PID A/D
UF
RAM
GLOBAL SUPPLIERS OF TURBINE
ID
AND COMPRESSOR CONTROL SYSTEMS
IM301
Series 3 Plus Antisurge Controlleruser manual
Series 3 Plus Antisurge Controllerfor Axial and Centrifugal
CompressorsPublication IM301 (6.1.3)Product Version: 756-004
September 2005
Documentation Feedback Form4725 121st Street Des Moines, Iowa
50323, U.S.A. Phone: (515) 270-0857 Fax: (515) 270-1331 Web:
www.cccglobal.com
1987-2003, Compressor Controls Corporation. All rights reserved.
This manual is for the use of Compressor Controls Corporation and
is not to be reproduced without written permission. Air Miser,
Guardian, Recycle Trip, Reliant, Safety On, SureLink, TTC, Total
Train Control, TrainTools, TrainView, TrainWare, Vanguard, Vantage,
WOIS, and the TTC and impeller logos are registered trademarks; and
COMMAND, TrainPanel, and the Series 3++ and Series 5 logos are
trademarks of Compressor Controls Corporation. Other company and
product names used in this manual are trademarks or registered
trademarks of their respective holders. The control methods and
products discussed in this manual may be covered by one or more of
the following patents, which have been granted to Compressor
Controls Corporation by the United States Patent and Trademark
Office: 4,949,276 5,622,042 5,879,133 6,116,258 6,494,672 5,347,467
5,699,267 5,908,462 6,217,288 6,503,048 5,508,943 5,743,715
5,951,240 6,317,655 5,609,465 5,752,378 5,967,742 6,332,336
Many of these methods have also been patented in other
countries, and additional patent applications are pending. The
purpose of this manual is only to describe the configuration and
use of the described products. It is not sufficiently detailed to
enable outside parties to duplicate or simulate their operation.
The completeness and accuracy of this document is not guaranteed,
and nothing herein should be construed as a warranty or guarantee,
expressed or implied, regarding the use or applicability of the
described products. CCC reserves the right to alter the designs or
specifications of its products at any time and without notice.
Series 3 Plus Antisurge Controller
3
Document ScopeThis manual tells how to configure, tune, and
operate a Series 3 Plus Antisurge Controller. It does not tell how
to install or maintain it (see the Series 3 Plus Hardware Reference
manual [IM300/H]), nor how to program a DCS to use its Modbus
interface (see the Series 3 Plus Modbus Reference manual
[IM300/M]). Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5
Chapter 6 Chapter 7 Chapter 8 Chapter 9 Appendix A Appendix B
Appendix F summarizes this controllers applications and features.
describes the operation of the Antisurge Controller. tells how to
configure the analog and discrete inputs and outputs and serial
communication ports. tells how the Antisurge Controller calculates
the values of various process conditions. tells how to set up the
proximity-to-surge calculation and fallbacks. tells how to set up
the algorithms that calculate various control responses and select
the required recycle flow rate. describes the additional features
used to protect multisection and networked compressors from surge.
tells how the valve position and actuator control signal are
derived. tells how to set up the Antisurge Controllers automatic
sequencing, manual operation, and redundant control features.
describes each Antisurge Controller configuration parameter.
describes the controller test procedures that can be executed from
the Engineering Panel. describes each fA mode of the standard
Antisurge Controller that is currently recommended for general use.
Appendix FS provides basic documentation of application functions
that are not recommended for general use. defines and references
various topics discussed in this manual. lists and describes the
default data items that the Series 3 Plus OPC Server provides for
this controller. lists this controllers Modbus coils, discrete
bits, and registers. describes the controllers Front-Panel operator
interface. describes the changes to each standard release of this
controller. lists the configuration and tuning parameters by key
sequence, organized by data group and page. lists the configuration
and tuning parameters by name, grouped according to the associated
controller feature.IM301 (6.1.3)
Glossary/Index DS301/D DS301/M DS301/O DS301/V FM301/C
FM301/L
Finally, the following supporting documents are included at the
back of this manual:
September 2005
4
Contents
Document ConventionsThe document title appears in the header of
each odd-numbered page, while the chapter or appendix title appears
in the header of even-numbered pages. Odd-page footers list the
document number and revision level [IM301 (6.1.3)], while even-page
footers provide the publication date (September 2005). Acronyms are
defined in the sections of this manual that discuss the
corresponding subjects, by placing them in parentheses following
the spelled-out terms they represent. As an example, a three-letter
acronym (TLA) is a way to represent a three-word subject by
combining and capitalizing the initial letters of those three
words. Most are also listed under Symbols and Acronyms on page 10.
Cross-references to other documents specify a section and chapter,
while cross-references between chapters of this document specify a
page number. References that do not specify a location are internal
to the chapter in which they appear. In computerized versions of
this manual, all such references are hot-linked to their target
locations and appear in green. Entries in the tables of contents,
illustration and table lists, and index are also hot-linked but are
not green. Attention may be drawn to information of special
importance by using this text styling or one of the following
structures:
Note: Caution: Warning!
Notes contain important information that needs to be emphasized.
Cautions contain instructions that, if not followed, could lead to
irreversible damage to equipment or loss of data. Warnings contain
instructions that, if not followed, could lead to personal injury.
The appearance of this electrical hazard warning symbol on CCC
equipment or the word Warning appearing in this manual indicates
dangerously-high voltages are present inside its enclosure. To
reduce the risk of fire or electrical shock, do not open the
enclosure or attempt to access areas where you are not instructed
to do so. Refer all servicing to qualified service personnel. The
appearance of this user caution symbol on CCC equipment or the word
Caution appearing in this manual indicates damage to the equipment
or injury to the operator could occur if operational procedures are
not followed. To reduce such risks, follow all procedures or steps
as instructed.
September 2005
IM301 (6.1.3)
Series 3 Plus Antisurge Controller
5
Table of ContentsDocument Scope . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . 3 Document
Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . 4 Table of Contents. . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . 5 List of
Figures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . 9 List of Tables . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Symbols and Acronyms . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . 10
Chapter 1
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . 15Applications . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. Major Features . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . Proximity to Surge Calculations .
. . . . . . . . . . . . . . . . . . . . . . . . . . Fallback
Strategies. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . Control Responses. . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . Limiting Control . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Loop Decoupling . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . Valve Sharing . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . Equivalent Flow
Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . Load Sharing . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . Operating States . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Automatic
or Manual Operation . . . . . . . . . . . . . . . . . . . . . . . .
. . . Redundant Controller Tracking . . . . . . . . . . . . . . . .
. . . . . . . . . . . Hardware Configurations . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . Analog and Discrete I/O .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Control Valve Features. . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . Serial Communication . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . Configuration and
Tuning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . 15 19 21 21 21 21 22 22 22 22 22 23 23 23 23 24 24 24 25 26 26
26 27 29 29 29 30 30 31 31 31 32 32 33 33
Chapter 2
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . 25Operator Interfaces . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Continuous Operation . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . Valve Position. . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . Valve Sharing
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . Surge Protection. . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . Pressure Limiting . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Performance Limiting . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . Load Sharing . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . Sequencing
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . Shutdown . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . Stop State. . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . Purge State. . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . Startup . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Manual Operation. . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . Initiating Manual . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . Restoring
Automatic . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . Manual Override. . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . .
September 2005
IM301 (6.1.3)
6
ContentsFault Indicators . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . .34 Tracking States . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . .36 Output Tracking . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . .36 Redundant Control. . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.36
Chapter 3
Input/Output Features . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . .37Hardware Options . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . .37 Disabling
Input Signals . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . .37 Analog Inputs. . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . .38
Analog-to-Digital Variables . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . .39 Transmitter Testing . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . .39 Signal
Variables. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . .39 Process Variables . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . .40 Measured
Variables. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . .40 Analog Outputs . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . .42 Output Loopback
Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . .42 Valve Position Test . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . .43 Discrete Inputs. . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. .44 Discrete Outputs . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . .45 Fault Relays. . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.45 External Alarms . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . .45 Serial Ports . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.48 ID Numbers . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . .49 Serial Communication Formats .
. . . . . . . . . . . . . . . . . . . . . . . . . . .49 Serial
Communication Errors. . . . . . . . . . . . . . . . . . . . . . . .
. . . . . .49 Modbus Configuration . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . .50
Chapter 4
Calculated Variables . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . .51Pressures . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
Temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . .51 Head . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. .52 Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . .52 Power . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . .53 Flow Rates. . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . .54 Reduced Flow . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . .54 Calculated Flow Measurement . . . . . . . . . . . . . .
. . . . . . . . . . . . . .54 Dual Flow Transmitters . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . .55 Control Valve
Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . .
