How to succeed at alarm management

Find out how you can improve the effectiveness of your distributed control alarm systems by better managing the techniques, tools, standards, and procedures you use in your process plant.

By D. Shook PhD, PE,

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THE INTRODUCTION OF the DCS has made it possible to create alarms more easily and at a lower cost. Although software alarms are convenient, the ease with which they can be created removed the incentive to limit alarms. As a result, operators today are faced with more alarms than they can effectively monitor. Alarm management seeks to identify unnecessary alarms, alarms set at the wrong value, and where improvements can be made to the current procedures for dealing with alarms.

What is Alarm Management, and why do I need it?
Alarm Management comprises a collection of techniques, tools, standards, and procedures that improve the operations of process plants by improving the effectiveness of alarm systems.

Nuisance Alarms
When alarms are functioning well, they perform three important tasks:

 

  • Alerting the operator that a change has occurred
  • Informing the operator of the nature of the change
  • Guiding the operator to take the correct action

Without a disciplined Alarm Management program, the process alarms in a plant become less and less functional over time. The number of nuisance alarms increases to a point where the alarms distract the operator from the plant, rather than doing what they are designed to do.

Alarm Proliferation
Alarm management has existed as long as there have been alarm systems, but it has become more important since the distributed control system (DCS) was introduced in the 1970’s. The distributed control system introduced software alarms - alarms that are created or changed by configuring a setting in a computer, rather than requiring a hardwired signal to a panel. As a result, more alarms could be configured for lower cost. This meant safer operations, but it also relaxed the engineering controls on the creation of alarms. Since there was now no cost to implement an alarm, there was no incentive to limit the number of alarms.

Naturally, some of the alarms that were configured were not really necessary, or were set at the wrong value. This leads to "nuisance alarms" - alarms that do not tell the operator anything he does not already know, or which require no action.

Since the 1970’s, as distributed control systems have become more sophisticated, more and more process units have been centralized under the control of fewer panel operators, so each operator has become responsible for more and more alarms. In addition, the number of alarms that can be configured on a single measurement has ballooned. Alarms are now commonly set on Low, High, Low-Low, High-High, Deviation, bad value, and sometimes other values.

An individual operator now is confronted with tens of thousands of configured alarms within his area of the plant. During upsets, hundreds or thousands of these alarms can occur in a very short period. To make matters even worse, organizations such as OSHA, the EPA or voluntary programs like Responsible Care?, ISO-9000 and ISO-14000 require periodic process hazard analyses or process assessments, which all result in the creation of additional alarms.

When there are too many alarms during an upset, they distract the operator and conceal the actual nature of secondary problems, instead of alerting the operator to real problems. So, in the absence of an alarm management program, manufacturing plants become less safe rather than safer; incidents become worse rather than better, and production losses increase.

What Does Alarm Management Include?
Alarm Management consists of the set of procedures, practices, tools and systems that jointly ensure that the alarm system in a plant is as effective as possible throughout the life of the plant. These can include:

  • Operator training on how to respond to alarms
  • Reducing the number of systems that can generate alarms
  • Documentation of the steps to be taken when an alarm occurs
  • Operator assistance in finding information regarding an alarm
  • Standardization and enforcement of the criteria for determining alarm priority
  • Risk-based evaluation of all alarms, to reconfigure or eliminate unnecessary alarms
  • Identification and elimination of nuisance alarms using alarm history
  • Alarm enforcement
  • Alarm change management
  • Automatic suppression of alarms
  • Definition of different alarm limits for different operating conditions or modes
  • Replacing early-warning" alarms with continuous monitoring

All Plants Need Alarm Management
The real question is: "Is my existing Alarm Management sufficient?" Ask yourself the following questions:

  • Do you need to know how many alarms you get in a day, how often alarm floods occur, or which tags are causing the most problems?
  • When you walk into the control room on a quiet day, do more than 10 to 15 alarms show up on the alarm summary screen for a single operating area?
  • Are there more than two systems that generate alarms, for example, DCS and a single additional emergency system panel?

When there is an upset,

  • Does the alarm annunciator sound continuously?
  • Does one operator lean on the alarm silencer button continuously?
  • Is the alarm annunciator disconnected?
  • Have there been any operating incidents where the operator missed an alarm that did occur?
  • Do more than 1000 alarms occur in a given operating area in a day?
  • Do operators change alarm limits?
  • Do operators use alarms to inform them of non-critical changes in the plant, such as end-of-batch?
  • Are there alarms that operators do not know how to respond to?
  • Does any operator not understand why each alarm is the priority it is?

If the answer to more than one of these questions is "I don’t know" or "yes", then your Alarm Management system needs improvement, or at least an assessment. Poorly-managed alarms are a disaster waiting to happen. At best, they distract the operator from important events and slow down the response to the upset. At worst, the alarms will not be noticed, won’t occur at all, or will not be understood-- not a situation you want to deal with in an EPA/OSHA or insurers audit.

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