In spite of the fact that a comprehensive onsite gearbox review is alluring in numerous circumstances, there may be limitations that constrain the degree of the review such as taken a toll, time, availability and qualified staff.
Fetched and shutdown time can be seen as restrictive by administration, but catching a issue in its earliest stages can spare time and money within the long run. Whereas it could seem as well troublesome to do a comprehensive review, a basic visual assessment of gear contact designs through an review harbour can avoid future disastrous disappointments. In the event that in-house assessment mastery isn't accessible, an master can be enlisted to perform the review and prepare personnel.
Overcoming imperatives in arrange to permit an review can offer assistance to amplify gearbox life and maintain a strategic distance from disastrous disappointment. This might too spare time, cash, harm to work force and harm to adjoining equipment.
This article portrays the gear and strategies fundamental to perform an on-site gearbox inspection.
Getting Prepared: Good Housekeeping is Essential Before beginning an inspection, prepare an inspection form for documenting your observations. It should be designed for your specific application. Next, assemble the necessary equipment.
There are several sources of gearbox contamination, including those that are built-in, internally generated, ingressed, and added during maintenance. Many gearboxes operate in dirty environments. Therefore, good housekeeping methods should be used during inspections. Areas around inspection ports and other openings should be cleaned before they are opened. Inspectors should take care not to drop anything into the gear- box. Shirt pockets should be empty and tools should be stored in a tool belt. Ports should never be left open during breaks and should be closed and secured after the inspection is complete.
Walk-around visual inspection. You should perform a thorough external examination before the gearbox inspection port is opened. Use an inspection form to record important data that would otherwise be lost once cleaning is completed. For example, before cleaning the exterior of the gear housing, inspect it for signs of overheating, corrosion, contamination, oil leaks and damage. Measure the tightening torque of structural fasteners that carry significant loads, such as torque arm bolts. Look for evidence of movement, including cracked paint or fretting corrosion at structural interfaces. Note the condition of the fasteners and inspect load-bearing surfaces of components for fretting corrosion or other evidence of movement.
The following are signs of overheating:
• Discolored or burnt paint on housings
• Water sprayed on the housing or shafts evaporates quickly, boils or crackles
• Temper colors on unpainted surfaces
• Melted plastic components, such as shipping plugs
• Low oil level in sight glass or on dipstick
• Dark oil in sight glass or on dipstick
• Foam in sight glass
• Water in sight glass or sludge on filter element (may indicate oil cooler failure)
• Metal chips on magnetic plugs, chip detectors or filters (may denote gear or bearing failure caused by overheating)
• Smoke from shafts, seals or breathers
Figure 1 Cracked paint at torque arm interface indicates movement; a = 45° direction of cracks; b = suggests component on right moved downward, relative to component on left.
Figure 2 Fixture used for measuring shaft endplay.
Figure 3 Severe misalignment can cause macropitting on helical pinion gears
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