.56 Discharge Flow Measurement . . . . . . . . . . . . . . . . . .
. . . . . . . . .57 Aftercooler Flow Measurement . . . . . . . . .
. . . . . . . . . . . . . . . . .57 Mass Flow Rates . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58
Compensating Pressure . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . .59 Compensating Temperature . . . . . . . . . . . .
. . . . . . . . . . . . . . . .59 Calculated Variable Displays. . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .60
Displayed Speed . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . .61 Displayed Flow . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . .61 Displayed
Net Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . .62
September 2005
IM301 (6.1.3)
Series 3 Plus Antisurge Controller
7
Chapter 5
Proximity to Surge . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . 63Application Function. . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Filtering. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . Characterizing Functions . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fixed-Geometry Compressors . . . . . . . . . . . . . . . . . . . .
. . . . . . Variable-Geometry Compressors . . . . . . . . . . . . .
. . . . . . . . . . . Fallback Strategies. . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . Default Output
Fallback . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . Minimum Flow Fallback . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . Compression Ratio Fallback . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . Sigma Fallback. . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . Speed Fallback. . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . Function 5 Fallback . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . Adjacent
Section Flow Fallback . . . . . . . . . . . . . . . . . . . . . . .
. . . . Valve-Sharing Fallback . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . Polytropic Head Fallback . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . 63 64 64 65 66
67 67 68 69 69 69 70 70 70 70 71 72 73 73 74 74 75 75 76 77 77 78
78 79 80 82 82 83 83 83
Chapter 6
Antisurge Control . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . 71Control Lines . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Surge Control Line . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . Recycle Trip Line . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . Safety On Line
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . Tight Shut-Off Line . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . Derivative Response . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Safety
On Response . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . Surge Detection . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . Surge Counters . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Antisurge
Control Response . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . PI and RT Signal Selection . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . General PI Algorithm . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . Dead Zone .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . Antisurge PI Response. . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . Recycle Trip Response . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . Pressure
Limiting . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . Pressure Limit Scaling . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . Auxiliary Limiting . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Performance Override . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . Loop Decoupling . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . .
September 2005
IM301 (6.1.3)
8
Contents
Chapter 7
Multi-Compressor Protection . . . . . . . . . . . . . . . . . .
. . . . . . . . . .85Multisection Compressors . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . .85 Equivalent Flow
Measurements. . . . . . . . . . . . . . . . . . . . . . . . . . .
.85 Reported Flow . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . .86 Upstream Section Flow Known . . . . .
. . . . . . . . . . . . . . . . . . . . .87 Downstream Section Flow
Known . . . . . . . . . . . . . . . . . . . . . . . .89 Valve
Sharing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . .91 Networked Compressors . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . .92 Primary Capacity
Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . .92 Load Balancing . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . .93 Recycle Balancing . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .94
Port 1 Balancing. . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .94 Port 2 Balancing. . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . .94 Cold-Recycle
Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . .95
Chapter 8
Output Variables . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . .97Intended Valve Position. . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .98 Valve
Flow Characterization . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . .98 Actuator Control Signal . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . .99 Valve Dead Band
Compensation. . . . . . . . . . . . . . . . . . . . . . . . . . .99
Output Clamps. . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . .100 Remote Low Output Clamp . . . . . . .
. . . . . . . . . . . . . . . . . . . . .100 Tight Shut Off
Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . .101 Output Reverse . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . .101 Output Tracking . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.102
Chapter 9
States and Transitions . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .103Operating State . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . .103
Operating State Request Signals . . . . . . . . . . . . . . . . . .
. . . . . . .103 Startup Configuration. . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . .104 Shutdown Configuration .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .104
Stop State . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . .104 Valve Sharing Shutdowns . . . . .
. . . . . . . . . . . . . . . . . . . . . . . .104 Manual Override
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . .105 Alternate Parameter Sets . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . .106 Redundant Tracking . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.106 Switching Conditions . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . .106
Appendix A Appendix B Appendix F Appendix FS
Configuration Parameters . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . .107 Controller Test Sequences . . . . . . . . .
. . . . . . . . . . . . . . . . . . . .139 Application Functions .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.151 fA Mode Supplement . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .193 Glossary/Index. . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . .213
September 2005
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Series 3 Plus Antisurge Controller
9
List of FiguresFigure 1-1 Figure 1-2 Figure 1-3 Figure 1-4
Figure 1-5 Figure 1-6 Figure 1-7 Figure 3-1 Figure 3-2 Figure 4-1
Figure 4-2 Figure 5-1 Figure 5-2 Figure 5-3 Figure 6-1 Figure 6-2
Figure 6-3 Figure 7-1 Figure 7-2 Figure 7-3 Figure 7-4 Figure 8-1
Figure 8-2 Figure 8-3 Dynamic compressors have at least two control
elements . . . . . . . . Basic compressor control system . . . . .
. . . . . . . . . . . . . . . . . . . . . . Multi-section
compressor with shared recycle valve . . . . . . . . . . . . .
Multi-section compressor with sidestreams . . . . . . . . . . . . .
. . . . . . . Simplified P&ID for compressors operating in
series . . . . . . . . . . . . . Simplified P&ID for
compressors operating in parallel . . . . . . . . . . . . Antisurge
Controller functional diagram . . . . . . . . . . . . . . . . . . .
. . . . 15 15 16 16 17 18 20
Analog input signal processing . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . 38 Communication with other controllers . .
. . . . . . . . . . . . . . . . . . . . . . 48 Using dual flow
transmitters . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . 55 Compensating Po for a suction control valve . . . . .
. . . . . . . . . . . . . 56 Defining the minimum safe flow as a
function of head. . . . . . . . . . . . 64 Proximity to surge for a
fixed-geometry compressor . . . . . . . . . . . . . 65 Proximity to
surge for a variable-geometry compressor. . . . . . . . . . . 66
Typical control lines for antisurge control responses . . . . . . .
. . . . . . 71 Dead-zone error (e) as a function of the DEViation .
. . . . . . . . . . . . . 78 Typical Recycle Trip response . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . 80 Imaginary
orifice coefficients and equivalent flow measurements . . .
Calculating equivalent flows when suction flow is measured. . . . .
. . Calculating equivalent flows when discharge flow is measured. .
. . . Setting Primary Capacity Control Thresholds . . . . . . . . .
. . . . . . . . . 85 88 90 92
Output transformations. . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . 97 Valve flow characterization . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 Valve
dead band compensation. . . . . . . . . . . . . . . . . . . . . . .
. . . . . . 99
List of TablesTable 2-1 Table 3-1 Table 3-2 Table 3-3 Table 3-4
Table 4-1 Table F-1 Operating states. . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . 30 Available
symbols for measured variable labels . . . . . . . . . . . . . . .
. Functions for OUT2 . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . Discrete input functions . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Discrete
output functions . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . 41 42 44 46
Available calculated variable readouts. . . . . . . . . . . . .
. . . . . . . . . . . 60 Analog inputs required by each fA Mode . .
