Commissioning software for evaluating a surge signal
SCAUT is a standardized automation solution that, thanks to its modular design, comprehensively fulfils requirements with regard to operation, monitoring, closed-loop and openloop control as well as the protection of compressors, drives and ancillary systems. The system is based on the worldwide leading SIMATIC S7 automation product family from Siemens, which is built on a unique symbiosis with our decades of experience in instrumentation and control for compressor installations.
General information
SCAUT surge protection is part of the extensive SCAUT family and is available in two variants:
As a “stand-alone” version with its own hardware as an independent unit for a process stage
As a software module for integration in the SCAUT equipment unit control system
Application
The SIMATIC S7 surge protection unit is used to protect the machinery from damage as a result of repeated surge events.
Principle of operation
The operating principle differs from that of a closed-loop control:
Whereas the closed-loop control defines a limit curve in the compressor map and prevents it from being overshot through continuously controlled opening of the surge control valve, the surge protection unit in contrast responds to real surge events. Surges are detected from the large time signal changes that accompany these events. The registered surges are evaluated in three stages: alarm output; full, rapid opening of the surge control valve; and if necessary, shutdown of the compressor.
Surge protection and availability
Unnecessary tripping and failure of the surge protection unit reduce the availability of the compressor. To prevent unnecessary tripping (and to enable reliable tripping of the unit in the case of a surge event), it is important that the relevant optimum operating point is monitored. For
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this reason, the SCAUT surge protection unit allows up to 4 signals to be evaluated. When several signals are
connected, the signal is used that is ideally suited to the purpose.
These signals can originate from the following measurements:
Discharge pressure
Suction pressure
Motor current
Differential pressure at a volume measuring point
Suction pressure or discharge pressure between the individual compressor stages
Intake temperature
Availability can be further enhanced by installing surge protection as a 2-out-of-3 configuration.
I) Controller set-up
As the size of the time signal change depends on the type of plant in which the compressor is running as well as on the operating point of the machine, a limit is determined on commissioning. Comprehensive data is available for this purpose from test operation in the customer plant that has already been automatically recorded. It is possible to set the monitoring algorithms so that tripping is only caused by actual surging to ensure that the availability of the machine is assured during process disturbances.
Safety of the machine
Surging poses a risk to any turbo-compressor. Despite perfect adjustment of the surge limit control, surging may nevertheless occur over an extended operating period due to instrumentation errors, limited cooling or fouling.
SCAUT surge protection is a stand-alone module that reliably detects surging based on signal gradients. This protection measure is therefore built on a different principle of operation from the surge limit control and therefore can also use different measured signals.
Diagnostic functions for service
In addition to the number, time and date for the last 400 surges, the measured values from the connected sensors are recorded for the last 10 events. This enables the service technician to establish a detailed diagnosis leading to fast rectification of the problem.
Tried-and-tested SIMATIC hardware
SCAUT is based on the globally leading and tried-andtested SIMATIC industrial controller.
Integration of “stand-alone” surge protection in the overall control system:
Surge protection stage 3: Shutdown
Surge control valve
Closed-loop control
RM main motor
Controller
Alarm annunciation system
Surge protection
(stand-alone)
Shutdown
(0 signal)
Surge protection not active
Surge protection error
Surging detected
Number of surges detected >= 50: Service!
Surge protection stage 2: Open valve
Reset (manual, isolated from alarm acknowledgement)
Galvanic isolation
(active)
Closed-loop control transmitters Surge protection transmitters
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Published by and copyright © 2012:
Siemens AG
Energy Sector
Freyeslebenstrasse 1
91058 Erlangen, Germany
Siemens Energy, Inc.
4400 N Alafaya Trail
Orlando, FL 32826-2399, USA
For more information, please contact our Customer Support Center.
Phone: +49 180 524 70 00
Fax: +49 180 524 24 71
(Charges depending on provider)
E-mail: support.energy@siemens.com
Energy Service Division
Order No. E5001-E510-A220X
Printed in Germany
Dispo 34805, bdk 110262, P WS 0512
Printed on elementary chlorine-free bleached paper.
All rights reserved.
Trademarks mentioned in this document are the property of Siemens AG, its affiliates or their respective owners.
Subject to change without prior notice.
The information in this document contains general descriptions of the technical options available, which may not apply in all cases. The required technical options should therefore be specified in the contract.