Diesel Generator Engine Starting Air System(VG)

Question 1

What is the purpose of the Diesel Generator Engine Starting Air System?

Answer 1

1. The Diesel Generator Engine Starting Air system provides fast start capability for the diesel engine by using high pressure air to rotate the engine until it starts and runs under its own power.
2. The Diesel Generator Engine Starting Air system also provides control air to the diesel engine and motive force for the barring device.

Question 2

What is the system designator for the Diesel Generator Engine Starting Air System?

Answer 2

VG

Question 3

How many Starting Air Compressor are there for each Diesel Generator, and what type are they?

Answer 3

1. There are two Starting Air Compressors for each Diesel Generator.
2. The Starting Air Compressors are AC motor driven, two-stage air compressors.

Question 4

What is the purpose of the Starting Air Compressors?

Answer 4

The Starting Air Compressor automatically maintain Starting Air Receiver pressure to ensure the D/G will successfully start.

Question 5

What is the power supply to the Starting Air Compressors?

Answer 5

EMXE and EMXF

Question 6

What are the automatic start and stop setpoints for the Starting Air Compressors?

Answer 6

1. Start - 235psig

2. Stop - 250psig

Question 7

What is the purpose of the Starting Air Aftercooler?

Answer 7

The Starting Air Aftercooler is a shell and tube heat exchanger at the outlet of the Starting Air Compressors that remove the heat of compression.

Question 8

What system provides the cooling water to the Starting Air Aftercooler?

Answer 8

1. Normally, the Drinking Water System(YD)

2. Backup, the Demineralized Water System(YM)

Question 9

What is the purpose of the Starting Air Moisture Separator?

Answer 9

The Starting Air Moisture Separator is a cyclone type moisture separator located on each aftercooler. The moisture separator removes condensate from the air and is equipped with an automatic drain trap.

Question 10

What is the purpose of the Starting Air Dryers?

Answer 10

The Starting Air Dryers remove and moisture from the air prior to it being discharged to the Starting Air Receivers using desiccant towers.

Question 11

What constant pressure is maintained on the Starting Air Dryers and how?

Answer 11

1. A constant pressure of 250psig is maintained on the dryer.
2. Pressure is maintained on the dryer using a downstream pressure regulating valve.

Question 12

Why is it important to maintain a constant pressure on the Starting Air Dryer?

Answer 12

The outlet of the desiccant dryer tower that’s in service provides purge air to the desiccant tower being regenerated. If the pressure were to drop to less than 250psig the purge flow would be insufficient.

Question 13

What are the times associated with the Starting Air Dryer activation/regeneration cycle?

Answer 13

1. The air dryers have a standard 10 minute cycle.
2. 5 minutes of activation - available for drying
3. 5 minutes of regeneration

Question 14

What is the interlock between the Starting Air Dryers and the Starting Air Compressors?

Answer 14

The air dryers are interlocked with their associated air compressor so that a dryer is only actuated when its compressor is in operation.

Question 15

What is the purpose of the Starting Air Storage Tanks(Receivers)?

Answer 15

The Starting Air Receivers store clean and dry compressed air used to start the diesel generators.

Question 16

What is the capacity of the Starting Air Receivers, and how many starts does that equate too?

Answer 16

1. 125 cubic feet for each receiver

2. The capacity of the two receivers allows for a minimum of 5 successive starts without the use of the air compressors.

Question 17

What is the purpose of the Starting Air Inlet Valves?

Answer 17

The Starting Air Inlet Valves admit starting air to the D/G to facilitate a start.

Question 18

What type of valves are the Starting Air Inlet Valves and how many are there?

Answer 18

1. The Starting Air Inlet Valves are solenoid operated valves.
2. There are 4 Starting Air Inlet Valves for each D/G.

Question 19

What is the power supply to the Starting Air Inlet Valves?

Answer 19

125VDC from the Emergency Diesel Generator Auxiliary Control Power(EPQ)

Question 20

How many Starting Air Inlet Valves are required to open to start a D/G?

Answer 20

Only one Starting Air Inlet Valve is required to open to start a D/G.

Question 21

What signals will close the Starting Air Inlet Valves on an automatic start?

Answer 21

1. Diesel Speed - 200rpm(44% speed)

2. Low Starting Air Pressure - 150psig

Question 22

Will a manual start of the Diesel Generator be locked out based on low Starting Air Pressure?

Answer 22

No, only automatic starts are locked out at 150psig in the air receivers.

Question 23

What controls and indications are located on the local control panel?

Answer 23

The Diesel Engine Control Panel contains:

1. Starting Air Pressures at the Starting Air Inlet Valves.
2. Control Air Pressure
3. Starting Air Compressors ON/OFF pushbuttons

Question 24

How is the D/G affected by a loss of Control Air?

Answer 24

A loss of Control Air pressure results in the inability to shutdown the D/G by normal means:

1. STOP pushbutton in the Control Room
2. STOP pushbutton at local panel
3. Automatica D/G trip
   The Run/Stop Valve can be used as long as the VG system is pressurized because it comes off a separate tap in the VG system

Question 25

How is the D/G affected by a loss of DC power to the Starting Air Inlet Valves?

Answer 25

If the D/G is in standby it will not start because the Starting Air Inlet Valves will not open to admit starting air.

Question 26

When do the Starting Air Inlet Valves close following a manual start?

Answer 26

The starting air valves close after three seconds allowing for multiple start attempts once the automatic starts are blocked at 150psig.