a compressor surge control system

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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