ELEVATOR MACHINE ROOM MAINTENANCE EXAM QUESTIONS AND ANSWERS 100% CORRECT!

Roller Bearings - ANSWER Roller Bearings Roller Bearings are mechanical assemblies that consist of cylindrical or tapered rolling elements usually captured between inner and outer races. They provide a means of supporting rotating shafts and minimizing friction between shafts and stationary machine members. Roller bearings are used primarily in machinery with rotating shafts that require the support of heavier loads than ball bearings provide. Tapered roller bearings are often used to accommodate higher thrust loads in addition to the radial loads. Types range from cylindrical to spherical rollers. Roller bearings are standardized like ball bearings, albeit to a lesser degree. Considerations include Higher load capacities than ball bearings Can withstand high axial loads Sleeve Bearings - ANSWER Sleeve bearings have a higher coefficient of friction than ball and roller bearings. Sleeve bearings can support heavy radial loads. Sleeve bearings (sometimes called bushings, journal bearings or plain bearings) facilitate linear movement between two parts. Sleeve bearings consist of a metal, plastic or fiber-reinforced composite sleeves that reduce vibrations and noise by absorbing friction between two moving parts using a sliding motion. MG SET - ANSWER A motor generator (M-G) set refers to a composite device consisting of a motor and a generator mechanically coupled through the common shaft. Practically a motor generator set is a system where a motor and a generator are connected or rather placed in a single circuit. Governors Cont. - ANSWER There are two major types of governors: centrifugal and the flyball types. The centrifugal type is used for all speed applications whereas the flyball type is usually found on older high-speed applications. For safety, the centrifugal type may have all of its moving components covered by a metal enclosure. The flyball type has exposed moving parts that can be hazardous. Governors Code - ANSWER The mechanical tripping speed of the governor is defined by A17.1 2001 2.18.2.1 and states that the minimum tripping speed to be not less than 115% of the rated speed. Before the safety is initiated there are electrical contacts that are actuated to stop the car. This switch shall not open at more than 90% of the mechanical tripping speed at which the governor is set to trip. For rated speeds above 500 FPM the switch shall open at not more than 95% of the mechanical tripping speed Selectors - ANSWER By definition, a "selector is a mechanically or electrically driven device which initiates and or controls some of the following functions: direction selection, acceleration, deceleration, leveling, stopping, call cancellation, door operation, position indication and hall lanterns." There are four major types of selectors: relay, mechanical, motor driven and electronic.