. . . . . . . . . . . . . . . . . . . 151
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IM301 (6.1.3)
10
Contents
Symbols and AcronymsMany of the terms and phrases represented by
the following symbols and acronyms are defined in the
Glossary/Index (see page 213): p a A ACR ACS AD1 to AD8 b CCC CH1
to CH8 CPU CR1 to CR5 CRD CRI CRI CRLD CRP CRPC CRRT CRSO CRC CRIC
CV D1 to D7 DCS dev DEV DEV'September 2005
guide vane angle polytropic efficiency polytropic head exponent
mechanical power loss series load-sharing domain selection variable
Antisurge Control Response Actuator Control Signal
Analog-to-Digital variables width coefficient for margin of safety,
sometimes called Total b Compressor Controls Corporation analog
input CHannels Central Processing Unit Control Relays (discrete
outputs) Derivative Control Response accumulated Integral Control
Response Integral Control Response Loop-Decoupling Control Response
Proportional Control Response Primary Capacity Control Response
Recycle Trip Control Response Safety On Control Response Cyclic
Redundancy Checksum Cold-Recycle (flow) Indicating Controller
Control Variable or Check Valve Discrete Inputs Distributed Control
System distance between operating point and specified control line
distance between operating point and surge control line parallel
compressor load-balancing variableIM301 (6.1.3)
Series 3 Plus Antisurge ControllerdevRT devSL devSO devTS DO1 to
DO5 DPT e EEPROM ESD fA FIC FIOM FT FY GTIC Hp hr I/O I/P IRF IT
IVP jr J k L LD LED LSIC M N Ne distance between operating point
and Recycle Trip control line distance between operating point and
surge limit line distance between operating point and Safety On
control line distance between operating point and Tight Shutoff
control line Discrete Outputs (control relays) Differential
Pressure Transmitter error (control loop deviation) Electrically
Erasable Programmable Read-Only Memory Emergency ShutDown
Application Function Flow Indicating Controller Field Input/Output
Module Flow Transmitter Flow Transducer Gas Turbine (fuel)
Indicating Controller polytropic Head reduced polytropic head Input
and Output circuits Current-to-Pneumatic signal converter Intended
Recycle Flow Current Transmitter Intended Valve Position reduced
power consumption power consumption isentropic exponent series
compressor load-balancing variable Loop Decoupling Light Emitting
Diode
11
Load-Sharing Indicating Controller (slave Performance
Controller) Molecular weight, occasionally Motor rotational speed
(generally, the Number of revolutions per unit time) equivalent
speed
September 2005
IM301 (6.1.3)
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ContentsNe,s NO/NC OP OutF OUT1 and OUT2 P Pac Pc Pc Pd Pdh Pfe
Po Po,ac Po,c Po,d Po,r Po,s Po,ss Ps Pss PCB PI PIC PID P&ID
POC psi PT PV1 to PV8 Q equivalent speed relative to suction
temperature Normally-Open/Normally-Closed Operating Point Output
Failure analog OUTputs Pressure Aftercooler Pressure Compensating
Pressure for mass flows Pressure rise across a Compressor Discharge
Pressure Discharge Header Pressure Pressure at the flow measuring
element Pressure drop across an Orifice plate (flow measurement)
Flow measurement downstream from an aftercooler Calculated flow
measurement Discharge flow measurement Reported flow measurement
Suction flow measurement Sidestream flow measurement Suction
Pressure SideStream Pressure Printed Circuit Board
Proportional-Integral Pressure Indicating Controller
Proportional-Integral-Derivative Piping and Instrumentation Diagram
Performance Override Control pounds per square inch Pressure
Transmitter Process Variables volumetric flow
September 2005
IM301 (6.1.3)
Series 3 Plus Antisurge ControllerQd qr qr,d qr,s Qs R RAM Rc Rt
RCS rpm RT RTL RTM S Ss SCL SCM SCS SL SLL SM SO SOL SOM ST STIC
SV1 to SV8 T Tac Tc TdSeptember 2005
13
volumetric flow in discharge reduced volumetric flow reduced
volumetric flow in discharge reduced volumetric flow in suction
volumetric flow in Suction universal gas law constant Random Access
Memory Compression Ratio Temperature Ratio Redundant Control
Selector revolutions per minute Recycle Trip Recycle Trip Line
Recycle Trip Margin proximity to the surge control line (1 - DEV)
Slope of the operating point line relative to the surge limit line,
represents proximity to surge limit Surge Control Line Surge
Control Margin Station Control Signal Surge Limit Surge Limit Line
Safety Margin Safety On Safety On Line Safety On Margin Speed
Transmitter Steam Turbine (speed) Indicating Controller Signal
Variables Temperature AfterCooler Temperature Compensating
Temperature for mass flows Discharge TemperatureIM301 (6.1.3)
14
ContentsTs Tss TIC TSL TSM TT TTC U4 , U5 UIC UsrQ V Vac Vdc W
Wr X, Y Z ZT Suction Temperature SideStream Temperature Temperature
Indicating Controller Tight Shutoff Line Tight Shutoff Margin
Temperature Transmitter Total Train Control User-defined argument
variables for control line (f4 ) and general (f5 ) characterizing
functions Antisurge Controller (User-defined multi-variable
Indicating Controller) net mass flow rate Voltage
alternating-current Voltage direct-current Voltage mass flow rate,
also Watt recycle mass flow rate generic coordinates for a
compressor map, also the argument and result of a characterizing
function [Y = f(X)] compressibility, also linear (Z-axis) position
position Transmitter
September 2005
IM301 (6.1.3)
Series 3 Plus Antisurge ControllerIM301
15
Chapter 1
Series 3 Plus Antisurge Controlleruser manual
Overview
This chapter summarizes this controllers applications and
features.Blowoff Recycle Discharge Suction Suction Discharge
Figure 1-1
Dynamic compressors have at least two control elementsAs shown
in Figure 1-1, a centrifugal or axial compressor requires at least
two control loops, one to regulate its through flow and one to
regulate its antisurge (recycle or blow-off) flow.
Applications
FY
FT
PT
TT
TT
PT
PT
PIC
UIC
FY
PIC Performance Controller UIC Antisurge Controller
Figure 1-2
Basic compressor control systemIn a single-section compressor
application, an Antisurge Controller can be combined with a
Performance Controller to provide precise capacity control with
minimum recycle or blowoff whether the speed, geometry (guide vane
angle), gas composition, and inlet conditions are fixed or
variable. In the example shown above (Figure 1-2), the Performance
Controller regulates a constant speed compressors discharge
pressure by positioning a throttle valve in the suction line,
September 2005
IM301 (6.1.3)
16
Chapter 1: Overview
FT
PT
PT
FT
PT
PT
FY
UIC 1
Port 1
UIC 2
UIC1 Valve-Sharing Master Antisurge Controller UIC2
Valve-Sharing Companion Antisurge Controller
Figure 1-3
Multi-section compressor with shared recycle valvewhile the
Antisurge Controller opens the recycle valve just enough to prevent
surge. To adequately protect a multisection compressor, especially
one that has sidestreams, each section should be protected by its
own controller. Series 3 Plus Antisurge Controllers can protect
such a machine even when it has only one recycle or blowoff valve
(see Figure 1-3) or the flow through some sections cannot be
directly measured (see Figure 1-4).
FT
PT
PT
FT
PT
FT
PT
UIC 1
Port 1
UIC 2
Port 1
UIC 3
FY
FY
FY
Figure 1-4
Multi-section compressor with sidestreams
September 2005
IM301 (6.1.3)
Series 3 Plus Antisurge Controller
17
FY
FY
FT PT
TT PT
TT
FT PT
TT PT
TT
PT
SICPort 1
LSICPort 1
UIC
FY
SICPort 1
LSICPort 1
UIC
FY
PIC
Port 2
Port 2
LSIC Load-Sharing Controller SIC Speed Controller
PIC Station Pressure Controller UIC Antisurge Controller
Figure 1-5
Simplified P&ID for compressors operating in seriesWhen
several compressors are connected in series or in parallel to
achieve a higher flow rate or compression ratio, networks of
Antisurge and Performance Controllers can distribute the total load
and prevent surge with a minimum of recycling. In such systems (see
Figure 1-5 and Figure 1-6), each compressor or compressor section
is equipped with a dedicated Antisurge Controller. In a parallel
loadsharing application, Antisurge Controllers can also be used to
regulate the flow through a cold recycle loop. In all of these
applications, Antisurge Controllers can also provide limiting
control of their maximum discharge and minimum suction pressures.
If a recycle valve would also be the best control element for
another limiting variable, a Performance Controller can serve as an
auxiliary limiting control loop for an Antisurge Controller.
September 2005
IM301 (6.1.3)
18
Chapter 1: Overview
FY
FY FT
PT
TT
PT
TT
SIC
LSIC
UIC Port 1
FY
Port 2
Hot Recycle Cold Recycle
PT
TT FY
FY
PIC
TIC
Port 1
CRIC
Hot RecyclePort 2 Port 1 SIC LSIC UIC FY
FY
FY FT
PT
TT
PT
TT
CRIC Cold Recycle Controller LSIC Load-Sharing Controller PIC
Station Pressure Controller
SIC Fuel Controller TIC Temperature Controller UIC Antisurge
Controller
Figure 1-6
Simplified P&ID for compressors operating in parallel
September 2005
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Series 3 Plus Antisurge Controller
19
Major Features
This software revision (756-004) offers the following features:
Proximity to Surge Calculations that are invariant to changing
process conditions Fallback Strategies that can provide continued
protection when the analog and serial communication inputs required
by the chosen proximity-to-surge calculation fail Closed- and
open-loop Control Responses that collectively protect against
surge-induced compressor damage and process upsets without
sacrificing energy efficiency or system capacity Limiting Control
features that can increase the recycle or blowoff rate as needed to
maintain minimum suction and maximum discharge pressures and to
help regulate a Performance Controllers capacity or performance
override control variable Loop Decoupling that minimizes adverse
interactions between a compressors capacity and antisurge control
loops Valve Sharing and Equivalent Flow Calculations for
multisection or series compressor applications Load Sharing for
compressors operating in series or in parallel Operating States
that protect the compressor while it is running or stopped and
during startups and shutdowns Automatic or Manual Operation from
the Front Panel or a host computer or control system Redundant
Controller Tracking that allows one Antisurge Controller to serve
as an on-line backup to another Basic or Extended I/O Hardware
Configurations Analog and Discrete I/O ports that can be assigned
functions appropriate to each application Control Valve Features
that adapt the analog output to virtually any recycle valve, allow
either that signal or its low clamp to track an analog input, and
test its accuracy Serial Communication with companion Series 3 Plus
Controllers, operator workstations, and Modbus host systems
Configuration and Tuning from either the Engineering Panel (from
which three alternate parameter sets can be stored and recalled) or
from a computer workstation Please refer to the Series 3 Plus
Antisurge Controller Revision History [DS301/V] for information
about previous revisions.
