MFP Controls

Question 1

What are the alarm limits for the MFP lube oil tank and where can operator see which tank is alarming?

Answer 1

Hi alarm: 18.25”

Lo alarm: 5.25”

Light indication on panel C02 gives indication of which tank and whether level is hi or lo.

Question 2

What are the power supplies for MFP LO pumps? When will standby pumps autostart and what alarms come in?

Answer 2

P-27A - B-22

P-27B - B-12

P-26A - B-12

P-26B - B-22

P-28A/B - D-41

Standby pump will autostart when discharge pressure < 140# and alarm will come in when standby pump discharge pressure > 123#.

Bearing oil pressure < 30# will autostart DC pump and alarm will come in when pressure > 40#.

Question 3

What type of control is the LP governor vs the HP governor and what controls the MFP at appropriate bands?

Answer 3

LP governor - consists of 6 poppets that lift sequentially providing linear steam flow characteristic throughout valve stroke. LP governor controls when gov valve demand is 0 - 50%.

HP governor - has a single poppet and control from main steam when governor valve demand is 50.1 to 100%.

Question 4

Discuss operation of the MFP autostop oil system and how system responds when trip is reached.

Answer 4

• Stop valves consist of four way solenoid valve which supplies high pressure to piston to open the stop valve against spring pressure. When trip is received, 2 solenoids trip open and low autostop oil pressure is sensed which opens the hydraulic trip valve and drains oil from stop valve.
• Autostop oil supply is limited by orifices so that supply pressure will not overcome the drain flow during a trip.
• To open stop valves, turbine must be latched with auto stop oil header pressurized and no hydraulic trip signal present.

Question 5

What will trip the MFP via turbine trip solenoids?

Answer 5

Low suction pressure - 230# initiates permissive, 200# for 40 sec trips preferred pump and 10 seconds later will trip other pump

High discharge pressure - 1350# (2/3)

Low bearing oil pressure @ 10# (2/3 with 3 sec delay)

Manual Trip on C02 or front standard

Question 6

What function does the mechanical overspeed trip device serve?

Answer 6

Also opens when autostop oil pressure decreases and will seal in a MFW pump trip from the solenoid.