Question: Does the audible annunciator on your alarm system seem to be sounding continuously, or do your operators appear stressed, and are they perhaps missing important alarms?

Perhaps the audible sounder has been turned off as your operators have no confidence in the alarm system, and treat it as an annoyance where they frequently acknowledge alarms without responding to them, rather than as a useful tool.

Nuisance alarms are extremely common in modern systems and devalue the usefulness of your alarm system, and if you recognize any of these situations, it is very likely that your system has a nuisance alarm problem that needs attention.

When operators are deluged with unnecessary, nuisance alarms; potentially the safety, and undoubtedly the operational effectiveness of your plant are likely to be compromised.

What is a nuisance alarm?

In the alarm management standard IEC 62682, the definition of a nuisance alarm is an:

“alarm that annunciates excessively, unnecessarily, or does not return to normal after the response is taken”.

Even in the best designed and well managed systems; you will at some point, experience periods when nuisance alarms become a problem during the Operation and Maintenance phases of the alarm management lifecycle (highlighted in the image to the right).

By the very nature of the term, these alarms are perceived as harmless; however, they represent an unnecessary burden to the operator especially during periods of plant upset when the operators' focus is essential.

Where do nuisance alarms come from?

Although there are many potential causes of nuisance alarms and in some cases more than one reason may be applicable, some of the more common causes are:

  • Inadequately designed and specified alarms
  • Alarms which are really events
  • Poor control loop tuning
  • Faulty instrumentation
  • Changes in process conditions away from the original design intent

How can I reduce nuisance alarm numbers?

Two of the most fundamental things you will need to help you successfully reduce the number of nuisance alarms in your system, are a current Alarm Philosophy; and dedicated alarm management software such as MAC Solutions’ ProcessVue, with which you will monitor, measure and analyse the alarms annunciated to your operators.

If you have these in place, then you can begin to effectively deal with your nuisance alarms.

In principle, nuisance alarm reduction breaks down into three simple questions.

  • Is the alarm a good alarm?
  • Does the alarm need to be modified?
  • Are there any other underlying problems to resolve?

The first two questions can be answered relatively simply through reference to your Alarm Philosophy and the analysis provided by your alarm management software.

Your alarm analysis software should give you a breakdown of the top most frequently occurring (nuisance) alarms as shown in the image to the right.

From the definitions in your Alarm Philosophy, you can determine if a frequently occurring alarm is a good alarm (to be kept and its nuisance behavior resolved), or if it can be demoted to an Event or removed altogether as it serves no useful purpose at all.

Your alarm analysis software should also present you with a ‘time in alarm’ chart for each frequently occurring alarm which will help you to determine if the nuisance behavior can be significantly reduced through the application of a simple delay timer as shown in the image to the right.

However, if the alarm is a good alarm and configuration parameters have been appropriately applied as per the guidelines in your Alarm Philosophy, but the alarm still exhibits nuisance behavior; then you must ask the third and more difficult question. Is there something else wrong?

The problem may be caused due to a change in process conditions, badly specified or failing equipment etc. These nuisance alarms are more difficult to resolve as potentially there may need to be a maintenance window obtained or the process or equipment may have to be modified. If this is the case, you will have to consider using the inbuilt alarm system functionality to temporarily ‘shelve’ the alarm until the process / equipment situation can be resolved.

Benefits of reducing nuisance alarms

  • The operating environment will improve and your operators will be less stressed
  • Your alarm system will become an effective tool to help your operators
  • Your operators can focus on managing your process instead of simply responding to alarms
  • You will have fewer process interruptions or trips thus saving you money
  • Potential reduction of maintenance related losses by reviewing alarms such as vibration alarms which may lead to significant equipment failures

How we can help you

In order to help you reduce your nuisance alarm problem, we can:

  • Carry out monthly reporting on your behalf based on data supplied from your site. The reports will not only provide you with a snapshot of your system’s current performance compared to your defined KPIs; but will also highlight nuisance alarm activity and recommend actions for improvement

Or:

  • Work with your Operations and C&I / Maintenance departments on site, to provide a comprehensive solution to your nuisance alarm problems

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