A ___ is used to remove oil from a rotating bearing as well as dewatered sludge at the end of a belt press

• A. Edge blade
• B. Squeegee blade
• C. Scraper blade
• D. Doctor blade

Answer: (D)

A blade that rides close to a moving surface to remove a thin, controlled layer is what’s being tested. A doctor blade is precisely that kind of scraper: it sits just above the surface to shave off a small amount of material, giving you a clean, uniform layer.

In a rotating bearing, this close-contact scraping allows wiping away excess oil from the bearing surface, helping prevent oil carryover and keeping the area clean. At the end of a belt press, the same principle applies to the dewatered sludge: the blade strips the sludge off the belt to produce a consistent cake while controlling moisture content. The other blade styles are aimed at different tasks—edge trimming, sweeping liquids, or general scraping—and don’t provide the same controlled, thin-slice removal needed for both oil on bearings and belt-press sludge.