September 2005
IM301 (6.1.3)
20
Chapter 1: OverviewAnalog Inputs
Calculated and Process Variables Pd Ps
Application Function (fA Mode) Ss
Safety On Surge Detector n b2
SP2
SP3 f4(X) 1S DEV Dead Zone e2 e3 e1 S dSs /dt b
b1
b3 Td0 dSs /dt Derivative Response Recycle Trip Response
Valve-Sharing
PI Algorithm
Valve-Sharing and Performance Override PIs Loop Decoupling
Interacting PIDs & RTsACR (IRF)
RTs Primary Capacity Control Station Controller Control Signal
Parallel ACSs Recycle Balancing
Valve Flow Characterizer IVP Remote Low Output Clamp Valve Dead
Band Compensation
Output Clamps
Manual
Tight Shut Off
Output Reverse
OUT Readout
Output Tracking
or ACS
Figure 1-7
Antisurge Controller functional diagram
September 2005
IM301 (6.1.3)
Series 3 Plus Antisurge Controller
21
Proximity to Surge Calculations
In order to prevent surge with a minimum of recycling, a
controller must accurately determine how close the compressor is
operating to its surge limit. But that distance is not something
that can be directly measured. Instead, it is a function of
compression ratio, flow rate, rotational speed, guide vane angle,
and gas pressure, temperature, and composition. The Antisurge
Controller can use a variety of functions to calculate proximity to
surge, each of which embodies a different set of simplifying
assumptions to define a coordinate system in which the surge limit
is invariant to process changes (see Calculated Variables on page
51, Application Function on page 63, and Appendix F).
Fallback Strategies
The Antisurge Controller also offers numerous fallback
strategies for calculating proximity to surge when analog input or
serial port failures preclude using the selected fA mode. This
enables it to provide continued compressor protection until the
failed inputs can be restored (see Fallback Strategies on page 67).
The Antisurge Controller employs a unique combination of control
responses that can prevent surge without needlessly upsetting your
process or requiring a large, energy-wasting surge control margin:
A proportional-integral response protects the compressor from
small, slow disturbances when it is moving toward surge and closes
the antisurge valve when the machine is moving away from its surge
limit (see Antisurge PI Response on page 79). Fast disturbances are
countered by temporarily raising the surge control margin when the
compressor is moving rapidly toward its surge limit, which will
increase the recycle rate only when operating close to that limit
(see Derivative Response on page 74). If the combined PI and
derivative responses fail to maintain an adequate margin of safety,
an open-loop response ratchets the control valve open to provide
the rapid increase in flow needed to prevent surge (see Recycle
Trip Response on page 80). Finally, if unanticipated circumstances
do produce a surge, the surge control margin is permanently
increased, which quickly stops the surging and prevents its
reoccurrence (see Safety On Response on page 75).
Control Responses
Limiting Control
The recycle rate can be increased as needed to limit the
discharge and suction pressures (see Pressure Limiting on page 82).
If there are other process constraints that can be satisfied by
opening the antisurge valve, additional limiting loops can be
implemented using companion Performance Controllers (see Auxiliary
Limiting on page 83 and Performance Override on page 83).
September 2005
IM301 (6.1.3)
22
Chapter 1: Overview
Loop Decoupling
The controller can counter the potentially destabilizing effects
that can result from interactions between the various control loops
regulating a single compressor by adjusting its control signal in
response to changes in the control responses of companion
controllers (see Loop Decoupling on page 83). When a multisection
compressor (or group of compressors operating in series) has only
one recycle or blowoff valve, you should still install a dedicated
Antisurge Controller for each section. The controller that actually
manipulates the recycle valve can then keep it open enough to
protect whichever section is closest to its surge limit (see Valve
Sharing on page 91). When the flow through one section of a
compressor (or group of compressors operating in series) cannot be
measured, its Antisurge Controller can calculate proximity to surge
by combining a sidestream or recycle flow measurement with the flow
reported by a companion controller protecting an adjacent
compressor section (see Equivalent Flow Measurements on page 85).
Networks of Performance and Antisurge Controllers can be used to
regulate and protect a group of compressors operating in series or
in parallel. Such control systems: vary the compressors performance
and recycle rates as needed to regulate the Station Controllers
capacity control variable (see Primary Capacity Control on page
92); raise the recycle rates to limit the station performance
override variable (see Performance Override on page 83); and
prevent any compressor from recycling until all are operating at
their surge limits, and balance their loads when operating at a
distance from those limits (see Load Balancing on page 93). For
parallel compressor systems, the Antisurge Controllers can also
equalize the recycle rates (see Recycle Balancing on page 94) and a
dedicated Antisurge Controller can regulate the flow through a
common recycle cooler (see Cold-Recycle Control on page 95).
Valve Sharing
Equivalent Flow Calculations
Load Sharing
Operating States
Compressor startups and shutdowns are sequenced primarily by the
Performance Controller. The Antisurge Controller participates by
holding its control valve in a position that minimizes the risk of
surge (see Operating State on page 103): The compressors status can
be monitored via flow, pressure, and/or speed inputs or by a
companion controller. When a shutdown is initiated or detected, the
Antisurge Controller can either ramp the recycle valve open or open
it as quickly
September 2005
IM301 (6.1.3)
Series 3 Plus Antisurge Controller
23
as possible. It will then hold that valve fully open as long as
the compressor is stopped, in order to minimize the possibility of
back flow and reverse rotation. It can also fully close the recycle
valve so purge gas can be forced through the compressor. When a
startup is initiated or detected, the Antisurge Controllers normal
operation will slowly close its control valve to a position that
minimizes recycle flow as efficiently as possible.
Automatic or Manual Operation
Because the Antisurge Controller is an automatic protective
device, its operation requires little (if any) operator
intervention. However, both its status and your process can be
monitored using various Front Panel, computer control, and
input/output features (see Continuous Operation on page 26). In
addition, the recycle valve position can be directly controlled
from the Front Panel or by a Modbus host (see Manual Operation on
page 32). Dual redundancy (that is, one-to-one fault tolerance) is
a standard feature of most Series 3 Plus Controllers. This means
you can install one Antisurge Controller as an on-line hot backup
to another, ready to take over instantly if the first should fail.
In a typical application (see Redundant Control on page 36), the
two controllers are interconnected via a Redundant Control Selector
(RCS) that connects the control element to the primary controller.
The backup controller then tracks (that is, monitors and
duplicates) the operating state and control response of the primary
controller via the Port 1 serial communications link. If that
controllers fault relay de-energizes, the system bumplessly
transfers control of your process to the back-up unit.
Redundant Controller Tracking
Hardware Congurations
The Antisurge Controller can use either of two compressor
controller configurations (see Hardware Options on page 37). The
basic configuration provides back-panel terminals for its I/O
circuits, while the extended I/O option uses external wiring
modules. Each of the eight analog inputs (see Analog Inputs on page
38) is tested by comparing it to individually-defined alarm limits.
Although the inputs for most features are fixed, some can use any
appropriate or otherwise unused channels. Analog OUT1 is usually
used to position a recycle or blow-off valve, while OUT2 can drive
a remote display for a user-selected variable (see Analog Outputs
on page 42). One or two of the five control relays can be set up to
signal hardware and self-test failures, the others can be assigned
a variety of controller and process conditions (see Discrete
Outputs on page 45 and Fault Relays on page 45). In contrast, the
functions of the seven
Analog and Discrete I/O
September 2005
IM301 (6.1.3)
24
Chapter 1: Overviewdiscrete inputs (see Discrete Inputs on page
44) are predefined and cannot be changed.
Control Valve Features
The actuator control signal can be clamped, adapted to a direct
or reverse, linear, quick-opening, or equal-percentage valve, and
compensated for a deadband or low-flow leakage (see Output
Variables on page 97). The controller can also detect an excessive
deviation of the actuator control signal from its intended value
(see Output Loopback Test on page 42) or of the recycle valve from
its intended position (see Valve Position Test on page 43). The
Antisurge Controller also offers low and absolute signal select
algorithms for sharing control of the recycle valve with another
device (see Remote Low Output Clamp on page 100 and Output Tracking
on page 102).
