Mechanical EPRI – Questions With Solutions
basic operation of a diesel engine ✔️Ans -- internal combustion
engines convert chemical energy into mechanical energy and turn a generator
reducers ✔️Ans -- pieces of pipe that change diameter from a
larger diameter to a smaller diameter
free vibration ✔️Ans -- vibrates at a natural frequency
- periodic motion of a system with no energy
- continues to oscillate without any dampening effects
- 'ideal' mass spring system
- example: Tacoma narrows bridge
forced vibration ✔️Ans -- a disturbing force is input into the
system, causing the system to vibrate at the frequency defined by the input
- example: all rotating equipment
flexible member ✔️Ans -- pumping and sealing action depends on
the elasticity of the flexible member
- flexible member can be a tube, vane, or liner
- used for various chemical applications
globe valve ✔️Ans -- resembles a disc or globe
- used to start/stop/regulate fluid flow
- flows beneath the valve seat
- reduces power required for the actuator to open the valve
- increases power to close the valve
- designed to operate above or below the seat
- little to no leakage occurs across the disc when closed
needle valve ✔️Ans -- make fine adjustments to the amount of fluid
allowed to flow through them
- not usually used as an isolation valve
- set to desired flow. another valve starts/stops flow
equilibrium ✔️Ans -- forces and moments on a system can be
summed up
, packing ✔️Ans -- soft braided graphite packing formed in
rectangular sections with butt joints staggered from ring to ring during
installation
- sealing is accomplished by compressing the packing around the shaft
torque tightening procedure ✔️Ans -- not be placed more than six
nominal diameters apart on the bolt circle
- at least three bolt diameters apart
- tightened in a crossing pattern
- first pass is at a reduced torque value and followed by several tightening
passes
oil ✔️Ans -- slippery, moderately viscous liquid used to lubricate a
mechanical interface to reduce friction and wear
hydraulic actuator ✔️Ans -- uses fluid and a piston to create valve
motion
- hydraulic fluid is typically loaded to one side of the piston while the other
side may be used as a return line
piping ✔️Ans -- hollow cylinders/tubes
- transports gasses, liquids, and fine solids in a slurry
- a system for containing/controlling/directing fluid flow
screws ✔️Ans -- threaded fasteners inserted into a tapped hole
mating with an internal thread/forming its own
- common: machine, self-tapping
- material: steel or aluminum
- failures: head falls off, head pulled through material, pull out mating threads
gate valve ✔️Ans -- start or stop flow
- not intended to regulate or throttle flow
- usually used only as isolation valves and normally fully closed or fully
opened
ball valve ✔️Ans -- used only to start/stop fluid flow
- little resistance to flow when open
- fast acting
basic operation of a diesel engine ✔️Ans -- internal combustion
engines convert chemical energy into mechanical energy and turn a generator
reducers ✔️Ans -- pieces of pipe that change diameter from a
larger diameter to a smaller diameter
free vibration ✔️Ans -- vibrates at a natural frequency
- periodic motion of a system with no energy
- continues to oscillate without any dampening effects
- 'ideal' mass spring system
- example: Tacoma narrows bridge
forced vibration ✔️Ans -- a disturbing force is input into the
system, causing the system to vibrate at the frequency defined by the input
- example: all rotating equipment
flexible member ✔️Ans -- pumping and sealing action depends on
the elasticity of the flexible member
- flexible member can be a tube, vane, or liner
- used for various chemical applications
globe valve ✔️Ans -- resembles a disc or globe
- used to start/stop/regulate fluid flow
- flows beneath the valve seat
- reduces power required for the actuator to open the valve
- increases power to close the valve
- designed to operate above or below the seat
- little to no leakage occurs across the disc when closed
needle valve ✔️Ans -- make fine adjustments to the amount of fluid
allowed to flow through them
- not usually used as an isolation valve
- set to desired flow. another valve starts/stops flow
equilibrium ✔️Ans -- forces and moments on a system can be
summed up
, packing ✔️Ans -- soft braided graphite packing formed in
rectangular sections with butt joints staggered from ring to ring during
installation
- sealing is accomplished by compressing the packing around the shaft
torque tightening procedure ✔️Ans -- not be placed more than six
nominal diameters apart on the bolt circle
- at least three bolt diameters apart
- tightened in a crossing pattern
- first pass is at a reduced torque value and followed by several tightening
passes
oil ✔️Ans -- slippery, moderately viscous liquid used to lubricate a
mechanical interface to reduce friction and wear
hydraulic actuator ✔️Ans -- uses fluid and a piston to create valve
motion
- hydraulic fluid is typically loaded to one side of the piston while the other
side may be used as a return line
piping ✔️Ans -- hollow cylinders/tubes
- transports gasses, liquids, and fine solids in a slurry
- a system for containing/controlling/directing fluid flow
screws ✔️Ans -- threaded fasteners inserted into a tapped hole
mating with an internal thread/forming its own
- common: machine, self-tapping
- material: steel or aluminum
- failures: head falls off, head pulled through material, pull out mating threads
gate valve ✔️Ans -- start or stop flow
- not intended to regulate or throttle flow
- usually used only as isolation valves and normally fully closed or fully
opened
ball valve ✔️Ans -- used only to start/stop fluid flow
- little resistance to flow when open
- fast acting
