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Time to re think alarm management strategies


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  • 1. 7LPH WR 5H7KLQN $ODUP 0DQDJHPHQW 6WUDWHJLHV % ,. +,// 129(0%(5 $5 ,16,*+76 0+ 03 .(:256 Alarm Management, ASM 6800$5 ARC estimates that $65 billion of process automation systems (PAS) installed and operat- ing throughout the world are 15 years or older and rapidly approaching the end of their useful life. Most of these legacy systems and the majority of all systems do not have the current PAS functionality. While nearly all are doing an adequate 8QOLNH FRQWURO ORRSV PDQ DFWLYH job of regulatory control, many are inadequate for the “first line ofDODUPV DUH VHW H[DFWO DV WKH ZHUH defense” against abnormal situations – alarm management. ZKHQ WKH HQJLQHHULQJ FRQWUDFWRU ILUP ILUVW FRPPLVVLRQHG WKH SODQW When control strategies are not operating properly, plant personnel generally have time to respond while the plant is still in a normal operating range. Furthermore, most companies are organized to constantly improve control strategies and deal with malfunctioning control immediately. When an alarm strategy is not working, often the time to respond is compressed since the plant may al- ready be in an abnormal range. Alarm strategies need to be reviewed and adjusted as process conditions change throughout the operating life just as control strategies need to be. $1$/6,6 Almost since the beginning of the concept of automatic control, there have been process alarms. For most manufacturing plants, automatic control has progressed far beyond early control devices that operated independently. Control loops today are commonly linked, cascaded and melded into coordinated control strategies to ensure that they work together in concert. If one measurement changes, the control loops affected will respond correctly in a cooperative way. Controller strategies are developed to drive toward the common goal of maintaining the equilibrium and status quo. When the status quo is interrupted many put their faith in the fact that alarms will warn operators of malfunc- tions and allow him to calmly return to normal. 6LJPD *RDOV 0DNHV $ODUP 0DQDJHPHQW 0RUH ,PSRUWDQW Maybe it is fitting that so much time, energy, and technology has been put into advanc- ing the state of control. After all, thanks in part to the advances over the years, automated control has been a significant contributor to manufacturers approaching 6 @IU@SQSDT@Ã6I9ÃH6IVA68UVSDIBÃTUS6U@BD@TÃAPSÃDI9VTUS`Ã@Y@8VUDW@TÃ
  • 2. 6S8ÃD†vtu‡†ÃQhtrÃ!à sigma levels of operation. Actually in the process industries it is closer to 4 Sigma, but this still represents 99.4 percent of the time the plant is operating correctly. A lot of attention is paid to improving control strategies to squeeze the last 0.6 percent out and eliminate failures all together. Very few active control loops are tuned or con- figured exactly as they were when the plant was first commissioned by the engineering contractor firm. Most manufacturers’ control departments devote a significant amount of time to maintain and improve control functions. This cannot be said for alarm set- tings. In order to squeeze the last 0.6 percent out and eliminate failures all together, traditional alarming approaches are just not good enough. Ideally, alarms should never happen, if the control strategies, production equipment and processes all work together, but when they don’t this is when alarms need to be at their best. Alarms are often set independ- ently and remain static until someone discovers that they are set incorrectly for the current operating conditions. Discovering this when a problem arises is the worst time. $ODUP 6KRZHUV DQG 2WKHU LJLWDOO ,QGXFHG 3KHQRPHQRQ The advances in control over the years to the pervasive use of digital control, has cer- tainly helped make interactive, coordinated control strategies possible and commonplace. It has also allowed the “loop count” that modern operators can handle to increase into the hundreds. In the days of hardwired controls and alarms, engineers were$ODUP 0DQDJHPHQW 6WUDWHJLHV very stingy with alarms partly due to the fact that each alarmo 0LQLPL]H DODUP FODVVHV point had a cost. Since each alarm today is virtually free with the measurement and control loop, the conventionalo $ODUPV IRU RSHUDWRU DFWLRQ RQO wisdom is often “when in doubt - put an alarm on it”. Witho RQVLGHU FRQGLWLRQEDVHG PDQDJHPHQW the potential for every measured point to have a “high”, “low” and other variations often there are more alarm pointso (VWDEOLVK QHZPRGLI DODUP SURFHVV then there are measured variables in the process.o 5HYLHZ RYHUDOO VWUDWHJ HDUO Furthermore, since these alarms are often related only to the process variable they are connected to, they are not aware of other alarms. This can result in a phenomenon called alarm showers. Alarm showers occur when one failure causes many process variables to trip their preset alarms. The result can be catastrophic when the quantity of alarms masks the real source of the prob- lem and causes delays in operator corrective actions. ‹Ã! ÇÃ6S8Ã6q‰v†‚…’ÃB…‚ˆƒÃ‡ÃÃ6yyvrqÃ9…v‰rÇÃ9rquh€ÃH6Ã!!%ÃVT6Çà # ÇÃ6S8rip‚€Ã VT6ÇÃVFÇÃBr…€h’ÇÃEhƒhÃ‡ÃDqvhÃ
