

Our service technician went to visit the client, at their site, to discuss the concerns they had with the machine, and then examined the crusher itself. 

While performing a detailed assessment of the machine, the service technician documents the issues and problems they detect and develops suggestions to fix the problem. In this case, while our technician was disassembling the HP 400, he discovered that the arm guards were not seated in their correct positions, which allowed wear on the main frame and arms. The main-frame pins and bushings had suffered damage, with some missing altogether, and the seat liners were destroyed. He also noted that poor housekeeping around the crusher had allowed buildup of spilled material, which then caused premature wear to components. Compounding the wear is that built-up spillage also covers any damage from being readily detected during daily visual inspection of the equipment.
Upon disassembling the machine and measuring the critical internal parts, our technician found that the eccentric O.D. (outer dimension) was out of specified tolerance, and bushing I.D. (inner dimension) was out-of-round. His recommendation was to replace these components, as no log books had been maintained to record operating data, such as fluid pressures and temperatures. A regular log can give the technician valuable clues in diagnosing the events to which the machine might have been subjected. In this case, the absence of a log meant that our technician could only recommend new parts, to avoid making a costly, incorrect guess on the condition of the existing parts. Although the socket for the machine was worn, it was still usable. However, he found that the socket liner O.D. was too small and needed to be replaced. The center of the socket liner showed signs of heat damage, likely caused by an event that allowed the parts to heat to the point of damage. Typical events that lead to excessive temperature might be tramp iron going through the crushing chamber or poor lubrication flow, both of which allow temperatures to rise catastrophically. High temperatures, in turn, cause the brass to deteriorate and eventually fail. While inspecting the counterweight, our technician also found that the counterweight guard needed replaced.
When our service technician was complete with his inspection, he reviewed his findings and suggestions with the customer. The customer went ahead and ordered replacement parts from us. After parts arrived on site, our technician returned to repair the crusher. Upon completion of the repairs, the technician confirmed that all temperatures and pressures were good, and he tested the machine to be sure it was running correctly. In the end, the crusher was repaired correctly, and the customer was back to full production!


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