Serial Communication
All Series 3 Plus Controllers have four Serial Ports (see page
48): Ports 1 and 2 are used to coordinate their actions with other
CCC controllers (see Limiting Control, Loop Decoupling, Equivalent
Flow Calculations, Valve Sharing, Load Sharing, Operating States,
and Redundant Controller Tracking). Ports 3 and 4 are used for
computer communication and control (see Continuous Operation on
page 26 and the Series 3 Plus Antisurge Controller Modbus Data
Sheet [DS301/M]) using Modbus RTU commands. This allows a host
control system or a computer running controller support software
(such as our COMMAND system) to monitor or even control the
operation of your compressor. Some of our support programs can also
change the configuration and tuning of the controller. Each
Antisurge Controller is adapted to its specific application by
assigning values to its configuration and tuning parameters (see
Appendix A). This can be done from the Engineering Panel or a
computer running one of our configuration programs. If your
application requires routine changes to a controllers configuration
or tuning, up to three sets of alternate parameter values can be
stored. Engineering Panel procedures are provided for defining
these alternate sets, determining which one is in use, and
switching to a different one (see Alternate Parameter Sets on page
106).
Conguration and Tuning
September 2005
IM301 (6.1.3)
Series 3 Plus Antisurge ControllerIM301
25
Chapter 2Operator Interfaces
Series 3 Plus Antisurge Controlleruser manual
Operation
This chapter describes the operation of the Antisurge
Controller. This section summarizes the features that can be
operated via the controllers front-panel, remote control, and
Modbus interfaces. The front-panel keys, LEDs, and readouts can be
used to select automatic or manual operation, monitor its antisurge
and limiting control loops, display and clear the surge count, and
display various internal and process variables, as described in the
Series 3 Plus Antisurge Controller Operator Interface Description
[DS301/O]. The controllers remote control inputs and outputs are
primarily for integration with other devices, although they could
also be used to implement a limited remote control panel. Discrete
Inputs (see page 44) can be used to select the operating state, to
trigger output tracking, or to clear the surge count. Discrete
Outputs (see page 45) can be connected to external alarms and
indicators for various operating conditions. Process variable
Analog Inputs (see page 38) can be monitored directly, while some
internal variables can be monitored via Analog Outputs (see page
42). The Modbus interface can be used to select automatic or manual
operation, monitor the antisurge and limiting control loops,
monitor and clear the surge count, change a limited number of
configuration parameters, and monitor various internal and process
variables, as described in the Series 3 Plus Antisurge Controller
Modbus Data Sheet [DS301/M].
Note:
Because all three interfaces are always active, the compressor
can be monitored and controlled using any combination of their
features.
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Chapter 2: Operation
Continuous Operation
When operating automatically in its Run state, the controller
varies the Valve Position to satisfy its Surge Protection, Pressure
Limiting, Performance Limiting, and Load Sharing objectives.
Because little intervention is needed, the Operator Interfaces
serve primarily as a means of monitoring its operation (and that of
the compressor). This state is selected whenever specified inputs
(usually speed, flow, and pressure) indicate the unit is running,
the controllers own D2 and D6 inputs are cleared, and a companion
controller (if one is designated) is also operating in its Run
state. The AUXiliary readout will then display the operating state
as Status RUN and any Run relays and the Modbus Run discrete bit
will be set.
Valve Position
The position of the recycle valve can be monitored via the OUT
readout, Modbus Displayed OUT register, or analog output OUT1. The
Modbus High Clamp or Low Clamp discrete bit will be set if the
control response equals the corresponding clamp, and any Valve Open
relays will be set if that response exceeds its low clamp. If an
analog Remote Low Output Clamp (see page 100) has been set up, the
Tracking LED will flash whenever that input exceeds the low clamp
parameter, regardless of the control response value. A group of
Antisurge Controllers protecting the same multi-section compressor
can use serial communications to share a single recycle or blow-off
valve (see Valve Sharing on page 91). The controller that directly
manipulates that valve is then referred to as the valve-sharing
master, while the rest are called valve-sharing companions. The OUT
readout of a valve-sharing companion is always blank, and its
actuator control signal (ACS) cannot be manipulated manually or by
a Modbus host. However, its Modbus Displayed OUT input register
will track the master controllers ACS. This feature can also be
applied to compressors that operate in series with a common recycle
or blow-off valve. In that case, some of their compressors might be
loaded while others are stopped or idled. The master will modulate
that valve as required to protect the compressors whose controllers
are operating in the Run state. If its own compressor is unloaded
but one or more others are not, it will operate in the Run state
but will display it as Status OFF.
Valve Sharing
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Surge Protection
The DEViation between the compressors operating point and the
controllers surge control line (SCL, see Chapter 5) can be
monitored via the DEV readout, DEViation register, or analog OUT2:
If DEV is at or near zero, the compressor is operating close to or
on its SCL. If a non-zero Dead Zone (see page 78) has been defined,
OUT should remain steady. Otherwise, it will vary as needed to keep
the operating point exactly on that line. When DEV is positive, the
compressor is operating to the right of its SCL. If the recycle
valve is not fully closed, the Antisurge PI Response (see page 79)
will gradually close it. If DEV becomes negative, the compressor is
operating to the left of the SCL, where the distance between the
operating point and surge limit is less than desired. As long as it
does not get too close to the actual surge limit, the controller
will rely on its PI algorithm to raise the margin of safety back to
the desired level. The distance between the SCL and the actual
surge limit depends on the rate at which the compressor is
approaching its surge limit (see Derivative Response on page 74)
and the number of times it has surged (see Safety On Response on
page 75). It can be displayed on the front-panel AUX readout by
pressing the SCROLL key to scroll from the STATUS display to the
Total B= ##.# variable, where ##.# is the distance between the SCL
and SLL in percent. The controllers analog inputs can be monitored
via the front-panel AUXiliary readout Measured Variables menu or
Modbus Channel # registers. Additional process conditions
calculated by the selected proximity-to-surge algorithm can be
monitored via the Calculated Variables menu and various Modbus
registers (for example, the Pressure Ratio, Temperature Ratio, and
Sigma). A continuing or sudden drop in the DEViation will trigger
the Recycle Trip Response (see page 80). The yellow RT LED will
then light and any RT relays and the Modbus Recycle Trip discrete
bit will be set while the controller ratchets open the antisurge
valve. Once a minimum safe DEViation is restored, the RT relays and
discrete will be cleared, the RT LED will go out (after a fixed
delay), and the RT response will decay to zero. A Recycle Trip
action should not be viewed as a cause for alarm, it simply means
the compressor is operating close enough to its surge limit to
justify aggressively increasing the recycle rate. By allowing your
compressor to safely operate that close to its surge limit, this
feature actually saves you money by reducing recycling costs. If
for some reason the compressor actually goes into surge, the
controller will detect the characteristic rapid fluctuations of
head and/or flow and trigger its Safety On Response (see page 75).
The red SO indicator will then light and any SO relays and the
Modbus Safety
Note:
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Chapter 2: OperationOn discrete and coil bits will be set to
indicate the surge control margin has been increased to prevent
additional surges from occurring. Each detected surge increments
the cumulative and event Surge Counters (see page 76) and triggers
a further increase in the surge control margin. The cumulative
count can be displayed in the ALT readout by pressing DISPLAY SURGE
COUNT, and can also be monitored via the Surge Count register. Any
Surge Event relays are set if the event count reaches a
user-defined threshold within a specified period of time (if not,
that count is automatically reset). If a Safety On condition is
indicated, you should determine why that response was tripped and
whether or not the controller needs to be reconfigured to provide a
larger, permanent margin of safety. Once that determination and any
needed reconfiguration are completed, you can reset the surge
counts to zero and restore the initial surge control margin by
pressing the RESET SAFETY ON key, asserting discrete input D5, or
clearing the Modbus Safety On coil.
Warning!
Do not reset the Safety On response until the cause of any
surging has been determined and corrected. In a system with
multiple control elements, the actions of any controller can affect
the control variables of the others. To minimize such destabilizing
loop interactions, Antisurge Controllers monitor changes in the
control responses of specified companions and adjust their own
output signals to keep their compressors operating at the same
distance from surge.