  • 3. 6S8ÃD†vtu‡†ÃQhtrÃÃ:KDW ,V WKH %HVW $ODUP 6WUDWHJAlarms and controls have another thing in common; they must be configured specificallyto meet the process application and operation philosophy. Just as all process controlstrategies are developed with the same basic building blocks but configured differentlyfor each application, alarm strategies are built using a common set of alarm tools. Justlike control, the best alarm strategy for one process is not necessarily the same for an-other. Each process requires its alarms to be configured and tuned to meet the specificprocess requirements.For example, processes that tend to have a large number of controlled and measuredvariables under the operational control of a single operator require strategies to preventoverwhelming the operator. These type of processes not only need to have a well-established process for setting alarms in the first place, but they also need to have a con-tinuous review process. Even processes that have few control points may need a uniquealarm strategy, if process dynamics, operating ranges or equipment status are constantlychanging.RQGLWLRQEDVHG $ODUP 0DQDJHPHQWAlarms should only be used to cause an operator to take action. It makes no sense for anoperator to have to respond to an alarm for low flow when the pump controlling theflow is shut down for maintenance. Having the system manage these situations can takeplace in many ways. Most modern PASs contains alarm management software that al-lows for grouping of alarms. Not all suppliers offer equally comprehensive alarmmanagement functions. Furthermore, some alarm management strategies while com-prehensive may be extremely complex to use. The user should make sure that alarmmanagement functionality is on the checklist for their next PAS purchase.If you have an older, legacy control system with inadequate alarm management, youhave other options. Most of the Process Automation System suppliers have HMI or PIMsoftware that can be added to your legacy control systems to provide additional alarmcapability. These include software such as Wonderware’s Intouch, Intellution’s iFix,Rockwell’s RSView, GE Fanuc’s CIMPLICITY, Honeywell Hi-Spec’s PHD, Yokogawa’s ITExaquantum, and ABB’s Inform .Plant Automation Services is headquartered in Houston and has specialized in the alarmmanagement software business for many years. Their AMO Suite is designed specifi-cally to optimize alarm management. Other third party software systems such asAspenTech’s InfoPlus.21, OSI’s PI, eMation’s WizFactory, and Wellspring’s OA2alarmsoffer alarm management as an integral part of their HIM or PIM systems. ‹Ã! ÇÃ6S8Ã6q‰v†‚…’ÃB…‚ˆƒÃ‡ÃÃ6yyvrqÃ9…v‰rÇÃ9rquh€ÃH6Ã!!%ÃVT6Çà # ÇÃ6S8rip‚€Ã VT6ÇÃVFÇÃBr…€h’ÇÃEhƒhÃ‡ÃDqvhÃ
  • 4. 6S8ÃD†vtu‡†ÃQhtrÃ#Ã%HRQG $ODUP 0DQDJHPHQWYes there is considerable help available both in terms of services as well as software ap-plications. ARC has previously written about software specifically designed to addressAbnormal Situation Management (ASM). This software tends to be more predictive andaimed at providing operators with intelligent guidance beyond the simple act of alarmnotification. Additional discussion of ASM will be provided in subsequent Insights. Thepurpose of this Insight is to help focus attention to the “first line of defense” against ab-normal situations – alarm management.5(200(1$7,216• Process Industry manufacturers should establish an Alarm Strategy with guidelines and procedures for periodic review and evaluation of alarms.• Manufacturers with older legacy systems with inadequate alarm functionality, should either look to automation system suppliers to replace or upgrade their sys- tems or look for third party software suppliers that can provide add-on alarm management functions to meet their alarm management strategies• Suppliers need to provide their users with alternatives that fit their specific alarm management requirements. Above all, alarm management should be made as easy as control strategy management is.For further information, contact your account manager or the author at circulation: All MAS-H and MAS-P clients. ‹Ã! ÇÃ6S8Ã6q‰v†‚…’ÃB…‚ˆƒÃ‡ÃÃ6yyvrqÃ9…v‰rÇÃ9rquh€ÃH6Ã!!%ÃVT6Çà # ÇÃ6S8rip‚€Ã VT6ÇÃVFÇÃBr…€h’ÇÃEhƒhÃ‡ÃDqvhÃ