This document discusses surge in centrifugal compressors and anti-surge control systems. It begins with an introduction to compressors and their classification. It then describes centrifugal compressors and the phenomenon of surge, where the gas flow reverses in the compressor. Surge occurs when the operating point crosses the surge line and can damage the compressor. The document then explains different anti-surge control systems that use a recycle valve to move the operating point away from the surge line when surge is detected, protecting the compressor. These systems include PI control, adaptive gain, recycle trip lines, and safety on line systems. In conclusion, the presentation covered surge characteristics and prevention using anti-surge control systems.

1. A Compressor Surge
Control System
Presented by:
Gaurav Ashara
ME IC
AITS Rajkot.
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2. Outline
 Introduction
 Types of compressor
 Centrifugal compressor
 Surge description
 Anti-surge system
 Conclusion
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3.  Function - take a definite quantity of
fluid and deliver it at a required pressure.
 Usually a gas, and most often air use.
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Introduction
Compressor

4. Classification of compressor
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5. Centrifugal Compressor
 velocity and pressure given to air or gas in a
radial direction by one or more impellers
diffuser combination.
 The centrifugal compressor may be single
stage or multistage.
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6. Single stage compressor fig.
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7. Multistage Compressor fig.
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8. Multistage Compressor
 Multistage containing a series of
impellers on a single shaft rotating at
high speed in a massive casing internal
channel
 It lead from the discharge of one
impeller to the inlet of next these
machines and compress measure volumes
of air.
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9. Surge
 Surge is the BACKFLOW of gas in compressor.
 Sustain oscillation
 Important element it protects the compressor from
surge over the range of compressor operations.
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10. Surge Description
 Flow reverses in 20 to 50 milisec.
 Surge cycle at a rate of 0.3 to 3 sec.
 Compressor Vibrates.
 Temperature rises.
 Whooshing noise.
 Trips may occur.
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11. Compressor Operating Curve
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Hp
Q
1
2
3
1. STONEWALL POINT
2. NORMAL POINT
3. SURGE POINT
.
MAX.STABLE COMP. FLOW POINT
MIN.STABLE FLOW POINT

12. Development of Surge Cycle
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13. Development of Surge Cycle
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From B TO C 20-50 ms
From D TO A 20-120 ms
ABCDA 0.3 TO 3 sec

14. Anti-surge control system
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DISCHARGE
SUCTION
VALVE TAKES COMPRESSOR
AWAY FROM SURGE
R PROCESS
R PROCESS
+VALVE
RECYCLE VALVE

15. Anti-surge control operation
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SLL
SCL
A
B
WHEN OPERATING POINT CROSSES
SCL, PI CONTROLLER WILL OPEN
RECYCLE VALVE
SUITABLE FOR SMALL DISTURBANCE
CLOSE LOOP CONTROL PI
Output
to valve
Tim
e
Medium disturbance
100%
0%
C

16. Anti-surge control operation
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ADAPTIVE GAIN
SLL
SCL
b
WHEN THE OPERATING POINT MOVES FAST
TOWARD SCL , ADAPTIVE GAIN MOVES
THE SCL TOWARD OPERATING POINT
THIS ALLOWS THE PI CONTROLLER TO
REACT EARLIER
SUITABLE FOR FAST DISTURBANCE
Large disturbance
Output
to valve
Tim
e
PI Control
Total
C

17. Anti-surge control operation
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RECYCLE TRIP LINE
SLL
SCL
RTL
A
BC
OPERATING POINT HITS RTL
OPERATING POINT MOVES BACK
TO SAFE SIDE OF RTL
OPEN LOOP RESPONSE IS TRIGGERED
O/P
VALVE
TOTAL
RTL
PI
PI Control
Recycle Trip®
Action
+
To antisurge valve

18. Anti-surge control operation
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SAFETY ON LINE (SOL)
SOL
SLL
RTL
SCL
IF OPERATING POINT CROSSES
THE SOL LINE THE COMP IS IN SURGE
SO RESPONSE SHIFTS THE SCL AND
RTL TO RIGHT
SO ADDITIONAL SURGE MARGIN IS
ADDED
BENEFITS OF SOL
1.ADDITIONAL SURGING IS
AVOIDED BY LARGE SURGE
MARGIN
2.ALARM OF SURGE IS
PRODUCED

19. Conclusion
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What we have presented so far in this presentation is that what is surge and it’s
generation. In this presentation we discussed characteristics of compressor,
phenomenon of surge like surge process, surge cycle, surge point, surge line,
surge control line, surge margin etc. We also mentioned here causes of surge in
centrifugal compressor and it’s effect and consequence centrifugal compressor
and also the prevention of surge occurrence(Anti-surge system).

20. Thank you
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