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Pressure Limiting
If either the discharge pressure is too high or its suction
pressure is too low (or both), and any Limit relays and the Modbus
Limit discrete bit will be set. The controller will then increase
the recycle rate (see Pressure Limiting on page 82), which should
raise the suction and lower the discharge pressure. The yellow
Limit LED will light if the limiting loop opens the recycle valve
faster than the surge protection features otherwise would. If you
press the DISPLAY LIMIT key, the AUX readout will identify the
out-of-range pressure, the DEV readout will display its value, and
the ALT readout will display its set point. You can also monitor
those pressures via the corresponding Modbus Channel # registers,
while the parameters that define their set points can be monitored
and even changed via the Pd Limit and Ps Limit holding
registers.
Performance Limiting
An Antisurge Controller can be configured to help a companion
Performance Controller counter excessive deviations of its
performance override control variable by increasing the recycle or
blow-off flow (see Performance Override in Chapter 6). At such
times, the frontpanel ALT readout displays the POC acronym and the
Modbus POC Active discrete bit is set. In a Series 3 Plus Control
System for multiple compressors operating in series or in parallel,
a Station (master Performance) Controller regulates a header
pressure or flow by indirectly manipulating the throttle and
antisurge control elements of the individual compressors (as
described in the Station Controller section in Chapter 2 of IM302).
In such a system, each Antisurge Controller will increase the
recycle rate of its compressor (which will reduce the discharge
header pressure and flow) when its operating point is already near
or on its surge control line and less throughput is needed (which
would move the compressor even closer to surge). Under any other
conditions, changes in the compressor networks throughput are
achieved by manipulating the control elements of the Load-Sharing
Performance Controllers.
Load Sharing
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Chapter 2: Operation
Sequencing Operation
The loading and unloading of a compressor is sequenced primarily
by its Performance Controller (see Chapter 2 of IM302). Startups
and shutdowns are usually sequenced by the controller for the
compressors driver. Provided neither output nor redundant
controller tracking is active (see Tracking States), an Antisurge
Controller will participate mainly by selecting an appropriate
operating state (see Table 2-1): While its machine is loaded, an
Antisurge Controller operates in its Run state (see Continuous
Operation), which modulates the recycle valve to prevent surge with
minimal recycling. When a Shutdown is initiated, the recycle valve
is either ramped open or opened as fast as possible. While its
machine is stopped or idling, an Antisurge Controller operates its
Stop State, which holds the recycle valve fully open. If the purge
input is then asserted, the controller selects its Purge State,
which holds the recycle valve fully closed. When a Startup is
initiated, the controller simply selects its Run state. Its PI loop
will then slowly close the recycle valve.
Shutdown
An Antisurge Controller can be set up to open the recycle valve
to its high clamp position (see Operating State on page 103) when
the compressor is idled or shut down: An emergency shutdown
immediately opens that valve. A normal shutdown usually ramps it
open, although it can be configured to open it immediately and will
always do so if the operating point moves to the left of the
RTL.
Table 2-1
Operating statesName DisplayRUN Run OFF STOP Stop ESD Purge
Track PURGE TRACK
DescriptionThe compressor is loaded and the control response is
being varied to prevent surge. This compressor section is unloaded
but the valve is being modulated to protect another. A normal
shutdown was or is being used to idle or shut down the compressor.
An emergency shutdown was used to idle or shut down the compressor.
The compressor is unloaded but the recycle valve is fully closed.
Actuator control signal is tracking the output of another device or
controller.
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In either case, any Run relays and the Modbus Run discrete are
immediately cleared, the operating state display changes to Status
STOP or Status ESD, and the Surge Counters (see page 76) are reset
to zero (if so configured). An ESD can be triggered only by this
controllers own D2 discrete input. A normal shutdown can be
triggered by its own D6 discrete input, by the stop or shutdown
sequence of a companion controller, or by a process condition that
indicates the compressor is being stopped or idled (abnormally low
flow, head, or rotational speed).
Stop State
While its compressor is stopped or idling, an Antisurge
Controller will operate in its Stop state with all Run indicators
cleared. It then holds the recycle valve fully open: If the
compressor is idling, this minimizes the drive power and risk of
surge. The displayed DEViation should show a positive value perhaps
as great as .A24 (1.024). If the compressor is stopped, this
minimizes any reverse flow or rotation that might occur if the
discharge check valve leaks. The DEViation display will be
unpredictable and perhaps erratic, but can be safely ignored (a
stopped compressor cannot surge). The operating status will display
as STOP or ESD, depending on how this state was selected. Manual
Operation can be initiated only if its selection while operating in
this state is enabled.
Purge State
If the controller is operating in its Stop state, asserting
either its own D3 discrete input or that of a designated companion
controller will select the Purge state. This sets the actuator
control signal to zero (100 percent for a signal-to-close valve),
thus completely closing the recycle valve. Purge gas can then be
forced through the compressor instead of bypassing it through the
recycle line. The AUXilliary readout will display this operating
state as Status PURGE. Requesting the Purge state while the
compressor is idling not only leaves the unit unprotected but might
even trigger a surge. An Antisurge Controller operating in its Stop
state will automatically switch to the Run state if its D2 and D6
discrete inputs are cleared, the designated companion controller
(if any) selects its Run state or initiates its startup sequence,
and the head, flow, and speed exceed user-defined minimums (thus
indicating the compressor is running). This immediately sets any
Run relays and the Modbus Run discrete bit and changes the
operating state display to Status RUN. The PI response will then
gradually reduce the recycle flow as far as surge protection and
process limiting conditions permit.
Warning!Startup
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Chapter 2: Operation
Manual Operation
When manual operation is selected, momentarily pressing the
Raise or Lower key will change the actuator control signal by 0.1
percent, holding either down changes it at a steadily increasing
rate. The resulting value can be monitored via the OUT readout, an
analog output assigned the Out function, or the Displayed OUT input
register. Alternately, the control signal can be set directly by
writing to the Actuator CS holding register. Although the Output
Clamps (see page 100) do not apply in manual, the Remote Low Output
Clamp (see page 100) does. Thus, you can raise the control signal
above the high or reduce it below the low clamp parameter, but
cannot reduce it below an analog low clamp. While in manual, the
controller will continue to calculate and display the deviation
between the operating point and the surge control limit, so you can
tell if you are moving the compressor too close to surge by
watching the DEV readout. If you inadvertently move the operating
point to the left of the Recycle Trip line, the RT LED lights and
the controller reverts to automatic operation. It will then remain
in automatic even after an adequate safety margin is restored. The
controller will also continue to monitor its operating state inputs
and the AUXiliary readout will continue to display the selected
state (for example, Status RUN). If those inputs dictate a transfer
out of the Run state, the controller will revert to automatic.
However, you can then switch back to manual by pressing the
AUTO/MAN key, provided manual operation in the newly selected state
is enabled. Although Pressure Limiting is suspended during manual
operation, the Limit LED and any Limit relays will continue to
indicate whether or not the suction and discharge pressures are
within their respective limits, and you can still use the DISPLAY
LIMIT key to display these control variables and their set
points.
Initiating Manual
Manual operation can be selected at any time unless the
controller is operating in its Stop or Purge state and manual
operation in those states has not been enabled (see Manual
Override). However: If manual operation and Output Tracking are
both selected, the remote device will control the output signal. In
a Redundant Control system, only the active controller can be
manually operated (the backup will track that selection). Manual is
initiated by pressing the AUTO/MAN key or clearing the Modbus
Automatic coil. The Manual LED then lights and the Auto LED, any
Auto relays, and the Automatic coil and discrete bit all clear.
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Restoring Automatic
Pressing the AUTO/MAN key while in manual or setting the Modbus
Automatic coil initiates a bumpless return to automatic control.
The Manual LED then clears and the Auto LED, any Auto relays, and
the Automatic coil and discrete bit all set. This action will not
change the actuator control signal unless it is above its high
clamp or below its low clamp, in which case it will jump back to
that clamp. In addition, the Valve Dead Band Compensation (see page
99) feature will remember which direction the operator last moved
the output while in manual and resume operation accordingly.
Manual Override
To prevent surge while the controller is in manual, it will
revert to automatic if the operating point moves to the left of the
Recycle Trip control line (RTL). However, you can enable an
override of this behavior (see Manual Override on page 105), in
which case the controller will remain in manual until the operator
restores automatic operation (even if the compressor surges). To
indicate this danger, the front-panel Man LED will flash and any
relays assigned the MOR function will trip, regardless of the
DEViation, whenever manual is selected while that override is
enabled. If the operating point then moves to the left of the RTL,
the RT LED will light and remain on until an adequate safety margin
is manually restored. We advise you not to permanently enable the
Manual Override parameter, because it disables all surge protection
while in manual. If the Manual Override is enabled, the controller
will also remain in manual when the operating state inputs dictate
a transfer out of the Run state and manual operation can be
initiated even when the Stop or Purge state is selected. When
manually operating the controller via its Modbus interface, you can
determine whether or not Manual Override is enabled by reading the
Manual Override coil or discrete, and can enable and disable this
feature by setting and clearing that coil. If the Manual Override
is disabled (as recommended), the Manual While Stopped parameter
determines whether or not manual can be initiated while the
Antisurge Controller is in its Stop or Purge state.
