ACADs (08-006) Covered
5.2.2.9
Keywords
Air compressors, aftercooler, afterfilter, moisture separator airflow.
Description
Supporting Material
Service
&
Instrument
Air
2
Objectives:
1. Describe the difference between service air
and instrument air; state the purpose of each.
2. List the main components of the service /
instrument air systems and describe their
functions.
3. Describe the flowpath of air through the
service / instrument air system using a oneline diagram.
5
Service & Instrument Air
Purpose:
Provide a source of reliable compressed
air to air operated plant equipment.
Uses:
Service air is generally of lesser quality than
instrument air. Service air is piped to outlets
for temporary equipment and instrument air is
piped to permanently-installed, pneumaticallyoperated equipment.
6
Rotary Air Compressor:
Turbine Building Level A
a. 2 per unit
b. Normal operating
pressure 117 psig
c. Capacity - 750 SCFM
d. 200 HP motor
e. Seal fluid seals the
intermesh of two
screw-type blades
f. Air coolant receiver cools seal fluid,
removes fluid, and
returns it back to
screws
7
Reciprocating Air Compressor
a. 1 per unit, 1 shared
b. Normal operating
pressure 125 psig
c. Capacity 885 SCFM
d. 200 hp motor
e. Piston and cylinder
type
f. Uses no seal fluid
therefore no air
coolant receiver
needed
8
Aftercooler
•Compressed air gets hot so must be cooled
•7 (1 for each compressor)
•Air/water Heat Exchanger
•Air on shell side
•Cooling water on tube side
•Cooling water from Turbine Plant Closed
Cooling Water (TPCCW)
9
Moisture Separator
a. 7 (1 per compressor)
b. Mechanical type -- air flow hits baffles inside and drops water out
c. Removes condensed moisture from cooled air
10
1st & 2nd Stage Contaminant
Filters
a. Used with
rotary
compressor
b. Backup seal
oil removal
c. 1st stage = .3
micron
2nd stage = .01
micron
11
Air Receiver
•7 (1 per compressor)
•150 ft. 3
•Rated pressure 150 psig
•Dampening effect
12
Prefilter
•3 total
•Coalescing type (oil vapor/particulate)
•Removes oil and contaminants before
dryer
13
Air Dryer
Each dryer = two
tanks w/ alumina
desiccant
Service Dryer:
•1 dryer
•1200 SCFM
capacity
Instrument Dryer:
•2 parallel dryers
•740 SCFM
capacity
14
Afterfilter
• 3 (1 after each dryer)
• Filter desiccant fines
• Remove .07 micron
15
Service
&
Instrument
Air
Intake Filter
Contaminant
Filter
After Cooler
1
2
3
4
Air Compressor
(Rotary)
FLOW PATH:
1. Compressors
2. Aftercooler
3. Moisture separator
4. Contaminant filter
5. Air receiver
LCV
5
Air
Receiver
First Second
Stage Stage
Moisture
Separator
LCV
Drain
Air Coolant
Receiver
Drain
Intake Filter
1
2
Contaminant
Filter
After Cooler
3
Air Compressor
(Rotary)
LCV
5
4
Air
Receiver
First Second
Stage Stage
Moisture
Separator
LCV
Drain
Air Coolant
Receiver
Drain
To Air
Dryer
Intake Filter
2
Air Compressor
(Reciprocating)
1
After
Cooler
5
3
Air
Receiver
Moisture
Separator
LCV
LCV
Drain
To
Unit 2
Drain
Intake Filter
2
Air Compressor
(Reciprocating)
1
After
Cooler
3
LCV
Drain
5
Air
Receiver
Moisture
Separator
LCV
Drain
16
Service & Instrument Air
9
FLOW PATH:
6. Pre-filter
7. Dryer
8. After Filter
9. To respective headers
8 F
F
To Instrument
Air Header
8
Instrument
Air Dryer "A"
Instrument
Air Dryer "B"
7
7
Exhaust
Exhaust Exhaust
F 6
Exhaust
6 F
Compressed
Air Inlet
8 F
Service
Air Dryer
9
To Other
Unit
7
Exhaust
To Service
Air Header
Exhaust
F 6
17
Objectives Review:
1. Describe the difference between service air
and instrument air; state the purpose of each.
2. List the main components of the service /
instrument air systems and describe their
functions.
3. Describe the flowpath of air through the
service / instrument air system using a oneline diagram.
18