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It is 6.00 in the evening after a hot summer’s afternoon and the shift has just changed over. The control room has been rather quiet through the day with the odd alarm punctuating the serene silence. In fact this plant has been a truly contented baby with no major problems for over 18 months since it was commissioned. Apart from the inevitable mechanical wear and tear associated with a new plant. Suddenly there is an explosive roar outside and the control room door bursts open with the shift foreman dripping with sweat shouting: “We’ve just lost Unit 3, I’m not sure what is happening…can you tell me what is going on”. Within seconds the alarms start pouring in. The operator starts to systematically work his way through the overview displays trying to identify what is going on. But he is slowly overwhelmed by the sheer number of alarms which are flitting across the screen so fast that he cannot even read them. And Unit 3 is now starting to lurch into a dangerous state with pressures, flows and temperatures well outside acceptable operating ranges. So it looks like an immediate shutdown of the plant is going to be required with some very unhappy customers over the next few weeks. Was there any other approach possible? Hopefully this is not the scenario on your plant; but could this just perhaps happen? Does your alarm system ensure the operator stays unerringly focussed on the source of the problem or is there a possibility that he could get overwhelmed and distracted by the number of alarms where many of them may not be relevant to the immediate problem? It is important that throughout the plant that a consistent philosophy is adopted for alarms and that your operators are not distracted from the main ball game of operating the plant. This workshop will give you the necessary information to ensure that your alarm system is well designed and provides your operators with the best picture of the operations of the plant. The workshop focuses on simple and practical information for personnel ranging from operators all the way up to supervisors, engineers and managers. WHO SHOULD ATTEND? Anyone involved in the installation, design and support of alarm systems Design engineers Electrical and instrumentation technicians Electrical engineers Instrumentation and control system engineers Instrumentation technologists and engineers IT managers working with networks Maintenance engineers and supervisors Operations managers Plant engineers Process control designers and systems engineers Process control engineers and technicians Process engineers Production engineers Project engineers Systems engineers MORE INFORMATION: http://www.idc-online.com/content/practical-alarm-systems-management-engineers-and-technicians-2
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Practical Alarm Management for Engineers and
Technicians
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Alarm Systems• Stand-alone Alarm
Annunciators with Lamps.• Alarm Systems within Process
Control Systems - DCS/SCADA
• Control Systems : Man-Machine-Interface (MMI).
• Alarm System is integrated part of Man-Machine-Interface.
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Purpose of Alarms Alarms bring the following to the notice of the operator :
• Problems that need operator attention • Process changes that require corrective actions• Un-safe operating conditions before Emergency Shut-down of plant• Hazardous conditions• Deviations from desired/normal conditions
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Functions of a Plant Operator• Safe and normal operation of plant /equipment• production at optimum levels• Identification of abnormal, hazardous and un-safe
plant / equipment conditions and take corrective actions
• Fault identification and communication of faults to maintenance
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Functions of a Plant Operator
The functions and priorities of a plant operator change with the changing plant conditions, such as:
• During start-up, • Plant under stabilization,• During plant running in normal condition, • Plant in abnormal or up-set conditions, • Plant in emergency shut-down,• Plant in planned shut-down,• Mode of operation (Auto, Semi-auto, Manual)
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Changing Plant Conditions & Functions of the Plant Operator
< Insert Figure 1-1 >
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Functions of the Operator during plant Abnormal/Upset Conditions
< Insert Figure 1-2 >
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Functions of Alarms
• To direct the attention of the operator towards the plant abnormal conditions which need timely assessment and/or timely corrective action(s).
• To guide the operator in an abnormal situation and help him to take timely corrective action(s) to bring the plant back to normal conditions.
• To provide feedback on the corrective actions taken by the operator in response to the alarms. (supplementary displays)
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Key points for Designing an Effective Alarm System
• Present only relevant and useful alarms to the operator• Each alarm should have a defined response from the operator• Allow adequate time for the operator to respond to an alarm • Configure and present only good alarms
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Present only Relevant & Useful Alarms
• Alarms that help an operator in monitoring and controlling the plant/equipment.
• Alarms should not be a nuisance or hindrance for the operator.• Operator’s time and attention should not be diverted on the
alarms which did not require any response or intervention from the operator and can be ignored.
• Otherwise, there is a possibility of the “Cry Wolf” effect with the operators feeling that they can afford to ignore alarms.
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Each Alarm should have a Defined Response
• Response should be in the form of a Preventive and/or Corrective Action(s) or an Acknowledgement.
• At times the response to an alarm can be conditional. • Some alarms, such as "plant start-up sequence completed” or
“equipment stopped/tripped” inform the operator to change his response i.e. how he is monitoring or paying attention to the plant/equipment. (A mental response is all that is needed for the operator to make such a cognitive change.)
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Allow Adequate Time for Response
• Adequate time for the operator to respond to the alarm.• The alarm should be given in advance to allow enough time for
corrective action in order to rectify the problem or fault.• Rate of alarms should not exceed the capability of the operator
to respond to the alarms.• Apart from responding to alarms, the operator also has various
other tasks/activities.• Alarm system design should be such that the overall functions
of an operator are manageable.
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Average Workload imposed by the Alarm System on an Operator
W = R . T
Where: R – average rate of alarms presented T – average time taken to respond to the alarm
Note : While designing an Alarm System, Human Limitations
and Ergonomic Factors must be taken into account to make the Alarms System effective.
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Configure & Present only Good Alarms
Characteristics of a Good Alarm :
• It must be relevant and not a spurious alarm• It must be presented on time, not in advance before the
operator response is needed, nor left too late, leaving no time for the operator to respond or take corrective action
• It must draw the attention of the operator towards important problems
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Configure & present only Good Alarms
Characteristics of a Good Alarm:• It must clearly identify the problem and indicate the action(s)
to be taken.• It must be understandable. The alarm message should be clear
and easy to understand.• It must indicate the priority of the problem.• It must be unique. It should not be a duplication of another
alarm creating redundancy and increasing the alarm load on operator.
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DO YOU WANT TO KNOW MORE?
If you are interested in further training or information, please visit:
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