Caution:
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Chapter 2: OperationIn addition to a General Fault, which would
be indicated via the Fault LED and relays, the Antisurge Controller
can use front-panel LEDs, assignable relays, and Modbus discrete
bits to indicate Serial Communication Errors, Analog Input or
Transmitter Failures, Output Failures, and Valve Position Failures.
It will also indicate a Fallback Condition if analog or serial
failures prevent it from calculating the selected
proximity-to-surge function. Each Series 3 Plus Controller has a
watchdog circuit that must be regularly reset by its control
program. If it does time out, it will deenergize the fault relay
and reset the CPU chip, thus causing the control program to
restart: If that restart succeeds, it will reset the timer, clear
the relay, and temporarily set the Modbus Reset discrete. The
Engineering Panel will beep and display Reset. If it fails, the
fault relay will remain de-energized and the Front Panel will light
its Fault LED (and turn the other thirteen off). This can indicate
either a software error or a hardware problem that prevents the
control program from running. If the fault relay has also been
assigned a second function (see Fault Relays on page 45), that
condition will not light the Fault LED. If that assigned function
is one that has its own LED, you can tell why the fault relay has
tripped by looking at the Front Panel.
Fault Indicators
General Fault
Caution:Serial Communication Errors
The controllers output signal is totally unpredictable when a
watchdog fault is indicated. Process disruptions or compressor
damage can result if it is not immediately disconnected from your
process. When the controller fails to detect expected serial
transmissions, it will light the ComErr LED and set any Serial
Communication Error (SerC) relays and the Modbus Port 1 Fail or
Port 2 Fail discrete (see Serial Communication Errors on page 49).
Because the exact meaning of these conditions depends on which
features have been enabled, their interpretation will be highly
site specific. Loss of Port 2 communications will disrupt
load-sharing and performance override control. A Port 1 serial
error can also disrupt those features, as well as loop decoupling,
multi-section compressor surge protection and valve sharing,
automatic sequencing and operating state selection, and redundant
control.
Analog Input or Transmitter Failures
Whenever one or more analog inputs is beyond its valid range,
the controller lights its TranFail LED and sets any Transmitter
Failure (Tran) relays and the Modbus Tran Fail discrete (see
Transmitter Testing on page 39). This condition usually indicates a
failure in the input loop (transmitter, signal wire, and Analog PCB
circuit), but might also be used to alarm undesirable process
conditions.
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If the controller detects a difference of more than five percent
between the intended and loopback values of the control signal (see
Output Loopback Test on page 42), it will set any Output Failure
(OutF) relays and the corresponding Modbus DO State discrete (there
is no dedicated bit nor front-panel LED for this condition). This
condition may indicate miscalibration of the input or output
circuitry, breaks or poor connections in the wiring between the
input, output and final control element, or actual failure of the
Analog PCB Assembly. It could be caused by failures in the
loop-back circuitry only the actual output signal may in fact have
the intended value. Even a genuine output signal miscalibration
might not be critical. The controllers integral action can often
overcome such a discrepancy, provided it is constant. However, such
problems can prevent the controller from fully opening or closing
the final control element.
Valve Position Failures
If the measured recycle valve position deviates significantly
from its intended value (see Valve Position Test on page 43), the
controller will set any Position Failure (PosF) relays and the
corresponding Modbus DO State discrete (there is no dedicated bit
nor front-panel LED for this condition). Although this condition
would be triggered by a malfunctioning valve positioner or position
transmitter, it might also indicate miscalibration or failure of
the input or output circuitry, breaks or poor connections in the
actuator control or position input loop, or a failure of the Analog
PCB Assembly.
Fallback Condition
If the controller is unable to calculate the selected
proximity-to-surge function due to an analog input or serial
communication failure, it will light its Fallback LED, set its
Modbus Fallback discrete, and switch to a simpler function,
maintain a minimum flow, or hold its output steady (see Fallback
Strategies on page 67). In the latter case, the Auto LED will flash
to indicate the controller is operating automatically but is
holding its actuator control signal steady.
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Chapter 2: OperationThe Antisurge Controller includes two
features that allow an external device to manipulate its actuator
control signal (ACS): When Output Tracking is active, the ACS
tracks an analog signal from a remote device. When Redundant
Control is active, it tracks the ACS of another Series 3 Plus
Antisurge Controller. If either feature is active, the operating
state will display as Status TRACK and the Tracking LED will either
light (redundant tracking) or flash (output tracking). Because they
are triggered by discrete inputs that can be monitored directly,
there are no relay functions that indicate either of these states.
A Modbus host can detect them by monitoring the corresponding DI
Condition discretes, and the Tracking discrete is set by redundant
but not output tracking.
Tracking States
Output Tracking
The Antisurge Controller can be set up as a signal selector for
its final control element (see Output Tracking on page 102), in
which case the actuator control signal is kept equal to a
designated analog input signal whenever discrete input D4 is
asserted. The Auto and Manual LEDs, relays, and bits will indicate
which mode the controller will return to when D4 is cleared, and
you can change that selection by pressing the AUTO/MAN key or
forcing the Automatic coil. In either case, the transfer will be
bumpless.
Redundant Control
If one Antisurge Controller has been installed as an on-line hot
backup to another (see Redundant Tracking on page 106), it will use
serial communications to track the outputs and states of that
active controller whenever its own D1 discrete input is cleared. In
a typical redundant system, each pair of Antisurge Controllers is
interconnected via a Redundant Control Selector (RCS) that monitors
their fault relays, controls their D1 inputs, and connects the
valve actuator to the selected controllers analog output. If the
main controllers fault relay de-energizes, the RCS automatically
transfers control of the recycle valve to the backup controller
(provided that it has not faulted as well). That controller then
initiates control beginning from the last conditions received from
the main controller. The RCS also indicates which controller is
active by lighting its green MAIN or red BACK-UP LED, and you can
manually select the active controller by pressing the Switch to
Back-Up or Switch to Main push-button. The RCS will not
automatically return control of your process to the main controller
after a fault is cleared (this must be done manually) and will
never automatically or manually transfer control to a controller
that appears to have failed.
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Chapter 3
Series 3 Plus Antisurge Controlleruser manual
Input/Output Features
This chapter tells how to configure the analog and discrete
inputs and outputs and serial communication ports.
Hardware Options
The Antisurge Controller uses either the Basic Compressor
Controller (BCC) or Extended Compressor Controller (ECC) hardware
configuration, as described in the Components and Configurations
section in Chapter 1 of IM300/H. Either provides the following
input and output circuits: eight Analog Inputs (CH1 to CH8), two
standard Analog Outputs (OUT1 and OUT2), seven Discrete Inputs (D1
to D7), five Discrete Outputs (CR1 to CR5), and four Serial Ports
(Port 1 to Port 4). When the ECC configuration is used, all I/O
terminals are provided on a separately mounted Field Input/Output
Module (FIOM), which is connected to an Extended I/O Back Panel by
a High-Density Interconnect Cable (HDIC).
Note:Disabling Input Signals
The availability of the discontinued FIOM cannot be guaranteed.
As an aid to developing and demonstrating Series 3 Plus Antisurge
Controllers, they include a CPU Inputs Lockout [MODE:D LOCK 6]
parameter that, when enabled, configures the controller to ignore
its analog and discrete inputs (which can then be updated via the
Port 3 or Port 4 Modbus serial link). An installed controller
should not be operated with LOCK 6 enabled, as that would prevent
it from receiving needed input signals.
