A Compressor Surge Control System
Presented by:
Gaurav Ashara
ME IC
AITS Rajkot.
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Outline
Introduction Types of compressor Centrifugal compressor Surge description Anti-surge system Conclusion
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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
Classification of compressor
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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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Single stage compressor fig.
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Multistage Compressor fig.
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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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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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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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Compressor Operating Curve
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Hp
Q
1
2
3
1. STONEWALL POINT2. NORMAL POINT3. SURGE POINT
.
MAX.STABLE COMP. FLOW POINT
MIN.STABLE FLOW POINT
Development of Surge Cycle
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Development of Surge Cycle
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From B TO C 20-50 msFrom D TO A 20-120 msABCDA 0.3 TO 3 sec
Anti-surge control system
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DISCHARGESUCTION
VALVE TAKES COMPRESSOR AWAY FROM SURGE
R PROCESS
R PROCESS +VALVE
RECYCLE VALVE
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
Time
Medium disturbance100%
0%
C
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 disturbanceOutput to valve
Time
PI Control
Total
C
Anti-surge control operation
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RECYCLE TRIP LINE
SLL
SCL
RTL
ABC
OPERATING POINT HITS RTL
OPERATING POINT MOVES BACKTO SAFE SIDE OF RTL
OPEN LOOP RESPONSE IS TRIGGERED
O/PVALVE
TOTAL
RTL
PI
PI Control Recycle Trip®
Action
+
To antisurge valve
Anti-surge control operation
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SAFETY ON LINE (SOL)
SOLSLL
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 SOL1.ADDITIONAL SURGING ISAVOIDED BY LARGE SURGE MARGIN2.ALARM OF SURGE IS PRODUCED
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).
Thank you
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