Caution:
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Chapter 3: Input/Output FeaturesAN IN OFF(e.g., 0 to 10 V)CH
(V)
AN IN ON(e.g., 4 to 20 mA)CH (mA)
Sampling Hardware Failed if: < AN IN LOW > AN IN HIGH TEST
4 Failed if: < AN IN LOW > AN IN HIGH TEST 4
Sampling Hardware
AD (%)
AD (%)
SV = AD
SV = 1.25 (AD - 20%)
SV (%)
SV (%)
SV (%)
SV (%)
MV = Min + (Span SV)
PV = Bias + (SV Gain)
MV = Min + (Span SV)
PV = Bias + (SV Gain)
MV
PV (%)
MV
PV (%)
Figure 3-1
Analog input signal processingEach Series 3 Plus Controller is
equipped with eight analog inputs. As described in the Analog Input
Installation section in Chapter 6 of IM300/H, they are set up as
either 0 to 5 Vdc or 4 to 20 mA inputs by installing resistors on
either the Field Input/Output Module or setting jumpers on the
Analog PCB Assembly (if not using FIOMs). In this manual, we will
refer to both the input circuits and their analog signals as
Channels 1 through 8 (CH1 to CH8) the meaning in each case should
be clear from its context. The processing of these inputs and the
terms used to distinguish their intermediate values are illustrated
by Figure 3-1: Step 1: The raw analog inputs are converted to
equivalent digital values called Analog-to-Digital Variables (AD1
to AD8). Step 2: Transmitter Testing compares each AD variable
against its individual alarm limits. Step 3: The AD variables are
converted into percent-of-range Signal Variables (SV1 to SV8). Step
4: Gains and biases are then applied to obtain the Process
Variables (PV1 to PV8) used by the control calculations. Step 5:
The signal variables are also independently scaled to obtain the
Measured Variables (MV1 to MV8) displayed by the AUXiliary readouts
Analog In Menu.
Analog Inputs
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Analog-to-Digital Variables
The input circuitry converts the analog input signals into
equivalent digital values for use by the CPU. Each signal is passed
through a hardware filter to remove unwanted high frequency
components, and a windowing filter that samples each signal several
times per scan cycle and reports the resulting average. Because
these values are generated by an analog-to-digital converter, we
refer to them as analog-to-digital variables (AD1 to AD8). They are
reported to the CPU as percentages of the analog signals full-scale
value. For example, a 20 mA signal would be reported as 100
percent, while 4 mA would be reported as 20 percent.
Transmitter Testing
The controller tests each analog input against a user-defined
range. If any of them is outside of its range, the front-panel
TranFail LED is lit, any Transmitter Failure (Tran) relays are
energized and the Modbus Tran Fail discrete is set. You can use the
Transmitter Status Test [MODE:D ANIN ] to identify the failed
input. This feature is configured by defining the Analog Input Low
Alarm Limit [MODE:D ANIN # LOW] and Analog Input High Alarm Limit
[MODE:D ANIN # HIGH] for each input, which are set as percentages
of the full-scale analog-to-digital variables. For example, you
would enter AN IN LOW as 15.0 percent to set the lower limit of a 4
to 20 mA signal to 3.0 mA. Because an analog input can never be
higher than 102.4 (A2.4) nor lower than 00.0, setting ANIN HIGH and
LOW to these values has the effect of excluding that channel from
the transmitter alarm feature. Using these values for unused inputs
prevents them from interfering with the proper operation of this
feature.
Signal Variables
Each analog-to-digital variable is then converted to a
percent-ofrange signal variable according to whether or not the
corresponding transmitter uses an offset zero (for example, 4 to 20
mA or 1 to 5 Vdc). Signals that are so offset are scaled as: SV =
1.25 ( AD 20 percent ) Otherwise, the signal variable is set equal
to the analog-to-digital variable (AD). In either case, the SV
values are constrained to the range 00.0 to 100.0 percent. Higher
values are changed to 100.0, lower values to 00.0. You can use the
Signal Values Test [MODE TEST 4] to directly examine these signal
variables from the Engineering Panel. Any signal that has an offset
zero (for example, a 4 to 20 mA input) must be identified by
enabling the corresponding Offset Zero Input [MODE:D ANIN #].
Signals that are not offset are identified by disabling the
corresponding parameter.
September 2005
IM301 (6.1.3)
40
Chapter 3: Input/Output Features
Process Variables
The analog inputs for some control calculations must be
converted to absolute values. For example, the pressure
measurements used to compute a compression ratio must be scaled as
percentages of the highest absolute pressure either of their
sensors can measure. To this end, the controller converts its
signal variables into process variables by applying appropriate
gains and biases: PV = Gain SV + Bias where: Bias = (Offset 100) /
Maximum Gain = Range / Maximum Maximum = absolute measurement
corresponding to the highest possible transmitter signal. If there
is more than one transmitter of a given type, this should be the
largest such value for the group Offset = absolute measurement
corresponding to lowest possible transmitter signal PV = Process
Variable, expressed as a percentage of absolute maximum Range =
span of the transmitter in question The gain and bias for each
process variable must be assigned to the corresponding Process
Variable Gain [COND:D GAIN #] and Process Variable Bias [COND:D
BIAS #]. For unused channels, set the gain to 1.000 (.A00) and the
bias to 00.0.
Measured Variables
The AUXiliary Displays Analog In menu is used to display the
controllers eight signal variables, scaled to appropriate ranges,
along with descriptive labels of your choosing. For example, you
might display an inlet temperature signal as:
TempIn:
400
The available choices are set up by each inputs five Measured
Variable [COND:D DISPLAY 0] parameters. For example, the DISPLAY 0
1 parameters govern the display of signal variable SV1: Each
Measured Variable Display [COND:D DISPLAY 0 #] parameter defines
whether the corresponding variable can be viewed (SV1 can be
displayed only if DISPLAY 0 1 is On). Each Measured Variable Label
[COND:D DISPLAY 0 # ] parameter defines the label that will precede
the numeric value of the input. Each can be any combination of
eight symbols from Table 3-1. The default labels [see page 5 of
DS301/O], can be restored by entering the COND:D DISPLAY 0 0 key
sequence.
September 2005
IM301 (6.1.3)
Series 3 Plus Antisurge Controller
41
Each signal variables Measured Variable Minimum [COND:D DISPLAY
0 # LOW] defines the digits shown when it is zero, its Measured
Variable Maximum [COND:D DISPLAY 0 # HIGH] defines the digits shown
when it is 100 percent, and its Measured Variable Decimal [COND:D
DISPLAY 0 # ] defines the decimal point position. Mathematically,
this can be stated as: MV = [ Min + ( SV ) ( Max Min ) ] 10n
dec
where nSV is the signal variables normalized value. Because the
decimal point is a character that requires one of the four display
positions, only three digits can be displayed unless that parameter
is disabled (Off). In other words, that parameter identifies the
digit the decimal should replace (that and all less-significant
digits are shifted one position to the right). A value of one
corresponds to the right-most, least-significant digit, while four
is the left-most, most-significant digit. Thus, if DISPLAY 0 1 HIGH
is 3210, the five possible values of DISPLAY 0 1 would yield the
following displays when SV1 is 100 percent: 0: 3210 1: 321. 2: 32.1
3: 3.21 4: .321 To obtain the most precise possible readouts, you
should always make the DISPLAY HIGH parameters as large as
possible. For example, if you want to display three digit numbers
from 0 to 600, set DISPLAY HIGH to 6000 and DISPLAY to 1 (for a
trailing decimal). This will give more precise readouts than you
would get by setting DISPLAY HIGH to 0600 and DISPLAY to 0. If
Auxiliary Display Reset [MODE:D LOCK 9] is disabled, Measured
Variables will be displayed until another variable is selected.
Otherwise, the operating state display is restored 60 seconds after
the MENU or SCROLL key was last pressed.
Table 3-1
Available symbols for measured variable labels
space ! " # $ %&'()*+,-./ 0123456789:;?@ ABCDEFGHIJKLMNOP
QRSTUVWXYZ[\]^_` abcdefghijklmnop qrstuvwxyzSeptember 2005 IM301
(6.1.3)
42
Chapter 3: Input/Output FeaturesThe Antisurge Controller has two
standard analog outputs, both of which are generated as both 4 to
20 mA and 0 to 5 Vdc signals (although only one of these signals
can be used for each output): Unless the control response is sent
to a companion valve-sharing controller (see Valve Sharing on page
91), OUT1 is used to manipulate the compressors recycle or blowoff
valve (see Actuator Control Signal on page 99). OUT 2 is generated
as the equivalent of one of the variables listed in Table 3-2, as
specified by the Second Output Assigned Variable [COND:D OUT 2]. It
can be used to drive a readout or graphical display or be connected
to a DCS analog input. The Output Loopback Test can be used to
compare the actual output signal to its intended value, while the
Valve Position Test can be used to compare the measured and
intended positions of the final control element.
Analog Outputs
Table 3-2
Functions for OUT2CodeOut Flow S UsrQ
SignalActuator Control Signal (see page 99) Displayed Flow (see
page 61) proximity to Surge Control Line (see page 72) Displayed
Net Flow (see page 62)
Output Loopback Test
The controller can be configured to energize one or more
discrete outputs to indicate an excessive deviation between the
measured and intended values of the actuator control signal. This
feature is set up by connecting OUT1 to analog input CH8, as
described in the Analog Output Installation section in Chapter 6 of
IM300/H. Any discrete output assigned the output failure (OutF)
function would then energize if SV8 differed from the intended
a